package middleware

import (
	"RenewCMS/api/pkg/apperr"
	"net/http"
	"strconv"
	"sync"
	"time"
)

type rateLimitWindow struct {
	start time.Time
	count int
}

func NewRateLimiter(maxAttempts int, window time.Duration) func(http.Handler) http.Handler {
	var mu sync.Mutex
	windows := make(map[string]*rateLimitWindow)

	return func(next http.Handler) http.Handler {
		return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
			retryAfter, allowed := recordAttempt(&mu, windows, r.RemoteAddr, maxAttempts, window)
			if !allowed {
				w.Header().Set("Retry-After", strconv.Itoa(retryAfter))
				http.Error(w, apperr.TooManyRequestsErrorMessage, http.StatusTooManyRequests)
				return
			}
			next.ServeHTTP(w, r)
		})
	}
}

func recordAttempt(mu *sync.Mutex, windows map[string]*rateLimitWindow, key string, maxAttempts int, window time.Duration) (int, bool) {
	mu.Lock()
	defer mu.Unlock()

	now := time.Now()
	current, exists := windows[key]
	if !exists || now.Sub(current.start) >= window {
		current = &rateLimitWindow{start: now}
		windows[key] = current
	}

	current.count++
	if current.count > maxAttempts {
		return retryAfterSeconds(window - now.Sub(current.start)), false
	}
	return 0, true
}

func retryAfterSeconds(remaining time.Duration) int {
	seconds := int(remaining / time.Second)
	if remaining%time.Second > 0 {
		seconds++
	}
	if seconds < 0 {
		return 0
	}
	return seconds
}