package middleware

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

	"github.com/gin-gonic/gin"

	"vision-tool/internal/model"
)

// CORS 跨域中间件（开发环境放开，生产环境应限制为具体域名）。
func CORS() gin.HandlerFunc {
	return func(c *gin.Context) {
		c.Header("Access-Control-Allow-Origin", "*")
		c.Header("Access-Control-Allow-Methods", "GET, POST, PUT, DELETE, OPTIONS")
		c.Header("Access-Control-Allow-Headers", "Content-Type, Authorization")
		if c.Request.Method == http.MethodOptions {
			c.AbortWithStatus(http.StatusNoContent)
			return
		}
		c.Next()
	}
}

// ============================================================================
// 内存令牌桶限流（全局限流，防匿名刷接口）
// ============================================================================

// RateLimiter 基于时间的令牌桶。
type RateLimiter struct {
	mu       sync.Mutex
	rate     float64 // 每秒补充令牌数
	burst    float64 // 桶容量
	tokens   float64
	lastTime time.Time
}

func NewRateLimiter(rps, burst int) *RateLimiter {
	return &RateLimiter{
		rate:     float64(rps),
		burst:    float64(burst),
		tokens:   float64(burst),
		lastTime: time.Now(),
	}
}

func (rl *RateLimiter) Allow() bool {
	rl.mu.Lock()
	defer rl.mu.Unlock()

	now := time.Now()
	rl.tokens = math.Min(rl.burst, rl.tokens+now.Sub(rl.lastTime).Seconds()*rl.rate)
	rl.lastTime = now

	if rl.tokens >= 1 {
		rl.tokens--
		return true
	}
	return false
}

// Middleware 返回限流 gin 中间件。
func (rl *RateLimiter) Middleware() gin.HandlerFunc {
	return func(c *gin.Context) {
		if !rl.Allow() {
			c.AbortWithStatusJSON(http.StatusTooManyRequests, model.Err(429, "请求过于频繁，请稍后再试"))
			return
		}
		c.Next()
	}
}