package mq

import (
	"context"
	"fmt"
	"log"
	"time"

	"accounting-app/internal/models"
	"accounting-app/internal/repository"

	"gorm.io/gorm"
)

// RecurringTransactionHandler 周期性交易任务处理器
type RecurringTransactionHandler struct {
	db              *gorm.DB
	recurringRepo   *repository.RecurringTransactionRepository
	transactionRepo *repository.TransactionRepository
	accountRepo     *repository.AccountRepository
	taskQueue       *TaskQueue
}

// NewRecurringTransactionHandler 创建处理器实例
func NewRecurringTransactionHandler(
	db *gorm.DB,
	recurringRepo *repository.RecurringTransactionRepository,
	transactionRepo *repository.TransactionRepository,
	accountRepo *repository.AccountRepository,
	taskQueue *TaskQueue,
) *RecurringTransactionHandler {
	return &RecurringTransactionHandler{
		db:              db,
		recurringRepo:   recurringRepo,
		transactionRepo: transactionRepo,
		accountRepo:     accountRepo,
		taskQueue:       taskQueue,
	}
}

// Handle 处理周期性交易任务
func (h *RecurringTransactionHandler) Handle(ctx context.Context, task *DelayedTask) error {
	payload, err := ParseRecurringPayload(task)
	if err != nil {
		return fmt.Errorf("failed to parse payload: %w", err)
	}

	log.Printf("[RecurringHandler] Processing recurring transaction %d for user %d",
		payload.RecurringTransactionID, task.UserID)

	// 获取周期性交易记录
	recurring, err := h.recurringRepo.GetByID(task.UserID, payload.RecurringTransactionID)
	if err != nil {
		if err == gorm.ErrRecordNotFound {
			log.Printf("[RecurringHandler] Recurring transaction %d not found, skipping", payload.RecurringTransactionID)
			return nil // 已被删除，不需要重试
		}
		return fmt.Errorf("failed to get recurring transaction: %w", err)
	}

	// 检查是否已禁用或已过期
	if !recurring.IsActive {
		log.Printf("[RecurringHandler] Recurring transaction %d is inactive, skipping", recurring.ID)
		return nil
	}

	if recurring.EndDate != nil && time.Now().After(*recurring.EndDate) {
		log.Printf("[RecurringHandler] Recurring transaction %d has ended, deactivating", recurring.ID)
		recurring.IsActive = false
		return h.recurringRepo.Update(recurring)
	}

	// 开始数据库事务
	tx := h.db.Begin()
	if tx.Error != nil {
		return fmt.Errorf("failed to begin transaction: %w", tx.Error)
	}

	// 创建实际交易记录
	transaction := &models.Transaction{
		UserID:          recurring.UserID,
		Amount:          recurring.Amount,
		Type:            recurring.Type,
		CategoryID:      recurring.CategoryID,
		AccountID:       recurring.AccountID,
		Currency:        recurring.Currency,
		TransactionDate: recurring.NextOccurrence,
		Note:            recurring.Note,
		RecurringID:     &recurring.ID,
	}

	if err := tx.Create(transaction).Error; err != nil {
		tx.Rollback()
		return fmt.Errorf("failed to create transaction: %w", err)
	}

	// 更新账户余额
	var account models.Account
	if err := tx.First(&account, recurring.AccountID).Error; err != nil {
		tx.Rollback()
		return fmt.Errorf("failed to get account: %w", err)
	}

	switch recurring.Type {
	case models.TransactionTypeIncome:
		account.Balance += recurring.Amount
	case models.TransactionTypeExpense:
		account.Balance -= recurring.Amount
	}

	if err := tx.Save(&account).Error; err != nil {
		tx.Rollback()
		return fmt.Errorf("failed to update account balance: %w", err)
	}

	// 计算下一次执行时间
	nextOccurrence := h.calculateNextOccurrence(recurring.NextOccurrence, recurring.Frequency)
	recurring.NextOccurrence = nextOccurrence

	// 检查下次执行是否超过结束日期
	if recurring.EndDate != nil && nextOccurrence.After(*recurring.EndDate) {
		recurring.IsActive = false
		log.Printf("[RecurringHandler] Recurring transaction %d will end after this execution", recurring.ID)
	}

	if err := tx.Save(recurring).Error; err != nil {
		tx.Rollback()
		return fmt.Errorf("failed to update recurring transaction: %w", err)
	}

	// 提交事务
	if err := tx.Commit().Error; err != nil {
		return fmt.Errorf("failed to commit transaction: %w", err)
	}

	log.Printf("[RecurringHandler] Created transaction %d from recurring %d, amount: %.2f %s",
		transaction.ID, recurring.ID, recurring.Amount, recurring.Currency)

	// 如果仍然活跃，调度下一次执行
	if recurring.IsActive {
		if err := h.scheduleNext(ctx, recurring); err != nil {
			log.Printf("[RecurringHandler] Warning: failed to schedule next execution: %v", err)
			// 不返回错误，当前任务已成功完成
		}
	}

	return nil
}

// calculateNextOccurrence 计算下一次执行时间
func (h *RecurringTransactionHandler) calculateNextOccurrence(current time.Time, frequency models.FrequencyType) time.Time {
	switch frequency {
	case models.FrequencyDaily:
		return current.AddDate(0, 0, 1)
	case models.FrequencyWeekly:
		return current.AddDate(0, 0, 7)
	case models.FrequencyMonthly:
		return current.AddDate(0, 1, 0)
	case models.FrequencyYearly:
		return current.AddDate(1, 0, 0)
	default:
		return current.AddDate(0, 1, 0) // 默认月度
	}
}

// scheduleNext 调度下一次执行
func (h *RecurringTransactionHandler) scheduleNext(ctx context.Context, recurring *models.RecurringTransaction) error {
	return h.taskQueue.ScheduleRecurringTransaction(
		ctx,
		recurring.UserID,
		recurring.ID,
		recurring.NextOccurrence,
	)
}

// ScheduleAllActive 调度所有活跃的周期性交易（启动时调用）
func (h *RecurringTransactionHandler) ScheduleAllActive(ctx context.Context) error {
	log.Println("[RecurringHandler] Scheduling all active recurring transactions...")

	// 获取所有活跃的周期性交易
	var recurringList []models.RecurringTransaction
	err := h.db.Where("is_active = ?", true).Find(&recurringList).Error
	if err != nil {
		return fmt.Errorf("failed to get active recurring transactions: %w", err)
	}

	scheduledCount := 0
	for _, recurring := range recurringList {
		// 跳过已过期的
		if recurring.EndDate != nil && time.Now().After(*recurring.EndDate) {
			recurring.IsActive = false
			h.db.Save(&recurring)
			continue
		}

		// 调度任务
		err := h.taskQueue.ScheduleRecurringTransaction(
			ctx,
			recurring.UserID,
			recurring.ID,
			recurring.NextOccurrence,
		)
		if err != nil {
			log.Printf("[RecurringHandler] Failed to schedule recurring %d: %v", recurring.ID, err)
			continue
		}
		scheduledCount++
	}

	log.Printf("[RecurringHandler] Scheduled %d recurring transactions", scheduledCount)
	return nil
}

// ProcessOverdue 处理所有逾期的周期性交易（补偿机制）
func (h *RecurringTransactionHandler) ProcessOverdue(ctx context.Context) error {
	log.Println("[RecurringHandler] Processing overdue recurring transactions...")

	now := time.Now()
	var overdueList []models.RecurringTransaction
	err := h.db.Where("is_active = ? AND next_occurrence <= ?", true, now).Find(&overdueList).Error
	if err != nil {
		return fmt.Errorf("failed to get overdue recurring transactions: %w", err)
	}

	if len(overdueList) == 0 {
		log.Println("[RecurringHandler] No overdue recurring transactions found")
		return nil
	}

	log.Printf("[RecurringHandler] Found %d overdue recurring transactions", len(overdueList))

	for _, recurring := range overdueList {
		err := h.taskQueue.ScheduleRecurringTransaction(
			ctx,
			recurring.UserID,
			recurring.ID,
			recurring.NextOccurrence,
		)
		if err != nil {
			log.Printf("[RecurringHandler] Failed to schedule overdue recurring %d: %v", recurring.ID, err)
		}
	}

	return nil
}