photoplaces/backend/internal/middleware/ratelimit.go

package middleware

import (
	"net/http"
	"sync"
	"time"

	"golang.org/x/time/rate"
)

type RateLimiter struct {
	visitors map[string]*rate.Limiter
	mu       sync.Mutex
	rate     rate.Limit
	burst    int
	lastSeen map[string]time.Time
}

func NewRateLimiter(r rate.Limit, burst int) *RateLimiter {
	rl := &RateLimiter{
		visitors: make(map[string]*rate.Limiter),
		rate:     r,
		burst:    burst,
		lastSeen: make(map[string]time.Time),
	}
	go rl.cleanup()
	return rl
}

func (rl *RateLimiter) cleanup() {
	for {
		time.Sleep(10 * time.Minute)
		rl.mu.Lock()
		for ip, last := range rl.lastSeen {
			if time.Since(last) > 30*time.Minute {
				delete(rl.visitors, ip)
				delete(rl.lastSeen, ip)
			}
		}
		rl.mu.Unlock()
	}
}

func (rl *RateLimiter) Middleware() func(http.Handler) http.Handler {
	return func(next http.Handler) http.Handler {
		return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
			ip := r.RemoteAddr
			rl.mu.Lock()
			limiter, ok := rl.visitors[ip]
			if !ok {
				limiter = rate.NewLimiter(rl.rate, rl.burst)
				rl.visitors[ip] = limiter
			}
			rl.lastSeen[ip] = time.Now()
			rl.mu.Unlock()

			if !limiter.Allow() {
				http.Error(w, `{"error":"rate limit exceeded"}`, http.StatusTooManyRequests)
				return
			}
			next.ServeHTTP(w, r)
		})
	}
}