small fix, don't worry about it

app/backend/internal/middleware/ratelimit.go

@@ -0,0 +1,167 @@
+package middleware
+
+import (
+	"net/http"
+	"sync"
+	"time"
+
+	"github.com/gin-gonic/gin"
+)
+
+// RateLimiter implements a token bucket rate limiter
+type RateLimiter struct {
+	mu       sync.RWMutex
+	buckets  map[string]*bucket
+	rate     int           // requests per window
+	window   time.Duration // time window
+	cleanupInterval time.Duration
+}
+
+type bucket struct {
+	tokens    int
+	lastReset time.Time
+	mu        sync.Mutex
+}
+
+// NewRateLimiter creates a new rate limiter
+func NewRateLimiter(rate int, window time.Duration) *RateLimiter {
+	rl := &RateLimiter{
+		buckets:  make(map[string]*bucket),
+		rate:     rate,
+		window:   window,
+		cleanupInterval: window * 2,
+	}
+	
+	// Start cleanup goroutine
+	go rl.cleanup()
+	
+	return rl
+}
+
+// Allow checks if a request should be allowed
+func (rl *RateLimiter) Allow(key string) bool {
+	rl.mu.RLock()
+	b, exists := rl.buckets[key]
+	rl.mu.RUnlock()
+
+	if !exists {
+		rl.mu.Lock()
+		b = &bucket{
+			tokens:    rl.rate,
+			lastReset: time.Now(),
+		}
+		rl.buckets[key] = b
+		rl.mu.Unlock()
+	}
+
+	b.mu.Lock()
+	defer b.mu.Unlock()
+
+	// Reset bucket if window has passed
+	if time.Since(b.lastReset) > rl.window {
+		b.tokens = rl.rate
+		b.lastReset = time.Now()
+	}
+
+	if b.tokens > 0 {
+		b.tokens--
+		return true
+	}
+
+	return false
+}
+
+// cleanup removes old buckets
+func (rl *RateLimiter) cleanup() {
+	ticker := time.NewTicker(rl.cleanupInterval)
+	defer ticker.Stop()
+
+	for range ticker.C {
+		rl.mu.Lock()
+		now := time.Now()
+		for key, b := range rl.buckets {
+			b.mu.Lock()
+			if now.Sub(b.lastReset) > rl.cleanupInterval {
+				delete(rl.buckets, key)
+			}
+			b.mu.Unlock()
+		}
+		rl.mu.Unlock()
+	}
+}
+
+// RateLimit returns a middleware that limits requests
+func RateLimit(rate int, window time.Duration) gin.HandlerFunc {
+	limiter := NewRateLimiter(rate, window)
+
+	return func(c *gin.Context) {
+		// Use IP address as key
+		key := c.ClientIP()
+
+		// For authenticated requests, use user ID if available
+		if userID, exists := c.Get("user_id"); exists {
+			if uid, ok := userID.(string); ok && uid != "" {
+				key = "user:" + uid
+			}
+		}
+
+		if !limiter.Allow(key) {
+			c.JSON(http.StatusTooManyRequests, gin.H{
+				"error": "rate_limit_exceeded",
+				"message": "Too many requests. Please try again later.",
+			})
+			c.Abort()
+			return
+		}
+
+		c.Next()
+	}
+}
+
+// RateLimitByIP limits requests by IP address
+func RateLimitByIP(rate int, window time.Duration) gin.HandlerFunc {
+	limiter := NewRateLimiter(rate, window)
+
+	return func(c *gin.Context) {
+		if !limiter.Allow(c.ClientIP()) {
+			c.JSON(http.StatusTooManyRequests, gin.H{
+				"error": "rate_limit_exceeded",
+				"message": "Too many requests from your IP. Please try again later.",
+			})
+			c.Abort()
+			return
+		}
+
+		c.Next()
+	}
+}
+
+// RateLimitByUser limits requests by authenticated user
+func RateLimitByUser(rate int, window time.Duration) gin.HandlerFunc {
+	limiter := NewRateLimiter(rate, window)
+
+	return func(c *gin.Context) {
+		userID, exists := c.Get("user_id")
+		if !exists {
+			c.Next()
+			return
+		}
+
+		uid, ok := userID.(string)
+		if !ok || uid == "" {
+			c.Next()
+			return
+		}
+
+		if !limiter.Allow("user:" + uid) {
+			c.JSON(http.StatusTooManyRequests, gin.H{
+				"error": "rate_limit_exceeded",
+				"message": "Too many requests. Please slow down.",
+			})
+			c.Abort()
+			return
+		}
+
+		c.Next()
+	}
+}