package middleware

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

	"github.com/gin-gonic/gin"
)

// RateLimiter 限流器
type RateLimiter struct {
	requests map[string][]time.Time
	mu       sync.Mutex
	limit    int
	window   time.Duration
}

// NewRateLimiter 创建限流器
func NewRateLimiter(limit int, window time.Duration) *RateLimiter {
	rl := &RateLimiter{
		requests: make(map[string][]time.Time),
		limit:    limit,
		window:   window,
	}

	// 定期清理过期的记录
	go func() {
		for {
			time.Sleep(window)
			rl.cleanup()
		}
	}()

	return rl
}

// cleanup 清理过期的记录
func (rl *RateLimiter) cleanup() {
	rl.mu.Lock()
	defer rl.mu.Unlock()

	now := time.Now()
	for key, times := range rl.requests {
		var valid []time.Time
		for _, t := range times {
			if now.Sub(t) < rl.window {
				valid = append(valid, t)
			}
		}
		if len(valid) == 0 {
			delete(rl.requests, key)
		} else {
			rl.requests[key] = valid
		}
	}
}

// isAllowed 检查是否允许请求
func (rl *RateLimiter) isAllowed(key string) bool {
	rl.mu.Lock()
	defer rl.mu.Unlock()

	now := time.Now()
	times := rl.requests[key]

	// 过滤掉过期的
	var valid []time.Time
	for _, t := range times {
		if now.Sub(t) < rl.window {
			valid = append(valid, t)
		}
	}

	if len(valid) >= rl.limit {
		rl.requests[key] = valid
		return false
	}

	rl.requests[key] = append(valid, now)
	return true
}

// RateLimit 限流中间件
func RateLimit(requestsPerMinute int) gin.HandlerFunc {
	limiter := NewRateLimiter(requestsPerMinute, time.Minute)

	return func(c *gin.Context) {
		ip := c.ClientIP()

		if !limiter.isAllowed(ip) {
			c.JSON(http.StatusTooManyRequests, gin.H{
				"code":    429,
				"message": "too many requests",
			})
			c.Abort()
			return
		}

		c.Next()
	}
}