package service

import (
	"context"
	"log/slog"
	"time"

	"git.lzcwy.cn/zhengchiliu/zt-closet-backend/global"
	"git.lzcwy.cn/zhengchiliu/zt-closet-backend/internal/mysqldao"
	"git.lzcwy.cn/zhengchiliu/zt-closet-backend/internal/mysqlmodel"
	"git.lzcwy.cn/zhengchiliu/zt-closet-backend/internal/redisdao"
	"gorm.io/gorm"
)

// StartBenefitCompensationScheduler 启动权益发放补偿定时任务：周期性重试发放失败的权益。
func StartBenefitCompensationScheduler() {
	go func() {
		slog.Info("benefit compensation scheduler started")
		for {
			func() {
				defer func() {
					if r := recover(); r != nil {
						slog.Error("benefit compensation scheduler panic", "recover", r)
					}
				}()
				runBenefitCompensation()
			}()
			time.Sleep(time.Minute)
		}
	}()
}

// runBenefitCompensation 扫描待发放补偿任务并重试，单实例通过 Redis 分布式锁防重。
func runBenefitCompensation() {
	ctx, cancel := context.WithTimeout(context.Background(), 3*time.Minute)
	defer cancel()

	ctx, span := global.Tracer.Start(ctx, "scheduler.BenefitCompensation")
	defer span.End()

	lockKey := "ztcloset:lock:benefit:compensation"
	lockVal := genUUID()
	ok, lerr := redisdao.TryLock(ctx, lockKey, lockVal, time.Minute)
	if lerr != nil || !ok {
		return
	}
	defer redisdao.Unlock(context.Background(), lockKey, lockVal)

	taskDao := mysqldao.NewBenefitGrantTaskDao()
	s := NewOrderService()
	// 对账已支付但任务未完整落库的订单，覆盖支付状态提交后进程崩溃/数据库瞬时错误。
	if orders, err := mysqldao.NewOrderDao().OrderListPaidMissingBenefitTasks(ctx, 100); err == nil {
		for i := range orders {
			s.grantOrderBenefits(ctx, &orders[i])
		}
	} else {
		slog.ErrorContext(ctx, "reconcile paid order benefits failed", "error", err)
	}

	// 恢复超时的「发放中」任务（认领后崩溃的场景），使其回到待发放继续重试。
	_, _ = taskDao.BenefitGrantTaskRecoverStale(ctx, nowUnix()-int64((10*time.Minute).Seconds()))

	tasks, err := taskDao.BenefitGrantTaskListPending(ctx, 100)
	if err != nil {
		slog.ErrorContext(ctx, "list pending benefit tasks failed", "error", err)
		return
	}
	for i := range tasks {
		s.retryBenefitTask(ctx, &tasks[i])
	}

	revokeDao := mysqldao.NewBenefitRevokeTaskDao()
	_ = revokeDao.RecoverStale(ctx, nowUnix()-int64((10*time.Minute).Seconds()))
	if revokeTasks, err := revokeDao.ListPending(ctx, 100); err == nil {
		for i := range revokeTasks {
			s.executeRevokeTask(ctx, &revokeTasks[i])
		}
	} else {
		slog.ErrorContext(ctx, "list pending benefit revoke tasks failed", "error", err)
	}
}

// retryBenefitTask 重试单个补偿任务（幂等：先查发放流水避免重复发放）。
func (s *OrderService) retryBenefitTask(ctx context.Context, task *mysqlmodel.BenefitGrantTask) {
	taskDao := mysqldao.NewBenefitGrantTaskDao()

	// 重试次数超限，标记失败并告警，等待人工介入。
	if task.RetryCount >= task.MaxRetry {
		_ = taskDao.BenefitGrantTaskUpdateByID(ctx, task.ID, map[string]any{"status": BenefitTaskFailed})
		slog.ErrorContext(ctx, "benefit grant task exhausted retries",
			"order_no", task.OrderNo, "benefit_type", task.BenefitType, "retry_count", task.RetryCount)
		return
	}

	// 幂等判断：若发放流水已存在（上次发放成功但未置 success 的崩溃窗口），直接置成功。
	if granted, err := s.benefitAlreadyGranted(ctx, task); err == nil && granted {
		_ = taskDao.BenefitGrantTaskUpdateByID(ctx, task.ID, map[string]any{"status": BenefitTaskSuccess})
		return
	} else if err != nil {
		slog.ErrorContext(ctx, "check benefit granted failed",
			"order_no", task.OrderNo, "benefit_type", task.BenefitType, "error", err)
		return
	}

	// 执行发放（claim 防并发，内部处理 retry_count 原子自增与状态流转）。
	s.executeGrant(ctx, task)
}

// benefitAlreadyGranted 判断该权益是否已发放（用于崩溃恢复幂等）。
// VIP 查 VIP 流水；额度类查额度凭证（quota_grants）。
func (s *OrderService) benefitAlreadyGranted(ctx context.Context, task *mysqlmodel.BenefitGrantTask) (bool, error) {
	grantDao := mysqldao.NewQuotaGrantDao()
	switch task.BenefitType {
	case BenefitTypeVIP:
		return s.vipDao.VIPFlowLogExistsByOrderNo(ctx, task.OrderNo)
	case BenefitTypeCos:
		return grantDao.QuotaGrantExistsByRefIDAndType(ctx, task.OrderNo, QuotaTypeCos)
	case BenefitTypeAI:
		return grantDao.QuotaGrantExistsByRefIDAndType(ctx, task.OrderNo, QuotaTypeAI)
	case BenefitTypeClosetShare:
		return grantDao.QuotaGrantExistsByRefIDAndType(ctx, task.OrderNo, QuotaTypeClosetShare)
	case BenefitTypeOutfitShare:
		return grantDao.QuotaGrantExistsByRefIDAndType(ctx, task.OrderNo, QuotaTypeOutfitShare)
	default:
		return false, nil
	}
}

func (s *OrderService) executeRevokeTaskByOrder(ctx context.Context, orderNo string) {
	task, err := mysqldao.NewBenefitRevokeTaskDao().GetByOrderNo(ctx, orderNo)
	if err == nil {
		s.executeRevokeTask(ctx, task)
	}
}

func (s *OrderService) executeRevokeTask(ctx context.Context, task *mysqlmodel.BenefitRevokeTask) {
	dao := mysqldao.NewBenefitRevokeTaskDao()
	if task.Status == BenefitTaskSuccess {
		return
	}
	if task.RetryCount >= task.MaxRetry {
		slog.ErrorContext(ctx, "benefit revoke task exceeded normal retry threshold; continuing for eventual consistency", "order_no", task.OrderNo, "retry_count", task.RetryCount)
	}
	claimed, err := dao.Claim(ctx, task.ID)
	if err != nil || !claimed {
		return
	}
	order, err := s.orderDao.OrderGetByOrderNo(ctx, task.OrderNo)
	if err == nil {
		err = s.revokeOrderBenefits(ctx, order)
	}
	if err != nil {
		_ = dao.Update(ctx, task.ID, map[string]any{"status": BenefitTaskPending, "retry_count": gorm.Expr("retry_count + 1"), "last_error": err.Error()})
		slog.ErrorContext(ctx, "revoke refunded order benefits failed", "order_no", task.OrderNo, "error", err)
		return
	}
	_ = dao.Update(ctx, task.ID, map[string]any{"status": BenefitTaskSuccess, "last_error": ""})
}