package middleware

import (
	"context"
	"fmt"
	"strings"
	"sync"
	"sync/atomic"
	"time"

	"github.com/alibaba/sentinel-golang/api"
	"github.com/alibaba/sentinel-golang/core/circuitbreaker"
	"github.com/gogf/gf/v2/frame/g"
	"github.com/gogf/gf/v2/net/ghttp"
)

// CircuitBreakerState 熔断器状态
type CircuitBreakerState string

const (
	StateClosed   CircuitBreakerState = "closed"    // 关闭：正常状态
	StateOpen     CircuitBreakerState = "open"      // 开启：熔断状态
	StateHalfOpen CircuitBreakerState = "half-open" // 半开：尝试恢复状态
)

// CircuitBreakerConfig 熔断器配置
type CircuitBreakerConfig struct {
	MaxFailures               int     // 连续失败次数
	Timeout                   string  // 熔断超时时间
	HalfOpenSuccess           int     // 半开状态连续成功次数
	SuccessStatusCodes        []int   // 视为成功的HTTP状态码
	SlowRequestThreshold      string  // 慢请求阈值
	HalfOpenRequestSampleRate float64 // 半开状态请求采样率
	Dimension                 string  // 熔断器维度: service/ip/user
	EnableSlidingWindow       bool    // 是否启用滑动窗口
	SlidingWindowSize         string  // 滑动窗口大小
	FailureRateThreshold      float64 // 失败率阈值
	EnableFallback            bool    // 是否启用降级
	FallbackMessage           string  // 降级提示消息
}

// CircuitBreakerMetrics 熔断器指标
type CircuitBreakerMetrics struct {
	TotalRequests   atomic.Int64 // 总请求数
	PassRequests    atomic.Int64 // 通过请求数
	BlockRequests   atomic.Int64 // 阻塞请求数
	FailureRequests atomic.Int64 // 失败请求数
	OpenCount       atomic.Int64 // 熔断开启次数
}

// CircuitBreakerInfo 熔断器信息
type CircuitBreakerInfo struct {
	ResourceName  string                 `json:"resourceName"`  // 资源名称
	State         CircuitBreakerState    `json:"state"`         // 当前状态
	Config        *CircuitBreakerConfig  `json:"config"`        // 配置信息
	FailCount     int64                  `json:"failCount"`     // 失败次数
	TotalCount    int64                  `json:"totalCount"`    // 总请求数
	LastOpenTime  time.Time              `json:"lastOpenTime"`  // 上次熔断时间
	NextRetryTime time.Time              `json:"nextRetryTime"` // 下次重试时间
	Metrics       *CircuitBreakerMetrics `json:"metrics"`       // 指标统计
	mu            sync.RWMutex           // 保护状态更新
}

var (
	// circuitBreakers 存储所有熔断器状态（用于健康检查）
	circuitBreakers sync.Map
	// enableDistributed 是否启用分布式熔断
	enableDistributed = false
	// circuitBreakerConfigs 熔断器配置缓存
	circuitBreakerConfigs sync.Map
	// distributedSyncLock 分布式同步锁
	distributedSyncLock sync.Mutex
)

// InitCircuitBreaker 初始化Sentinel熔断器
func InitCircuitBreaker() error {
	ctx := context.Background()
	// 从配置文件读取是否启用分布式熔断
	enableDistributed = g.Cfg().MustGet(ctx, "circuitBreaker.enableDistributed", false).Bool()

	// 初始化Sentinel
	err := api.InitDefault()
	if err != nil {
		return fmt.Errorf("Sentinel初始化失败: %v", err)
	}

	g.Log().Infof(ctx, "Sentinel熔断器初始化成功，分布式熔断: %v", enableDistributed)

	// 动态从配置文件读取服务列表
	services := g.Cfg().MustGet(ctx, "circuitBreaker.services", []string{
		"customerService", "order", "assets", "cid", "oss",
		"wallet", "market", "knapsack",
	}).Strings()

	if len(services) == 0 {
		return fmt.Errorf("未配置熔断器服务列表")
	}

	// 为每个服务创建熔断器
	for _, service := range services {
		serviceConfig := loadServiceCircuitBreakerConfig(service)
		if serviceConfig != nil {
			circuitBreakerConfigs.Store(service, serviceConfig)
			initErr := initServiceCircuitBreaker(service, serviceConfig)
			if initErr != nil {
				g.Log().Errorf(ctx, "服务 %s 熔断器初始化失败: %v", service, initErr)
			} else {
				g.Log().Infof(ctx, "服务 %s 熔断器初始化成功", service)
			}
		}
	}

	g.Log().Infof(ctx, "共初始化 %d 个服务熔断器", len(services))
	return nil
}

// ReloadCircuitBreakerConfig 动态重新加载熔断器配置
func ReloadCircuitBreakerConfig(serviceName string) error {
	ctx := context.Background()

	// 重新加载配置
	serviceConfig := loadServiceCircuitBreakerConfig(serviceName)
	if serviceConfig == nil {
		return fmt.Errorf("未找到服务 %s 的配置", serviceName)
	}

	// 更新配置缓存
	circuitBreakerConfigs.Store(serviceName, serviceConfig)

	// 重新初始化熔断器
	err := initServiceCircuitBreaker(serviceName, serviceConfig)
	if err != nil {
		return fmt.Errorf("重新初始化熔断器失败: %v", err)
	}

	g.Log().Infof(ctx, "服务 %s 熔断器配置重新加载成功", serviceName)
	return nil
}

// loadServiceCircuitBreakerConfig 加载单个服务的熔断器配置
func loadServiceCircuitBreakerConfig(serviceName string) *CircuitBreakerConfig {
	ctx := context.Background()
	key := fmt.Sprintf("circuitBreaker.%s", serviceName)

	maxFailures := g.Cfg().MustGet(ctx, key+".maxFailures", 5).Int()
	timeout := g.Cfg().MustGet(ctx, key+".timeout", "60s").String()
	halfOpenSuccess := g.Cfg().MustGet(ctx, key+".halfOpenSuccess", 2).Int()
	slowRequestThreshold := g.Cfg().MustGet(ctx, key+".slowRequestThreshold", "3s").String()
	dimension := g.Cfg().MustGet(ctx, key+".dimension", "service").String()
	enableSlidingWindow := g.Cfg().MustGet(ctx, key+".enableSlidingWindow", false).Bool()
	slidingWindowSize := g.Cfg().MustGet(ctx, key+".slidingWindowSize", "60s").String()
	failureRateThreshold := g.Cfg().MustGet(ctx, key+".failureRateThreshold", 0.5).Float64()
	halfOpenRequestSampleRate := g.Cfg().MustGet(ctx, key+".halfOpenRequestSampleRate", 1.0).Float64()
	enableFallback := g.Cfg().MustGet(ctx, key+".enableFallback", false).Bool()
	fallbackMessage := g.Cfg().MustGet(ctx, key+".fallbackMessage", "").String()

	// 解析成功状态码
	successCodes := g.Cfg().MustGet(ctx, key+".successStatusCodes", "200,201,204").String()
	statusCodes := parseStatusCodes(successCodes)

	return &CircuitBreakerConfig{
		MaxFailures:               maxFailures,
		Timeout:                   timeout,
		HalfOpenSuccess:           halfOpenSuccess,
		SuccessStatusCodes:        statusCodes,
		SlowRequestThreshold:      slowRequestThreshold,
		HalfOpenRequestSampleRate: halfOpenRequestSampleRate,
		Dimension:                 dimension,
		EnableSlidingWindow:       enableSlidingWindow,
		SlidingWindowSize:         slidingWindowSize,
		FailureRateThreshold:      failureRateThreshold,
		EnableFallback:            enableFallback,
		FallbackMessage:           fallbackMessage,
	}
}

// parseStatusCodes 解析HTTP状态码
func parseStatusCodes(str string) []int {
	parts := strings.Split(str, ",")
	codes := make([]int, 0, len(parts))
	for _, part := range parts {
		var code int
		if _, err := fmt.Sscanf(strings.TrimSpace(part), "%d", &code); err == nil {
			codes = append(codes, code)
		}
	}
	return codes
}

// initServiceCircuitBreaker 初始化服务熔断器
func initServiceCircuitBreaker(serviceName string, config *CircuitBreakerConfig) error {
	timeout, _ := time.ParseDuration(config.Timeout)
	slowRequestThreshold, _ := time.ParseDuration(config.SlowRequestThreshold)
	_, _ = time.ParseDuration(config.SlidingWindowSize)

	resourceName := fmt.Sprintf("service:%s", serviceName)

	var rule []*circuitbreaker.Rule
	if config.EnableSlidingWindow {
		// 使用滑动窗口统计（更精确）- 慢调用比例策略
		rule = []*circuitbreaker.Rule{
			{
				Resource:                     resourceName,
				Strategy:                     circuitbreaker.SlowRequestRatio,
				RetryTimeoutMs:               uint32(timeout.Milliseconds()),
				MinRequestAmount:             uint64(config.MaxFailures),
				StatIntervalMs:               1000,
				StatSlidingWindowBucketCount: 10,
				MaxAllowedRtMs:               uint64(slowRequestThreshold.Milliseconds()),
				Threshold:                    config.FailureRateThreshold,
			},
		}
	} else {
		// 使用连续失败计数（更简单快速）- 异常数策略
		rule = []*circuitbreaker.Rule{
			{
				Resource:         resourceName,
				Strategy:         circuitbreaker.ErrorCount,
				RetryTimeoutMs:   uint32(timeout.Milliseconds()),
				MinRequestAmount: uint64(config.MaxFailures),
				StatIntervalMs:   1000, // 1秒统计窗口
				Threshold:        float64(config.MaxFailures),
			},
		}
	}

	// 加载规则到Sentinel
	_, err := circuitbreaker.LoadRules(rule)
	if err != nil {
		return fmt.Errorf("加载熔断规则失败: %v", err)
	}

	// 初始化熔断器信息
	cbInfo := &CircuitBreakerInfo{
		ResourceName: resourceName,
		State:        StateClosed,
		Config:       config,
		Metrics:      &CircuitBreakerMetrics{},
	}
	circuitBreakers.Store(serviceName, cbInfo)

	strategy := "error_count"
	if config.EnableSlidingWindow {
		strategy = "slow_ratio"
	}

	g.Log().Infof(context.Background(), "服务 %s 熔断器初始化成功: resource=%s, strategy=%s, timeout=%v",
		serviceName, resourceName, strategy, timeout)

	return nil
}

// CircuitBreakerMiddleware 熔断降级中间件（使用阿里Sentinel）
func CircuitBreakerMiddleware(r *ghttp.Request) {
	startTime := time.Now()

	// 从URL路径提取服务名
	pathParts := strings.Split(strings.Trim(r.URL.Path, "/"), "/")
	if len(pathParts) == 0 {
		r.Middleware.Next()
		return
	}

	serviceName := pathParts[0]
	resourceName := fmt.Sprintf("service:%s", serviceName)

	// 获取熔断器信息
	val, ok := circuitBreakers.Load(serviceName)
	if !ok {
		// 未配置熔断器，直接放行
		r.Middleware.Next()
		return
	}

	cbInfo := val.(*CircuitBreakerInfo)
	cbInfo.Metrics.TotalRequests.Add(1)

	// 检查是否启用分布式熔断
	if enableDistributed {
		if isCircuitBreakerOpenInDistributed(r.GetCtx(), resourceName) {
			cbInfo.Metrics.BlockRequests.Add(1)
			g.Log().Warningf(r.GetCtx(), "分布式熔断触发: %s", resourceName)
			sendFallbackResponse(r, serviceName, cbInfo.Config)
			return
		}
	}

	// 使用Sentinel进行熔断保护
	entry, blockError := api.Entry(resourceName)
	if blockError != nil {
		// 被熔断拦截
		cbInfo.Metrics.BlockRequests.Add(1)
		cbInfo.Metrics.OpenCount.Add(1)
		g.Log().Warningf(r.GetCtx(), "熔断触发: %s, reason: %v", resourceName, blockError)

		// 更新熔断器状态
		cbInfo.mu.Lock()
		cbInfo.State = StateOpen
		cbInfo.LastOpenTime = time.Now()
		if timeout, err := time.ParseDuration(cbInfo.Config.Timeout); err == nil {
			cbInfo.NextRetryTime = time.Now().Add(timeout)
		}
		cbInfo.mu.Unlock()

		// 同步到分布式存储
		if enableDistributed {
			syncCircuitBreakerStateToDistributed(r.GetCtx(), resourceName, "open")
		}

		sendFallbackResponse(r, serviceName, cbInfo.Config)
		return
	}

	// 执行后续中间件和业务逻辑
	r.Middleware.Next()

	// 记录请求结果（基于HTTP状态码）
	statusCode := r.Response.Status
	duration := time.Since(startTime)

	if !isSuccessStatusCode(resourceName, statusCode) {
		// 记录异常
		cbInfo.Metrics.FailureRequests.Add(1)
		api.TraceError(entry, fmt.Errorf("request failed with status: %d", statusCode))
		g.Log().Debugf(r.GetCtx(), "服务 %s 请求失败: status=%d, duration=%v", serviceName, statusCode, duration)
	} else {
		cbInfo.Metrics.PassRequests.Add(1)
	}

	// 退出Sentinel资源
	entry.Exit()
}

// sendFallbackResponse 发送降级响应
func sendFallbackResponse(r *ghttp.Request, serviceName string, config *CircuitBreakerConfig) {
	if config.EnableFallback && config.FallbackMessage != "" {
		// 自定义降级消息
		r.Response.WriteStatusExit(503, config.FallbackMessage)
	} else {
		// 默认消息
		r.Response.WriteStatusExit(503, fmt.Sprintf("服务 '%s' 暂时不可用，请稍后再试", serviceName))
	}
}

// isSuccessStatusCode 判断HTTP状态码是否成功
func isSuccessStatusCode(resourceName string, statusCode int) bool {
	serviceName := strings.TrimPrefix(resourceName, "service:")
	if serviceName == "" {
		// 默认只认为2xx是成功
		return statusCode >= 200 && statusCode < 300
	}

	// 从配置中获取成功状态码列表
	var serviceConfig *CircuitBreakerConfig
	if val, ok := circuitBreakerConfigs.Load(serviceName); ok {
		serviceConfig = val.(*CircuitBreakerConfig)
	}

	if serviceConfig != nil && len(serviceConfig.SuccessStatusCodes) > 0 {
		for _, code := range serviceConfig.SuccessStatusCodes {
			if statusCode == code {
				return true
			}
		}
		return false
	}

	// 默认：2xx状态码为成功
	return statusCode >= 200 && statusCode < 300
}

// isCircuitBreakerOpenInDistributed 检查分布式熔断状态
func isCircuitBreakerOpenInDistributed(ctx context.Context, resourceName string) bool {
	key := fmt.Sprintf("circuit_breaker:%s:state", resourceName)
	value, err := g.Redis().Get(ctx, key)
	if err != nil || value.IsNil() {
		return false
	}
	state := value.String()
	return state == "open"
}

// syncCircuitBreakerStateToDistributed 同步熔断器状态到分布式存储
func syncCircuitBreakerStateToDistributed(ctx context.Context, resourceName, state string) {
	distributedSyncLock.Lock()
	defer distributedSyncLock.Unlock()

	key := fmt.Sprintf("circuit_breaker:%s:state", resourceName)
	// 设置过期时间为5分钟，使用SetEX
	_, err := g.Redis().Do(ctx, "SETEX", key, 300, state)
	if err != nil {
		g.Log().Errorf(ctx, "同步熔断状态到Redis失败: %v", err)
	}
}

// CircuitBreakerHealthCheckHandler 熔断器健康检查接口
func CircuitBreakerHealthCheckHandler(r *ghttp.Request) {
	status := make(map[string]interface{})
	totalServices := 0
	openServices := 0

	// 遍历所有熔断器
	circuitBreakers.Range(func(key, value interface{}) bool {
		serviceName := key.(string)
		cbInfo := value.(*CircuitBreakerInfo)

		totalServices++
		cbInfo.mu.RLock()
		isOpen := cbInfo.State == StateOpen
		if isOpen {
			openServices++
		}

		status[serviceName] = map[string]interface{}{
			"resource":        cbInfo.ResourceName,
			"state":           string(cbInfo.State),
			"lastOpenTime":    cbInfo.LastOpenTime,
			"nextRetryTime":   cbInfo.NextRetryTime,
			"totalRequests":   cbInfo.Metrics.TotalRequests.Load(),
			"passRequests":    cbInfo.Metrics.PassRequests.Load(),
			"blockRequests":   cbInfo.Metrics.BlockRequests.Load(),
			"failureRequests": cbInfo.Metrics.FailureRequests.Load(),
			"openCount":       cbInfo.Metrics.OpenCount.Load(),
		}
		cbInfo.mu.RUnlock()

		return true
	})

	summary := map[string]interface{}{
		"totalServices":  totalServices,
		"openServices":   openServices,
		"closedServices": totalServices - openServices,
		"distributed":    enableDistributed,
	}

	r.Response.WriteJsonExit(ghttp.DefaultHandlerResponse{
		Code:    200,
		Message: "熔断器状态",
		Data: map[string]interface{}{
			"summary":  summary,
			"services": status,
		},
	})
}

// getSentinelStateString 转换Sentinel状态为字符串
func getSentinelStateString(state circuitbreaker.State) string {
	switch state {
	case circuitbreaker.Closed:
		return string(StateClosed)
	case circuitbreaker.Open:
		return string(StateOpen)
	case circuitbreaker.HalfOpen:
		return string(StateHalfOpen)
	default:
		return "unknown"
	}
}

// CircuitBreakerResetHandler 熔断器手动重置接口（仅限管理后台调用）
func CircuitBreakerResetHandler(r *ghttp.Request) {
	serviceName := r.Get("service").String()
	if serviceName == "" {
		r.Response.WriteJsonExit(ghttp.DefaultHandlerResponse{
			Code:    400,
			Message: "缺少service参数",
		})
		return
	}

	resourceName := fmt.Sprintf("service:%s", serviceName)

	// 获取当前服务的所有规则
	currentRules := circuitbreaker.GetRulesOfResource(resourceName)

	// 只删除当前服务的规则
	if len(currentRules) > 0 {
		_, err := circuitbreaker.LoadRulesOfResource(resourceName, []*circuitbreaker.Rule{})
		if err != nil {
			r.Response.WriteJsonExit(ghttp.DefaultHandlerResponse{
				Code:    500,
				Message: fmt.Sprintf("重置熔断器失败: %v", err),
			})
			return
		}
	}

	// 重新加载该服务的规则
	if val, ok := circuitBreakerConfigs.Load(serviceName); ok {
		config := val.(*CircuitBreakerConfig)
		err := initServiceCircuitBreaker(serviceName, config)
		if err != nil {
			r.Response.WriteJsonExit(ghttp.DefaultHandlerResponse{
				Code:    500,
				Message: fmt.Sprintf("重置熔断器失败: %v", err),
			})
			return
		}
	}

	// 更新内存状态
	if val, ok := circuitBreakers.Load(serviceName); ok {
		cbInfo := val.(*CircuitBreakerInfo)
		cbInfo.mu.Lock()
		cbInfo.State = StateClosed
		cbInfo.LastOpenTime = time.Time{}
		cbInfo.NextRetryTime = time.Time{}
		cbInfo.mu.Unlock()
	}

	// 重置分布式状态（如果启用）
	if enableDistributed {
		key := fmt.Sprintf("circuit_breaker:%s:state", resourceName)
		_, _ = g.Redis().Del(r.GetCtx(), key)
	}

	g.Log().Infof(r.GetCtx(), "熔断器已手动重置: %s", resourceName)

	r.Response.WriteJsonExit(ghttp.DefaultHandlerResponse{
		Code:    200,
		Message: fmt.Sprintf("服务 '%s' 的熔断器已重置", serviceName),
	})
}

// CircuitBreakerReloadHandler 熔断器配置重载接口
func CircuitBreakerReloadHandler(r *ghttp.Request) {
	serviceName := r.Get("service").String()

	if serviceName == "" {
		// 重载所有服务
		services := g.Cfg().MustGet(r.GetCtx(), "circuitBreaker.services", []string{}).Strings()
		successCount := 0
		failCount := 0

		for _, service := range services {
			err := ReloadCircuitBreakerConfig(service)
			if err != nil {
				g.Log().Errorf(r.GetCtx(), "服务 %s 配置重载失败: %v", service, err)
				failCount++
			} else {
				successCount++
			}
		}

		r.Response.WriteJsonExit(ghttp.DefaultHandlerResponse{
			Code:    200,
			Message: fmt.Sprintf("配置重载完成: 成功 %d, 失败 %d", successCount, failCount),
			Data: map[string]interface{}{
				"success": successCount,
				"failed":  failCount,
			},
		})
		return
	}

	// 重载单个服务
	err := ReloadCircuitBreakerConfig(serviceName)
	if err != nil {
		r.Response.WriteJsonExit(ghttp.DefaultHandlerResponse{
			Code:    500,
			Message: fmt.Sprintf("重载失败: %v", err),
		})
		return
	}

	r.Response.WriteJsonExit(ghttp.DefaultHandlerResponse{
		Code:    200,
		Message: fmt.Sprintf("服务 '%s' 的熔断器配置已重载", serviceName),
	})
}