package gameking

import (
	"context"
	"errors"
	"fmt"
	"net/http"
	"strconv"
	"time"

	"chatapp3-golang/internal/model"
	"chatapp3-golang/internal/utils"

	"gorm.io/gorm"
)

const (
	settlementDispatchBatch = 4
	settlementDueBatch      = 10
	staleDeliveryBatch      = 20
)

// Settle 在结算截点后冻结 TYCOON/OVERALL Top30，并发送尚未开始的 PENDING 奖励。
// 重复调用不会重建快照，也不会自动重试 FAILED/UNKNOWN。
func (s *Service) Settle(ctx context.Context, activityID int64) error {
	if activityID <= 0 {
		return NewAppError(http.StatusBadRequest, "invalid_activity_id", "activityId is required")
	}
	if err := s.freezeSettlement(ctx, activityID); err != nil {
		return err
	}
	var items []model.YumiGameKingDeliveryItem
	if err := s.db.WithContext(ctx).
		Where("activity_id = ? AND owner_type = ? AND delivery_status = ?", activityID, OwnerSettlement, DeliveryPending).
		Order("id ASC").Limit(settlementDispatchBatch).Find(&items).Error; err != nil {
		return err
	}
	// 人工结算同样限制每次最多发送 4 组，最坏外部调用约 80 秒并为 DB 留出余量；
	// 剩余 PENDING 由后续 settle-due 批次继续恢复，FAILED/UNKNOWN 不会自动发送。
	var lastErr error
	for _, item := range items {
		if err := s.dispatchDeliveryItem(ctx, item.ID, false); err != nil {
			lastErr = err
		}
	}
	return lastErr
}

func (s *Service) freezeSettlement(ctx context.Context, activityID int64) error {
	return s.db.WithContext(ctx).Transaction(func(tx *gorm.DB) error {
		var activity model.YumiGameKingActivity
		// 排他活动锁与事件/抽奖共享锁构成冻结闸门：先进入的业务事务完成后，状态在同一
		// 事务切为 PROCESSING；此后新事件会在共享锁放行后看到非 NOT_STARTED 并拒绝入账。
		if err := withWriteLock(tx).Where("id = ?", activityID).First(&activity).Error; err != nil {
			if errors.Is(err, gorm.ErrRecordNotFound) {
				return NewAppError(http.StatusNotFound, "activity_not_found", "game king activity was not found")
			}
			return err
		}
		now := time.Now()
		if !activity.Enabled {
			return NewAppError(http.StatusConflict, "activity_disabled", "disabled activity cannot be settled")
		}
		if now.Before(activity.SettlementTime) {
			return NewAppError(http.StatusConflict, "settlement_not_due", "activity settlement time has not arrived")
		}
		if activity.SettlementStatus != SettlementNotStarted {
			return nil
		}
		if err := tx.Model(&model.YumiGameKingActivity{}).Where("id = ?", activity.ID).
			Updates(map[string]any{"settlement_status": SettlementProcessing, "update_time": now}).Error; err != nil {
			return err
		}

		var users []model.YumiGameKingUser
		if err := tx.Where("activity_id = ? AND total_consumed > 0", activity.ID).
			Order("total_consumed DESC, consume_reached_time ASC, user_id ASC").Limit(30).Find(&users).Error; err != nil {
			return err
		}
		if len(users) == 0 {
			return tx.Model(&model.YumiGameKingActivity{}).Where("id = ?", activity.ID).
				Updates(map[string]any{"settlement_status": SettlementCompleted, "update_time": now}).Error
		}
		var rewards []model.YumiGameKingRankReward
		if err := tx.Where("activity_id = ?", activity.ID).Order("start_rank ASC").Find(&rewards).Error; err != nil {
			return err
		}
		if len(rewards) != len(fixedRankRanges) {
			return NewAppError(http.StatusConflict, "rank_reward_config_invalid", "six rank reward tiers are required for settlement")
		}
		for index, user := range users {
			rank := index + 1
			reward, ok := rankRewardFor(rewards, rank)
			if !ok {
				return NewAppError(http.StatusConflict, "rank_reward_config_invalid", "rank reward tier does not cover Top30")
			}
			recordID, err := utils.NextID()
			if err != nil {
				return err
			}
			itemID, err := utils.NextID()
			if err != nil {
				return err
			}
			businessNo := fmt.Sprintf("YUMI_GAME_KING_SETTLEMENT:%d:%d", activity.ID, rank)
			record := model.YumiGameKingSettlementRecord{
				ID: recordID, ActivityID: activity.ID, UserID: user.UserID, RankNo: rank,
				TotalConsumed: user.TotalConsumed, RankRewardID: reward.ID, ResourceGroupID: reward.ResourceGroupID,
				BusinessNo: businessNo, DeliveryStatus: DeliveryPending, CreateTime: now, UpdateTime: now,
			}
			if err := tx.Create(&record).Error; err != nil {
				return err
			}
			if err := tx.Create(&model.YumiGameKingDeliveryItem{
				ID: itemID, OwnerType: OwnerSettlement, OwnerID: record.ID, ActivityID: activity.ID,
				UserID: user.UserID, ResourceGroupID: reward.ResourceGroupID,
				DeliveryStatus: DeliveryPending, CreateTime: now, UpdateTime: now,
			}).Error; err != nil {
				return err
			}
		}
		return nil
	})
}

func rankRewardFor(rows []model.YumiGameKingRankReward, rank int) (model.YumiGameKingRankReward, bool) {
	for _, row := range rows {
		if rank >= row.StartRank && rank <= row.EndRank {
			return row, true
		}
	}
	return model.YumiGameKingRankReward{}, false
}

// SettleDue 是外部 cron 的唯一批量触发业务方法；本仓库不启动 ticker。
func (s *Service) SettleDue(ctx context.Context) (*SettleDueResult, error) {
	// 先把过期 PROCESSING 保守转 UNKNOWN；只做状态修复，不盲发。
	if err := s.markStaleProcessingUnknown(ctx, staleDeliveryBatch); err != nil {
		return nil, err
	}
	var activities []model.YumiGameKingActivity
	if err := s.db.WithContext(ctx).
		Where("enabled = ? AND settlement_time <= ? AND settlement_status = ?", true, time.Now(), SettlementNotStarted).
		Order("settlement_time ASC, id ASC").Limit(settlementDueBatch).Find(&activities).Error; err != nil {
		return nil, err
	}
	result := &SettleDueResult{FailedIDs: []string{}}
	for _, activity := range activities {
		result.Scanned++
		// 批量端点只快速冻结排名并生成 PENDING，不在单个活动内串行发送 Top30。
		if err := s.freezeSettlement(ctx, activity.ID); err != nil {
			result.FailedIDs = append(result.FailedIDs, strconv.FormatInt(activity.ID, 10))
			continue
		}
		result.Settled++
	}
	// 每次最多领取 4 个全局 PENDING；单项 dispatch 硬超时 20 秒，外部调用上界约
	// 80 秒，为冻结/状态修复留约 40 秒，chatapp-cron 应配置 >=120 秒超时。
	if _, err := s.RecoverPendingDeliveries(ctx, settlementDispatchBatch); err != nil {
		return nil, err
	}
	return result, nil
}