package engine

import (
	"context"
	"sort"

	"cellbot/internal/protocol"
	"go.uber.org/zap"
)

// Dispatcher 事件分发器
// 管理事件处理器并按照优先级分发事件
type Dispatcher struct {
	handlers []protocol.EventHandler
	middlewares []protocol.Middleware
	logger   *zap.Logger
	eventBus *EventBus
}

// NewDispatcher 创建事件分发器
func NewDispatcher(eventBus *EventBus, logger *zap.Logger) *Dispatcher {
	return &Dispatcher{
		handlers:    make([]protocol.EventHandler, 0),
		middlewares: make([]protocol.Middleware, 0),
		logger:      logger.Named("dispatcher"),
		eventBus:    eventBus,
	}
}

// RegisterHandler 注册事件处理器
func (d *Dispatcher) RegisterHandler(handler protocol.EventHandler) {
	d.handlers = append(d.handlers, handler)
	// 按优先级排序(数值越小优先级越高)
	sort.Slice(d.handlers, func(i, j int) bool {
		return d.handlers[i].Priority() < d.handlers[j].Priority()
	})

	d.logger.Debug("Handler registered",
		zap.Int("priority", handler.Priority()),
		zap.Int("total_handlers", len(d.handlers)))
}

// UnregisterHandler 取消注册事件处理器
func (d *Dispatcher) UnregisterHandler(handler protocol.EventHandler) {
	for i, h := range d.handlers {
		if h == handler {
			d.handlers = append(d.handlers[:i], d.handlers[i+1:]...)
			break
		}
	}
	d.logger.Debug("Handler unregistered",
		zap.Int("total_handlers", len(d.handlers)))
}

// RegisterMiddleware 注册中间件
func (d *Dispatcher) RegisterMiddleware(middleware protocol.Middleware) {
	d.middlewares = append(d.middlewares, middleware)
	d.logger.Debug("Middleware registered",
		zap.Int("total_middlewares", len(d.middlewares)))
}

// Start 启动分发器
func (d *Dispatcher) Start(ctx context.Context) {
	// 订阅所有类型的事件
	for _, eventType := range []protocol.EventType{
		protocol.EventTypeMessage,
		protocol.EventTypeNotice,
		protocol.EventTypeRequest,
		protocol.EventTypeMeta,
	} {
		eventChan := d.eventBus.Subscribe(eventType, nil)
		go d.eventLoop(ctx, eventChan)
	}

	d.logger.Info("Dispatcher started")
}

// Stop 停止分发器
func (d *Dispatcher) Stop() {
	d.logger.Info("Dispatcher stopped")
}

// eventLoop 事件循环
func (d *Dispatcher) eventLoop(ctx context.Context, eventChan chan protocol.Event) {
	for {
		select {
		case event, ok := <-eventChan:
			if !ok {
				return
			}
			d.handleEvent(ctx, event)
		case <-ctx.Done():
			return
		}
	}
}

// handleEvent 处理单个事件
func (d *Dispatcher) handleEvent(ctx context.Context, event protocol.Event) {
	d.logger.Debug("Processing event",
		zap.String("type", string(event.GetType())),
		zap.String("detail_type", event.GetDetailType()))

	// 通过中间件链处理事件
	next := d.createHandlerChain(ctx, event)

	// 执行中间件链
	if len(d.middlewares) > 0 {
		d.executeMiddlewares(ctx, event, func(ctx context.Context, e protocol.Event) error {
			next(ctx, e)
			return nil
		})
	} else {
		next(ctx, event)
	}
}

// createHandlerChain 创建处理器链
func (d *Dispatcher) createHandlerChain(ctx context.Context, event protocol.Event) func(context.Context, protocol.Event) {
	return func(ctx context.Context, e protocol.Event) {
		for _, handler := range d.handlers {
			if handler.Match(event) {
				if err := handler.Handle(ctx, e); err != nil {
					d.logger.Error("Handler execution failed",
						zap.Error(err),
						zap.String("event_type", string(e.GetType())))
				}
			}
		}
	}
}

// executeMiddlewares 执行中间件链
func (d *Dispatcher) executeMiddlewares(ctx context.Context, event protocol.Event, next func(context.Context, protocol.Event) error) {
	// 从后向前构建中间件链
	handler := next
	for i := len(d.middlewares) - 1; i >= 0; i-- {
		middleware := d.middlewares[i]
		currentHandler := handler
		handler = func(ctx context.Context, e protocol.Event) error {
			if err := middleware.Process(ctx, e, currentHandler); err != nil {
				d.logger.Error("Middleware execution failed",
					zap.Error(err),
					zap.String("event_type", string(e.GetType())))
			}
			return nil
		}
	}

	// 执行中间件链
	handler(ctx, event)
}

// GetHandlerCount 获取处理器数量
func (d *Dispatcher) GetHandlerCount() int {
	return len(d.handlers)
}

// GetMiddlewareCount 获取中间件数量
func (d *Dispatcher) GetMiddlewareCount() int {
	return len(d.middlewares)
}