Примеры Сетевого Программирования Web Go

// Web Go HTTP Requests Examples
// Sending HTTP GET/POST requests with proper handling

package main

import (
	"bytes"
	"encoding/json"
	"fmt"
	"io/ioutil"
	"net/http"
	"net/url"
	"time"
)

// 1. Simple GET Request

// SimpleGet performs a simple HTTP GET request
func SimpleGet(url string) (string, error) {
	resp, err := http.Get(url)
	if err != nil {
		return "", fmt.Errorf("GET request failed: %v", err)
	}
	defer resp.Body.Close()

	body, err := ioutil.ReadAll(resp.Body)
	if err != nil {
		return "", fmt.Errorf("error reading response: %v", err)
	}

	if resp.StatusCode != http.StatusOK {
		return "", fmt.Errorf("unexpected status code: %d", resp.StatusCode)
	}

	return string(body), nil
}

// SimpleGetExample demonstrates simple GET request
func SimpleGetExample() {
	fmt.Println("--- Simple GET Request ---")

	url := "https://jsonplaceholder.typicode.com/posts/1"
	body, err := SimpleGet(url)
	if err != nil {
		fmt.Printf("Error: %v\n", err)
		return
	}

	fmt.Printf("Response: %s\n", body)
}

// 2. GET Request with Headers

// GetWithHeaders performs GET request with custom headers
func GetWithHeaders(url string, headers map[string]string) (string, error) {
	req, err := http.NewRequest("GET", url, nil)
	if err != nil {
		return "", err
	}

	// Add headers
	for key, value := range headers {
		req.Header.Set(key, value)
	}

	client := &http.Client{Timeout: 10 * time.Second}
	resp, err := client.Do(req)
	if err != nil {
		return "", fmt.Errorf("request failed: %v", err)
	}
	defer resp.Body.Close()

	body, err := ioutil.ReadAll(resp.Body)
	if err != nil {
		return "", fmt.Errorf("error reading response: %v", err)
	}

	return string(body), nil
}

// GetWithHeadersExample demonstrates GET with headers
func GetWithHeadersExample() {
	fmt.Println("\n--- GET with Headers ---")

	url := "https://jsonplaceholder.typicode.com/posts/1"
	headers := map[string]string{
		"Accept":        "application/json",
		"User-Agent":    "MyGoApp/1.0",
		"Authorization": "Bearer token123",
	}

	body, err := GetWithHeaders(url, headers)
	if err != nil {
		fmt.Printf("Error: %v\n", err)
		return
	}

	fmt.Printf("Response: %s\n", body)
}

// 3. GET Request with Query Parameters

// GetWithQueryParams performs GET with query parameters
func GetWithQueryParams(baseURL string, params map[string]string) (string, error) {
	// Build URL with query parameters
	u, err := url.Parse(baseURL)
	if err != nil {
		return "", err
	}

	query := u.Query()
	for key, value := range params {
		query.Set(key, value)
	}
	u.RawQuery = query.Encode()

	url = u.String()

	resp, err := http.Get(url)
	if err != nil {
		return "", fmt.Errorf("GET request failed: %v", err)
	}
	defer resp.Body.Close()

	body, err := ioutil.ReadAll(resp.Body)
	if err != nil {
		return "", fmt.Errorf("error reading response: %v", err)
	}

	return string(body), nil
}

// GetWithQueryParamsExample demonstrates GET with query parameters
func GetWithQueryParamsExample() {
	fmt.Println("\n--- GET with Query Parameters ---")

	baseURL := "https://jsonplaceholder.typicode.com/posts"
	params := map[string]string{
		"userId": "1",
		"_limit": "5",
	}

	body, err := GetWithQueryParams(baseURL, params)
	if err != nil {
		fmt.Printf("Error: %v\n", err)
		return
	}

	fmt.Printf("Response: %s\n", body)
}

// 4. POST Request with JSON Body

// PostJSON sends a POST request with JSON body
func PostJSON(url string, data map[string]interface{}) (string, error) {
	jsonData, err := json.Marshal(data)
	if err != nil {
		return "", fmt.Errorf("error marshaling JSON: %v", err)
	}

	resp, err := http.Post(url, "application/json", bytes.NewBuffer(jsonData))
	if err != nil {
		return "", fmt.Errorf("POST request failed: %v", err)
	}
	defer resp.Body.Close()

	body, err := ioutil.ReadAll(resp.Body)
	if err != nil {
		return "", fmt.Errorf("error reading response: %v", err)
	}

	if resp.StatusCode != http.StatusCreated && resp.StatusCode != http.StatusOK {
		return "", fmt.Errorf("unexpected status code: %d", resp.StatusCode)
	}

	return string(body), nil
}

// PostJSONExample demonstrates POST with JSON
func PostJSONExample() {
	fmt.Println("\n--- POST JSON Request ---")

	url := "https://jsonplaceholder.typicode.com/posts"
	data := map[string]interface{}{
		"title":  "Test Post",
		"body":   "This is a test post",
		"userId": 1,
	}

	body, err := PostJSON(url, data)
	if err != nil {
		fmt.Printf("Error: %v\n", err)
		return
	}

	fmt.Printf("Response: %s\n", body)
}

// 5. POST Request with Form Data

// PostForm sends a POST request with form data
func PostForm(url string, formData map[string]string) (string, error) {
	// Build form data
	values := url.Values{}
	for key, value := range formData {
		values.Set(key, value)
	}

	resp, err := http.PostForm(url, values)
	if err != nil {
		return "", fmt.Errorf("POST form request failed: %v", err)
	}
	defer resp.Body.Close()

	body, err := ioutil.ReadAll(resp.Body)
	if err != nil {
		return "", fmt.Errorf("error reading response: %v", err)
	}

	return string(body), nil
}

// PostFormExample demonstrates POST with form data
func PostFormExample() {
	fmt.Println("\n--- POST Form Request ---")

	url := "https://jsonplaceholder.typicode.com/posts"
	formData := map[string]string{
		"title":  "Test Form",
		"body":   "Form data content",
		"userId": "1",
	}

	body, err := PostForm(url, formData)
	if err != nil {
		fmt.Printf("Error: %v\n", err)
		return
	}

	fmt.Printf("Response: %s\n", body)
}

// 6. PUT Request

// PutJSON sends a PUT request with JSON body
func PutJSON(url string, data map[string]interface{}) (string, error) {
	jsonData, err := json.Marshal(data)
	if err != nil {
		return "", fmt.Errorf("error marshaling JSON: %v", err)
	}

	req, err := http.NewRequest("PUT", url, bytes.NewBuffer(jsonData))
	if err != nil {
		return "", err
	}

	req.Header.Set("Content-Type", "application/json")

	client := &http.Client{}
	resp, err := client.Do(req)
	if err != nil {
		return "", fmt.Errorf("PUT request failed: %v", err)
	}
	defer resp.Body.Close()

	body, err := ioutil.ReadAll(resp.Body)
	if err != nil {
		return "", fmt.Errorf("error reading response: %v", err)
	}

	return string(body), nil
}

// PutJSONExample demonstrates PUT request
func PutJSONExample() {
	fmt.Println("\n--- PUT Request ---")

	url := "https://jsonplaceholder.typicode.com/posts/1"
	data := map[string]interface{}{
		"id":     1,
		"title":  "Updated Post",
		"body":   "Updated content",
		"userId": 1,
	}

	body, err := PutJSON(url, data)
	if err != nil {
		fmt.Printf("Error: %v\n", err)
		return
	}

	fmt.Printf("Response: %s\n", body)
}

// 7. DELETE Request

// DeleteResource sends a DELETE request
func DeleteResource(url string) (int, error) {
	req, err := http.NewRequest("DELETE", url, nil)
	if err != nil {
		return 0, err
	}

	client := &http.Client{}
	resp, err := client.Do(req)
	if err != nil {
		return 0, fmt.Errorf("DELETE request failed: %v", err)
	}
	defer resp.Body.Close()

	return resp.StatusCode, nil
}

// DeleteRequestExample demonstrates DELETE request
func DeleteRequestExample() {
	fmt.Println("\n--- DELETE Request ---")

	url := "https://jsonplaceholder.typicode.com/posts/1"
	statusCode, err := DeleteResource(url)
	if err != nil {
		fmt.Printf("Error: %v\n", err)
		return
	}

	fmt.Printf("Status Code: %d\n", statusCode)
}

// 8. Custom HTTP Client with Timeout

// HTTPClient represents a custom HTTP client
type HTTPClient struct {
	client      *http.Client
	baseURL     string
	defaultHeaders map[string]string
}

// NewHTTPClient creates a new HTTP client
func NewHTTPClient(timeout time.Duration) *HTTPClient {
	return &HTTPClient{
		client: &http.Client{
			Timeout: timeout,
		},
		defaultHeaders: make(map[string]string),
	}
}

// SetBaseURL sets the base URL for requests
func (c *HTTPClient) SetBaseURL(baseURL string) {
	c.baseURL = baseURL
}

// SetDefaultHeader sets a default header for all requests
func (c *HTTPClient) SetDefaultHeader(key, value string) {
	c.defaultHeaders[key] = value
}

// Get performs a GET request
func (c *HTTPClient) Get(path string) (string, error) {
	url := c.baseURL + path
	req, err := http.NewRequest("GET", url, nil)
	if err != nil {
		return "", err
	}

	// Add default headers
	for key, value := range c.defaultHeaders {
		req.Header.Set(key, value)
	}

	resp, err := c.client.Do(req)
	if err != nil {
		return "", fmt.Errorf("GET request failed: %v", err)
	}
	defer resp.Body.Close()

	body, err := ioutil.ReadAll(resp.Body)
	if err != nil {
		return "", fmt.Errorf("error reading response: %v", err)
	}

	if resp.StatusCode >= 400 {
		return "", fmt.Errorf("HTTP error: %d", resp.StatusCode)
	}

	return string(body), nil
}

// Post performs a POST request
func (c *HTTPClient) Post(path string, data map[string]interface{}) (string, error) {
	url := c.baseURL + path
	jsonData, err := json.Marshal(data)
	if err != nil {
		return "", err
	}

	req, err := http.NewRequest("POST", url, bytes.NewBuffer(jsonData))
	if err != nil {
		return "", err
	}

	req.Header.Set("Content-Type", "application/json")

	// Add default headers
	for key, value := range c.defaultHeaders {
		if key != "Content-Type" {
			req.Header.Set(key, value)
		}
	}

	resp, err := c.client.Do(req)
	if err != nil {
		return "", fmt.Errorf("POST request failed: %v", err)
	}
	defer resp.Body.Close()

	body, err := ioutil.ReadAll(resp.Body)
	if err != nil {
		return "", fmt.Errorf("error reading response: %v", err)
	}

	if resp.StatusCode >= 400 {
		return "", fmt.Errorf("HTTP error: %d", resp.StatusCode)
	}

	return string(body), nil
}

// CustomClientExample demonstrates custom HTTP client
func CustomClientExample() {
	fmt.Println("\n--- Custom HTTP Client ---")

	client := NewHTTPClient(10 * time.Second)
	client.SetBaseURL("https://jsonplaceholder.typicode.com")
	client.SetDefaultHeader("User-Agent", "MyGoApp/1.0")

	// GET request
	body, err := client.Get("/posts/1")
	if err != nil {
		fmt.Printf("GET Error: %v\n", err)
		return
	}
	fmt.Printf("GET Response: %s\n", body)

	// POST request
	data := map[string]interface{}{
		"title":  "New Post",
		"body":   "Post content",
		"userId": 1,
	}

	body, err = client.Post("/posts", data)
	if err != nil {
		fmt.Printf("POST Error: %v\n", err)
		return
	}
	fmt.Printf("POST Response: %s\n", body)
}

// 9. Handling Response Headers

// GetWithResponseHeaders performs GET and returns headers
func GetWithResponseHeaders(url string) (string, http.Header, error) {
	resp, err := http.Get(url)
	if err != nil {
		return "", nil, err
	}
	defer resp.Body.Close()

	body, err := ioutil.ReadAll(resp.Body)
	if err != nil {
		return "", nil, err
	}

	return string(body), resp.Header, nil
}

// ResponseHeadersExample demonstrates reading response headers
func ResponseHeadersExample() {
	fmt.Println("\n--- Response Headers ---")

	url := "https://jsonplaceholder.typicode.com/posts/1"
	body, headers, err := GetWithResponseHeaders(url)
	if err != nil {
		fmt.Printf("Error: %v\n", err)
		return
	}

	fmt.Println("Response Headers:")
	for key, values := range headers {
		for _, value := range values {
			fmt.Printf("  %s: %s\n", key, value)
		}
	}

	fmt.Printf("\nBody: %s\n", body)
}

// 10. Request with Context (Timeout)

// GetWithContext performs GET with context timeout
func GetWithContext(url string, timeout time.Duration) (string, error) {
	ctx, cancel := context.WithTimeout(context.Background(), timeout)
	defer cancel()

	req, err := http.NewRequestWithContext(ctx, "GET", url, nil)
	if err != nil {
		return "", err
	}

	client := &http.Client{}
	resp, err := client.Do(req)
	if err != nil {
		return "", fmt.Errorf("request failed: %v", err)
	}
	defer resp.Body.Close()

	body, err := ioutil.ReadAll(resp.Body)
	if err != nil {
		return "", fmt.Errorf("error reading response: %v", err)
	}

	return string(body), nil
}

// ContextExample demonstrates context with timeout
func ContextExample() {
	fmt.Println("\n--- Request with Context Timeout ---")

	url := "https://jsonplaceholder.typicode.com/posts/1"

	body, err := GetWithContext(url, 5*time.Second)
	if err != nil {
		fmt.Printf("Error: %v\n", err)
		return
	}

	fmt.Printf("Response: %s\n", body)
}

// Main function
func main() {
	fmt.Println("=== Web Go HTTP Requests Examples ===\n")

	SimpleGetExample()
	GetWithHeadersExample()
	GetWithQueryParamsExample()
	PostJSONExample()
	PostFormExample()
	PutJSONExample()
	DeleteRequestExample()
	CustomClientExample()
	ResponseHeadersExample()
	ContextExample()

	fmt.Println("\n=== All HTTP Request Examples Completed ===")
}

// Web Go HTTP Server Examples
// Creating HTTP servers with routing and handlers

package main

import (
	"context"
	"encoding/json"
	"fmt"
	"io/ioutil"
	"log"
	"net/http"
	"strings"
	"time"
)

// 1. Basic HTTP Server

// BasicHTTPServer demonstrates a simple HTTP server
func BasicHTTPServerExample() {
	fmt.Println("--- Basic HTTP Server ---")

	// Define handler
	http.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
		fmt.Fprintf(w, "Hello, World!\n")
		fmt.Fprintf(w, "Path: %s\n", r.URL.Path)
		fmt.Fprintf(w, "Method: %s\n", r.Method)
	})

	http.HandleFunc("/about", func(w http.ResponseWriter, r *http.Request) {
		fmt.Fprintf(w, "About Page\n")
	})

	http.HandleFunc("/contact", func(w http.ResponseWriter, r *http.Request) {
		fmt.Fprintf(w, "Contact Page\n")
	})

	fmt.Println("Server starting on http://localhost:8080")
	// In real usage: log.Fatal(http.ListenAndServe(":8080", nil))
	fmt.Println("(Server would run here)")
}

// 2. Server with Custom ServeMux

// CustomServeMuxExample demonstrates using custom ServeMux
func CustomServeMuxExample() {
	fmt.Println("\n--- Custom ServeMux ---")

	mux := http.NewServeMux()

	mux.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
		fmt.Fprintf(w, "Home Page\n")
	})

	mux.HandleFunc("/api", func(w http.ResponseWriter, r *http.Request) {
		fmt.Fprintf(w, "API Endpoint\n")
	})

	mux.HandleFunc("/health", func(w http.ResponseWriter, r *http.Request) {
		w.Header().Set("Content-Type", "application/json")
		json.NewEncoder(w).Encode(map[string]string{"status": "healthy"})
	})

	server := &http.Server{
		Addr:    ":8080",
		Handler: mux,
	}

	fmt.Println("Server configured on :8080")
	// In real usage: log.Fatal(server.ListenAndServe())
	fmt.Println("(Server would run here)")
}

// 3. RESTful API Server

// Post represents a blog post
type Post struct {
	ID     int    `json:"id"`
	Title  string `json:"title"`
	Body   string `json:"body"`
	UserID int    `json:"userId"`
}

var posts = []Post{
	{ID: 1, Title: "First Post", Body: "Content 1", UserID: 1},
	{ID: 2, Title: "Second Post", Body: "Content 2", UserID: 1},
}

// RestfulAPIServer demonstrates RESTful API server
func RestfulAPIServerExample() {
	fmt.Println("\n--- RESTful API Server ---")

	mux := http.NewServeMux()

	// GET /posts - get all posts
	mux.HandleFunc("/posts", func(w http.ResponseWriter, r *http.Request) {
		if r.Method == http.MethodGet {
			w.Header().Set("Content-Type", "application/json")
			json.NewEncoder(w).Encode(posts)
		} else {
			http.Error(w, "Method not allowed", http.StatusMethodNotAllowed)
		}
	})

	// GET /posts/{id} - get single post
	mux.HandleFunc("/posts/", func(w http.ResponseWriter, r *http.Request) {
		if r.Method == http.MethodGet {
			// Extract ID from URL path
			idStr := strings.TrimPrefix(r.URL.Path, "/posts/")
			var id int
			fmt.Sscanf(idStr, "%d", &id)

			for _, post := range posts {
				if post.ID == id {
					w.Header().Set("Content-Type", "application/json")
					json.NewEncoder(w).Encode(post)
					return
				}
			}

			http.Error(w, "Post not found", http.StatusNotFound)
		} else {
			http.Error(w, "Method not allowed", http.StatusMethodNotAllowed)
		}
	})

	// POST /posts - create new post
	mux.HandleFunc("/posts/create", func(w http.ResponseWriter, r *http.Request) {
		if r.Method == http.MethodPost {
			var newPost Post
			err := json.NewDecoder(r.Body).Decode(&newPost)
			if err != nil {
				http.Error(w, "Invalid request body", http.StatusBadRequest)
				return
			}

			newPost.ID = len(posts) + 1
			posts = append(posts, newPost)

			w.Header().Set("Content-Type", "application/json")
			w.WriteHeader(http.StatusCreated)
			json.NewEncoder(w).Encode(newPost)
		} else {
			http.Error(w, "Method not allowed", http.StatusMethodNotAllowed)
		}
	})

	fmt.Println("RESTful API Server configured")
	// In real usage: log.Fatal(http.ListenAndServe(":8080", mux))
	fmt.Println("(Server would run here)")
}

// 4. Server with Middleware

// LoggerMiddleware logs all requests
func LoggerMiddleware(next http.Handler) http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		start := time.Now()
		fmt.Printf("[%s] %s %s\n", start.Format("2006-01-02 15:04:05"), r.Method, r.URL.Path)

		// Call next handler
		next.ServeHTTP(w, r)

		fmt.Printf("Completed in %v\n", time.Since(start))
	})
}

// CORSMiddleware adds CORS headers
func CORSMiddleware(next http.Handler) http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		w.Header().Set("Access-Control-Allow-Origin", "*")
		w.Header().Set("Access-Control-Allow-Methods", "GET, POST, PUT, DELETE, OPTIONS")
		w.Header().Set("Access-Control-Allow-Headers", "Content-Type, Authorization")

		if r.Method == "OPTIONS" {
			w.WriteHeader(http.StatusOK)
			return
		}

		next.ServeHTTP(w, r)
	})
}

// AuthMiddleware validates authentication
func AuthMiddleware(next http.Handler) http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		token := r.Header.Get("Authorization")

		if token == "" {
			http.Error(w, "Unauthorized", http.StatusUnauthorized)
			return
		}

		if token != "Bearer valid-token" {
			http.Error(w, "Forbidden", http.StatusForbidden)
			return
		}

		next.ServeHTTP(w, r)
	})
}

// MiddlewareServerExample demonstrates server with middleware
func MiddlewareServerExample() {
	fmt.Println("\n--- Server with Middleware ---")

	mux := http.NewServeMux()

	mux.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
		fmt.Fprintf(w, "Public endpoint\n")
	})

	mux.HandleFunc("/protected", func(w http.ResponseWriter, r *http.Request) {
		fmt.Fprintf(w, "Protected endpoint\n")
	})

	// Wrap middleware
	handler := CORSMiddleware(LoggerMiddleware(mux))

	server := &http.Server{
		Addr:    ":8080",
		Handler: handler,
	}

	fmt.Println("Server with middleware configured")
	// In real usage: log.Fatal(server.ListenAndServe())
	fmt.Println("(Server would run here)")
}

// 5. Server with Query Parameters

// QueryParamsServer demonstrates handling query parameters
func QueryParamsServerExample() {
	fmt.Println("\n--- Server with Query Parameters ---")

	mux := http.NewServeMux()

	mux.HandleFunc("/search", func(w http.ResponseWriter, r *http.Request) {
		query := r.URL.Query()
		keyword := query.Get("q")
		page := query.Get("page")
		limit := query.Get("limit")

		result := map[string]interface{}{
			"keyword": keyword,
			"page":    page,
			"limit":   limit,
			"results": []string{"Result 1", "Result 2", "Result 3"},
		}

		w.Header().Set("Content-Type", "application/json")
		json.NewEncoder(w).Encode(result)
	})

	fmt.Println("Server with query parameters configured")
}

// 6. Static File Server

// StaticFileServerExample demonstrates serving static files
func StaticFileServerExample() {
	fmt.Println("\n--- Static File Server ---")

	mux := http.NewServeMux()

	// Serve static files from ./static directory
	fs := http.FileServer(http.Dir("./static"))
	mux.Handle("/static/", http.StripPrefix("/static/", fs))

	mux.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
		fmt.Fprintf(w, "Welcome! Static files at /static/\n")
	})

	fmt.Println("Static file server configured")
	// In real usage: log.Fatal(http.ListenAndServe(":8080", mux))
}

// 7. Server with Graceful Shutdown

// GracefulShutdownExample demonstrates graceful shutdown
func GracefulShutdownExample() {
	fmt.Println("\n--- Graceful Shutdown ---")

	mux := http.NewServeMux()

	mux.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
		fmt.Fprintf(w, "Server running\n")
	})

	server := &http.Server{
		Addr:    ":8080",
		Handler: mux,
	}

	// Start server in goroutine
	go func() {
		fmt.Println("Server starting...")
		// In real usage: if err := server.ListenAndServe(); err != nil && err != http.ErrServerClosed {
		// 	log.Fatal(err)
		// }
	}()

	// Simulate graceful shutdown
	time.Sleep(1 * time.Second)

	ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
	defer cancel()

	fmt.Println("Shutting down server...")
	// In real usage: if err := server.Shutdown(ctx); err != nil {
	// 	log.Printf("Server shutdown error: %v", err)
	// }

	fmt.Println("Server gracefully stopped")
}

// 8. JSON Request/Response Handler

// User represents a user
type User struct {
	Name  string `json:"name"`
	Email string `json:"email"`
}

// JSONHandlerExample demonstrates JSON handling
func JSONHandlerExample() {
	fmt.Println("\n--- JSON Request/Response Handler ---")

	mux := http.NewServeMux()

	mux.HandleFunc("/api/user", func(w http.ResponseWriter, r *http.Request) {
		switch r.Method {
		case http.MethodPost:
			var user User
			err := json.NewDecoder(r.Body).Decode(&user)
			if err != nil {
				http.Error(w, "Invalid JSON", http.StatusBadRequest)
				return
			}

			w.Header().Set("Content-Type", "application/json")
			w.WriteHeader(http.StatusCreated)
			json.NewEncoder(w).Encode(map[string]interface{}{
				"message": "User created",
				"user":    user,
			})

		default:
			http.Error(w, "Method not allowed", http.StatusMethodNotAllowed)
		}
	})

	fmt.Println("JSON handler configured")
}

// 9. File Upload Handler

// FileUploadExample demonstrates file upload handling
func FileUploadExample() {
	fmt.Println("\n--- File Upload Handler ---")

	mux := http.NewServeMux()

	mux.HandleFunc("/upload", func(w http.ResponseWriter, r *http.Request) {
		if r.Method != http.MethodPost {
			http.Error(w, "Method not allowed", http.StatusMethodNotAllowed)
			return
		}

		// Parse multipart form (max 10MB)
		err := r.ParseMultipartForm(10 << 20)
		if err != nil {
			http.Error(w, "Unable to parse form", http.StatusBadRequest)
			return
		}

		// Get file from form
		file, handler, err := r.FormFile("file")
		if err != nil {
			http.Error(w, "Error retrieving file", http.StatusBadRequest)
			return
		}
		defer file.Close()

		fmt.Printf("Uploaded file: %s (%d bytes)\n", handler.Filename, handler.Size)

		// Read file content
		fileBytes, err := ioutil.ReadAll(file)
		if err != nil {
			http.Error(w, "Error reading file", http.StatusInternalServerError)
			return
		}

		w.WriteHeader(http.StatusOK)
		fmt.Fprintf(w, "File uploaded successfully: %s (%d bytes)\n", handler.Filename, len(fileBytes))
	})

	fmt.Println("File upload handler configured")
}

// 10. Server with TLS/HTTPS

// HTTPSServerExample demonstrates HTTPS server
func HTTPSServerExample() {
	fmt.Println("\n--- HTTPS Server ---")

	mux := http.NewServeMux()

	mux.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
		fmt.Fprintf(w, "Secure connection!\n")
	})

	// Server configuration
	server := &http.Server{
		Addr:    ":8443",
		Handler: mux,
	}

	fmt.Println("HTTPS server configured on :8443")
	// In real usage:
	// log.Fatal(server.ListenAndServeTLS("server.crt", "server.key"))
	fmt.Println("(HTTPS server would run here)")
}

// Main function
func main() {
	fmt.Println("=== Web Go HTTP Server Examples ===\n")

	BasicHTTPServerExample()
	CustomServeMuxExample()
	RestfulAPIServerExample()
	MiddlewareServerExample()
	QueryParamsServerExample()
	StaticFileServerExample()
	GracefulShutdownExample()
	JSONHandlerExample()
	FileUploadExample()
	HTTPSServerExample()

	fmt.Println("\n=== All HTTP Server Examples Completed ===")
}

// Web Go TCP Sockets Examples
// TCP socket programming for network communication

package main

import (
	"bufio"
	"encoding/binary"
	"fmt"
	"io"
	"net"
	"strings"
	"time"
)

// 1. TCP Client

// TCPClient connects to a TCP server
func TCPClient(host string, port int) (net.Conn, error) {
	address := fmt.Sprintf("%s:%d", host, port)
	conn, err := net.Dial("tcp", address)
	if err != nil {
		return nil, fmt.Errorf("failed to connect: %v", err)
	}

	fmt.Printf("Connected to %s\n", address)
	return conn, nil
}

// TCPClientExample demonstrates TCP client
func TCPClientExample() {
	fmt.Println("--- TCP Client ---")

	// Note: This example requires a running TCP server
	conn, err := TCPClient("localhost", 8080)
	if err != nil {
		fmt.Printf("Error: %v\n", err)
		fmt.Println("(Note: This requires a running TCP server)")
		return
	}
	defer conn.Close()

	// Send data
	message := "Hello, TCP Server!\n"
	_, err = conn.Write([]byte(message))
	if err != nil {
		fmt.Printf("Error writing: %v\n", err)
		return
	}

	fmt.Printf("Sent: %s", message)

	// Read response
	buffer := make([]byte, 1024)
	n, err := conn.Read(buffer)
	if err != nil {
		fmt.Printf("Error reading: %v\n", err)
		return
	}

	fmt.Printf("Received: %s\n", string(buffer[:n]))
}

// 2. TCP Server

// TCPServer starts a simple TCP server
func TCPServer(port int) error {
	address := fmt.Sprintf(":%d", port)
	listener, err := net.Listen("tcp", address)
	if err != nil {
		return fmt.Errorf("failed to listen: %v", err)
	}
	defer listener.Close()

	fmt.Printf("TCP Server listening on %s\n", address)

	for {
		conn, err := listener.Accept()
		if err != nil {
			fmt.Printf("Error accepting connection: %v\n", err)
			continue
		}

		fmt.Printf("New connection from %s\n", conn.RemoteAddr())

		// Handle connection in goroutine
		go handleConnection(conn)
	}
}

// handleConnection handles a client connection
func handleConnection(conn net.Conn) {
	defer conn.Close()

	remoteAddr := conn.RemoteAddr().String()
	fmt.Printf("Handling connection from %s\n", remoteAddr)

	// Read data
	buffer := make([]byte, 1024)
	n, err := conn.Read(buffer)
	if err != nil {
		fmt.Printf("Error reading from %s: %v\n", remoteAddr, err)
		return
	}

	fmt.Printf("Received from %s: %s\n", remoteAddr, string(buffer[:n]))

	// Send response
	response := fmt.Sprintf("Echo: %s", string(buffer[:n]))
	_, err = conn.Write([]byte(response))
	if err != nil {
		fmt.Printf("Error writing to %s: %v\n", remoteAddr, err)
		return
	}

	fmt.Printf("Response sent to %s\n", remoteAddr)
}

// TCPServerExample demonstrates TCP server
func TCPServerExample() {
	fmt.Println("\n--- TCP Server ---")

	fmt.Println("Starting TCP server on :8080")
	fmt.Println("(In production, server.ListenAndServe() would block here)")

	// In real usage:
	// err := TCPServer(8080)
	// if err != nil {
	// 	log.Fatal(err)
	// }

	// For demonstration, just show the concept
	conn, err := net.Listen("tcp", ":8080")
	if err != nil {
		fmt.Printf("Error: %v\n", err)
		return
	}
	defer conn.Close()

	fmt.Println("Server would accept connections here")
}

// 3. TCP Client with Timeout

// TCPClientWithTimeout connects with timeout
func TCPClientWithTimeout(host string, port int, timeout time.Duration) (net.Conn, error) {
	address := fmt.Sprintf("%s:%d", host, port)

	conn, err := net.DialTimeout("tcp", address, timeout)
	if err != nil {
		return nil, fmt.Errorf("connection timeout: %v", err)
	}

	fmt.Printf("Connected to %s (with timeout)\n", address)
	return conn, nil
}

// TimeoutClientExample demonstrates client with timeout
func TimeoutClientExample() {
	fmt.Println("\n--- TCP Client with Timeout ---")

	conn, err := TCPClientWithTimeout("localhost", 8080, 5*time.Second)
	if err != nil {
		fmt.Printf("Error: %v\n", err)
		fmt.Println("(Note: This requires a running TCP server)")
		return
	}
	defer conn.Close()

	fmt.Println("Connection established with timeout")
}

// 4. Bidirectional Communication

// ChatClient demonstrates bidirectional chat
func ChatClient(host string, port int) error {
	address := fmt.Sprintf("%s:%d", host, port)
	conn, err := net.Dial("tcp", address)
	if err != nil {
		return err
	}
	defer conn.Close()

	fmt.Printf("Connected to chat server %s\n", address)

	// Start goroutine to read messages
	go func() {
		scanner := bufio.NewScanner(conn)
		for scanner.Scan() {
			fmt.Printf("Server: %s\n", scanner.Text())
		}
	}()

	// Read from stdin and send to server
	scanner := bufio.NewScanner(conn)
	for scanner.Scan() {
		text := scanner.Text()
		if strings.ToLower(text) == "quit" {
			break
		}

		_, err := conn.Write([]byte(text + "\n"))
		if err != nil {
			return err
		}
	}

	return nil
}

// BidirectionalExample demonstrates bidirectional communication
func BidirectionalExample() {
	fmt.Println("\n--- Bidirectional Communication ---")

	fmt.Println("Chat client (requires running chat server)")
	fmt.Println("(In production, would run ChatClient here)")
}

// 5. UDP Client/Server

// UDPServer starts a UDP server
func UDPServer(port int) error {
	address := fmt.Sprintf(":%d", port)
	conn, err := net.ListenPacket("udp", address)
	if err != nil {
		return fmt.Errorf("failed to listen: %v", err)
	}
	defer conn.Close()

	fmt.Printf("UDP Server listening on %s\n", address)

	buffer := make([]byte, 1024)
	for {
		n, addr, err := conn.ReadFrom(buffer)
		if err != nil {
			fmt.Printf("Error reading: %v\n", err)
			continue
		}

		fmt.Printf("Received from %s: %s\n", addr, string(buffer[:n]))

		// Send response
		response := []byte("UDP Acknowledgment")
		_, err = conn.WriteTo(response, addr)
		if err != nil {
			fmt.Printf("Error writing: %v\n", err)
		}
	}
}

// UDPClient sends data to UDP server
func UDPClient(host string, port int, message string) error {
	address := fmt.Sprintf("%s:%d", host, port)
	conn, err := net.Dial("udp", address)
	if err != nil {
		return fmt.Errorf("failed to connect: %v", err)
	}
	defer conn.Close()

	fmt.Printf("Sending to %s: %s\n", address, message)

	_, err = conn.Write([]byte(message))
	if err != nil {
		return fmt.Errorf("error sending: %v", err)
	}

	// Read response
	buffer := make([]byte, 1024)
	n, err := conn.Read(buffer)
	if err != nil {
		return fmt.Errorf("error reading: %v", err)
	}

	fmt.Printf("Received: %s\n", string(buffer[:n]))
	return nil
}

// UDPExample demonstrates UDP communication
func UDPExample() {
	fmt.Println("\n--- UDP Client/Server ---")

	fmt.Println("UDP Server starting on :8081")
	fmt.Println("(In production, UDPServer would run here)")

	// Client example
	fmt.Println("\nUDP Client (requires running UDP server)")
	err := UDPClient("localhost", 8081, "Hello UDP!")
	if err != nil {
		fmt.Printf("Error: %v\n", err)
	}
}

// 6. Protocol Buffers over TCP

// SendBinaryMessage sends binary data with length prefix
func SendBinaryMessage(conn net.Conn, data []byte) error {
	// Send message length first (4 bytes)
	length := uint32(len(data))
	err := binary.Write(conn, binary.BigEndian, length)
	if err != nil {
		return fmt.Errorf("error writing length: %v", err)
	}

	// Send data
	_, err = conn.Write(data)
	if err != nil {
		return fmt.Errorf("error writing data: %v", err)
	}

	return nil
}

// ReceiveBinaryMessage receives binary data with length prefix
func ReceiveBinaryMessage(conn net.Conn) ([]byte, error) {
	// Read message length
	var length uint32
	err := binary.Read(conn, binary.BigEndian, &length)
	if err != nil {
		return nil, fmt.Errorf("error reading length: %v", err)
	}

	// Read data
	data := make([]byte, length)
	_, err = io.ReadFull(conn, data)
	if err != nil {
		return nil, fmt.Errorf("error reading data: %v", err)
	}

	return data, nil
}

// BinaryProtocolExample demonstrates binary protocol
func BinaryProtocolExample() {
	fmt.Println("\n--- Binary Protocol over TCP ---")

	fmt.Println("Binary protocol demonstration")
	fmt.Println("(Would use SendBinaryMessage and ReceiveBinaryMessage)")
}

// 7. Connection Pool

// ConnPool represents a connection pool
type ConnPool struct {
	conns chan net.Conn
	factory func() (net.Conn, error)
}

// NewConnPool creates a new connection pool
func NewConnPool(size int, factory func() (net.Conn, error)) (*ConnPool, error) {
	pool := &ConnPool{
		conns:   make(chan net.Conn, size),
		factory: factory,
	}

	// Initialize connections
	for i := 0; i < size; i++ {
		conn, err := factory()
		if err != nil {
			return nil, err
		}
		pool.conns <- conn
	}

	return pool, nil
}

// Get gets a connection from the pool
func (p *ConnPool) Get() (net.Conn, error) {
	select {
	case conn := <-p.conns:
		return conn, nil
	default:
		// Pool exhausted, create new connection
		return p.factory()
	}
}

// Put returns a connection to the pool
func (p *ConnPool) Put(conn net.Conn) {
	select {
	case p.conns <- conn:
		// Connection returned to pool
	default:
		// Pool full, close connection
		conn.Close()
	}
}

// Close closes all connections in the pool
func (p *ConnPool) Close() {
	close(p.conns)
	for conn := range p.conns {
		conn.Close()
	}
}

// ConnectionPoolExample demonstrates connection pooling
func ConnectionPoolExample() {
	fmt.Println("\n--- Connection Pool ---")

	// Create pool
	pool, err := NewConnPool(3, func() (net.Conn, error) {
		return net.Dial("tcp", "localhost:8080")
	})

	if err != nil {
		fmt.Printf("Error creating pool: %v\n", err)
		fmt.Println("(Note: This requires a running TCP server)")
		return
	}

	defer pool.Close()

	// Get connection
	conn, err := pool.Get()
	if err != nil {
		fmt.Printf("Error getting connection: %v\n", err)
		return
	}

	fmt.Printf("Got connection from pool: %v\n", conn.RemoteAddr())

	// Return connection
	pool.Put(conn)

	fmt.Println("Connection returned to pool")
}

// 8. Socket Options

// SetSocketOptions configures socket options
func SetSocketOptions(conn net.Conn) error {
	tcpConn, ok := conn.(*net.TCPConn)
	if !ok {
		return fmt.Errorf("not a TCP connection")
	}

	// Set keep-alive
	err := tcpConn.SetKeepAlive(true)
	if err != nil {
		return fmt.Errorf("error setting keep-alive: %v", err)
	}

	// Set keep-alive period
	err = tcpConn.SetKeepAlivePeriod(30 * time.Second)
	if err != nil {
		return fmt.Errorf("error setting keep-alive period: %v", err)
	}

	// Set no delay
	err = tcpConn.SetNoDelay(true)
	if err != nil {
		return fmt.Errorf("error setting no delay: %v", err)
	}

	return nil
}

// SocketOptionsExample demonstrates socket options
func SocketOptionsExample() {
	fmt.Println("\n--- Socket Options ---")

	fmt.Println("Socket options configured (keep-alive, no delay)")
	fmt.Println("(Would use SetSocketOptions on TCP connections)")
}

// Main function
func main() {
	fmt.Println("=== Web Go TCP Sockets Examples ===\n")

	TCPClientExample()
	TCPServerExample()
	TimeoutClientExample()
	BidirectionalExample()
	UDPExample()
	BinaryProtocolExample()
	ConnectionPoolExample()
	SocketOptionsExample()

	fmt.Println("\n=== All TCP Sockets Examples Completed ===")
}