package mq

import (
	"context"
	"encoding/json"
	"log"
	"sync"
	"time"
)

// TaskHandler 任务处理函数类型
type TaskHandler func(ctx context.Context, task *DelayedTask) error

// TaskWorker 任务工作器，负责消费和执行任务
type TaskWorker struct {
	queue        *TaskQueue
	handlers     map[TaskType]TaskHandler
	pollInterval time.Duration // 检查延迟任务间隔
	workerCount  int           // 并发工作器数量

	mu       sync.RWMutex
	running  bool
	stopChan chan struct{}
	wg       sync.WaitGroup

	// 统计信息
	processedCount int64
	errorCount     int64
	lastProcessed  time.Time
}

// NewTaskWorker 创建任务工作器
func NewTaskWorker(queue *TaskQueue, pollInterval time.Duration, workerCount int) *TaskWorker {
	if pollInterval < time.Second {
		pollInterval = time.Second
	}
	if workerCount < 1 {
		workerCount = 1
	}

	return &TaskWorker{
		queue:        queue,
		handlers:     make(map[TaskType]TaskHandler),
		pollInterval: pollInterval,
		workerCount:  workerCount,
		stopChan:     make(chan struct{}),
	}
}

// RegisterHandler 注册任务处理器
func (w *TaskWorker) RegisterHandler(taskType TaskType, handler TaskHandler) {
	w.mu.Lock()
	defer w.mu.Unlock()
	w.handlers[taskType] = handler
	log.Printf("[TaskWorker] Registered handler for task type: %s", taskType)
}

// Start 启动工作器
func (w *TaskWorker) Start(ctx context.Context) {
	w.mu.Lock()
	if w.running {
		w.mu.Unlock()
		log.Println("[TaskWorker] Already running")
		return
	}
	w.running = true
	w.stopChan = make(chan struct{})
	w.mu.Unlock()

	log.Printf("[TaskWorker] Starting with %d workers, poll interval: %v", w.workerCount, w.pollInterval)

	// 启动延迟任务轮询器
	w.wg.Add(1)
	go w.pollDelayedTasks(ctx)

	// 启动工作器
	for i := 0; i < w.workerCount; i++ {
		w.wg.Add(1)
		go w.worker(ctx, i)
	}
}

// Stop 停止工作器
func (w *TaskWorker) Stop() {
	w.mu.Lock()
	if !w.running {
		w.mu.Unlock()
		return
	}
	w.running = false
	close(w.stopChan)
	w.mu.Unlock()

	log.Println("[TaskWorker] Stopping...")
	w.wg.Wait()
	log.Println("[TaskWorker] Stopped")
}

// pollDelayedTasks 定期检查并移动到期的延迟任务
func (w *TaskWorker) pollDelayedTasks(ctx context.Context) {
	defer w.wg.Done()

	ticker := time.NewTicker(w.pollInterval)
	defer ticker.Stop()

	for {
		select {
		case <-ctx.Done():
			return
		case <-w.stopChan:
			return
		case <-ticker.C:
			moved, err := w.queue.MoveReadyTasks(ctx)
			if err != nil {
				log.Printf("[TaskWorker] Error moving ready tasks: %v", err)
			} else if moved > 0 {
				log.Printf("[TaskWorker] Moved %d tasks to ready queue", moved)
			}
		}
	}
}

// worker 工作器协程
func (w *TaskWorker) worker(ctx context.Context, id int) {
	defer w.wg.Done()

	log.Printf("[TaskWorker] Worker %d started", id)

	for {
		select {
		case <-ctx.Done():
			log.Printf("[TaskWorker] Worker %d stopping (context done)", id)
			return
		case <-w.stopChan:
			log.Printf("[TaskWorker] Worker %d stopping (stop signal)", id)
			return
		default:
			// 尝试获取任务
			task, err := w.queue.PopTask(ctx, time.Second)
			if err != nil {
				log.Printf("[TaskWorker] Worker %d error popping task: %v", id, err)
				time.Sleep(time.Second) // 错误后等待
				continue
			}

			if task == nil {
				continue // 没有任务，继续轮询
			}

			// 处理任务
			w.processTask(ctx, id, task)
		}
	}
}

// processTask 处理单个任务
func (w *TaskWorker) processTask(ctx context.Context, workerID int, task *DelayedTask) {
	startTime := time.Now()
	log.Printf("[TaskWorker] Worker %d processing task %s (type: %s, user: %d)",
		workerID, task.ID, task.Type, task.UserID)

	w.mu.RLock()
	handler, exists := w.handlers[task.Type]
	w.mu.RUnlock()

	if !exists {
		log.Printf("[TaskWorker] No handler for task type: %s", task.Type)
		w.queue.CompleteTask(ctx, task)
		return
	}

	// 执行任务
	err := handler(ctx, task)
	duration := time.Since(startTime)

	if err != nil {
		log.Printf("[TaskWorker] Task %s failed (attempt %d/%d): %v",
			task.ID, task.RetryCount+1, task.MaxRetries, err)

		w.mu.Lock()
		w.errorCount++
		w.mu.Unlock()

		// 重试（指数退避）
		retryDelay := time.Duration(1<<task.RetryCount) * time.Minute
		if err := w.queue.RetryTask(ctx, task, retryDelay); err != nil {
			log.Printf("[TaskWorker] Failed to retry task %s: %v", task.ID, err)
		}
		return
	}

	// 完成任务
	if err := w.queue.CompleteTask(ctx, task); err != nil {
		log.Printf("[TaskWorker] Failed to complete task %s: %v", task.ID, err)
	}

	w.mu.Lock()
	w.processedCount++
	w.lastProcessed = time.Now()
	w.mu.Unlock()

	log.Printf("[TaskWorker] Task %s completed in %v", task.ID, duration)
}

// GetStats 获取工作器统计信息
func (w *TaskWorker) GetStats() map[string]interface{} {
	w.mu.RLock()
	defer w.mu.RUnlock()

	return map[string]interface{}{
		"running":         w.running,
		"worker_count":    w.workerCount,
		"poll_interval":   w.pollInterval.String(),
		"processed_count": w.processedCount,
		"error_count":     w.errorCount,
		"last_processed":  w.lastProcessed,
	}
}

// ParseRecurringPayload 解析周期性交易任务载荷
func ParseRecurringPayload(task *DelayedTask) (*RecurringTransactionPayload, error) {
	var payload RecurringTransactionPayload
	if err := json.Unmarshal(task.Payload, &payload); err != nil {
		return nil, err
	}
	return &payload, nil
}