Android Multithreading Kotlin Samples

// Android Kotlin Thread Creation Examples
// Using Thread, Runnable, and Coroutines

import android.os.Handler
import android.os.Looper
import kotlinx.coroutines.*

// 1. Basic Thread Creation
class BasicThreadCreation {

    // Create thread using Thread class
    fun createBasicThread() {
        val thread = Thread {
            println("Thread running: ${Thread.currentThread().name}")
            // Perform background work
            Thread.sleep(1000)
            println("Thread completed")
        }

        thread.start()
    }

    // Create thread with custom name
    fun createNamedThread(name: String) {
        val thread = Thread({
            println("Named thread: ${Thread.currentThread().name}")
            // Perform work
        }, name)

        thread.start()
    }

    // Create thread using Runnable
    fun createThreadWithRunnable() {
        val runnable = Runnable {
            println("Runnable thread: ${Thread.currentThread().name}")
        }

        val thread = Thread(runnable)
        thread.start()
    }

    // Create thread with lambda
    fun createThreadWithLambda() {
        Thread {
            println("Lambda thread: ${Thread.currentThread().name}")
            performWork()
        }.start()
    }

    private fun performWork() {
        // Simulate work
        Thread.sleep(500)
        println("Work completed")
    }
}

// 2. Kotlin Coroutines (Recommended for Android)
class CoroutineExamples {

    private val scope = CoroutineScope(Dispatchers.Default + Job())

    // Launch a coroutine
    fun launchCoroutine() {
        scope.launch {
            println("Coroutine running on: ${Thread.currentThread().name}")
            delay(1000)
            println("Coroutine completed")
        }
    }

    // Launch coroutine on IO dispatcher
    fun launchIOCoroutine() {
        scope.launch(Dispatchers.IO) {
            println("IO coroutine on: ${Thread.currentThread().name}")
            // Perform IO operations
        }
    }

    // Launch coroutine on Main thread
    fun launchMainCoroutine() {
        scope.launch(Dispatchers.Main) {
            println("Main coroutine on: ${Thread.currentThread().name}")
            // Update UI
        }
    }

    // Async coroutine with return value
    suspend fun asyncCoroutine(): Int = withContext(Dispatchers.Default) {
        println("Async coroutine on: ${Thread.currentThread().name}")
        delay(1000)
        42
    }

    // Run blocking coroutine
    fun runBlockingCoroutine() {
        runBlocking {
            println("Blocking coroutine on: ${Thread.currentThread().name}")
            launch {
                delay(500)
                println("Child coroutine completed")
            }
            println("Parent coroutine continuing")
        }
    }

    // Cancel scope
    fun cancelAll() {
        scope.cancel()
    }
}

// 3. Advanced Thread Operations
class AdvancedThreadOperations {

    // Thread with exception handling
    fun createThreadWithExceptionHandling() {
        val thread = Thread {
            try {
                println("Thread working...")
                // Simulate error
                throw RuntimeException("Thread error!")
            } catch (e: Exception) {
                println("Caught exception in thread: ${e.message}")
            }
        }

        thread.setUncaughtExceptionHandler { t, e ->
            println("Uncaught exception in ${t.name}: ${e.message}")
        }

        thread.start()
    }

    // Thread with priority
    fun createThreadWithPriority() {
        val thread = Thread {
            println("High priority thread running")
        }.apply {
            priority = Thread.MAX_PRIORITY
        }

        thread.start()
    }

    // Daemon thread
    fun createDaemonThread() {
        val thread = Thread {
            var count = 0
            while (true) {
                println("Daemon thread: $count")
                Thread.sleep(1000)
                count++
            }
        }.apply {
            isDaemon = true
        }

        thread.start()

        // Main thread exits, daemon thread terminates
    }

    // Thread sleep and join
    fun createThreadWithJoin() {
        val thread1 = Thread {
            println("Thread 1 starting")
            Thread.sleep(1000)
            println("Thread 1 completed")
        }

        val thread2 = Thread {
            println("Thread 2 starting")
            Thread.sleep(500)
            println("Thread 2 completed")
        }

        thread1.start()
        thread2.start()

        // Wait for both threads to complete
        thread1.join()
        thread2.join()

        println("All threads completed")
    }
}

// 4. Handler and Looper (Android Specific)
class HandlerLooperExamples {

    private val handler = Handler(Looper.getMainLooper())

    // Post runnable to main thread
    fun postToMainThread() {
        Thread {
            println("Background thread: ${Thread.currentThread().name}")

            // Post result to main thread
            handler.post {
                println("Main thread: ${Thread.currentThread().name}")
                // Update UI
            }
        }.start()
    }

    // Post delayed
    fun postDelayed() {
        handler.postDelayed({
            println("Delayed execution on main thread")
        }, 2000) // 2 seconds delay
    }

    // Post at front of queue
    fun postAtFrontOfQueue() {
        handler.postAtFrontOfQueue {
            println("Execute immediately on main thread")
        }
    }

    // Remove callbacks
    fun removeCallbacks() {
        val runnable = Runnable {
            println("This won't execute")
        }

        handler.post(runnable)
        handler.removeCallbacks(runnable)
    }
}

// 5. Thread Communication
class ThreadCommunication {

    private var sharedData: String = ""

    // Wait and notify
    fun waitNotifyExample() {
        val lock = Object()

        val producerThread = Thread {
            synchronized(lock) {
                println("Producer: Producing data...")
                Thread.sleep(1000)
                sharedData = "Hello from producer"
                println("Producer: Data ready, notifying...")
                lock.notifyAll()
            }
        }

        val consumerThread = Thread {
            synchronized(lock) {
                println("Consumer: Waiting for data...")
                while (sharedData.isEmpty()) {
                    lock.wait()
                }
                println("Consumer: Received: $sharedData")
            }
        }

        consumerThread.start()
        producerThread.start()
    }
}

// 6. Coroutine Context and Scope
class CoroutineContextExamples {

    // Using viewModelScope (requires ViewModel)
    // This is a simulation
    fun viewModelScopeExample() {
        // In a real ViewModel:
        // viewModelScope.launch {
        //     // Work that is cancelled when ViewModel is cleared
        // }

        // Simulation with custom scope
        val customScope = CoroutineScope(Dispatchers.Default)

        customScope.launch {
            println("Custom scope coroutine")
        }
    }

    // Using lifecycleScope (requires LifecycleOwner)
    // This is a simulation
    fun lifecycleScopeExample() {
        // In a Fragment or Activity:
        // lifecycleScope.launch {
        //     // Work that is cancelled when Lifecycle is destroyed
        // }
    }

    // Supervisor job
    fun supervisorJobExample() {
        val supervisor = SupervisorJob()
        val scope = CoroutineScope(Dispatchers.Default + supervisor)

        scope.launch {
            throw RuntimeException("Child 1 failed")
        }

        scope.launch {
            delay(1000)
            println("Child 2 completed")
        }

        // Child 2 continues even though Child 1 failed
    }

    // Coroutine context switching
    suspend fun contextSwitchingExample() {
        withContext(Dispatchers.IO) {
            println("IO work: ${Thread.currentThread().name}")
        }

        withContext(Dispatchers.Main) {
            println("Main work: ${Thread.currentThread().name}")
        }

        withContext(Dispatchers.Default) {
            println("CPU work: ${Thread.currentThread().name}")
        }
    }
}

// 7. Thread Local Storage
class ThreadLocalStorageExample {

    private val threadLocal = ThreadLocal<String>()

    fun threadLocalDemo() {
        val thread1 = Thread {
            threadLocal.set("Value from Thread 1")
            println("Thread 1: ${threadLocal.get()}")
        }

        val thread2 = Thread {
            threadLocal.set("Value from Thread 2")
            println("Thread 2: ${threadLocal.get()}")
        }

        thread1.start()
        thread2.start()

        thread1.join()
        thread2.join()

        println("Main thread: ${threadLocal.get()}")
    }
}

// Main demonstration
fun demonstrateThreadCreation() {
    println("=== Android Kotlin Thread Creation Examples ===\n")

    // 1. Basic thread creation
    println("--- 1. Basic Thread Creation ---")
    val basicThread = BasicThreadCreation()
    basicThread.createBasicThread()
    basicThread.createNamedThread("MyCustomThread")

    // 2. Coroutines (recommended)
    println("\n--- 2. Kotlin Coroutines ---")
    val coroutineExamples = CoroutineExamples()
    coroutineExamples.launchCoroutine()

    // 3. Advanced operations
    println("\n--- 3. Advanced Thread Operations ---")
    val advancedOps = AdvancedThreadOperations()
    advancedOps.createThreadWithJoin()

    // 4. Handler and Looper
    println("\n--- 4. Handler and Looper ---")
    val handlerExamples = HandlerLooperExamples()
    handlerExamples.postToMainThread()

    // 5. Thread communication
    println("\n--- 5. Thread Communication ---")
    val communication = ThreadCommunication()
    communication.waitNotifyExample()

    println("\n=== All Thread Creation Examples Completed ===")
}

// Android Kotlin Thread Synchronization Examples
// Using locks, semaphores, and synchronization mechanisms

import kotlinx.coroutines.*
import kotlinx.coroutines.sync.*
import java.util.concurrent.*
import java.util.concurrent.atomic.*
import java.util.concurrent.locks.*

// 1. Synchronized Block
class SynchronizedBlockExample {
    private var counter = 0

    // Using synchronized block
    fun incrementCounter() {
        synchronized(this) {
            counter++
            println("Counter: $counter (Thread: ${Thread.currentThread().name})")
        }
    }

    // Synchronized method
    @Synchronized
    fun decrementCounter() {
        counter--
        println("Counter: $counter (Thread: ${Thread.currentThread().name})")
    }

    fun getCounter(): Int {
        synchronized(this) {
            return counter
        }
    }
}

// 2. ReentrantLock
class ReentrantLockExample {
    private val lock = ReentrantLock()
    private var sharedResource = 0

    fun performTask() {
        lock.lock()
        try {
            println("Lock acquired by ${Thread.currentThread().name}")
            // Critical section
            sharedResource++
            Thread.sleep(100)
            println("Shared resource: $sharedResource")
        } finally {
            lock.unlock()
            println("Lock released by ${Thread.currentThread().name}")
        }
    }

    fun tryLockExample() {
        if (lock.tryLock(1, TimeUnit.SECONDS)) {
            try {
                println("TryLock succeeded")
                // Perform work
            } finally {
                lock.unlock()
            }
        } else {
            println("Could not acquire lock")
        }
    }

    // ReadWriteLock for multiple readers
    private val readWriteLock = ReentrantReadWriteLock()
    private var data = "Initial Data"

    fun readData(): String {
        readWriteLock.readLock().lock()
        try {
            println("Reading: $data")
            return data
        } finally {
            readWriteLock.readLock().unlock()
        }
    }

    fun writeData(newValue: String) {
        readWriteLock.writeLock().lock()
        try {
            println("Writing: $newValue")
            data = newValue
        } finally {
            readWriteLock.writeLock().unlock()
        }
    }
}

// 3. Semaphore
class SemaphoreExample {
    private val semaphore = Semaphore(3) // Allow 3 concurrent accesses

    fun accessResource(id: Int) {
        try {
            semaphore.acquire()
            println("Resource $id acquired by ${Thread.currentThread().name}")

            // Simulate work
            Thread.sleep(1000)
            println("Resource $id released")
        } catch (e: InterruptedException) {
            println("Interrupted: ${e.message}")
        } finally {
            semaphore.release()
        }
    }

    fun tryAcquireExample(id: Int) {
        if (semaphore.tryAcquire()) {
            try {
                println("Resource $id accessed immediately")
                Thread.sleep(500)
            } finally {
                semaphore.release()
            }
        } else {
            println("Resource $id not available")
        }
    }
}

// 4. Atomic Variables
class AtomicVariableExample {
    private val atomicCounter = AtomicInteger(0)
    private val atomicBoolean = AtomicBoolean(false)
    private val atomicReference = AtomicReference("Initial")

    fun atomicIncrement() {
        val newValue = atomicCounter.incrementAndGet()
        println("Atomic counter: $newValue")
    }

    fun compareAndSet() {
        val success = atomicBoolean.compareAndSet(false, true)
        println("CAS result: $success, Value: ${atomicBoolean.get()}")
    }

    fun atomicUpdate() {
        atomicReference.updateAndGet { current ->
            println("Current: $current")
            "Updated"
        }
        println("Final: ${atomicReference.get()}")
    }

    fun getAndAdd() {
        val oldValue = atomicCounter.getAndAdd(5)
        println("Old: $oldValue, New: ${atomicCounter.get()}")
    }
}

// 5. Kotlin Coroutine Mutex
class CoroutineMutexExample {
    private val mutex = Mutex()
    private var sharedCounter = 0

    suspend fun safeIncrement() {
        mutex.withLock {
            sharedCounter++
            println("Counter: $sharedCounter (Coroutine: ${Thread.currentThread().name})")
        }
    }

    suspend fun tryLockExample() {
        if (mutex.tryLock()) {
            try {
                println("Mutex acquired")
                sharedCounter++
            } finally {
                mutex.unlock()
            }
        } else {
            println("Could not acquire mutex")
        }
    }
}

// 6. CountDownLatch
class CountDownLatchExample {
    fun demonstrateLatch() {
        val latch = CountDownLatch(3)

        // Create worker threads
        repeat(3) { index ->
            Thread {
                try {
                    println("Worker $index starting")
                    Thread.sleep((1000..2000).random().toLong())
                    println("Worker $index completed")
                } finally {
                    latch.countDown()
                }
            }.start()
        }

        // Main thread waits
        println("Main thread waiting for workers...")
        latch.await()
        println("All workers completed!")
    }

    fun awaitWithTimeout() {
        val latch = CountDownLatch(5)

        repeat(5) { index ->
            Thread {
                Thread.sleep(1000)
                latch.countDown()
            }.start()
        }

        // Wait with timeout
        if (latch.await(2, TimeUnit.SECONDS)) {
            println("Completed within timeout")
        } else {
            println("Timeout - not all completed")
        }
    }
}

// 7. CyclicBarrier
class CyclicBarrierExample {
    fun demonstrateBarrier() {
        val barrier = CyclicBarrier(3) {
            println("\n*** All threads reached barrier ***\n")
        }

        repeat(3) { index ->
            Thread {
                println("Thread $index: Phase 1")
                Thread.sleep(500)
                println("Thread $index: Waiting at barrier")

                try {
                    barrier.await()
                    println("Thread $index: Phase 2")
                } catch (e: Exception) {
                    println("Barrier error: ${e.message}")
                }
            }.start()
        }
    }
}

// 8. BlockingQueue (Producer-Consumer)
class BlockingQueueExample {
    private val queue = ArrayBlockingQueue<Int>(5)
    private var running = true

    fun startProducer() {
        Thread {
            var item = 0
            while (running) {
                try {
                    queue.put(item)
                    println("Produced: $item (Queue size: ${queue.size})")
                    item++
                    Thread.sleep(500)
                } catch (e: InterruptedException) {
                    break
                }
            }
        }.start()
    }

    fun startConsumer() {
        Thread {
            while (running) {
                try {
                    val item = queue.take()
                    println("Consumed: $item")
                    Thread.sleep(1000)
                } catch (e: InterruptedException) {
                    break
                }
            }
        }.start()
    }

    fun stop() {
        running = false
    }
}

// 9. Volatile Variables
class VolatileExample {
    @Volatile
    private var flag = false

    fun startFlagWatcher() {
        Thread {
            println("Watcher: Waiting for flag...")
            while (!flag) {
                // Busy wait (not recommended, use proper synchronization)
            }
            println("Watcher: Flag is now true!")
        }.start()
    }

    fun setFlag() {
        Thread.sleep(2000)
        flag = true
        println("Main: Flag set to true")
    }
}

// 10. Thread-safe Collections
class ThreadSafeCollectionsExample {
    // ConcurrentHashMap
    private val concurrentMap = ConcurrentHashMap<String, Int>()

    fun addToConcurrentMap() {
        repeat(10) { index ->
            Thread {
                concurrentMap["key$index"] = index
                println("Added key$index: $index")
            }.start()
        }

        Thread.sleep(1000)
        println("Map size: ${concurrentMap.size}")
    }

    // CopyOnWriteArrayList
    private val concurrentList = CopyOnWriteArrayList<String>()

    fun addToList() {
        repeat(5) { index ->
            Thread {
                concurrentList.add("Item $index")
                println("List size: ${concurrentList.size}")
            }.start()
        }

        Thread.sleep(1000)
        println("List: $concurrentList")
    }

    // Concurrent Linked Queue
    private val concurrentQueue = ConcurrentLinkedQueue<Int>()

    fun addToQueue() {
        repeat(5) { index ->
            Thread {
                concurrentQueue.offer(index)
                println("Queue size: ${concurrentQueue.size}")
            }.start()
        }

        Thread.sleep(1000)
        println("Queue: $concurrentQueue")
    }
}

// Main demonstration
fun demonstrateThreadSynchronization() {
    println("=== Android Kotlin Thread Synchronization Examples ===\n")

    // 1. Synchronized block
    println("--- 1. Synchronized Block ---")
    val syncExample = SynchronizedBlockExample()

    repeat(5) {
        Thread {
            syncExample.incrementCounter()
        }.start()
    }

    Thread.sleep(1000)

    // 2. ReentrantLock
    println("\n--- 2. ReentrantLock ---")
    val lockExample = ReentrantLockExample()

    repeat(3) {
        Thread {
            lockExample.performTask()
        }.start()
    }

    Thread.sleep(1000)

    // 3. Semaphore
    println("\n--- 3. Semaphore ---")
    val semaphoreExample = SemaphoreExample()

    repeat(5) { index ->
        Thread {
            semaphoreExample.accessResource(index)
        }.start()
    }

    Thread.sleep(3000)

    // 4. Atomic variables
    println("\n--- 4. Atomic Variables ---")
    val atomicExample = AtomicVariableExample()

    repeat(5) {
        Thread {
            atomicExample.atomicIncrement()
        }.start()
    }

    Thread.sleep(500)

    // 5. CountDownLatch
    println("\n--- 5. CountDownLatch ---")
    val latchExample = CountDownLatchExample()
    latchExample.demonstrateLatch()

    Thread.sleep(3000)

    // 6. Thread-safe collections
    println("\n--- 6. Thread-safe Collections ---")
    val collectionsExample = ThreadSafeCollectionsExample()
    collectionsExample.addToConcurrentMap()

    Thread.sleep(1000)

    println("\n=== All Thread Synchronization Examples Completed ===")
}

// Android Kotlin Thread Pool Examples
// Using ExecutorService, Coroutine Dispatchers, and Custom Thread Pools

import kotlinx.coroutines.*
import java.util.concurrent.*
import kotlin.system.measureTimeMillis

// 1. ExecutorService Thread Pools
class ExecutorServicePools {

    // Fixed thread pool
    fun fixedThreadPoolExample() {
        val executor = Executors.newFixedThreadPool(4)

        println("--- Fixed Thread Pool (4 threads) ---")

        val time = measureTimeMillis {
            val tasks = (1..8).map { taskId ->
                executor.submit {
                    println("Task $taskId starting on ${Thread.currentThread().name}")
                    Thread.sleep(1000)
                    println("Task $taskId completed")
                }
            }

            // Wait for all tasks to complete
            tasks.forEach { it.get() }
        }

        println("Total time: ${time}ms")
        executor.shutdown()
    }

    // Cached thread pool
    fun cachedThreadPoolExample() {
        val executor = Executors.newCachedThreadPool()

        println("\n--- Cached Thread Pool ---")

        val tasks = (1..10).map { taskId ->
            executor.submit<Int> {
                println("Task $taskId on ${Thread.currentThread().name}")
                Thread.sleep((100..500).random().toLong())
                taskId * 2
            }
        }

        tasks.forEach { future ->
            val result = future.get()
            println("Result: $result")
        }

        executor.shutdown()
    }

    // Single thread executor
    fun singleThreadExecutorExample() {
        val executor = Executors.newSingleThreadExecutor()

        println("\n--- Single Thread Executor ---")

        (1..5).forEach { taskId ->
            executor.submit {
                println("Task $taskId on ${Thread.currentThread().name}")
                Thread.sleep(200)
            }
        }

        executor.shutdown()
        executor.awaitTermination(5, TimeUnit.SECONDS)
    }

    // Scheduled executor
    fun scheduledExecutorExample() {
        val executor = Executors.newScheduledThreadPool(2)

        println("\n--- Scheduled Executor ---")

        // Schedule one-time task
        executor.schedule({
            println("Delayed task executed")
        }, 2, TimeUnit.SECONDS)

        // Schedule at fixed rate
        executor.scheduleAtFixedRate({
            println("Periodic task at ${System.currentTimeMillis()}")
        }, 0, 1, TimeUnit.SECONDS)

        // Run for 5 seconds then shutdown
        Thread.sleep(5000)
        executor.shutdown()
    }
}

// 2. Custom Thread Pool
class CustomThreadPoolExample {

    fun customThreadPoolExample() {
        // Create custom thread pool
        val threadFactory = ThreadFactory { runnable ->
            Thread(runnable).apply {
                name = "CustomPool-${System.currentTimeMillis()}"
                isDaemon = false
                priority = Thread.NORM_PRIORITY
            }
        }

        val executor = ThreadPoolExecutor(
            2, // Core pool size
            5, // Maximum pool size
            60L, // Keep-alive time
            TimeUnit.SECONDS,
            LinkedBlockingQueue(10), // Work queue
            threadFactory,
            ThreadPoolExecutor.CallerRunsPolicy() // Rejection policy
        )

        println("\n--- Custom Thread Pool ---")

        // Submit tasks
        for (i in 1..10) {
            try {
                executor.submit {
                    println("Task $i on ${Thread.currentThread().name}")
                    Thread.sleep(500)
                }
            } catch (e: RejectedExecutionException) {
                println("Task $i rejected")
            }
        }

        executor.shutdown()
        executor.awaitTermination(10, TimeUnit.SECONDS)
    }
}

// 3. Kotlin Coroutine Dispatchers
class CoroutineDispatchersExample {

    private val scope = CoroutineScope(SupervisorJob())

    // Main dispatcher (UI thread)
    fun mainDispatcherExample() {
        scope.launch(Dispatchers.Main) {
            println("Main dispatcher: ${Thread.currentThread().name}")
        }
    }

    // IO dispatcher (for IO operations)
    fun ioDispatcherExample() {
        scope.launch(Dispatchers.IO) {
            println("IO dispatcher: ${Thread.currentThread().name}")
            // Simulate IO operation
            delay(1000)
            println("IO operation completed")
        }
    }

    // Default dispatcher (CPU intensive)
    fun defaultDispatcherExample() {
        scope.launch(Dispatchers.Default) {
            println("Default dispatcher: ${Thread.currentThread().name}")
            // CPU intensive work
            var result = 0
            for (i in 1..1000000) {
                result += i
            }
            println("Computation result: $result")
        }
    }

    // Unconfined dispatcher
    fun unconfinedDispatcherExample() {
        scope.launch(Dispatchers.Unconfined) {
            println("Unconfined start: ${Thread.currentThread().name}")
            delay(100)
            println("Unconfined after delay: ${Thread.currentThread().name}")
        }
    }

    // Custom dispatcher with fixed thread pool
    fun customDispatcherExample() {
        val customDispatcher = newFixedThreadPoolContext(4, "CustomPool")

        scope.launch(customDispatcher) {
            println("Custom dispatcher: ${Thread.currentThread().name}")
            delay(500)
        }

        customDispatcher.close()
    }
}

// 4. Coroutine Async and Await
class CoroutineAsyncExample {

    private val scope = CoroutineScope(Dispatchers.Default)

    suspend fun parallelTasks(): Int = coroutineScope {
        println("\n--- Parallel Tasks with Async ---")

        val time = measureTimeMillis {
            val deferred1 = async {
                println("Task 1 starting")
                delay(1000)
                println("Task 1 completed")
                10
            }

            val deferred2 = async {
                println("Task 2 starting")
                delay(1500)
                println("Task 2 completed")
                20
            }

            val deferred3 = async {
                println("Task 3 starting")
                delay(500)
                println("Task 3 completed")
                30
            }

            // Wait for all and sum results
            val result = deferred1.await() + deferred2.await() + deferred3.await()
            println("Total result: $result")
        }

        println("Total time: ${time}ms")
        return@coroutineScope time.toInt()
    }

    suspend fun sequentialTasks(): Int = coroutineScope {
        println("\n--- Sequential Tasks ---")

        val time = measureTimeMillis {
            val result1 = withContext(Dispatchers.Default) {
                delay(1000)
                10
            }

            val result2 = withContext(Dispatchers.Default) {
                delay(1500)
                20
            }

            val result3 = withContext(Dispatchers.Default) {
                delay(500)
                30
            }

            println("Total result: ${result1 + result2 + result3}")
        }

        println("Total time: ${time}ms")
        return@coroutineScope time.toInt()
    }
}

// 5. Work Manager (Android Jetpack)
class WorkManagerExample {

    // This is a conceptual example
    // In actual Android code, you would use androidx.work.WorkManager

    fun enqueueWork() {
        // Concept: Enqueue one-time work
        // val workRequest = OneTimeWorkRequestBuilder<MyWorker>()
        //     .setConstraints(Constraints.Builder()
        //         .setRequiredNetworkType(NetworkType.CONNECTED)
        //         .build())
        //     .build()
        //
        // WorkManager.getInstance(context).enqueue(workRequest)

        println("Work enqueued (conceptual example)")
    }

    fun enqueuePeriodicWork() {
        // Concept: Enqueue periodic work
        // val periodicWork = PeriodicWorkRequestBuilder<MyWorker>(
        //     15, TimeUnit.MINUTES
        // ).build()
        //
        // WorkManager.getInstance(context).enqueue(periodicWork)

        println("Periodic work enqueued (conceptual example)")
    }
}

// 6. ExecutorService with Future
class FutureExample {

    fun submitWithFuture() {
        val executor = Executors.newFixedThreadPool(3)

        println("\n--- ExecutorService with Future ---")

        // Submit callable tasks
        val futures = (1..5).map { taskId ->
            executor.submit<Int> {
                println("Task $taskId starting")
                Thread.sleep((500..1500).random().toLong())
                println("Task $taskId completed")
                taskId * 10
            }
        }

        // Process results as they complete
        futures.forEach { future ->
            try {
                val result = future.get()
                println("Future result: $result")
            } catch (e: Exception) {
                println("Future error: ${e.message}")
            }
        }

        executor.shutdown()
    }

    fun invokeAllExample() {
        val executor = Executors.newFixedThreadPool(4)

        val tasks = (1..10).map { taskId ->
            Callable<Int> {
                Thread.sleep(1000)
                taskId
            }
        }

        val time = measureTimeMillis {
            val futures = executor.invokeAll(tasks)

            futures.forEach { future ->
                println("Completed: ${future.get()}")
            }
        }

        println("InvokeAll time: ${time}ms")
        executor.shutdown()
    }
}

// 7. Completion Service
class CompletionServiceExample {

    fun completionServiceDemo() {
        val executor = Executors.newFixedThreadPool(4)
        val completionService = ExecutorCompletionService<Int>(executor)

        println("\n--- Completion Service ---")

        // Submit tasks
        (1..5).forEach { taskId ->
            completionService.submit(Callable<Int> {
                val sleepTime = (1000..3000).random().toLong()
                println("Task $taskId will take ${sleepTime}ms")
                Thread.sleep(sleepTime)
                taskId
            }
        }

        // Process as they complete
        repeat(5) {
            val future = completionService.take()
            val result = future.get()
            println("Completed task: $result")
        }

        executor.shutdown()
    }
}

// 8. ForkJoin Pool (Parallel processing)
class ForkJoinPoolExample {

    fun parallelSum(): Int {
        val pool = ForkJoinPool()

        println("\n--- ForkJoin Pool ---")

        val task = RecursiveSumTask(1, 1000000)
        val result = pool.invoke(task)

        println("Parallel sum result: $result")
        pool.shutdown()

        return result
    }

    class RecursiveSumTask(private val start: Int, private val end: Int) : RecursiveTask<Int>() {
        override fun compute(): Int {
            return if (end - start <= 10000) {
                // Compute directly
                (start..end).sum()
            } else {
                // Split task
                val mid = (start + end) / 2
                val leftTask = RecursiveSumTask(start, mid)
                val rightTask = RecursiveSumTask(mid + 1, end)

                leftTask.fork()
                val rightResult = rightTask.compute()
                val leftResult = leftTask.join()

                leftResult + rightResult
            }
        }
    }
}

// Main demonstration
suspend fun demonstrateThreadPoolUsage() {
    println("=== Android Kotlin Thread Pool Examples ===\n")

    // 1. ExecutorService pools
    val executorPools = ExecutorServicePools()
    executorPools.fixedThreadPoolExample()
    delay(2000)
    executorPools.cachedThreadPoolExample()
    delay(2000)
    executorPools.singleThreadExecutorExample()
    delay(1000)
    executorPools.scheduledExecutorExample()

    // 2. Custom thread pool
    val customPool = CustomThreadPoolExample()
    customPool.customThreadPoolExample()

    delay(2000)

    // 3. Coroutine dispatchers
    println("\n--- Coroutine Dispatchers ---")
    val dispatcherExample = CoroutineDispatchersExample()
    dispatcherExample.mainDispatcherExample()
    dispatcherExample.ioDispatcherExample()
    dispatcherExample.defaultDispatcherExample()
    dispatcherExample.unconfinedDispatcherExample()
    dispatcherExample.customDispatcherExample()

    delay(2000)

    // 4. Async and await
    val asyncExample = CoroutineAsyncExample()
    asyncExample.parallelTasks()
    asyncExample.sequentialTasks()

    delay(3000)

    // 5. Future example
    val futureExample = FutureExample()
    futureExample.submitWithFuture()
    delay(2000)
    futureExample.invokeAllExample()

    delay(2000)

    // 6. Completion service
    val completionExample = CompletionServiceExample()
    completionExample.completionServiceDemo()

    delay(5000)

    // 7. ForkJoin pool
    val forkJoinExample = ForkJoinPoolExample()
    forkJoinExample.parallelSum()

    println("\n=== All Thread Pool Examples Completed ===")
}

// Synchronous entry point
fun demonstrateThreadPoolUsageSync() {
    runBlocking {
        demonstrateThreadPoolUsage()
    }
}