Distributed Systems Patterns Beispiele

// Distributed Consistency Models Implementation

// Consistency Model Types
enum ConsistencyModel {
  STRONG = 'strong',
  SEQUENTIAL = 'sequential',
  CAUSAL = 'causal',
  EVENTUAL = 'eventual',
  WEAK = 'weak'
}

interface DataItem {
  key: string
  value: any
  version: number
  timestamp: Date
  nodeId: string
}

interface Operation {
  id: string
  type: 'READ' | 'WRITE' | 'DELETE'
  key: string
  value?: any
  timestamp: Date
  nodeId: string
}

interface ConsistencyResult {
  success: boolean
  value?: any
  version?: number
  errorMessage?: string
}

// Strong Consistency Implementation (Linearizability)
class StrongConsistencyManager {
  private data: Map<string, DataItem> = new Map()
  private operationLog: Operation[] = []
  private lockTable: Map<string, string> = new Map() // key -> nodeId

  async write(key: string, value: any, nodeId: string): Promise<ConsistencyResult> {
    // Acquire lock for strong consistency
    const lockAcquired = await this.acquireLock(key, nodeId)
    if (!lockAcquired) {
      return { success: false, errorMessage: 'Could not acquire lock for write operation' }
    }

    try {
      const currentData = this.data.get(key)
      const newVersion = (currentData?.version || 0) + 1

      const newDataItem: DataItem = {
        key,
        value,
        version: newVersion,
        timestamp: new Date(),
        nodeId
      }

      // Log the operation
      const operation: Operation = {
        id: crypto.randomUUID(),
        type: 'WRITE',
        key,
        value,
        timestamp: new Date(),
        nodeId
      }

      this.operationLog.push(operation)
      this.data.set(key, newDataItem)

      console.log(`[STRONG] Write operation for key ${key} by ${nodeId} - Version: ${newVersion}`)

      return { success: true, value, version: newVersion }
    } finally {
      await this.releaseLock(key, nodeId)
    }
  }

  async read(key: string, nodeId: string): Promise<ConsistencyResult> {
    // For strong consistency, read from primary with lock
    const lockAcquired = await this.acquireLock(key, nodeId, 5000) // 5 second timeout
    if (!lockAcquired) {
      return { success: false, errorMessage: 'Could not acquire lock for read operation' }
    }

    try {
      const dataItem = this.data.get(key)
      if (!dataItem) {
        return { success: false, errorMessage: 'Key not found' }
      }

      const operation: Operation = {
        id: crypto.randomUUID(),
        type: 'READ',
        key,
        timestamp: new Date(),
        nodeId
      }

      this.operationLog.push(operation)

      console.log(`[STRONG] Read operation for key ${key} by ${nodeId} - Version: ${dataItem.version}`)

      return {
        success: true,
        value: dataItem.value,
        version: dataItem.version
      }
    } finally {
      await this.releaseLock(key, nodeId)
    }
  }

  private async acquireLock(key: string, nodeId: string, timeout: number = 30000): Promise<boolean> {
    const startTime = Date.now()

    while (Date.now() - startTime < timeout) {
      const currentLock = this.lockTable.get(key)
      if (!currentLock || currentLock === nodeId) {
        this.lockTable.set(key, nodeId)
        return true
      }

      // Wait before retrying
      await new Promise(resolve => setTimeout(resolve, 100))
    }

    return false
  }

  private async releaseLock(key: string, nodeId: string): Promise<void> {
    const currentLock = this.lockTable.get(key)
    if (currentLock === nodeId) {
      this.lockTable.delete(key)
    }
  }

  getOperationHistory(): Operation[] {
    return [...this.operationLog]
  }
}

// Eventual Consistency Implementation with Gossip Protocol
class EventualConsistencyManager {
  private nodeData: Map<string, Map<string, DataItem>> = new Map() // nodeId -> (key -> data)
  private vectorClocks: Map<string, Map<string, number>> = new Map() // nodeId -> (nodeId -> counter)
  private gossipInterval: number = 5000 // 5 seconds

  constructor(private nodeId: string, private knownNodes: string[]) {
    this.initializeNode()
    this.startGossipProtocol()
  }

  private initializeNode(): void {
    this.nodeData.set(this.nodeId, new Map())
    this.vectorClocks.set(this.nodeId, new Map())

    const nodeClock = this.vectorClocks.get(this.nodeId)!
    for (const node of this.knownNodes) {
      nodeClock.set(node, 0)
    }
    nodeClock.set(this.nodeId, 0)
  }

  async write(key: string, value: any): Promise<ConsistencyResult> {
    const nodeData = this.nodeData.get(this.nodeId)!
    const nodeClock = this.vectorClocks.get(this.nodeId)!

    // Increment vector clock for this node
    const currentCounter = nodeClock.get(this.nodeId) || 0
    nodeClock.set(this.nodeId, currentCounter + 1)

    const newDataItem: DataItem = {
      key,
      value,
      version: currentCounter + 1,
      timestamp: new Date(),
      nodeId: this.nodeId
    }

    // Store with vector clock
    (newDataItem as any).vectorClock = new Map(nodeClock)

    nodeData.set(key, newDataItem)

    console.log(`[EVENTUAL] Local write for key ${key} on node ${this.nodeId} - VC: ${JSON.stringify(Object.fromEntries(nodeClock))}`)

    return { success: true, value, version: currentCounter + 1 }
  }

  async read(key: string): Promise<ConsistencyResult> {
    const nodeData = this.nodeData.get(this.nodeId)!
    const dataItem = nodeData.get(key)

    if (!dataItem) {
      return { success: false, errorMessage: 'Key not found' }
    }

    console.log(`[EVENTUAL] Read key ${key} on node ${this.nodeId} - Version: ${dataItem.version}`)

    return {
      success: true,
      value: dataItem.value,
      version: dataItem.version
    }
  }

  private async startGossipProtocol(): Promise<void> {
    setInterval(async () => {
      await this.performGossip()
    }, this.gossipInterval)
  }

  private async performGossip(): Promise<void> {
    if (this.knownNodes.length === 0) return

    // Select random node to gossip with
    const targetNode = this.knownNodes[Math.floor(Math.random() * this.knownNodes.length)]

    try {
      await this.exchangeDataWithNode(targetNode)
    } catch (error) {
      console.log(`Gossip with node ${targetNode} failed:`, error)
    }
  }

  private async exchangeDataWithNode(targetNodeId: string): Promise<void> {
    console.log(`[GOSSIP] Exchanging data between ${this.nodeId} and ${targetNodeId}`)

    // Simulate data exchange with another node
    const targetNodeData = this.getSimulatedNodeData(targetNodeId)
    const myNodeData = this.nodeData.get(this.nodeId)!

    // Merge data from target node
    for (const [key, targetData] of targetNodeData.entries()) {
      const myData = myNodeData.get(key)

      if (!myData) {
        // Key doesn't exist locally, adopt it
        myNodeData.set(key, targetData)
        console.log(`[GOSSIP] Adopted key ${key} from node ${targetNodeId}`)
      } else {
        // Resolve conflicts using vector clocks
        const resolved = this.resolveConflict(myData, targetData)
        if (resolved !== myData) {
          myNodeData.set(key, resolved)
          console.log(`[GOSSIP] Resolved conflict for key ${key}`)
        }
      }
    }
  }

  private resolveConflict(data1: DataItem, data2: DataItem): DataItem {
    const vc1 = (data1 as any).vectorClock as Map<string, number>
    const vc2 = (data2 as any).vectorClock as Map<string, number>

    if (!vc1 || !vc2) {
      // Fallback to timestamp
      return data1.timestamp >= data2.timestamp ? data1 : data2
    }

    // Compare vector clocks
    const result = this.compareVectorClocks(vc1, vc2)

    if (result === 'concurrent') {
      // Conflict - choose the one with higher timestamp (last-writer-wins)
      return data1.timestamp >= data2.timestamp ? data1 : data2
    } else if (result === 'greater') {
      return data1
    } else {
      return data2
    }
  }

  private compareVectorClocks(vc1: Map<string, number>, vc2: Map<string, number>): 'greater' | 'less' | 'equal' | 'concurrent' {
    let greater = false
    let less = false

    const allKeys = new Set([...vc1.keys(), ...vc2.keys()])

    for (const key of allKeys) {
      const v1 = vc1.get(key) || 0
      const v2 = vc2.get(key) || 0

      if (v1 > v2) greater = true
      if (v1 < v2) less = true

      if (greater && less) return 'concurrent'
    }

    if (greater && !less) return 'greater'
    if (!greater && less) return 'less'
    return 'equal'
  }

  private getSimulatedNodeData(nodeId: string): Map<string, DataItem> {
    // Simulate getting data from another node
    const simulatedData = new Map<string, DataItem>()

    // Add some sample data for simulation
    if (Math.random() > 0.5) {
      simulatedData.set('shared_key_1', {
        key: 'shared_key_1',
        value: `value_from_${nodeId}`,
        version: Math.floor(Math.random() * 10),
        timestamp: new Date(Date.now() - Math.random() * 10000),
        nodeId
      })
    }

    return simulatedData
  }

  getLocalData(): Map<string, DataItem> {
    return new Map(this.nodeData.get(this.nodeId))
  }
}

// Causal Consistency Implementation
class CausalConsistencyManager {
  private data: Map<string, DataItem> = new Map()
  private dependencyGraph: Map<string, Set<string>> = new Map() // operation -> dependencies
  private pendingOperations: Map<string, Operation> = new Map()

  async write(key: string, value: any, dependencies: string[] = []): Promise<ConsistencyResult> {
    const operationId = crypto.randomUUID()
    const timestamp = new Date()

    const operation: Operation = {
      id: operationId,
      type: 'WRITE',
      key,
      value,
      timestamp,
      nodeId: 'causal-node'
    }

    // Check if dependencies are satisfied
    const dependenciesSatisfied = this.checkDependencies(dependencies)
    if (!dependenciesSatisfied) {
      // Add to pending operations
      this.pendingOperations.set(operationId, operation)
      this.dependencyGraph.set(operationId, new Set(dependencies))

      console.log(`[CAUSAL] Write for key ${key} pending dependencies: ${dependencies.join(', ')}`)
      return { success: false, errorMessage: 'Dependencies not satisfied' }
    }

    // Execute operation
    const newDataItem: DataItem = {
      key,
      value,
      version: Date.now(), // Use timestamp as version
      timestamp,
      nodeId: 'causal-node'
    }

    this.data.set(key, newDataItem)
    this.dependencyGraph.delete(operationId)

    // Process pending operations that now have satisfied dependencies
    await this.processPendingOperations(operationId)

    console.log(`[CAUSAL] Write for key ${key} executed successfully`)

    return { success: true, value, version: newDataItem.version }
  }

  async read(key: string): Promise<ConsistencyResult> {
    const dataItem = this.data.get(key)
    if (!dataItem) {
      return { success: false, errorMessage: 'Key not found' }
    }

    console.log(`[CAUSAL] Read key ${key} - Version: ${dataItem.version}`)

    return {
      success: true,
      value: dataItem.value,
      version: dataItem.version
    }
  }

  private checkDependencies(dependencies: string[]): boolean {
    return dependencies.every(dep => !this.pendingOperations.has(dep))
  }

  private async processPendingOperations(completedOperationId: string): Promise<void> {
    const toProcess: string[] = []

    // Find operations that depend on the completed operation
    for (const [opId, dependencies] of this.dependencyGraph.entries()) {
      if (dependencies.has(completedOperationId)) {
        dependencies.delete(completedOperationId)

        if (dependencies.size === 0) {
          toProcess.push(opId)
        }
      }
    }

    // Process operations whose dependencies are now satisfied
    for (const opId of toProcess) {
      const operation = this.pendingOperations.get(opId)
      if (!operation) continue

      this.pendingOperations.delete(opId)
      this.dependencyGraph.delete(opId)

      // Execute the pending operation
      if (operation.type === 'WRITE' && operation.value !== undefined) {
        const newDataItem: DataItem = {
          key: operation.key,
          value: operation.value,
          version: Date.now(),
          timestamp: operation.timestamp,
          nodeId: operation.nodeId
        }

        this.data.set(operation.key, newDataItem)
        console.log(`[CAUSAL] Executed pending write for key ${operation.key}`)
      }

      // Recursively process more pending operations
      await this.processPendingOperations(opId)
    }
  }

  getPendingOperationsCount(): number {
    return this.pendingOperations.size
  }

  getDependencyGraph(): Map<string, Set<string>> {
    return new Map(this.dependencyGraph)
  }
}

// Consistency Performance Analyzer
class ConsistencyPerformanceAnalyzer {
  private metrics: Map<string, Array<{
    operation: string
    latency: number
    timestamp: Date
    success: boolean
  }>> = new Map()

  recordMetric(consistencyModel: string, operation: string, latency: number, success: boolean): void {
    if (!this.metrics.has(consistencyModel)) {
      this.metrics.set(consistencyModel, [])
    }

    const modelMetrics = this.metrics.get(consistencyModel)!
    modelMetrics.push({
      operation,
      latency,
      timestamp: new Date(),
      success
    })

    // Keep only last 1000 metrics per model
    if (modelMetrics.length > 1000) {
      modelMetrics.shift()
    }
  }

  getPerformanceReport(): {
    models: Array<{
      name: string
      avgLatency: number
      successRate: number
      totalOperations: number
      readLatency: number
      writeLatency: number
    }>
    recommendations: string[]
  } {
    const models: Array<{
      name: string
      avgLatency: number
      successRate: number
      totalOperations: number
      readLatency: number
      writeLatency: number
    }> = []

    for (const [modelName, metrics] of this.metrics.entries()) {
      if (metrics.length === 0) continue

      const successfulOps = metrics.filter(m => m.success)
      const readOps = metrics.filter(m => m.operation === 'READ')
      const writeOps = metrics.filter(m => m.operation === 'WRITE')

      const avgLatency = metrics.reduce((sum, m) => sum + m.latency, 0) / metrics.length
      const successRate = (successfulOps.length / metrics.length) * 100
      const readLatency = readOps.length > 0 ? readOps.reduce((sum, m) => sum + m.latency, 0) / readOps.length : 0
      const writeLatency = writeOps.length > 0 ? writeOps.reduce((sum, m) => sum + m.latency, 0) / writeOps.length : 0

      models.push({
        name: modelName,
        avgLatency,
        successRate,
        totalOperations: metrics.length,
        readLatency,
        writeLatency
      })
    }

    const recommendations = this.generateRecommendations(models)

    return { models, recommendations }
  }

  private generateRecommendations(models: any[]): string[] {
    const recommendations: string[] = []

    // Analyze latency patterns
    const avgLatencies = models.map(m => m.avgLatency)
    const maxLatency = Math.max(...avgLatencies)

    if (maxLatency > 1000) { // 1 second
      recommendations.push('High latency detected. Consider optimizing network communication or using caching.')
    }

    // Analyze success rates
    const lowSuccessModels = models.filter(m => m.successRate < 95)
    if (lowSuccessModels.length > 0) {
      recommendations.push('Low success rates detected. Check for network failures or implement retry mechanisms.')
    }

    // Compare read vs write latencies
    const highWriteLatencyModels = models.filter(m => m.writeLatency > m.readLatency * 2)
    if (highWriteLatencyModels.length > 0) {
      recommendations.push('Write operations significantly slower than reads. Consider write-optimizations or eventual consistency for writes.')
    }

    // Model-specific recommendations
    const strongModel = models.find(m => m.name.includes('STRONG'))
    const eventualModel = models.find(m => m.name.includes('EVENTUAL'))

    if (strongModel && eventualModel) {
      if (strongModel.avgLatency > eventualModel.avgLatency * 3) {
        recommendations.push('Strong consistency shows high latency penalty. Evaluate if eventual consistency could be sufficient for your use case.')
      }
    }

    if (recommendations.length === 0) {
      recommendations.push('Performance metrics look good. Continue monitoring for any degradation.')
    }

    return recommendations
  }
}

// Usage Example
async function consistencyModelsExample() {
  console.log('=== Distributed Consistency Models ===\n')

  // Initialize different consistency managers
  const strongManager = new StrongConsistencyManager()
  const eventualManager1 = new EventualConsistencyManager('node-1', ['node-2', 'node-3'])
  const eventualManager2 = new EventualConsistencyManager('node-2', ['node-1', 'node-3'])
  const causalManager = new CausalConsistencyManager()
  const analyzer = new ConsistencyPerformanceAnalyzer()

  console.log('1. Testing Strong Consistency')

  // Test strong consistency with concurrent operations
  const strongStartTime = Date.now()
  await strongManager.write('key1', 'value1', 'node-1')
  await strongManager.read('key1', 'node-2')
  await strongManager.write('key1', 'value2', 'node-2')
  const strongResult = await strongManager.read('key1', 'node-1')
  const strongLatency = Date.now() - strongStartTime

  console.log(`Strong consistency result: ${JSON.stringify(strongResult)}`)
  analyzer.recordMetric('STRONG', 'WRITE', strongLatency / 2, true)
  analyzer.recordMetric('STRONG', 'READ', strongLatency / 2, true)

  console.log('\n2. Testing Eventual Consistency')

  // Test eventual consistency
  const eventualStartTime = Date.now()
  await eventualManager1.write('key1', 'value1')
  await eventualManager2.write('key2', 'value2')

  // Wait for gossip to propagate
  await new Promise(resolve => setTimeout(resolve, 6000))

  const read1 = await eventualManager1.read('key1')
  const read2 = await eventualManager2.read('key2')
  const eventualLatency = Date.now() - eventualStartTime

  console.log(`Eventual consistency results: node1=${JSON.stringify(read1)}, node2=${JSON.stringify(read2)}`)
  analyzer.recordMetric('EVENTUAL', 'WRITE', eventualLatency / 2, true)
  analyzer.recordMetric('EVENTUAL', 'READ', eventualLatency / 2, true)

  // Show data convergence
  console.log('\nNode 1 data:', Array.from(eventualManager1.getLocalData().keys()))
  console.log('Node 2 data:', Array.from(eventualManager2.getLocalData().keys()))

  console.log('\n3. Testing Causal Consistency')

  // Test causal consistency with dependencies
  const causalStartTime = Date.now()
  await causalManager.write('key1', 'value1') // First operation
  await causalManager.write('key2', 'value2', ['op-1']) // Depends on first operation
  const causalResult = await causalManager.read('key2')
  const causalLatency = Date.now() - causalStartTime

  console.log(`Causal consistency result: ${JSON.stringify(causalResult)}`)
  console.log(`Pending operations: ${causalManager.getPendingOperationsCount()}`)
  analyzer.recordMetric('CAUSAL', 'WRITE', causalLatency / 2, true)
  analyzer.recordMetric('CAUSAL', 'READ', causalLatency / 2, true)

  // Test concurrent operations with potential conflicts
  console.log('\n4. Testing Concurrent Operations')

  const concurrentPromises = []

  // Strong consistency - should serialize
  for (let i = 0; i < 5; i++) {
    concurrentPromises.push(strongManager.write(`concurrent_key_${i}`, `value_${i}`, `node-${i}`))
  }

  const concurrentStartTime = Date.now()
  await Promise.all(concurrentPromises)
  const concurrentLatency = Date.now() - concurrentStartTime

  console.log(`Concurrent strong operations completed in ${concurrentLatency}ms`)

  // Performance analysis
  console.log('\n5. Performance Analysis Report')

  // Add some more sample metrics
  for (let i = 0; i < 10; i++) {
    analyzer.recordMetric('STRONG', 'READ', Math.random() * 200 + 50, true)
    analyzer.recordMetric('STRONG', 'WRITE', Math.random() * 500 + 200, true)
    analyzer.recordMetric('EVENTUAL', 'READ', Math.random() * 50 + 10, true)
    analyzer.recordMetric('EVENTUAL', 'WRITE', Math.random() * 100 + 20, true)
    analyzer.recordMetric('CAUSAL', 'READ', Math.random() * 150 + 30, true)
    analyzer.recordMetric('CAUSAL', 'WRITE', Math.random() * 300 + 100, true)
  }

  const report = analyzer.getPerformanceReport()
  console.log('\nPerformance by Model:')
  report.models.forEach(model => {
    console.log(`  ${model.name}:`)
    console.log(`    Average Latency: ${model.avgLatency.toFixed(2)}ms`)
    console.log(`    Success Rate: ${model.successRate.toFixed(1)}%`)
    console.log(`    Read Latency: ${model.readLatency.toFixed(2)}ms`)
    console.log(`    Write Latency: ${model.writeLatency.toFixed(2)}ms`)
    console.log(`    Total Operations: ${model.totalOperations}`)
  })

  console.log('\nRecommendations:')
  report.recommendations.forEach(rec => {
    console.log(`  • ${rec}`)
  })
}

export {
  ConsistencyModel,
  DataItem,
  Operation,
  ConsistencyResult,
  StrongConsistencyManager,
  EventualConsistencyManager,
  CausalConsistencyManager,
  ConsistencyPerformanceAnalyzer,
  consistencyModelsExample
}
        

// Consensus Algorithms Implementation

// Node Types and States
enum NodeState {
  FOLLOWER = 'FOLLOWER',
  CANDIDATE = 'CANDIDATE',
  LEADER = 'LEADER'
}

enum RaftMessageType {
  APPEND_ENTRIES = 'APPEND_ENTRIES',
  APPEND_ENTRIES_RESPONSE = 'APPEND_ENTRIES_RESPONSE',
  REQUEST_VOTE = 'REQUEST_VOTE',
  REQUEST_VOTE_RESPONSE = 'REQUEST_VOTE_RESPONSE',
  HEARTBEAT = 'HEARTBEAT'
}

enum PBFTMessageType {
  PRE_PREPARE = 'PRE_PREPARE',
  PREPARE = 'PREPARE',
  COMMIT = 'COMMIT',
  VIEW_CHANGE = 'VIEW_CHANGE',
  NEW_VIEW = 'NEW_VIEW'
}

interface RaftMessage {
  type: RaftMessageType
  term: number
  senderId: string
  receiverId: string
  data?: any
}

interface PBFTMessage {
  type: PBFTMessageType
  view: number
  sequenceNumber: number
  senderId: string
  digest: string
  data?: any
  signatures?: string[]
}

interface LogEntry {
  term: number
  index: number
  command: any
  timestamp: Date
}

// Raft Consensus Algorithm Implementation
class RaftNode {
  private state: NodeState = NodeState.FOLLOWER
  private currentTerm: number = 0
  private votedFor: string | null = null
  private log: LogEntry[] = []
  private commitIndex: number = 0
  private lastApplied: number = 0

  // Leader state
  private leaderId: string | null = null
  private nextIndex: Map<string, number> = new Map()
  private matchIndex: Map<string, number> = new Map()

  // Timing
  private electionTimeout: number
  private heartbeatInterval: number
  private lastHeartbeat: number = Date.now()
  private electionTimer: ReturnType<typeof setTimeout> | null = null
  private heartbeatTimer: ReturnType<typeof setInterval> | null = null

  constructor(
    public nodeId: string,
    public clusterNodes: string[],
    private messageHandler: (message: RaftMessage) => void
  ) {
    this.electionTimeout = Math.random() * 3000 + 5000 // 5-8 seconds
    this.heartbeatInterval = 1000 // 1 second
    this.initializeNode()
  }

  private initializeNode(): void {
    // Initialize nextIndex for all nodes
    for (const nodeId of this.clusterNodes) {
      if (nodeId !== this.nodeId) {
        this.nextIndex.set(nodeId, 1)
        this.matchIndex.set(nodeId, 0)
      }
    }
    this.startElectionTimer()
  }

  // Client request to append command
  async clientRequest(command: any): Promise<{
    success: boolean
    message?: string
    term?: number
  }> {
    if (this.state !== NodeState.LEADER) {
      return {
        success: false,
        message: `Not a leader. Current leader: ${this.leaderId || 'unknown'}`,
        term: this.currentTerm
      }
    }

    const logEntry: LogEntry = {
      term: this.currentTerm,
      index: this.log.length + 1,
      command,
      timestamp: new Date()
    }

    this.log.push(logEntry)
    console.log(`[RAFT-${this.nodeId}] Client request appended to log at index ${logEntry.index}`)

    // Replicate to followers
    const success = await this.replicateLog()
    if (success) {
      return { success: true, term: this.currentTerm }
    } else {
      return { success: false, message: 'Failed to replicate to majority', term: this.currentTerm }
    }
  }

  private async replicateLog(): Promise<boolean> {
    let successCount = 1 // Count self
    const majority = Math.floor(this.clusterNodes.length / 2) + 1

    for (const followerId of this.clusterNodes) {
      if (followerId === this.nodeId) continue

      const nextIdx = this.nextIndex.get(followerId) || 1
      const entries = this.log.slice(nextIdx - 1)

      if (entries.length === 0) {
        // Send heartbeat
        this.sendHeartbeat(followerId)
        successCount++
      } else {
        // Send append entries
        const success = await this.sendAppendEntries(followerId, entries)
        if (success) successCount++
      }
    }

    return successCount >= majority
  }

  private sendHeartbeat(followerId: string): void {
    const message: RaftMessage = {
      type: RaftMessageType.HEARTBEAT,
      term: this.currentTerm,
      senderId: this.nodeId,
      receiverId: followerId,
      data: { leaderId: this.nodeId }
    }

    this.messageHandler(message)
  }

  private async sendAppendEntries(followerId: string, entries: LogEntry[]): Promise<boolean> {
    const prevLogIndex = (this.nextIndex.get(followerId) || 1) - 1
    const prevLogTerm = prevLogIndex > 0 ? this.log[prevLogIndex - 1].term : 0

    const message: RaftMessage = {
      type: RaftMessageType.APPEND_ENTRIES,
      term: this.currentTerm,
      senderId: this.nodeId,
      receiverId: followerId,
      data: {
        entries,
        prevLogIndex,
        prevLogTerm,
        leaderCommit: this.commitIndex
      }
    }

    // Simulate sending message and getting response
    const response = await this.simulateMessageExchange(message)

    if (response && response.data?.success) {
      const nextIdx = (this.nextIndex.get(followerId) || 1) + entries.length
      this.nextIndex.set(followerId, nextIdx)
      this.matchIndex.set(followerId, nextIdx - 1)

      // Try to commit entries
      this.updateCommitIndex()
      return true
    } else {
      // Decrement nextIndex and retry
      this.nextIndex.set(followerId, Math.max(1, (this.nextIndex.get(followerId) || 1) - 1))
      return false
    }
  }

  private async simulateMessageExchange(message: RaftMessage): Promise<RaftMessage | null> {
    // Simulate network delay and potential failure
    await new Promise(resolve => setTimeout(resolve, Math.random() * 100 + 50))

    // 90% success rate
    if (Math.random() > 0.1) {
      return {
        type: RaftMessageType.APPEND_ENTRIES_RESPONSE,
        term: message.term,
        senderId: message.receiverId,
        receiverId: message.senderId,
        data: { success: true }
      }
    }
    return null
  }

  // Handle incoming messages
  handleMessage(message: RaftMessage): void {
    if (message.term > this.currentTerm) {
      this.currentTerm = message.term
      this.votedFor = null
      this.state = NodeState.FOLLOWER
      this.leaderId = null
    }

    switch (message.type) {
      case RaftMessageType.APPEND_ENTRIES:
        this.handleAppendEntries(message)
        break

      case RaftMessageType.APPEND_ENTRIES_RESPONSE:
        this.handleAppendEntriesResponse(message)
        break

      case RaftMessageType.REQUEST_VOTE:
        this.handleRequestVote(message)
        break

      case RaftMessageType.REQUEST_VOTE_RESPONSE:
        this.handleRequestVoteResponse(message)
        break

      case RaftMessageType.HEARTBEAT:
        this.handleHeartbeat(message)
        break
    }
  }

  private handleAppendEntries(message: RaftMessage): void {
    const { entries, prevLogIndex, prevLogTerm, leaderCommit } = message.data || {}

    // Check if we can accept the entries
    if (prevLogIndex > 0) {
      if (this.log.length < prevLogIndex || this.log[prevLogIndex - 1].term !== prevLogTerm) {
        // Reject append entries
        this.sendMessage({
          type: RaftMessageType.APPEND_ENTRIES_RESPONSE,
          term: this.currentTerm,
          senderId: this.nodeId,
          receiverId: message.senderId,
          data: { success: false }
        })
        return
      }
    }

    // Accept and append entries
    this.log = this.log.slice(0, prevLogIndex)
    this.log.push(...entries)

    // Update commit index
    if (leaderCommit > this.commitIndex) {
      this.commitIndex = Math.min(leaderCommit, this.log.length)
    }

    // Reset election timer
    this.lastHeartbeat = Date.now()
    this.leaderId = message.senderId

    // Send success response
    this.sendMessage({
      type: RaftMessageType.APPEND_ENTRIES_RESPONSE,
      term: this.currentTerm,
      senderId: this.nodeId,
      receiverId: message.senderId,
      data: { success: true }
    })

    console.log(`[RAFT-${this.nodeId}] Appended ${entries.length} entries from leader ${message.senderId}`)
  }

  private handleHeartbeat(message: RaftMessage): void {
    this.lastHeartbeat = Date.now()
    this.leaderId = message.senderId
    this.state = NodeState.FOLLOWER
  }

  private handleRequestVote(message: RaftMessage): void {
    const { candidateId, lastLogIndex, lastLogTerm } = message.data || {}

    let voteGranted = false

    if (this.votedFor === null || this.votedFor === candidateId) {
      // Check if candidate's log is at least as up-to-date as ours
      const ourLastLog = this.log[this.log.length - 1]
      const ourLastTerm = ourLastLog ? ourLastLog.term : 0
      const ourLastIndex = this.log.length

      if (message.term > ourLastTerm ||
          (message.term === ourLastTerm && lastLogIndex >= ourLastIndex)) {
        voteGranted = true
        this.votedFor = candidateId
      }
    }

    this.sendMessage({
      type: RaftMessageType.REQUEST_VOTE_RESPONSE,
      term: this.currentTerm,
      senderId: this.nodeId,
      receiverId: message.senderId,
      data: { voteGranted }
    })

    console.log(`[RAFT-${this.nodeId}] Voted for ${candidateId}: ${voteGranted}`)
  }

  private handleAppendEntriesResponse(message: RaftMessage): void {
    if (this.state !== NodeState.LEADER) return

    const { success } = message.data || {}
    if (success) {
      // Update follower's match index
      const nextIdx = (this.nextIndex.get(message.senderId) || 1)
      this.matchIndex.set(message.senderId, nextIdx - 1)
    } else {
      // Decrement next index and retry
      this.nextIndex.set(message.senderId, Math.max(1, (this.nextIndex.get(message.senderId) || 1) - 1))
    }
  }

  private handleRequestVoteResponse(message: RaftMessage): void {
    if (this.state !== NodeState.CANDIDATE) return

    const { voteGranted } = message.data || {}
    if (voteGranted) {
      // Count votes (simplified - in real implementation, track votes)
      console.log(`[RAFT-${this.nodeId}] Received vote from ${message.senderId}`)
    }
  }

  private updateCommitIndex(): void {
    for (let n = this.log.length; n > this.commitIndex; n--) {
      let count = 0
      for (const nodeId of this.clusterNodes) {
        if (nodeId === this.nodeId) {
          count++
        } else {
          const matchIdx = this.matchIndex.get(nodeId) || 0
          if (matchIdx >= n) count++
        }
      }

      if (count >= Math.floor(this.clusterNodes.length / 2) + 1) {
        this.commitIndex = n
        console.log(`[RAFT-${this.nodeId}] Committed log entry ${n}`)
        break
      }
    }
  }

  private startElectionTimer(): void {
    if (this.electionTimer) {
      clearTimeout(this.electionTimer)
    }

    this.electionTimer = setTimeout(() => {
      this.startElection()
    }, this.electionTimeout)
  }

  private startElection(): void {
    console.log(`[RAFT-${this.nodeId}] Starting election for term ${this.currentTerm + 1}`)

    this.currentTerm++
    this.state = NodeState.CANDIDATE
    this.votedFor = this.nodeId

    // Request votes from all nodes
    const lastLog = this.log[this.log.length - 1]
    const lastLogIndex = this.log.length
    const lastLogTerm = lastLog ? lastLog.term : 0

    for (const nodeId of this.clusterNodes) {
      if (nodeId === this.nodeId) continue

      this.sendMessage({
        type: RaftMessageType.REQUEST_VOTE,
        term: this.currentTerm,
        senderId: this.nodeId,
        receiverId: nodeId,
        data: {
          candidateId: this.nodeId,
          lastLogIndex,
          lastLogTerm
        }
      })
    }

    // Restart election timer
    this.startElectionTimer()
  }

  private becomeLeader(): void {
    console.log(`[RAFT-${this.nodeId}] Became leader for term ${this.currentTerm}`)
    this.state = NodeState.LEADER
    this.leaderId = this.nodeId

    // Initialize leader state
    for (const nodeId of this.clusterNodes) {
      if (nodeId !== this.nodeId) {
        this.nextIndex.set(nodeId, this.log.length + 1)
        this.matchIndex.set(nodeId, 0)
      }
    }

    // Start sending heartbeats
    if (this.heartbeatTimer) {
      clearInterval(this.heartbeatTimer)
    }

    this.heartbeatTimer = setInterval(() => {
      if (this.state === NodeState.LEADER) {
        this.sendHeartbeats()
      }
    }, this.heartbeatInterval)
  }

  private sendHeartbeats(): void {
    for (const nodeId of this.clusterNodes) {
      if (nodeId !== this.nodeId) {
        this.sendHeartbeat(nodeId)
      }
    }
  }

  private sendMessage(message: RaftMessage): void {
    this.messageHandler(message)
  }

  getState(): {
    state: NodeState
    term: number
    leaderId: string | null
    logLength: number
    commitIndex: number
  } {
    return {
      state: this.state,
      term: this.currentTerm,
      leaderId: this.leaderId,
      logLength: this.log.length,
      commitIndex: this.commitIndex
    }
  }
}

// PBFT (Practical Byzantine Fault Tolerance) Implementation
class PBFTNode {
  private view: number = 0
  private sequenceNumber: number = 0
  private primary: string
  private replicas: string[]
  private log: Map<string, PBFTMessage[]> = new Map()
  private prepared: Map<string, Set<string>> = new Map()
  private committed: Map<string, Set<string>> = new Map()
  private pendingRequests: Map<string, any> = new Map()

  constructor(
    public nodeId: string,
    public clusterNodes: string[],
    private f: number = 1 // Number of Byzantine faults tolerated
  ) {
    this.replicas = [...clusterNodes]
    this.primary = this.replicas[0]
  }

  async clientRequest(operation: any): Promise<{
    success: boolean
    result?: any
    message?: string
  }> {
    const digest = this.calculateDigest(operation)
    const requestId = `req_${Date.now()}_${Math.random()}`

    this.pendingRequests.set(requestId, operation)

    if (this.nodeId === this.primary) {
      // Primary starts the PBFT protocol
      await this.startPrePrepare(digest, operation, requestId)
    } else {
      // Forward to primary
      console.log(`[PBFT-${this.nodeId}] Forwarding request to primary ${this.primary}`)
    }

    // Wait for completion (simplified)
    return new Promise((resolve) => {
      setTimeout(() => {
        const committed = this.committed.get(digest)
        if (committed && committed.size >= 2 * this.f + 1) {
          resolve({
            success: true,
            result: `Operation ${operation} executed successfully`,
            message: 'PBFT consensus reached'
          })
        } else {
          resolve({
            success: false,
            message: 'PBFT consensus not reached'
          })
        }
      }, 2000)
    })
  }

  private async startPrePrepare(digest: string, operation: any, requestId: string): Promise<void> {
    const message: PBFTMessage = {
      type: PBFTMessageType.PRE_PREPARE,
      view: this.view,
      sequenceNumber: ++this.sequenceNumber,
      senderId: this.nodeId,
      digest,
      data: { operation, requestId }
    }

    console.log(`[PBFT-${this.nodeId}] Sending PRE-PREPARE for sequence ${this.sequenceNumber}`)

    // Broadcast to all replicas
    for (const replicaId of this.replicas) {
      if (replicaId !== this.nodeId) {
        await this.sendPBFTMessage(replicaId, message)
      }
    }

    // Store in log
    this.addToLog(digest, message)
  }

  async handlePBFTMessage(message: PBFTMessage): Promise<void> {
    const logKey = `${message.view}_${message.sequenceNumber}_${message.digest}`

    switch (message.type) {
      case PBFTMessageType.PRE_PREPARE:
        await this.handlePrePrepare(message, logKey)
        break

      case PBFTMessageType.PREPARE:
        await this.handlePrepare(message, logKey)
        break

      case PBFTMessageType.COMMIT:
        await this.handleCommit(message, logKey)
        break

      case PBFTMessageType.VIEW_CHANGE:
        await this.handleViewChange(message)
        break
    }
  }

  private async handlePrePrepare(message: PBFTMessage, logKey: string): Promise<void> {
    if (this.nodeId === this.primary) {
      console.log(`[PBFT-${this.nodeId}] Ignoring own PRE-PREPARE`)
      return
    }

    console.log(`[PBFT-${this.nodeId}] Received PRE-PREPARE from primary ${message.senderId}`)

    // Validate pre-prepare message
    if (!this.validatePrePrepare(message)) {
      console.log(`[PBFT-${this.nodeId}] Invalid PRE-PREPARE message`)
      return
    }

    // Store and broadcast prepare
    this.addToLog(message.digest, message)

    const prepareMessage: PBFTMessage = {
      type: PBFTMessageType.PREPARE,
      view: message.view,
      sequenceNumber: message.sequenceNumber,
      senderId: this.nodeId,
      digest: message.digest
    }

    // Broadcast prepare to all replicas
    for (const replicaId of this.replicas) {
      if (replicaId !== this.nodeId) {
        await this.sendPBFTMessage(replicaId, prepareMessage)
      }
    }
  }

  private async handlePrepare(message: PBFTMessage, logKey: string): Promise<void> {
    console.log(`[PBFT-${this.nodeId}] Received PREPARE from ${message.senderId}`)

    // Add to prepared set
    if (!this.prepared.has(message.digest)) {
      this.prepared.set(message.digest, new Set())
    }
    this.prepared.get(message.digest)!.add(message.senderId)

    // Check if we have 2f prepares
    const prepares = this.prepared.get(message.digest)!
    if (prepares.size >= 2 * this.f) {
      console.log(`[PBFT-${this.nodeId}] Quorum reached for PREPARE phase`)

      // Move to commit phase
      const commitMessage: PBFTMessage = {
        type: PBFTMessageType.COMMIT,
        view: message.view,
        sequenceNumber: message.sequenceNumber,
        senderId: this.nodeId,
        digest: message.digest
      }

      // Broadcast commit
      for (const replicaId of this.replicas) {
        if (replicaId !== this.nodeId) {
          await this.sendPBFTMessage(replicaId, commitMessage)
        }
      }
    }
  }

  private async handleCommit(message: PBFTMessage, logKey: string): Promise<void> {
    console.log(`[PBFT-${this.nodeId}] Received COMMIT from ${message.senderId}`)

    // Add to committed set
    if (!this.committed.has(message.digest)) {
      this.committed.set(message.digest, new Set())
    }
    this.committed.get(message.digest)!.add(message.senderId)

    // Check if we have 2f+1 commits
    const commits = this.committed.get(message.digest)!
    if (commits.size >= 2 * this.f + 1) {
      console.log(`[PBFT-${this.nodeId}] Quorum reached for COMMIT phase - EXECUTING`)

      // Execute the operation
      const logMessages = this.log.get(message.digest) || []
      const prePrepare = logMessages.find(m => m.type === PBFTMessageType.PRE_PREPARE)
      if (prePrepare && prePrepare.data?.operation) {
        this.executeOperation(prePrepare.data.operation)
      }
    }
  }

  private async handleViewChange(message: PBFTMessage): Promise<void> {
    console.log(`[PBFT-${this.nodeId}] Received VIEW_CHANGE from ${message.senderId}`)

    // Simplified view change handling
    // In real implementation, would collect view-change messages and select new primary
    if (this.view < message.view) {
      this.view = message.view
      this.primary = this.replicas[this.view % this.replicas.length]
      console.log(`[PBFT-${this.nodeId}] View changed to ${this.view}, new primary: ${this.primary}`)
    }
  }

  private validatePrePrepare(message: PBFTMessage): boolean {
    // Simplified validation
    return message.senderId === this.primary && message.view === this.view
  }

  private addToLog(digest: string, message: PBFTMessage): void {
    if (!this.log.has(digest)) {
      this.log.set(digest, [])
    }
    this.log.get(digest)!.push(message)
  }

  private executeOperation(operation: any): void {
    console.log(`[PBFT-${this.nodeId}] Executing operation: ${operation}`)
    // In real implementation, would execute the actual operation
  }

  private calculateDigest(data: any): string {
    // Simple hash function for demo
    return btoa(JSON.stringify(data)).slice(0, 16)
  }

  private async sendPBFTMessage(targetId: string, message: PBFTMessage): Promise<void> {
    // Simulate network delay
    await new Promise(resolve => setTimeout(resolve, Math.random() * 100 + 50))

    console.log(`[PBFT-${this.nodeId}] Sent ${message.type} to ${targetId}`)
    // In real implementation, would send over network
  }

  getViewChange(): void {
    console.log(`[PBFT-${this.nodeId}] Initiating view change`)
    this.view++

    const viewChangeMessage: PBFTMessage = {
      type: PBFTMessageType.VIEW_CHANGE,
      view: this.view,
      sequenceNumber: 0,
      senderId: this.nodeId,
      digest: ''
    }

    // Broadcast view change
    for (const replicaId of this.replicas) {
      if (replicaId !== this.nodeId) {
        this.sendPBFTMessage(replicaId, viewChangeMessage)
      }
    }
  }

  getConsensusStats(): {
    view: number
    sequenceNumber: number
    primary: string
    preparedCount: number
    committedCount: number
  } {
    return {
      view: this.view,
      sequenceNumber: this.sequenceNumber,
      primary: this.primary,
      preparedCount: this.prepared.size,
      committedCount: this.committed.size
    }
  }
}

// Consensus Performance Analyzer
class ConsensusAnalyzer {
  private metrics: Map<string, Array<{
    algorithm: string
    operation: string
    latency: number
    success: boolean
    timestamp: Date
    nodes: number
  }>> = new Map()

  recordMetric(
    algorithm: string,
    operation: string,
    latency: number,
    success: boolean,
    nodeCount: number
  ): void {
    const key = `${algorithm}_${operation}`
    if (!this.metrics.has(key)) {
      this.metrics.set(key, [])
    }

    this.metrics.get(key)!.push({
      algorithm,
      operation,
      latency,
      success,
      timestamp: new Date(),
      nodes: nodeCount
    })
  }

  compareAlgorithms(nodeCounts: number[]): {
    raft: { avgLatency: number; throughput: number; successRate: number }
    pbft: { avgLatency: number; throughput: number; successRate: number }
    recommendation: string
  } {
    const raftMetrics = this.getAlgorithmMetrics('RAFT', nodeCounts)
    const pbftMetrics = this.getAlgorithmMetrics('PBFT', nodeCounts)

    let recommendation = ''

    if (raftMetrics.avgLatency < pbftMetrics.avgLatency) {
      recommendation = 'Raft shows better performance for this configuration'
    } else {
      recommendation = 'PBFT provides better fault tolerance despite higher latency'
    }

    if (nodeCounts.some(n => n > 10)) {
      recommendation += '. Consider Raft for larger clusters due to lower overhead'
    } else {
      recommendation += '. PBFT is suitable for smaller clusters requiring Byzantine fault tolerance'
    }

    return {
      raft: raftMetrics,
      pbft: pbftMetrics,
      recommendation
    }
  }

  private getAlgorithmMetrics(algorithm: string, nodeCounts: number[]): {
    avgLatency: number
    throughput: number
    successRate: number
  } {
    let totalLatency = 0
    let totalOperations = 0
    let successfulOperations = 0

    for (const nodeCount of nodeCounts) {
      const key = `${algorithm}_WRITE`
      const metrics = this.metrics.get(key) || []
      const relevantMetrics = metrics.filter(m => m.nodes === nodeCount)

      for (const metric of relevantMetrics) {
        totalLatency += metric.latency
        totalOperations++
        if (metric.success) successfulOperations++
      }
    }

    return {
      avgLatency: totalOperations > 0 ? totalLatency / totalOperations : 0,
      throughput: totalOperations > 0 ? (successfulOperations / totalOperations) * 100 : 0,
      successRate: totalOperations > 0 ? (successfulOperations / totalOperations) * 100 : 0
    }
  }
}

// Usage Example
async function consensusAlgorithmsExample() {
  console.log('=== Consensus Algorithms (Raft & PBFT) ===\n')

  // Setup Raft cluster
  console.log('1. Setting up Raft Cluster')

  const raftNodes: RaftNode[] = []
  const raftMessageHandler = (message: RaftMessage) => {
    const targetNode = raftNodes.find(n => n.nodeId === message.receiverId)
    if (targetNode) {
      targetNode.handleMessage(message)
    }
  }

  for (let i = 1; i <= 5; i++) {
    const node = new RaftNode(`raft-node-${i}`,
      ['raft-node-1', 'raft-node-2', 'raft-node-3', 'raft-node-4', 'raft-node-5'],
      raftMessageHandler
    )
    raftNodes.push(node)
  }

  // Wait for election to complete
  await new Promise(resolve => setTimeout(resolve, 10000))

  console.log('Raft cluster states:')
  raftNodes.forEach(node => {
    const state = node.getState()
    console.log(`  ${node.nodeId}: ${state.state} (term: ${state.term}, leader: ${state.leaderId})`)
  })

  // Test Raft operations
  console.log('\n2. Testing Raft Operations')

  const leaderNode = raftNodes.find(n => n.getState().state === NodeState.LEADER)
  if (leaderNode) {
    const raftStartTime = Date.now()
    const raftResult = await leaderNode.clientRequest({ action: 'set', key: 'test', value: 'raft_value' })
    const raftLatency = Date.now() - raftStartTime

    console.log(`Raft result: ${JSON.stringify(raftResult)}, Latency: ${raftLatency}ms`)
  } else {
    console.log('No Raft leader elected yet')
  }

  // Setup PBFT cluster
  console.log('\n3. Setting up PBFT Cluster')

  const pbftNodes: PBFTNode[] = []
  const pbftNodesList = ['pbft-node-1', 'pbft-node-2', 'pbft-node-3', 'pbft-node-4']

  for (const nodeId of pbftNodesList) {
    const node = new PBFTNode(nodeId, pbftNodesList, 1) // f=1, can tolerate 1 Byzantine fault
    pbftNodes.push(node)
  }

  console.log('PBFT cluster stats:')
  pbftNodes.forEach(node => {
    const stats = node.getConsensusStats()
    console.log(`  ${node.nodeId}: view=${stats.view}, primary=${stats.primary}`)
  })

  // Test PBFT operations
  console.log('\n4. Testing PBFT Operations')

  const primaryNode = pbftNodes[0] // First node is primary in view 0
  const pbftStartTime = Date.now()
  const pbftResult = await primaryNode.clientRequest('transfer_amount_100')
  const pbftLatency = Date.now() - pbftStartTime

  console.log(`PBFT result: ${JSON.stringify(pbftResult)}, Latency: ${pbftLatency}ms`)

  // Simulate message passing between PBFT nodes
  for (const sender of pbftNodes) {
    for (const receiver of pbftNodes) {
      if (sender.nodeId !== receiver.nodeId) {
        // Simulate some messages
        if (Math.random() > 0.7) {
          const message: PBFTMessage = {
            type: PBFTMessageType.PREPARE,
            view: 0,
            sequenceNumber: 1,
            senderId: sender.nodeId,
            digest: 'test_digest'
          }
          await receiver.handlePBFTMessage(message)
        }
      }
    }
  }

  // Performance comparison
  console.log('\n5. Performance Analysis')

  const analyzer = new ConsensusAnalyzer()

  // Add sample metrics
  for (let i = 0; i < 20; i++) {
    analyzer.recordMetric('RAFT', 'WRITE', Math.random() * 200 + 100, Math.random() > 0.1, 5)
    analyzer.recordMetric('PBFT', 'WRITE', Math.random() * 400 + 200, Math.random() > 0.05, 4)
  }

  const comparison = analyzer.compareAlgorithms([5])
  console.log('\nPerformance Comparison:')
  console.log(`Raft - Latency: ${comparison.raft.avgLatency.toFixed(2)}ms, Success Rate: ${comparison.raft.successRate.toFixed(1)}%`)
  console.log(`PBFT - Latency: ${comparison.pbft.avgLatency.toFixed(2)}ms, Success Rate: ${comparison.pbft.successRate.toFixed(1)}%`)
  console.log(`\nRecommendation: ${comparison.recommendation}`)

  // Final cluster states
  console.log('\n6. Final Cluster States')

  console.log('\nRaft cluster final states:')
  raftNodes.forEach(node => {
    const state = node.getState()
    console.log(`  ${node.nodeId}: ${state.state} (log: ${state.logLength}, committed: ${state.commitIndex})`)
  })

  console.log('\nPBFT cluster final stats:')
  pbftNodes.forEach(node => {
    const stats = node.getConsensusStats()
    console.log(`  ${node.nodeId}: prepared=${stats.preparedCount}, committed=${stats.committedCount}`)
  })
}

export {
  NodeState,
  RaftMessageType,
  PBFTMessageType,
  RaftNode,
  PBFTNode,
  ConsensusAnalyzer,
  consensusAlgorithmsExample
}
        

// Sharding and Partitioning Implementation

// Partitioning Strategies
enum PartitioningStrategy {
  HASH = 'HASH',
  RANGE = 'RANGE',
  CONSISTENT_HASH = 'CONSISTENT_HASH',
  DIRECTORY = 'DIRECTORY',
  GEOGRAPHIC = 'GEOGRAPHIC'
}

interface Shard {
  id: string
  nodeId: string
  range?: {
    start: any
    end: any
  }
  hashRange?: {
    start: number
    end: number
  }
  keyRange?: string[]
 地理位置?: {
    region: string
    country?: string
    city?: string
  }
  status: 'ACTIVE' | 'MIGRATING' | 'OFFLINE'
  weight: number
  lastHealthCheck: Date
}

interface PartitionMetadata {
  shardId: string
  key: string
  partitionKey: any
  nodeId: string
  createdAt: Date
  lastAccessed: Date
  accessCount: number
}

// Hash-based Sharding
class HashShardingManager {
  private shards: Map<string, Shard> = new Map()
  private shardRing: number[] = []
  private virtualNodes: number = 150 // Virtual nodes per physical node

  constructor(private nodes: string[]) {
    this.initializeShards()
  }

  private initializeShards(): void {
    for (const nodeId of this.nodes) {
      this.addNode(nodeId)
    }
  }

  addNode(nodeId: string): void {
    console.log(`[HASH] Adding node ${nodeId} to shard ring`)

    // Create virtual nodes for better distribution
    for (let i = 0; i < this.virtualNodes; i++) {
      const virtualNodeId = `${nodeId}_${i}`
      const hash = this.hash(`${virtualNodeId}`)

      this.shards.set(virtualNodeId, {
        id: virtualNodeId,
        nodeId,
        hashRange: { start: hash, end: hash },
        status: 'ACTIVE',
        weight: 1,
        lastHealthCheck: new Date()
      })

      this.shardRing.push(hash)
    }

    this.shardRing.sort((a, b) => a - b)
  }

  removeNode(nodeId: string): void {
    console.log(`[HASH] Removing node ${nodeId} from shard ring`)

    // Remove all virtual nodes for this physical node
    const toRemove: string[] = []
    for (const [virtualNodeId, shard] of this.shards.entries()) {
      if (shard.nodeId === nodeId) {
        toRemove.push(virtualNodeId)
      }
    }

    for (const virtualNodeId of toRemove) {
      const shard = this.shards.get(virtualNodeId)!
      this.shardRing = this.shardRing.filter(hash => hash !== shard.hashRange!.start)
      this.shards.delete(virtualNodeId)
    }

    console.log(`[HASH] Removed ${toRemove.length} virtual nodes for ${nodeId}`)
  }

  getShard(key: string): Shard | null {
    const keyHash = this.hash(key)

    // Find the first shard with hash >= keyHash
    for (const hash of this.shardRing) {
      if (hash >= keyHash) {
        const shard = this.findShardByHash(hash)
        if (shard) return shard
      }
    }

    // Wrap around to the first shard
    if (this.shardRing.length > 0) {
      const shard = this.findShardByHash(this.shardRing[0])
      if (shard) return shard
    }

    return null
  }

  private findShardByHash(hash: number): Shard | null {
    for (const shard of this.shards.values()) {
      if (shard.hashRange && shard.hashRange.start === hash) {
        return shard
      }
    }
    return null
  }

  private hash(input: string): number {
    // Simple hash function for demo
    let hash = 0
    for (let i = 0; i < input.length; i++) {
      const char = input.charCodeAt(i)
      hash = ((hash << 5) - hash) + char
      hash = hash & hash // Convert to 32-bit integer
    }
    return Math.abs(hash)
  }

  getDistribution(): Record<string, number> {
    const distribution: Record<string, number> = {}

    // Test with sample keys to see distribution
    const testKeys = Array.from({ length: 10000 }, (_, i) => `test_key_${i}`)

    for (const key of testKeys) {
      const shard = this.getShard(key)
      if (shard) {
        distribution[shard.nodeId] = (distribution[shard.nodeId] || 0) + 1
      }
    }

    return distribution
  }
}

// Range-based Sharding
class RangeShardingManager {
  private shards: Map<string, Shard> = new Map()
  private ranges: Array<{ start: any; end: any; shardId: string }> = []

  constructor() {
    this.initializeRanges()
  }

  private initializeRanges(): void {
    // Example: User ID ranges
    const ranges = [
      { start: 0, end: 1000000, nodeId: 'node-1', shardId: 'shard-1' },
      { start: 1000001, end: 2000000, nodeId: 'node-2', shardId: 'shard-2' },
      { start: 2000001, end: 3000000, nodeId: 'node-3', shardId: 'shard-3' },
      { start: 3000001, end: 4000000, nodeId: 'node-4', shardId: 'shard-4' },
      { start: 4000001, end: Number.MAX_SAFE_INTEGER, nodeId: 'node-5', shardId: 'shard-5' }
    ]

    for (const range of ranges) {
      this.shards.set(range.shardId, {
        id: range.shardId,
        nodeId: range.nodeId,
        range: { start: range.start, end: range.end },
        status: 'ACTIVE',
        weight: 1,
        lastHealthCheck: new Date()
      })

      this.ranges.push({
        start: range.start,
        end: range.end,
        shardId: range.shardId
      })
    }

    this.ranges.sort((a, b) => a.start - b.start)
  }

  getShard(key: any): Shard | null {
    const keyValue = typeof key === 'number' ? key : parseInt(key)

    for (const range of this.ranges) {
      if (keyValue >= range.start && keyValue <= range.end) {
        return this.shards.get(range.shardId) || null
      }
    }

    return null
  }

  addRange(start: any, end: any, nodeId: string): void {
    const shardId = `shard_${Date.now()}`

    this.shards.set(shardId, {
      id: shardId,
      nodeId,
      range: { start, end },
      status: 'ACTIVE',
      weight: 1,
      lastHealthCheck: new Date()
    })

    this.ranges.push({ start, end, shardId })
    this.ranges.sort((a, b) => a.start - b.start)

    console.log(`[RANGE] Added range [${start}, ${end}] to node ${nodeId}`)
  }

  splitRange(shardId: string, splitPoint: any, newNodeId: string): void {
    const shard = this.shards.get(shardId)
    if (!shard || !shard.range) {
      throw new Error(`Shard ${shardId} not found or has no range`)
    }

    const { start, end } = shard.range

    // Remove old range
    this.ranges = this.ranges.filter(r => r.shardId !== shardId)
    this.shards.delete(shardId)

    // Create two new ranges
    this.addRange(start, splitPoint, shard.nodeId)
    this.addRange(splitPoint + 1, end, newNodeId)

    console.log(`[RANGE] Split shard ${shardId} at ${splitPoint}`)
  }

  mergeRanges(shardId1: string, shardId2: string): void {
    const shard1 = this.shards.get(shardId1)
    const shard2 = this.shards.get(shardId2)

    if (!shard1 || !shard2 || !shard1.range || !shard2.range) {
      throw new Error('Both shards must exist and have ranges')
    }

    const newStart = Math.min(shard1.range.start, shard2.range.start)
    const newEnd = Math.max(shard1.range.end, shard2.range.end)

    // Remove old ranges
    this.ranges = this.ranges.filter(r => r.shardId !== shardId1 && r.shardId !== shardId2)
    this.shards.delete(shardId1)
    this.shards.delete(shardId2)

    // Create merged range
    this.addRange(newStart, newEnd, shard1.nodeId)

    console.log(`[RANGE] Merged shards ${shardId1} and ${shardId2}`)
  }

  getRanges(): Array<{ shardId: string; nodeId: string; start: any; end: any }> {
    return this.ranges.map(range => {
      const shard = this.shards.get(range.shardId)!
      return {
        shardId: range.shardId,
        nodeId: shard.nodeId,
        start: range.start,
        end: range.end
      }
    })
  }
}

// Consistent Hash Ring Implementation
class ConsistentHashRing {
  private ring: number[] = []
  private nodes: Map<number, string> = new Map()
  private virtualNodes: number = 100
  private replicas: number = 3

  constructor(nodes: string[], virtualNodes: number = 100) {
    this.virtualNodes = virtualNodes
    this.initialize(nodes)
  }

  private initialize(nodes: string[]): void {
    for (const node of nodes) {
      this.addNode(node)
    }
  }

  addNode(node: string): void {
    for (let i = 0; i < this.virtualNodes; i++) {
      const virtualNodeKey = `${node}#${i}`
      const hash = this.md5(virtualNodeKey)

      this.ring.push(hash)
      this.nodes.set(hash, node)
    }

    this.ring.sort((a, b) => a - b)
    console.log(`[CONSISTENT_HASH] Added node ${node} with ${this.virtualNodes} virtual nodes`)
  }

  removeNode(node: string): void {
    const toRemove: number[] = []

    for (const [hash, nodeId] of this.nodes.entries()) {
      if (nodeId === node) {
        toRemove.push(hash)
      }
    }

    for (const hash of toRemove) {
      this.ring = this.ring.filter(h => h !== hash)
      this.nodes.delete(hash)
    }

    console.log(`[CONSISTENT_HASH] Removed node ${node} and ${toRemove.length} virtual nodes`)
  }

  getNode(key: string): string | null {
    if (this.ring.length === 0) return null

    const hash = this.md5(key)

    // Find first node with hash >= key hash
    for (let i = 0; i < this.ring.length; i++) {
      if (this.ring[i] >= hash) {
        return this.nodes.get(this.ring[i]) || null
      }
    }

    // Wrap around to first node
    return this.nodes.get(this.ring[0]) || null
  }

  getNodesForKey(key: string, count: number = this.replicas): string[] {
    const nodes: string[] = []
    const hash = this.md5(key)

    let startIndex = 0
    for (let i = 0; i < this.ring.length; i++) {
      if (this.ring[i] >= hash) {
        startIndex = i
        break
      }
    }

    // Get next N unique nodes
    const visitedNodes = new Set<string>()
    let index = startIndex

    while (nodes.length < count && visitedNodes.size < this.nodes.size) {
      const nodeHash = this.ring[index % this.ring.length]
      const node = this.nodes.get(nodeHash)

      if (node && !visitedNodes.has(node)) {
        nodes.push(node)
        visitedNodes.add(node)
      }

      index++
    }

    return nodes
  }

  private md5(input: string): number {
    // Simplified hash function - in real implementation use crypto
    let hash = 0
    for (let i = 0; i < input.length; i++) {
      const char = input.charCodeAt(i)
      hash = ((hash << 5) - hash) + char
      hash = hash & hash
    }
    return Math.abs(hash) % 1000000 // Modulo to keep numbers manageable
  }

  getDistribution(): Record<string, number> {
    const distribution: Record<string, number> = {}
    const testKeys = Array.from({ length: 10000 }, (_, i) => `test_key_${i}`)

    for (const key of testKeys) {
      const node = this.getNode(key)
      if (node) {
        distribution[node] = (distribution[node] || 0) + 1
      }
    }

    return distribution
  }

  getRingInfo(): { totalNodes: number; totalVirtualNodes: number; balanceScore: number } {
    const distribution = this.getDistribution()
    const values = Object.values(distribution)
    const avg = values.reduce((sum, val) => sum + val, 0) / values.length
    const variance = values.reduce((sum, val) => sum + Math.pow(val - avg, 2), 0) / values.length
    const balanceScore = 1 - (Math.sqrt(variance) / avg) // Lower variance = higher score

    return {
      totalNodes: new Set(this.nodes.values()).size,
      totalVirtualNodes: this.ring.length,
      balanceScore: Math.max(0, balanceScore)
    }
  }
}

// Directory-based Sharding
class DirectoryBasedSharding {
  private directory: Map<string, PartitionMetadata> = new Map()
  private shards: Map<string, Shard> = new Map()
  private loadBalancer: ShardingLoadBalancer

  constructor(nodes: string[]) {
    this.loadBalancer = new ShardingLoadBalancer(nodes)
    this.initializeShards(nodes)
  }

  private initializeShards(nodes: string[]): void {
    for (const nodeId of nodes) {
      this.shards.set(`shard_${nodeId}`, {
        id: `shard_${nodeId}`,
        nodeId,
        status: 'ACTIVE',
        weight: 1,
        lastHealthCheck: new Date()
      })
    }
  }

  async assignPartition(key: string, partitionKey: any): Promise<string> {
    // Check if key already assigned
    if (this.directory.has(key)) {
      return this.directory.get(key)!.shardId
    }

    // Select shard based on load balancing
    const shardId = await this.loadBalancer.selectShard(partitionKey)
    const shard = this.shards.get(shardId)

    if (!shard || shard.status !== 'ACTIVE') {
      throw new Error('No active shard available')
    }

    const metadata: PartitionMetadata = {
      shardId,
      key,
      partitionKey,
      nodeId: shard.nodeId,
      createdAt: new Date(),
      lastAccessed: new Date(),
      accessCount: 0
    }

    this.directory.set(key, metadata)
    console.log(`[DIRECTORY] Assigned key ${key} to shard ${shardId} (node: ${shard.nodeId})`)

    return shardId
  }

  getShard(key: string): Shard | null {
    const metadata = this.directory.get(key)
    if (!metadata) return null

    return this.shards.get(metadata.shardId) || null
  }

  async rebalance(): Promise<{
    migratedPartitions: number
    newDistribution: Record<string, number>
  }> {
    console.log('[DIRECTORY] Starting rebalancing...')

    const currentLoad = this.calculateLoad()
    const targetLoad = Object.keys(currentLoad).length * 0.2 // Target 20% per node

    const toMigrate: Array<{ key: string; fromShard: string; toShard: string }> = []
    let migratedCount = 0

    // Find overloaded shards
    for (const [shardId, load] of Object.entries(currentLoad)) {
      if (load > targetLoad * 1.2) { // 20% threshold
        const underloadedShard = this.findUnderloadedShard(currentLoad, targetLoad)
        if (underloadedShard) {
          // Find keys to migrate (least recently accessed)
          const shardKeys = Array.from(this.directory.entries())
            .filter(([_, metadata]) => metadata.shardId === shardId)
            .sort((a, b) => a[1].lastAccessed.getTime() - b[1].lastAccessed.getTime())
            .slice(0, Math.floor((load - targetLoad) / 2))

          for (const [key, metadata] of shardKeys) {
            toMigrate.push({
              key,
              fromShard: shardId,
              toShard: underloadedShard
            })

            if (toMigrate.length >= 10) break // Limit migrations per rebalance
          }
        }
      }
    }

    // Execute migrations
    for (const migration of toMigrate) {
      const metadata = this.directory.get(migration.key)!
      metadata.shardId = migration.toShard
      metadata.nodeId = this.shards.get(migration.toShard)!.nodeId
      migratedCount++

      console.log(`[DIRECTORY] Migrated key ${migration.key} from ${migration.fromShard} to ${migration.toShard}`)
    }

    const newDistribution = this.calculateLoad()

    return {
      migratedPartitions: migratedCount,
      newDistribution
    }
  }

  private calculateLoad(): Record<string, number> {
    const load: Record<string, number> = {}

    for (const metadata of this.directory.values()) {
      load[metadata.shardId] = (load[metadata.shardId] || 0) + 1
    }

    return load
  }

  private findUnderloadedShard(currentLoad: Record<string, number>, targetLoad: number): string | null {
    for (const [shardId, load] of Object.entries(currentLoad)) {
      if (load < targetLoad * 0.8) { // 20% threshold
        return shardId
      }
    }
    return null
  }

  getDirectoryStats(): {
    totalPartitions: number
    distribution: Record<string, number>
    hotKeys: Array<{ key: string; accessCount: number; shardId: string }>
  } {
    const distribution = this.calculateLoad()
    const totalPartitions = this.directory.size

    // Find hot keys (high access count)
    const hotKeys = Array.from(this.directory.entries())
      .sort((a, b) => b[1].accessCount - a[1].accessCount)
      .slice(0, 10)
      .map(([key, metadata]) => ({
        key,
        accessCount: metadata.accessCount,
        shardId: metadata.shardId
      }))

    return {
      totalPartitions,
      distribution,
      hotKeys
    }
  }

  recordAccess(key: string): void {
    const metadata = this.directory.get(key)
    if (metadata) {
      metadata.lastAccessed = new Date()
      metadata.accessCount++
    }
  }
}

// Load Balancer for Sharding
class ShardingLoadBalancer {
  private nodeLoads: Map<string, { connections: number; cpu: number; memory: number }> = new Map()

  constructor(nodes: string[]) {
    for (const node of nodes) {
      this.nodeLoads.set(node, { connections: 0, cpu: 0, memory: 0 })
    }
  }

  async selectShard(partitionKey: any): Promise<string> {
    // Find least loaded node
    let bestNode = ''
    let minScore = Infinity

    for (const [nodeId, load] of this.nodeLoads.entries()) {
      const score = load.connections * 0.4 + load.cpu * 0.3 + load.memory * 0.3
      if (score < minScore) {
        minScore = score
        bestNode = nodeId
      }
    }

    return `shard_${bestNode}`
  }

  updateNodeLoad(nodeId: string, load: { connections: number; cpu: number; memory: number }): void {
    this.nodeLoads.set(nodeId, load)
  }

  getLoadDistribution(): Record<string, { connections: number; cpu: number; memory: number }> {
    const distribution: Record<string, { connections: number; cpu: number; memory: number }> = {}

    for (const [nodeId, load] of this.nodeLoads.entries()) {
      distribution[nodeId] = { ...load }
    }

    return distribution
  }
}

// Cross-Shard Query Coordinator
class CrossShardQueryCoordinator {
  constructor(
    private hashSharding: HashShardingManager,
    private rangeSharding: RangeShardingManager,
    private directorySharding: DirectoryBasedSharding
  ) {}

  async executeCrossShardQuery(
    query: {
      type: 'SELECT' | 'JOIN' | 'AGGREGATE'
      tables: string[]
      conditions?: Record<string, any>
      joinKeys?: string[]
    }
  ): Promise<{
    results: any[]
    shardsQueried: string[]
    executionTime: number
  }> {
    const startTime = Date.now()
    const shardsQueried: string[] = []
    const results: any[] = []

    console.log(`[QUERY] Executing cross-shard query: ${query.type} on ${query.tables.join(', ')}`)

    // Determine which shards to query based on query type
    switch (query.type) {
      case 'SELECT':
        await this.executeSelectQuery(query, shardsQueried, results)
        break

      case 'JOIN':
        await this.executeJoinQuery(query, shardsQueried, results)
        break

      case 'AGGREGATE':
        await this.executeAggregateQuery(query, shardsQueried, results)
        break
    }

    const executionTime = Date.now() - startTime

    return {
      results,
      shardsQueried: [...new Set(shardsQueried)],
      executionTime
    }
  }

  private async executeSelectQuery(
    query: any,
    shardsQueried: string[],
    results: any[]
  ): Promise<void> {
    // For demo, simulate querying all sharding strategies
    const strategies = [
      { name: 'hash', manager: this.hashSharding },
      { name: 'range', manager: this.rangeSharding },
      { name: 'directory', manager: this.directorySharding }
    ]

    for (const strategy of strategies) {
      // Simulate finding relevant shards
      const relevantShards = this.findRelevantShards(strategy, query.conditions)

      for (const shardId of relevantShards) {
        shardsQueried.push(`${strategy.name}_${shardId}`)

        // Simulate querying the shard
        const shardResults = await this.queryShard(shardId, query)
        results.push(...shardResults)
      }
    }
  }

  private async executeJoinQuery(
    query: any,
    shardsQueried: string[],
    results: any[]
  ): Promise<void> {
    // Simplified join execution - in real implementation would be more complex
    if (!query.joinKeys || query.joinKeys.length === 0) {
      throw new Error('Join query requires join keys')
    }

    // For each join key, find which shards contain the data
    for (const joinKey of query.joinKeys) {
      const shard = this.hashSharding.getShard(joinKey)
      if (shard) {
        shardsQueried.push(`hash_${shard.id}`)
        const shardResults = await this.queryShard(joinKey, query)
        results.push(...shardResults)
      }
    }
  }

  private async executeAggregateQuery(
    query: any,
    shardsQueried: string[],
    results: any[]
  ): Promise<void> {
    // For aggregate queries, need to query all shards and combine results
    const allShards = [
      ...Array.from(this.hashSharding.getDistribution().keys()),
      ...this.rangeSharding.getRanges().map(r => r.shardId)
    ]

    for (const shardId of allShards) {
      shardsQueried.push(shardId)
      const shardResults = await this.queryShard(shardId, query)
      results.push(...shardResults)
    }

    // Combine aggregate results
    if (query.conditions?.aggregate === 'COUNT') {
      const totalCount = results.reduce((sum, result) => sum + (result.count || 0), 0)
      results.length = 0
      results.push({ aggregate: 'COUNT', value: totalCount })
    }
  }

  private findRelevantShards(strategy: any, conditions?: Record<string, any>): string[] {
    // Simplified shard selection based on conditions
    if (conditions?.id) {
      const shard = strategy.manager.getShard?.(conditions.id)
      return shard ? [shard.id] : []
    }

    // If no specific conditions, return all shards for the strategy
    if (strategy.name === 'hash') {
      return Object.keys(strategy.manager.getDistribution())
    } else if (strategy.name === 'range') {
      return strategy.manager.getRanges().map(r => r.shardId)
    }

    return []
  }

  private async queryShard(shardId: string, query: any): Promise<any[]> {
    // Simulate network delay and query execution
    await new Promise(resolve => setTimeout(resolve, Math.random() * 50 + 10))

    // Generate mock results
    const resultCount = Math.floor(Math.random() * 10) + 1
    const results: any[] = []

    for (let i = 0; i < resultCount; i++) {
      results.push({
        id: `${shardId}_${i}`,
        shardId,
        data: `Mock data from ${shardId}`,
        timestamp: new Date()
      })
    }

    return results
  }
}

// Usage Example
async function shardingExample() {
  console.log('=== Sharding and Partitioning Strategies ===\n')

  // Test Hash Sharding
  console.log('1. Hash-based Sharding')

  const hashSharding = new HashShardingManager(['node-1', 'node-2', 'node-3', 'node-4'])

  // Test key distribution
  const testKeys = ['user_123', 'user_456', 'user_789', 'user_999', 'user_111']
  console.log('\nKey distribution:')
  testKeys.forEach(key => {
    const shard = hashSharding.getShard(key)
    console.log(`  ${key} -> ${shard?.nodeId}`)
  })

  // Add and remove nodes
  console.log('\nAdding node-5 to cluster...')
  hashSharding.addNode('node-5')

  console.log('\nRemoving node-2 from cluster...')
  hashSharding.removeNode('node-2')

  // Show distribution
  const hashDistribution = hashSharding.getDistribution()
  console.log('\nHash sharding distribution:')
  Object.entries(hashDistribution).forEach(([node, count]) => {
    console.log(`  ${node}: ${count} keys`)
  })

  // Test Range Sharding
  console.log('\n2. Range-based Sharding')

  const rangeSharding = new RangeShardingManager()

  const userIds = [500, 1500, 2500, 3500, 4500]
  console.log('\nUser ID distribution:')
  userIds.forEach(userId => {
    const shard = rangeSharding.getShard(userId)
    console.log(`  User ${userId} -> ${shard?.nodeId}`)
  })

  // Split and merge ranges
  console.log('\nSplitting shard-1 at 500000...')
  rangeSharding.splitRange('shard-1', 500000, 'node-6')

  console.log('\nCurrent ranges:')
  const ranges = rangeSharding.getRanges()
  ranges.forEach(range => {
    console.log(`  ${range.shardId} (${range.nodeId}): [${range.start}, ${range.end}]`)
  })

  // Test Consistent Hashing
  console.log('\n3. Consistent Hash Ring')

  const consistentHash = new ConsistentHashRing(['node-1', 'node-2', 'node-3'], 50)

  const testKeys2 = ['key1', 'key2', 'key3', 'key4', 'key5']
  console.log('\nKey assignment with replicas:')
  testKeys2.forEach(key => {
    const nodes = consistentHash.getNodesForKey(key, 2)
    console.log(`  ${key} -> [${nodes.join(', ')}]`)
  })

  // Add node and show minimal key movement
  console.log('\nAdding node-4 and checking key movement...')
  const beforeDistribution = consistentHash.getDistribution()
  consistentHash.addNode('node-4')
  const afterDistribution = consistentHash.getDistribution()

  console.log('Distribution before adding node-4:', beforeDistribution)
  console.log('Distribution after adding node-4:', afterDistribution)

  const ringInfo = consistentHash.getRingInfo()
  console.log(`\nRing info: ${ringInfo.totalNodes} nodes, ${ringInfo.totalVirtualNodes} virtual nodes, balance score: ${ringInfo.balanceScore.toFixed(3)}`)

  // Test Directory-based Sharding
  console.log('\n4. Directory-based Sharding')

  const directorySharding = new DirectoryBasedSharding(['node-1', 'node-2', 'node-3'])

  // Assign some partitions
  const partitions = [
    { key: 'product_a', partitionKey: 'electronics' },
    { key: 'product_b', partitionKey: 'books' },
    { key: 'user_x', partitionKey: 'premium' },
    { key: 'user_y', partitionKey: 'basic' },
    { key: 'order_1', partitionKey: 'electronics' },
    { key: 'order_2', partitionKey: 'books' }
  ]

  console.log('\nAssigning partitions:')
  for (const partition of partitions) {
    const shardId = await directorySharding.assignPartition(partition.key, partition.partitionKey)
    const shard = directorySharding.getShard(partition.key)
    console.log(`  ${partition.key} -> ${shard?.nodeId}`)
  }

  // Simulate some access patterns
  for (let i = 0; i < 10; i++) {
    directorySharding.recordAccess('product_a') // Make this a hot key
    directorySharding.recordAccess('order_1')
  }

  // Get directory stats
  const stats = directorySharding.getDirectoryStats()
  console.log('\nDirectory stats:')
  console.log(`  Total partitions: ${stats.totalPartitions}`)
  console.log('  Distribution:', stats.distribution)
  console.log('  Hot keys:', stats.hotKeys)

  // Rebalancing
  console.log('\n5. Rebalancing')
  const rebalanceResult = await directorySharding.rebalance()
  console.log(`Migrated ${rebalanceResult.migratedPartitions} partitions`)
  console.log('New distribution:', rebalanceResult.newDistribution)

  // Cross-Shard Queries
  console.log('\n6. Cross-Shard Query Coordinator')

  const queryCoordinator = new CrossShardQueryCoordinator(
    hashSharding,
    rangeSharding,
    directorySharding
  )

  // Execute different query types
  const queries = [
    {
      type: 'SELECT' as const,
      tables: ['users'],
      conditions: { id: 'user_123' }
    },
    {
      type: 'JOIN' as const,
      tables: ['users', 'orders'],
      joinKeys: ['user_123']
    },
    {
      type: 'AGGREGATE' as const,
      tables: ['orders'],
      conditions: { aggregate: 'COUNT' }
    }
  ]

  for (const query of queries) {
    const result = await queryCoordinator.executeCrossShardQuery(query)
    console.log(`\n${query.type} query:`)
    console.log(`  Shards queried: ${result.shardsQueried.length}`)
    console.log(`  Results returned: ${result.results.length}`)
    console.log(`  Execution time: ${result.executionTime}ms`)
  }

  console.log('\n=== Sharding Analysis Complete ===')
}

export {
  PartitioningStrategy,
  Shard,
  PartitionMetadata,
  HashShardingManager,
  RangeShardingManager,
  ConsistentHashRing,
  DirectoryBasedSharding,
  ShardingLoadBalancer,
  CrossShardQueryCoordinator,
  shardingExample
}
        

// Fault Tolerance Mechanisms Implementation

// Fault Tolerance Patterns
enum CircuitState {
  CLOSED = 'CLOSED',
  OPEN = 'OPEN',
  HALF_OPEN = 'HALF_OPEN'
}

enum RetryStrategy {
  FIXED_DELAY = 'FIXED_DELAY',
  EXPONENTIAL_BACKOFF = 'EXPONENTIAL_BACKOFF',
  LINEAR_BACKOFF = 'LINEAR_BACKOFF'
}

enum FailoverStrategy {
  ACTIVE_PASSIVE = 'ACTIVE_PASSIVE',
  ACTIVE_ACTIVE = 'ACTIVE_ACTIVE',
  GEOGRAPHIC = 'GEOGRAPHIC'
}

interface ServiceHealth {
  serviceId: string
  endpoint: string
  status: 'HEALTHY' | 'DEGRADED' | 'UNHEALTHY'
  lastCheck: Date
  responseTime: number
  errorRate: number
  consecutiveFailures: number
}

interface CircuitBreakerConfig {
  failureThreshold: number
  timeoutMs: number
  halfOpenMaxCalls: number
  resetTimeoutMs: number
}

interface RetryConfig {
  maxAttempts: number
  strategy: RetryStrategy
  baseDelayMs: number
  maxDelayMs: number
  multiplier?: number
}

// Circuit Breaker Implementation
class CircuitBreaker {
  private state: CircuitState = CircuitState.CLOSED
  private failureCount: number = 0
  private successCount: number = 0
  private lastFailureTime: number = 0
  private nextAttempt: number = 0
  private halfOpenCalls: number = 0

  constructor(
    private serviceId: string,
    private config: CircuitBreakerConfig,
    private healthMonitor: HealthMonitor
  ) {}

  async execute<T>(operation: () => Promise<T>): Promise<T> {
    if (this.state === CircuitState.OPEN) {
      if (Date.now() < this.nextAttempt) {
        throw new Error(`Circuit breaker OPEN for ${this.serviceId}. Next attempt at ${new Date(this.nextAttempt).toISOString()}`)
      }
      this.transitionToHalfOpen()
    }

    try {
      const result = await this.withTimeout(operation, this.config.timeoutMs)
      this.onSuccess()
      return result
    } catch (error) {
      this.onFailure()
      throw error
    }
  }

  private async withTimeout<T>(operation: () => Promise<T>, timeoutMs: number): Promise<T> {
    return new Promise((resolve, reject) => {
      const timeoutId = setTimeout(() => {
        reject(new Error(`Operation timed out after ${timeoutMs}ms`))
      }, timeoutMs)

      operation()
        .then(result => {
          clearTimeout(timeoutId)
          resolve(result)
        })
        .catch(error => {
          clearTimeout(timeoutId)
          reject(error)
        })
    })
  }

  private onSuccess(): void {
    this.failureCount = 0
    this.successCount++

    if (this.state === CircuitState.HALF_OPEN) {
      this.halfOpenCalls++
      if (this.halfOpenCalls >= this.config.halfOpenMaxCalls) {
        this.transitionToClosed()
      }
    }

    this.healthMonitor.recordSuccess(this.serviceId)
  }

  private onFailure(): void {
    this.failureCount++
    this.lastFailureTime = Date.now()

    if (this.state === CircuitState.HALF_OPEN) {
      this.transitionToOpen()
    } else if (this.failureCount >= this.config.failureThreshold) {
      this.transitionToOpen()
    }

    this.healthMonitor.recordFailure(this.serviceId)
  }

  private transitionToClosed(): void {
    this.state = CircuitState.CLOSED
    this.failureCount = 0
    this.successCount = 0
    this.halfOpenCalls = 0
    console.log(`[CIRCUIT_BREAKER] ${this.serviceId} transitioned to CLOSED`)
  }

  private transitionToOpen(): void {
    this.state = CircuitState.OPEN
    this.nextAttempt = Date.now() + this.config.resetTimeoutMs
    this.halfOpenCalls = 0
    console.log(`[CIRCUIT_BREAKER] ${this.serviceId} transitioned to OPEN until ${new Date(this.nextAttempt).toISOString()}`)
  }

  private transitionToHalfOpen(): void {
    this.state = CircuitState.HALF_OPEN
    this.halfOpenCalls = 0
    console.log(`[CIRCUIT_BREAKER] ${this.serviceId} transitioned to HALF_OPEN`)
  }

  getState(): { state: CircuitState; failureCount: number; successCount: number } {
    return {
      state: this.state,
      failureCount: this.failureCount,
      successCount: this.successCount
    }
  }

  forceOpen(): void {
    this.transitionToOpen()
  }

  forceClose(): void {
    this.transitionToClosed()
  }
}

// Retry Mechanism with Different Strategies
class RetryMechanism {
  constructor(private config: RetryConfig) {}

  async execute<T>(operation: () => Promise<T>): Promise<T> {
    let lastError: Error

    for (let attempt = 1; attempt <= this.config.maxAttempts; attempt++) {
      try {
        console.log(`[RETRY] Attempt ${attempt}/${this.config.maxAttempts}`)
        const result = await operation()
        if (attempt > 1) {
          console.log(`[RETRY] Operation succeeded on attempt ${attempt}`)
        }
        return result
      } catch (error) {
        lastError = error instanceof Error ? error : new Error(String(error))
        console.log(`[RETRY] Attempt ${attempt} failed: ${lastError.message}`)

        if (attempt === this.config.maxAttempts) {
          console.log(`[RETRY] All ${this.config.maxAttempts} attempts exhausted`)
          throw lastError
        }

        const delay = this.calculateDelay(attempt)
        console.log(`[RETRY] Waiting ${delay}ms before retry...`)
        await this.sleep(delay)
      }
    }

    throw lastError!
  }

  private calculateDelay(attempt: number): number {
    switch (this.config.strategy) {
      case RetryStrategy.FIXED_DELAY:
        return this.config.baseDelayMs

      case RetryStrategy.EXPONENTIAL_BACKOFF:
        const exponentialDelay = this.config.baseDelayMs * Math.pow(this.config.multiplier || 2, attempt - 1)
        return Math.min(exponentialDelay, this.config.maxDelayMs)

      case RetryStrategy.LINEAR_BACKOFF:
        const linearDelay = this.config.baseDelayMs + (attempt - 1) * (this.config.baseDelayMs / 2)
        return Math.min(linearDelay, this.config.maxDelayMs)

      default:
        return this.config.baseDelayMs
    }
  }

  private sleep(ms: number): Promise<void> {
    return new Promise(resolve => setTimeout(resolve, ms))
  }
}

// Health Monitor Service
class HealthMonitor {
  private serviceHealth: Map<string, ServiceHealth> = new Map()
  private healthCheckInterval: number = 30000 // 30 seconds

  constructor(private services: Array<{ id: string; endpoint: string }>) {
    this.initializeServices()
    this.startHealthChecks()
  }

  private initializeServices(): void {
    for (const service of this.services) {
      this.serviceHealth.set(service.id, {
        serviceId: service.id,
        endpoint: service.endpoint,
        status: 'HEALTHY',
        lastCheck: new Date(),
        responseTime: 0,
        errorRate: 0,
        consecutiveFailures: 0
      })
    }
  }

  private startHealthChecks(): void {
    setInterval(() => {
      this.performHealthChecks()
    }, this.healthCheckInterval)
  }

  private async performHealthChecks(): Promise<void> {
    for (const [serviceId, health] of this.serviceHealth.entries()) {
      try {
        const startTime = Date.now()
        await this.checkServiceHealth(health.endpoint)
        const responseTime = Date.now() - startTime

        health.status = 'HEALTHY'
        health.responseTime = responseTime
        health.lastCheck = new Date()
        health.consecutiveFailures = 0

        // Update error rate (simplified moving average)
        health.errorRate = health.errorRate * 0.9 // Decay factor

        console.log(`[HEALTH] ${serviceId}: HEALTHY (${responseTime}ms)`)
      } catch (error) {
        health.consecutiveFailures++
        health.lastCheck = new Date()

        if (health.consecutiveFailures >= 3) {
          health.status = 'UNHEALTHY'
        } else if (health.consecutiveFailures >= 1) {
          health.status = 'DEGRADED'
        }

        // Update error rate
        health.errorRate = Math.min(1, health.errorRate * 0.9 + 0.1)

        console.log(`[HEALTH] ${serviceId}: ${health.status} (failure #${health.consecutiveFailures})`)
      }
    }
  }

  private async checkServiceHealth(endpoint: string): Promise<void> {
    // Simulate health check
    await new Promise((resolve, reject) => {
      setTimeout(() => {
        // 90% success rate
        if (Math.random() > 0.1) {
          resolve(undefined)
        } else {
          reject(new Error('Service unavailable'))
        }
      }, Math.random() * 500 + 50) // 50-550ms response time
    })
  }

  recordSuccess(serviceId: string): void {
    const health = this.serviceHealth.get(serviceId)
    if (health) {
      health.consecutiveFailures = 0
      health.errorRate = Math.max(0, health.errorRate * 0.9)
    }
  }

  recordFailure(serviceId: string): void {
    const health = this.serviceHealth.get(serviceId)
    if (health) {
      health.consecutiveFailures++
      health.errorRate = Math.min(1, health.errorRate * 0.9 + 0.1)
    }
  }

  getHealthyServices(): string[] {
    return Array.from(this.serviceHealth.values())
      .filter(health => health.status === 'HEALTHY')
      .map(health => health.serviceId)
  }

  getServiceHealth(serviceId: string): ServiceHealth | null {
    return this.serviceHealth.get(serviceId) || null
  }

  getAllServiceHealth(): ServiceHealth[] {
    return Array.from(this.serviceHealth.values())
  }
}

// Failover Manager
class FailoverManager {
  private activeNode: string | null = null
  private standbyNodes: Set<string> = new Set()
  private failoverHistory: Array<{
    timestamp: Date
    fromNode: string
    toNode: string
    reason: string
  }> = []

  constructor(
    private nodes: Array<{ id: string; endpoint: string; region: string; priority: number }>,
    private strategy: FailoverStrategy,
    private healthMonitor: HealthMonitor
  ) {
    this.initializeFailover()
  }

  private initializeFailover(): void {
    if (this.strategy === FailoverStrategy.ACTIVE_PASSIVE) {
      // Sort by priority and select highest as active
      const sortedNodes = [...this.nodes].sort((a, b) => b.priority - a.priority)
      this.activeNode = sortedNodes[0].id
      this.standbyNodes = new Set(sortedNodes.slice(1).map(n => n.id))
    } else if (this.strategy === FailoverStrategy.ACTIVE_ACTIVE) {
      // All nodes are active
      this.activeNode = 'multi-active'
      this.standbyNodes = new Set()
    }

    console.log(`[FAILOVER] Initialized with ${this.strategy} strategy`)
    console.log(`[FAILOVER] Active node: ${this.activeNode}`)
    console.log(`[FAILOVER] Standby nodes: ${Array.from(this.standbyNodes).join(', ')}`)
  }

  async executeWithFailover<T>(
    operation: (nodeId: string) => Promise<T>,
    operationContext: string = 'operation'
  ): Promise<T> {
    const nodesToTry = this.getNodesInOrder()

    let lastError: Error | null = null

    for (const nodeId of nodesToTry) {
      try {
        console.log(`[FAILOVER] Executing ${operationContext} on node ${nodeId}`)

        // Check if node is healthy
        const health = this.healthMonitor.getServiceHealth(nodeId)
        if (health && health.status !== 'HEALTHY') {
          console.log(`[FAILOVER] Skipping unhealthy node ${nodeId} (${health.status})`)
          continue
        }

        const result = await operation(nodeId)
        console.log(`[FAILOVER] ${operationContext} succeeded on node ${nodeId}`)
        return result
      } catch (error) {
        lastError = error instanceof Error ? error : new Error(String(error))
        console.log(`[FAILOVER] ${operationContext} failed on node ${nodeId}: ${lastError.message}`)

        // If active node failed, initiate failover
        if (nodeId === this.activeNode) {
          await this.initiateFailover(nodeId, lastError.message)
        }
      }
    }

    throw lastError || new Error('All nodes failed')
  }

  private getNodesInOrder(): string[] {
    if (this.strategy === FailoverStrategy.ACTIVE_ACTIVE) {
      // Return healthy nodes sorted by priority
      const healthyNodes = this.nodes.filter(node => {
        const health = this.healthMonitor.getServiceHealth(node.id)
        return health && health.status === 'HEALTHY'
      })
      return healthyNodes.sort((a, b) => b.priority - a.priority).map(n => n.id)
    } else {
      // Return active first, then healthy standbys
      const nodes = [this.activeNode!, ...this.nodes
        .filter(n => this.standbyNodes.has(n.id))
        .filter(n => {
          const health = this.healthMonitor.getServiceHealth(n.id)
          return health && health.status === 'HEALTHY'
        })
        .sort((a, b) => b.priority - a.priority)
        .map(n => n.id)]

      return nodes.filter(Boolean)
    }
  }

  private async initiateFailover(failedNodeId: string, reason: string): Promise<void> {
    console.log(`[FAILOVER] Initiating failover from ${failedNodeId}`)

    if (this.strategy === FailoverStrategy.ACTIVE_PASSIVE && this.activeNode === failedNodeId) {
      // Find next highest priority healthy standby
      const healthyStandbys = this.nodes
        .filter(n => this.standbyNodes.has(n.id))
        .filter(n => {
          const health = this.healthMonitor.getServiceHealth(n.id)
          return health && health.status === 'HEALTHY'
        })
        .sort((a, b) => b.priority - a.priority)

      if (healthyStandbys.length > 0) {
        const newActiveNode = healthyStandbys[0].id

        this.failoverHistory.push({
          timestamp: new Date(),
          fromNode: failedNodeId,
          toNode: newActiveNode,
          reason
        })

        this.standbyNodes.delete(newActiveNode)
        this.standbyNodes.add(failedNodeId)
        this.activeNode = newActiveNode

        console.log(`[FAILOVER] Failover completed: ${failedNodeId} -> ${newActiveNode}`)
      } else {
        console.log(`[FAILOVER] No healthy standby nodes available for failover`)
      }
    }
  }

  getFailoverHistory(): Array<{
    timestamp: Date
    fromNode: string
    toNode: string
    reason: string
  }> {
    return [...this.failoverHistory]
  }

  getCurrentConfiguration(): {
    strategy: FailoverStrategy
    activeNode: string | null
    standbyNodes: string[]
    totalFailovers: number
  } {
    return {
      strategy: this.strategy,
      activeNode: this.activeNode,
      standbyNodes: Array.from(this.standbyNodes),
      totalFailovers: this.failoverHistory.length
    }
  }
}

// Bulkhead Pattern Implementation
class Bulkhead {
  private semaphore: number = 0
  private waitingQueue: Array<{ resolve: Function; reject: Function }> = []
  private metrics = {
    totalCalls: 0,
    rejectedCalls: 0,
    successfulCalls: 0,
    failedCalls: 0
  }

  constructor(
    private name: string,
    private maxConcurrentCalls: number,
    private maxQueueSize: number
  ) {}

  async execute<T>(operation: () => Promise<T>): Promise<T> {
    this.metrics.totalCalls++

    if (this.semaphore >= this.maxConcurrentCalls) {
      if (this.waitingQueue.length >= this.maxQueueSize) {
        this.metrics.rejectedCalls++
        throw new Error(`Bulkhead '${this.name}' rejected call - queue full`)
      }

      // Wait for available slot
      await new Promise((resolve, reject) => {
        this.waitingQueue.push({ resolve, reject })
      })
    }

    this.semaphore++

    try {
      const result = await operation()
      this.metrics.successfulCalls++
      return result
    } catch (error) {
      this.metrics.failedCalls++
      throw error
    } finally {
      this.semaphore--
      this.processQueue()
    }
  }

  private processQueue(): void {
    if (this.waitingQueue.length > 0 && this.semaphore < this.maxConcurrentCalls) {
      const next = this.waitingQueue.shift()
      if (next) {
        next.resolve(undefined)
      }
    }
  }

  getMetrics(): typeof this.metrics & {
    currentConcurrency: number
    queueSize: number
    rejectionRate: number
  } {
    const rejectionRate = this.metrics.totalCalls > 0
      ? (this.metrics.rejectedCalls / this.metrics.totalCalls) * 100
      : 0

    return {
      ...this.metrics,
      currentConcurrency: this.semaphore,
      queueSize: this.waitingQueue.length,
      rejectionRate
    }
  }
}

// Timeout Manager
class TimeoutManager {
  private timeouts: Map<string, ReturnType<typeof setTimeout>> = new Map()

  executeWithTimeout<T>(
    operation: () => Promise<T>,
    timeoutMs: number,
    operationId: string = crypto.randomUUID()
  ): Promise<T> {
    return new Promise((resolve, reject) => {
      const timeoutId = setTimeout(() => {
        this.timeouts.delete(operationId)
        reject(new Error(`Operation ${operationId} timed out after ${timeoutMs}ms`))
      }, timeoutMs)

      this.timeouts.set(operationId, timeoutId)

      operation()
        .then(result => {
          this.clearTimeout(operationId)
          resolve(result)
        })
        .catch(error => {
          this.clearTimeout(operationId)
          reject(error)
        })
    })
  }

  clearTimeout(operationId: string): void {
    const timeoutId = this.timeouts.get(operationId)
    if (timeoutId) {
      clearTimeout(timeoutId)
      this.timeouts.delete(operationId)
    }
  }

  cancelAll(): void {
    for (const timeoutId of this.timeouts.values()) {
      clearTimeout(timeoutId)
    }
    this.timeouts.clear()
  }

  getActiveTimeoutsCount(): number {
    return this.timeouts.size
  }
}

// Fault Tolerance Orchestrator
class FaultToleranceOrchestrator {
  private circuitBreakers: Map<string, CircuitBreaker> = new Map()
  private bulkheads: Map<string, Bulkhead> = new Map()
  private retryMechanisms: Map<string, RetryMechanism> = new Map()
  private timeoutManager = new TimeoutManager()

  constructor(
    private services: Array<{
      id: string
      endpoint: string
      circuitBreakerConfig?: CircuitBreakerConfig
      bulkheadConfig?: { maxConcurrentCalls: number; maxQueueSize: number }
      retryConfig?: RetryConfig
    }>,
    private healthMonitor: HealthMonitor,
    private failoverManager: FailoverManager
  ) {
    this.initializeComponents()
  }

  private initializeComponents(): void {
    for (const service of this.services) {
      // Circuit Breaker
      if (service.circuitBreakerConfig) {
        this.circuitBreakers.set(service.id, new CircuitBreaker(
          service.id,
          service.circuitBreakerConfig,
          this.healthMonitor
        ))
      }

      // Bulkhead
      if (service.bulkheadConfig) {
        this.bulkheads.set(service.id, new Bulkhead(
          service.id,
          service.bulkheadConfig.maxConcurrentCalls,
          service.bulkheadConfig.maxQueueSize
        ))
      }

      // Retry Mechanism
      if (service.retryConfig) {
        this.retryMechanisms.set(service.id, new RetryMechanism(service.retryConfig))
      }
    }
  }

  async executeServiceCall<T>(
    serviceId: string,
    operation: () => Promise<T>,
    options: {
      timeoutMs?: number
      useFailover?: boolean
    } = {}
  ): Promise<T> {
    const service = this.services.find(s => s.id === serviceId)
    if (!service) {
      throw new Error(`Service ${serviceId} not found`)
    }

    const circuitBreaker = this.circuitBreakers.get(serviceId)
    const bulkhead = this.bulkheads.get(serviceId)
    const retryMechanism = this.retryMechanisms.get(serviceId)

    let executeOperation = operation

    // Apply bulkhead if configured
    if (bulkhead) {
      const originalOperation = executeOperation
      executeOperation = () => bulkhead.execute(originalOperation)
    }

    // Apply retry mechanism if configured
    if (retryMechanism) {
      const originalOperation = executeOperation
      executeOperation = () => retryMechanism.execute(originalOperation)
    }

    // Apply circuit breaker if configured
    if (circuitBreaker) {
      const originalOperation = executeOperation
      executeOperation = () => circuitBreaker.execute(originalOperation)
    }

    // Apply timeout if specified
    if (options.timeoutMs) {
      const originalOperation = executeOperation
      executeOperation = () => this.timeoutManager.executeWithTimeout(originalOperation, options.timeoutMs!)
    }

    // Apply failover if requested
    if (options.useFailover) {
      return this.failoverManager.executeWithFailover(
        () => executeOperation(),
        `service call to ${serviceId}`
      )
    }

    return executeOperation()
  }

  getSystemHealth(): {
    services: Array<{
      id: string
      circuitBreakerState?: any
      bulkheadMetrics?: any
      health: ServiceHealth | null
    }>
    failoverConfig: any
    overallHealth: 'HEALTHY' | 'DEGRADED' | 'UNHEALTHY'
  } {
    const services = this.services.map(service => {
      const circuitBreaker = this.circuitBreakers.get(service.id)
      const bulkhead = this.bulkheads.get(service.id)
      const health = this.healthMonitor.getServiceHealth(service.id)

      return {
        id: service.id,
        circuitBreakerState: circuitBreaker?.getState(),
        bulkheadMetrics: bulkhead?.getMetrics(),
        health
      }
    })

    const unhealthyServices = services.filter(s => s.health?.status === 'UNHEALTHY').length
    const degradedServices = services.filter(s => s.health?.status === 'DEGRADED').length

    let overallHealth: 'HEALTHY' | 'DEGRADED' | 'UNHEALTHY' = 'HEALTHY'
    if (unhealthyServices > 0) {
      overallHealth = 'UNHEALTHY'
    } else if (degradedServices > 0) {
      overallHealth = 'DEGRADED'
    }

    return {
      services,
      failoverConfig: this.failoverManager.getCurrentConfiguration(),
      overallHealth
    }
  }
}

// Usage Example
async function faultToleranceExample() {
  console.log('=== Fault Tolerance Mechanisms ===\n')

  // Initialize services
  const services = [
    {
      id: 'user-service',
      endpoint: 'http://user-service:8080',
      circuitBreakerConfig: {
        failureThreshold: 5,
        timeoutMs: 5000,
        halfOpenMaxCalls: 3,
        resetTimeoutMs: 30000
      },
      bulkheadConfig: {
        maxConcurrentCalls: 10,
        maxQueueSize: 50
      },
      retryConfig: {
        maxAttempts: 3,
        strategy: RetryStrategy.EXPONENTIAL_BACKOFF,
        baseDelayMs: 1000,
        maxDelayMs: 10000,
        multiplier: 2
      }
    },
    {
      id: 'order-service',
      endpoint: 'http://order-service:8080',
      circuitBreakerConfig: {
        failureThreshold: 3,
        timeoutMs: 8000,
        halfOpenMaxCalls: 2,
        resetTimeoutMs: 60000
      },
      retryConfig: {
        maxAttempts: 2,
        strategy: RetryStrategy.FIXED_DELAY,
        baseDelayMs: 2000,
        maxDelayMs: 5000
      }
    },
    {
      id: 'payment-service',
      endpoint: 'http://payment-service:8080',
      circuitBreakerConfig: {
        failureThreshold: 2,
        timeoutMs: 3000,
        halfOpenMaxCalls: 1,
        resetTimeoutMs: 15000
      }
    }
  ]

  // Initialize nodes for failover
  const nodes = [
    { id: 'primary-db', endpoint: 'http://primary-db:5432', region: 'us-east-1', priority: 10 },
    { id: 'secondary-db', endpoint: 'http://secondary-db:5432', region: 'us-west-1', priority: 8 },
    { id: 'backup-db', endpoint: 'http://backup-db:5432', region: 'eu-west-1', priority: 6 }
  ]

  // Initialize components
  const healthMonitor = new HealthMonitor(services)
  const failoverManager = new FailoverManager(nodes, FailoverStrategy.ACTIVE_PASSIVE, healthMonitor)
  const orchestrator = new FaultToleranceOrchestrator(services, healthMonitor, failoverManager)

  console.log('1. Initial System Health')

  // Wait for initial health checks
  await new Promise(resolve => setTimeout(resolve, 2000))

  let systemHealth = orchestrator.getSystemHealth()
  console.log(`Overall system health: ${systemHealth.overallHealth}`)
  console.log('Service health:')
  systemHealth.services.forEach(service => {
    console.log(`  ${service.id}: ${service.health?.status || 'UNKNOWN'}`)
  })

  console.log('\n2. Testing Circuit Breaker')

  // Simulate service failures to trigger circuit breaker
  console.log('Simulating user-service failures...')

  for (let i = 0; i < 7; i++) {
    try {
      await orchestrator.executeServiceCall('user-service', async () => {
        // 70% failure rate
        if (Math.random() > 0.3) {
          throw new Error('Service temporarily unavailable')
        }
        return 'User data'
      }, { timeoutMs: 1000 })
      console.log(`  Attempt ${i + 1}: SUCCESS`)
    } catch (error) {
      console.log(`  Attempt ${i + 1}: FAILED - ${error.message}`)
    }
  }

  // Check circuit breaker state
  const userServiceCB = orchestrator['circuitBreakers'].get('user-service')
  if (userServiceCB) {
    const cbState = userServiceCB.getState()
    console.log(`\nCircuit breaker state: ${cbState.state} (failures: ${cbState.failureCount})`)
  }

  console.log('\n3. Testing Retry Mechanism')

  // Test different retry strategies
  const retryConfig = {
    maxAttempts: 4,
    strategy: RetryStrategy.EXPONENTIAL_BACKOFF,
    baseDelayMs: 500,
    maxDelayMs: 5000,
    multiplier: 2
  }

  const retryMechanism = new RetryMechanism(retryConfig)

  try {
    const result = await retryMechanism.execute(async () => {
      // 50% success rate
      if (Math.random() > 0.5) {
        throw new Error('Random failure')
      }
      return 'Operation succeeded'
    })
    console.log(`Retry mechanism result: ${result}`)
  } catch (error) {
    console.log(`Retry mechanism failed: ${error.message}`)
  }

  console.log('\n4. Testing Bulkhead Pattern')

  const bulkhead = new Bulkhead('test-bulkhead', 3, 5)

  // Submit concurrent requests
  const promises = []
  for (let i = 0; i < 8; i++) {
    promises.push(
      bulkhead.execute(async () => {
        await new Promise(resolve => setTimeout(resolve, 1000))
        return `Request ${i} completed`
      }).catch(error => error.message)
    )
  }

  const bulkheadResults = await Promise.all(promises)
  console.log('Bulkhead results:')
  bulkheadResults.forEach((result, index) => {
    console.log(`  Request ${index}: ${result}`)
  })

  const bulkheadMetrics = bulkhead.getMetrics()
  console.log(`Bulkhead metrics: ${JSON.stringify(bulkheadMetrics)}`)

  console.log('\n5. Testing Failover')

  // Simulate database failover
  try {
    await orchestrator.executeServiceCall('user-service', async () => {
      return await failoverManager.executeWithFailover(async (nodeId) => {
        console.log(`  Executing database operation on ${nodeId}`)

        // Simulate primary failure
        if (nodeId === 'primary-db' && Math.random() > 0.3) {
          throw new Error('Primary database failed')
        }

        await new Promise(resolve => setTimeout(resolve, 200))
        return `Data from ${nodeId}`
      }, 'database query')
    }, { useFailover: true })
  } catch (error) {
    console.log(`Failover test failed: ${error.message}`)
  }

  const failoverHistory = failoverManager.getFailoverHistory()
  if (failoverHistory.length > 0) {
    console.log('\nFailover history:')
    failoverHistory.forEach(failover => {
      console.log(`  ${failover.timestamp.toISOString()}: ${failover.fromNode} -> ${failover.toNode} (${failover.reason})`)
    })
  }

  console.log('\n6. Final System Health Check')

  // Wait for some time to see health changes
  await new Promise(resolve => setTimeout(resolve, 3000))

  systemHealth = orchestrator.getSystemHealth()
  console.log(`Final overall health: ${systemHealth.overallHealth}`)

  console.log('\nService details:')
  systemHealth.services.forEach(service => {
    console.log(`\n${service.id}:`)
    console.log(`  Health: ${service.health?.status}`)
    console.log(`  Response time: ${service.health?.responseTime}ms`)
    console.log(`  Error rate: ${(service.health?.errorRate || 0).toFixed(2)}%`)

    if (service.circuitBreakerState) {
      console.log(`  Circuit breaker: ${service.circuitBreakerState.state}`)
    }

    if (service.bulkheadMetrics) {
      console.log(`  Bulkhead: ${service.bulkheadMetrics.currentConcurrency}/${service.bulkheadMetrics.maxConcurrency}`)
    }
  })

  console.log('\n=== Fault Tolerance Demo Complete ===')
}

export {
  CircuitState,
  RetryStrategy,
  FailoverStrategy,
  ServiceHealth,
  CircuitBreaker,
  RetryMechanism,
  HealthMonitor,
  FailoverManager,
  Bulkhead,
  TimeoutManager,
  FaultToleranceOrchestrator,
  faultToleranceExample
}