refactor: use dependency injection in backend

backend/internal/middleware/rate_limit.go

@@ -0,0 +1,81 @@
+package middleware
+
+import (
+	"github.com/stonith404/pocket-id/backend/internal/common"
+	"github.com/stonith404/pocket-id/backend/internal/utils"
+	"net/http"
+	"sync"
+	"time"
+
+	"github.com/gin-gonic/gin"
+	"golang.org/x/time/rate"
+)
+
+type RateLimitMiddleware struct{}
+
+func NewRateLimitMiddleware() *RateLimitMiddleware {
+	return &RateLimitMiddleware{}
+}
+
+func (m *RateLimitMiddleware) Add(limit rate.Limit, burst int) gin.HandlerFunc {
+	// Start the cleanup routine
+	go cleanupClients()
+
+	return func(c *gin.Context) {
+		ip := c.ClientIP()
+
+		// Skip rate limiting for localhost and test environment
+		// If the client ip is localhost the request comes from the frontend
+		if ip == "127.0.0.1" || ip == "::1" || common.EnvConfig.AppEnv == "test" {
+			c.Next()
+			return
+		}
+
+		limiter := getLimiter(ip, limit, burst)
+		if !limiter.Allow() {
+			utils.HandlerError(c, http.StatusTooManyRequests, "Too many requests. Please wait a while before trying again.")
+			c.Abort()
+			return
+		}
+
+		c.Next()
+	}
+}
+
+type client struct {
+	limiter  *rate.Limiter
+	lastSeen time.Time
+}
+
+// Map to store the rate limiters per IP
+var clients = make(map[string]*client)
+var mu sync.Mutex
+
+// Cleanup routine to remove stale clients that haven't been seen for a while
+func cleanupClients() {
+	for {
+		time.Sleep(time.Minute)
+		mu.Lock()
+		for ip, client := range clients {
+			if time.Since(client.lastSeen) > 3*time.Minute {
+				delete(clients, ip)
+			}
+		}
+		mu.Unlock()
+	}
+}
+
+// getLimiter retrieves the rate limiter for a given IP address, creating one if it doesn't exist
+func getLimiter(ip string, limit rate.Limit, burst int) *rate.Limiter {
+	mu.Lock()
+	defer mu.Unlock()
+
+	if client, exists := clients[ip]; exists {
+		client.lastSeen = time.Now()
+		return client.limiter
+	}
+
+	limiter := rate.NewLimiter(limit, burst)
+	clients[ip] = &client{limiter: limiter, lastSeen: time.Now()}
+	return limiter
+}