package events

import (
	"context"
	"fmt"
	"sync"
	"time"

	"go.uber.org/zap"

	"tyapi-server/internal/shared/interfaces"
)

// MemoryEventBus 内存事件总线实现
type MemoryEventBus struct {
	subscribers map[string][]interfaces.EventHandler
	mutex       sync.RWMutex
	logger      *zap.Logger
	running     bool
	stopCh      chan struct{}
	eventQueue  chan eventTask
	workerCount int
}

// eventTask 事件任务
type eventTask struct {
	event   interfaces.Event
	handler interfaces.EventHandler
	retries int
}

// NewMemoryEventBus 创建内存事件总线
func NewMemoryEventBus(logger *zap.Logger, workerCount int) *MemoryEventBus {
	if workerCount <= 0 {
		workerCount = 5 // 默认5个工作协程
	}

	return &MemoryEventBus{
		subscribers: make(map[string][]interfaces.EventHandler),
		logger:      logger,
		eventQueue:  make(chan eventTask, 1000), // 缓冲1000个事件
		workerCount: workerCount,
		stopCh:      make(chan struct{}),
	}
}

// Name 返回服务名称
func (bus *MemoryEventBus) Name() string {
	return "memory-event-bus"
}

// Initialize 初始化服务
func (bus *MemoryEventBus) Initialize(ctx context.Context) error {
	bus.logger.Info("Memory event bus service initialized")
	return nil
}

// HealthCheck 健康检查
func (bus *MemoryEventBus) HealthCheck(ctx context.Context) error {
	if !bus.running {
		return fmt.Errorf("event bus is not running")
	}
	return nil
}

// Shutdown 关闭服务
func (bus *MemoryEventBus) Shutdown(ctx context.Context) error {
	bus.Stop(ctx)
	return nil
}

// Start 启动事件总线
func (bus *MemoryEventBus) Start(ctx context.Context) error {
	bus.mutex.Lock()
	defer bus.mutex.Unlock()

	if bus.running {
		return nil
	}

	bus.running = true

	// 启动工作协程
	for i := 0; i < bus.workerCount; i++ {
		go bus.worker(i)
	}

	bus.logger.Info("Event bus started", zap.Int("workers", bus.workerCount))
	return nil
}

// Stop 停止事件总线
func (bus *MemoryEventBus) Stop(ctx context.Context) error {
	bus.mutex.Lock()
	defer bus.mutex.Unlock()

	if !bus.running {
		return nil
	}

	bus.running = false
	close(bus.stopCh)

	// 等待所有工作协程结束或超时
	done := make(chan struct{})
	go func() {
		time.Sleep(5 * time.Second) // 给工作协程5秒时间结束
		close(done)
	}()

	select {
	case <-done:
	case <-ctx.Done():
	}

	bus.logger.Info("Event bus stopped")
	return nil
}

// Publish 发布事件（同步）
func (bus *MemoryEventBus) Publish(ctx context.Context, event interfaces.Event) error {
	bus.logger.Info("📤 开始发布事件",
		zap.String("event_type", event.GetType()),
		zap.String("event_id", event.GetID()),
		zap.String("aggregate_id", event.GetAggregateID()),
	)

	bus.mutex.RLock()
	handlers := bus.subscribers[event.GetType()]
	bus.mutex.RUnlock()

	if len(handlers) == 0 {
		bus.logger.Warn("⚠️ 没有找到事件处理器",
			zap.String("event_type", event.GetType()),
			zap.String("event_id", event.GetID()),
		)
		return nil
	}

	bus.logger.Info("📋 找到事件处理器",
		zap.String("event_type", event.GetType()),
		zap.Int("handler_count", len(handlers)),
	)

	for i, handler := range handlers {
		bus.logger.Info("🔄 处理事件",
			zap.String("event_type", event.GetType()),
			zap.String("handler_name", handler.GetName()),
			zap.Int("handler_index", i),
			zap.Bool("is_async", handler.IsAsync()),
		)

		if handler.IsAsync() {
			// 异步处理
			select {
			case bus.eventQueue <- eventTask{event: event, handler: handler, retries: 0}:
				bus.logger.Info("✅ 事件已加入异步队列",
					zap.String("event_type", event.GetType()),
					zap.String("handler_name", handler.GetName()),
					zap.Int("queue_length", len(bus.eventQueue)),
				)
			default:
				bus.logger.Error("❌ 事件队列已满，丢弃事件",
					zap.String("event_type", event.GetType()),
					zap.String("handler_name", handler.GetName()),
					zap.Int("queue_length", len(bus.eventQueue)),
					zap.Int("queue_capacity", cap(bus.eventQueue)),
				)
			}
		} else {
			// 同步处理
			bus.logger.Info("⚡ 开始同步处理事件",
				zap.String("event_type", event.GetType()),
				zap.String("handler_name", handler.GetName()),
			)
			if err := bus.handleEventWithRetry(ctx, event, handler); err != nil {
				bus.logger.Error("❌ 同步处理事件失败",
					zap.String("event_type", event.GetType()),
					zap.String("handler_name", handler.GetName()),
					zap.Error(err),
				)
			} else {
				bus.logger.Info("✅ 同步处理事件成功",
					zap.String("event_type", event.GetType()),
					zap.String("handler_name", handler.GetName()),
				)
			}
		}
	}

	bus.logger.Info("✅ 事件发布完成",
		zap.String("event_type", event.GetType()),
		zap.String("event_id", event.GetID()),
	)

	return nil
}

// PublishBatch 批量发布事件
func (bus *MemoryEventBus) PublishBatch(ctx context.Context, events []interfaces.Event) error {
	for _, event := range events {
		if err := bus.Publish(ctx, event); err != nil {
			return err
		}
	}
	return nil
}

// Subscribe 订阅事件
func (bus *MemoryEventBus) Subscribe(eventType string, handler interfaces.EventHandler) error {
	bus.mutex.Lock()
	defer bus.mutex.Unlock()

	handlers := bus.subscribers[eventType]

	// 检查是否已经订阅
	for _, h := range handlers {
		if h.GetName() == handler.GetName() {
			return fmt.Errorf("handler %s already subscribed to event type %s", handler.GetName(), eventType)
		}
	}

	bus.subscribers[eventType] = append(handlers, handler)

	bus.logger.Info("Handler subscribed to event",
		zap.String("handler", handler.GetName()),
		zap.String("event_type", eventType))

	return nil
}

// Unsubscribe 取消订阅
func (bus *MemoryEventBus) Unsubscribe(eventType string, handler interfaces.EventHandler) error {
	bus.mutex.Lock()
	defer bus.mutex.Unlock()

	handlers := bus.subscribers[eventType]
	for i, h := range handlers {
		if h.GetName() == handler.GetName() {
			// 删除处理器
			bus.subscribers[eventType] = append(handlers[:i], handlers[i+1:]...)

			bus.logger.Info("Handler unsubscribed from event",
				zap.String("handler", handler.GetName()),
				zap.String("event_type", eventType))

			return nil
		}
	}

	return fmt.Errorf("handler %s not found for event type %s", handler.GetName(), eventType)
}

// GetSubscribers 获取订阅者
func (bus *MemoryEventBus) GetSubscribers(eventType string) []interfaces.EventHandler {
	bus.mutex.RLock()
	defer bus.mutex.RUnlock()

	handlers := bus.subscribers[eventType]
	result := make([]interfaces.EventHandler, len(handlers))
	copy(result, handlers)

	return result
}

// worker 工作协程
func (bus *MemoryEventBus) worker(id int) {
	bus.logger.Info("👷 事件工作协程启动", zap.Int("worker_id", id))

	for {
		select {
		case task := <-bus.eventQueue:
			bus.logger.Info("📥 工作协程接收到事件任务",
				zap.Int("worker_id", id),
				zap.String("event_type", task.event.GetType()),
				zap.String("handler_name", task.handler.GetName()),
			)
			bus.processEventTask(task)
		case <-bus.stopCh:
			bus.logger.Info("🛑 事件工作协程停止", zap.Int("worker_id", id))
			return
		}
	}
}

// processEventTask 处理事件任务
func (bus *MemoryEventBus) processEventTask(task eventTask) {
	ctx := context.Background()

	bus.logger.Info("🔧 开始处理事件任务",
		zap.String("event_type", task.event.GetType()),
		zap.String("handler_name", task.handler.GetName()),
		zap.Int("retries", task.retries),
	)

	err := bus.handleEventWithRetry(ctx, task.event, task.handler)
	if err != nil {
		bus.logger.Error("❌ 事件任务处理失败",
			zap.String("event_type", task.event.GetType()),
			zap.String("handler_name", task.handler.GetName()),
			zap.Error(err),
		)

		retryConfig := task.handler.GetRetryConfig()

		if task.retries < retryConfig.MaxRetries {
			// 重试
			delay := time.Duration(float64(retryConfig.RetryDelay) *
				(1 + retryConfig.BackoffFactor*float64(task.retries)))

			if delay > retryConfig.MaxDelay {
				delay = retryConfig.MaxDelay
			}

			bus.logger.Info("🔄 准备重试事件任务",
				zap.String("event_type", task.event.GetType()),
				zap.String("handler_name", task.handler.GetName()),
				zap.Int("retries", task.retries),
				zap.Int("max_retries", retryConfig.MaxRetries),
				zap.Duration("delay", delay),
			)

			go func() {
				time.Sleep(delay)
				task.retries++

				select {
				case bus.eventQueue <- task:
					bus.logger.Info("✅ 事件任务重新加入队列",
						zap.String("event_type", task.event.GetType()),
						zap.String("handler_name", task.handler.GetName()),
						zap.Int("retries", task.retries),
					)
				default:
					bus.logger.Error("❌ 事件队列已满，无法重新加入任务",
						zap.String("event_type", task.event.GetType()),
						zap.String("handler_name", task.handler.GetName()),
						zap.Int("retries", task.retries),
					)
				}
			}()
		} else {
			bus.logger.Error("💥 事件处理失败，已达到最大重试次数",
				zap.String("event_type", task.event.GetType()),
				zap.String("handler_name", task.handler.GetName()),
				zap.Int("retries", task.retries),
				zap.Error(err),
			)
		}
	} else {
		bus.logger.Info("✅ 事件任务处理成功",
			zap.String("event_type", task.event.GetType()),
			zap.String("handler_name", task.handler.GetName()),
		)
	}
}

// handleEventWithRetry 处理事件并支持重试
func (bus *MemoryEventBus) handleEventWithRetry(ctx context.Context, event interfaces.Event, handler interfaces.EventHandler) error {
	start := time.Now()

	defer func() {
		duration := time.Since(start)
		bus.logger.Debug("Event handled",
			zap.String("type", event.GetType()),
			zap.String("handler", handler.GetName()),
			zap.Duration("duration", duration))
	}()

	return handler.Handle(ctx, event)
}

// GetStats 获取事件总线统计信息
func (bus *MemoryEventBus) GetStats() map[string]interface{} {
	bus.mutex.RLock()
	defer bus.mutex.RUnlock()

	stats := map[string]interface{}{
		"running":        bus.running,
		"worker_count":   bus.workerCount,
		"queue_length":   len(bus.eventQueue),
		"queue_capacity": cap(bus.eventQueue),
		"event_types":    len(bus.subscribers),
	}

	// 各事件类型的订阅者数量
	eventTypes := make(map[string]int)
	for eventType, handlers := range bus.subscribers {
		eventTypes[eventType] = len(handlers)
	}
	stats["subscribers"] = eventTypes

	return stats
}