mirror of
https://github.com/andwati/telecom-platform.git
synced 2026-10-23 05:02:17 +00:00
feat: Add comprehensive ETag middleware with content-based generation, validation, and cache invalidation support
- Add ResponseWriterWrapper struct with Write/Body methods for response body capture - Add ETagData/ETagGenerator structs with GenerateETag/GenerateWeakETag/GetCachedETag/CacheETag/InvalidateCache methods for sophisticated ETag generation and caching - Add generateETag/generateContentETag/generateWeakETag helper functions with path/method/content/timestamp/user context hashing - Add ETagValid
This commit is contained in:
nutcas3
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package middleware
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import (
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"bytes"
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"crypto/sha256"
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"fmt"
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"net/http"
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"strings"
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"sync"
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"time"
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"github.com/gin-gonic/gin"
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)
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// ResponseWriterWrapper wraps gin.ResponseWriter to capture response body
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type ResponseWriterWrapper struct {
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gin.ResponseWriter
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body *bytes.Buffer
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}
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// Write captures the response body while writing to the original writer
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func (w *ResponseWriterWrapper) Write(data []byte) (int, error) {
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w.body.Write(data)
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return w.ResponseWriter.Write(data)
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}
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// Body returns the captured response body
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func (w *ResponseWriterWrapper) Body() []byte {
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return w.body.Bytes()
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}
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// ETagData represents the components used for ETag generation
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type ETagData struct {
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Path string
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Method string
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Content []byte
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Timestamp time.Time
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UserID string
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Params string
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}
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// ETagGenerator handles sophisticated ETag generation
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type ETagGenerator struct {
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secretKey []byte
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cacheStorage sync.Map // For storing computed ETags
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}
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// NewETagGenerator creates a new ETag generator instance
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func NewETagGenerator(secretKey string) *ETagGenerator {
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return &ETagGenerator{
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secretKey: []byte(secretKey),
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}
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}
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// GenerateETag creates a sophisticated ETag based on multiple factors
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func (g *ETagGenerator) GenerateETag(data ETagData) string {
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// Create a composite hash from multiple factors
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h := sha256.New()
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// Include path and method
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h.Write([]byte(data.Path))
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h.Write([]byte(data.Method))
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// Include content if available
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if len(data.Content) > 0 {
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h.Write(data.Content)
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}
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// Include timestamp (rounded to second for consistency)
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timestampBytes := []byte(fmt.Sprintf("%d", data.Timestamp.Unix()))
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h.Write(timestampBytes)
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// Include user context for personalized responses
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if data.UserID != "" {
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h.Write([]byte(data.UserID))
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}
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// Include query parameters for cache differentiation
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if data.Params != "" {
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h.Write([]byte(data.Params))
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}
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// Add secret key for security
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h.Write(g.secretKey)
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// Generate final ETag
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hash := h.Sum(nil)
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return fmt.Sprintf("\"%x\"", hash)
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}
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// GenerateWeakETag creates a weak ETag for dynamic content
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func (g *ETagGenerator) GenerateWeakETag(data ETagData) string {
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etag := g.GenerateETag(data)
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return "W/" + etag
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}
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// GetCachedETag retrieves a cached ETag if available
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func (g *ETagGenerator) GetCachedETag(key string) (string, bool) {
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if cached, ok := g.cacheStorage.Load(key); ok {
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if etag, ok := cached.(string); ok {
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return etag, true
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}
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}
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return "", false
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}
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// CacheETag stores an ETag in the cache
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func (g *ETagGenerator) CacheETag(key, etag string) {
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g.cacheStorage.Store(key, etag)
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}
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// InvalidateCache removes ETag entries matching a pattern
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func (g *ETagGenerator) InvalidateCache(pattern string) {
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g.cacheStorage.Range(func(key, value interface{}) bool {
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if keyStr, ok := key.(string); ok {
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if strings.Contains(keyStr, pattern) {
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g.cacheStorage.Delete(key)
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}
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}
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return true
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})
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}
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// Global ETag generator instance
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var etagGenerator = NewETagGenerator("telecom-platform-etag-secret")
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// generateETag generates a sophisticated ETag for caching
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func generateETag(c *gin.Context) string {
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// Extract relevant data for ETag generation
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data := ETagData{
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Path: c.Request.URL.Path,
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Method: c.Request.Method,
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Timestamp: time.Now(),
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Params: c.Request.URL.RawQuery,
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}
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// Add user context if available
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if userID, exists := c.Get("user_id"); exists {
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if idStr, ok := userID.(string); ok {
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data.UserID = idStr
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}
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}
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// Try to get cached ETag first
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cacheKey := fmt.Sprintf("%s:%s:%s", data.Method, data.Path, data.Params)
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if cached, exists := etagGenerator.GetCachedETag(cacheKey); exists {
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return cached
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}
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// Generate new ETag
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etag := etagGenerator.GenerateETag(data)
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// Cache the ETag for future use
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etagGenerator.CacheETag(cacheKey, etag)
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return etag
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}
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// generateContentETag creates an ETag based on response content
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func generateContentETag(c *gin.Context, content []byte) string {
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data := ETagData{
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Path: c.Request.URL.Path,
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Method: c.Request.Method,
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Content: content,
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Timestamp: time.Now(),
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Params: c.Request.URL.RawQuery,
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}
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// Add user context if available
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if userID, exists := c.Get("user_id"); exists {
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if idStr, ok := userID.(string); ok {
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data.UserID = idStr
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}
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}
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return etagGenerator.GenerateETag(data)
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}
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// generateWeakETag creates a weak ETag for dynamic content
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func generateWeakETag(c *gin.Context) string {
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data := ETagData{
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Path: c.Request.URL.Path,
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Method: c.Request.Method,
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Timestamp: time.Now(),
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Params: c.Request.URL.RawQuery,
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}
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// Add user context if available
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if userID, exists := c.Get("user_id"); exists {
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if idStr, ok := userID.(string); ok {
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data.UserID = idStr
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}
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}
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return etagGenerator.GenerateWeakETag(data)
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}
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// ETagValidationMiddleware handles ETag validation for conditional requests
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func ETagValidationMiddleware() gin.HandlerFunc {
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return func(c *gin.Context) {
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// Only handle GET and HEAD requests for ETag validation
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if c.Request.Method != "GET" && c.Request.Method != "HEAD" {
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c.Next()
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return
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}
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// Check If-None-Match header (for GET requests)
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if noneMatch := c.GetHeader("If-None-Match"); noneMatch != "" {
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// Generate current ETag
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currentETag := generateETag(c)
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// Check if any of the ETags match
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if etagMatches(noneMatch, currentETag) {
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c.Header("ETag", currentETag)
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c.Status(http.StatusNotModified)
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c.Abort()
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return
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}
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}
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// Check If-Match header (for PUT/PATCH/DELETE requests)
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if match := c.GetHeader("If-Match"); match != "" {
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currentETag := generateETag(c)
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if !etagMatches(match, currentETag) {
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c.Status(http.StatusPreconditionFailed)
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c.Abort()
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return
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}
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}
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c.Next()
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}
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}
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// ContentBasedETagMiddleware generates ETags based on response content
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func ContentBasedETagMiddleware() gin.HandlerFunc {
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return func(c *gin.Context) {
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// Wrap the response writer to capture the body
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wrapper := &ResponseWriterWrapper{
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ResponseWriter: c.Writer,
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body: bytes.NewBuffer(nil),
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}
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c.Writer = wrapper
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c.Next()
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// Only generate ETags for successful GET requests
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if c.Request.Method != "GET" || c.Writer.Status() != http.StatusOK {
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return
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}
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// Generate ETag based on captured response content
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responseBody := wrapper.Body()
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if len(responseBody) > 0 {
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etag := generateContentETag(c, responseBody)
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c.Header("ETag", etag)
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} else {
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// Fallback to weak ETag for empty responses
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etag := generateWeakETag(c)
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c.Header("ETag", etag)
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}
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}
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}
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// CacheInvalidationMiddleware handles cache invalidation for modified resources
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func CacheInvalidationMiddleware() gin.HandlerFunc {
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return func(c *gin.Context) {
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// Store original request for post-processing
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c.Next()
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// Invalidate cache for POST, PUT, PATCH, DELETE requests
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if c.Request.Method == "POST" || c.Request.Method == "PUT" ||
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c.Request.Method == "PATCH" || c.Request.Method == "DELETE" {
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// Invalidate ETags for this resource pattern
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pattern := c.Request.URL.Path
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etagGenerator.InvalidateCache(pattern)
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// Also invalidate related collection resources
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if strings.Contains(pattern, "/") {
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parts := strings.Split(strings.Trim(pattern, "/"), "/")
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if len(parts) > 0 {
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collectionPattern := "/" + parts[0]
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etagGenerator.InvalidateCache(collectionPattern)
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}
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}
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}
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}
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}
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// etagMatches checks if any of the provided ETags match the current ETag
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func etagMatches(headerValue, currentETag string) bool {
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// Handle wildcard
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if headerValue == "*" {
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return true
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}
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// Parse the header value (can contain multiple ETags)
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etags := strings.Split(headerValue, ",")
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for _, etag := range etags {
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etag = strings.TrimSpace(etag)
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// Remove quotes for comparison
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etag = strings.Trim(etag, "\"")
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current := strings.Trim(currentETag, "\"W/")
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if etag == current || etag == "W/"+current {
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return true
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}
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}
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return false
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}
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