package distribution

import (
	"context"
	"errors"
	"fmt"
	"slices"
	"strings"
	"time"

	"hfb_sys/backend/internal/model"
	"hfb_sys/backend/internal/modules/wallet"

	"gorm.io/gorm"
	"gorm.io/gorm/clause"
)

// autoBatchPrefix 区分自动释放批次与主站财务手工创建的结算批次（DS 前缀）。
const autoBatchPrefix = "DA"

// autoReleaseBlockedRefundStatuses 进行中的退款不得自动释放，避免先入账再回冲。
var autoReleaseBlockedRefundStatuses = []string{"pending", "pending_review", "refunding"}

// autoReleaseBlockedDisputeStatuses 开放中的维权订单暂缓释放。
var autoReleaseBlockedDisputeStatuses = []string{"open", "processing"}

// AutoReleaseDueSettlements 扫描到达释放时间的分销订单，按站点自动创建批次并释放到可提现余额。
// 返回实际触达释放的订单数。
func (r *Repository) AutoReleaseDueSettlements(ctx context.Context) (int, error) {
	if r == nil || r.db == nil {
		return 0, ErrDependencyUnavailable
	}
	now := time.Now()
	var orderIDs []uint64
	if err := r.db.WithContext(ctx).
		Table("distribution_order_financials f").
		Select("DISTINCT f.order_id").
		Joins("JOIN rental_orders ro ON ro.id = f.order_id").
		Where("f.settlement_status = ? AND f.release_at IS NOT NULL AND f.release_at <= ?", "pending", now).
		Where("ro.status IN ?", settlementReadyOrderStatuses).
		Where("ro.refund_status NOT IN ?", autoReleaseBlockedRefundStatuses).
		Where("NOT EXISTS (SELECT 1 FROM disputes d WHERE d.order_id = ro.id AND d.status IN ?)", autoReleaseBlockedDisputeStatuses).
		Order("f.order_id ASC").
		Limit(1000).
		Scan(&orderIDs).Error; err != nil {
		return 0, err
	}
	if len(orderIDs) == 0 {
		return 0, nil
	}

	var siteIDs []uint64
	if err := r.db.WithContext(ctx).
		Table("distribution_order_parties p").
		Select("DISTINCT p.party_id").
		Where("p.order_id IN ? AND p.party_type = ?", orderIDs, PartyTypeSite).
		Where("NOT EXISTS (SELECT 1 FROM distribution_settlement_items i WHERE i.party_id = p.id)").
		Order("p.party_id ASC").
		Scan(&siteIDs).Error; err != nil {
		return 0, err
	}

	released := 0
	for _, siteID := range siteIDs {
		if siteID == 0 {
			continue
		}
		count, err := r.releaseSiteSettlements(ctx, siteID, orderIDs, now)
		if err != nil {
			return released, fmt.Errorf("释放站点 %d 分销结算失败: %w", siteID, err)
		}
		released += count
	}
	return released, nil
}

// releaseSiteSettlements 在事务内释放指定站点上所有到期订单的份额：
// 复用当天的自动批次，生成结算明细并把总额入账到站点钱包。
func (r *Repository) releaseSiteSettlements(ctx context.Context, siteID uint64, orderIDs []uint64, now time.Time) (int, error) {
	releasedOrders := 0
	err := r.db.WithContext(ctx).Transaction(func(tx *gorm.DB) error {
		// 先不加锁筛出本站尚未入账的候选参与方对应的订单，收敛后续加锁范围：
		// 调用方传入的是全站到期订单，其中可能大多数已被手工批次纳入，无需加锁。
		var candidateOrderIDs []uint64
		if err := tx.Table("distribution_order_parties p").
			Select("DISTINCT p.order_id").
			Where("p.order_id IN ? AND p.party_type = ? AND p.party_id = ?", orderIDs, PartyTypeSite, siteID).
			Where("NOT EXISTS (SELECT 1 FROM distribution_settlement_items i WHERE i.party_id = p.id)").
			Order("p.order_id ASC").
			Scan(&candidateOrderIDs).Error; err != nil {
			return err
		}
		if len(candidateOrderIDs) == 0 {
			return nil
		}
		// 先锁财务快照再锁参与方，与 ApplyRefundTx 保持同一顺序，避免并发退款回冲时死锁。
		var lockedFinancials []model.DistributionOrderFinancial
		if err := tx.Clauses(clause.Locking{Strength: "UPDATE"}).
			Where("order_id IN ?", candidateOrderIDs).
			Order("id ASC").Find(&lockedFinancials).Error; err != nil {
			return err
		}
		var parties []model.DistributionOrderParty
		if err := tx.Clauses(clause.Locking{Strength: "UPDATE"}).
			Where("order_id IN ? AND party_type = ? AND party_id = ?", candidateOrderIDs, PartyTypeSite, siteID).
			Where("NOT EXISTS (SELECT 1 FROM distribution_settlement_items i WHERE i.party_id = distribution_order_parties.id)").
			Order("order_id ASC, id ASC").Find(&parties).Error; err != nil {
			return err
		}

		releasable := make(map[uint64]bool, len(parties))
		checked := make(map[uint64]struct{}, len(parties))
		eligible := make([]model.DistributionOrderParty, 0, len(parties))
		for _, party := range parties {
			if _, done := checked[party.OrderID]; !done {
				ok, err := releasableOrder(tx, party.OrderID, now)
				if err != nil {
					return err
				}
				checked[party.OrderID] = struct{}{}
				releasable[party.OrderID] = ok
			}
			if !releasable[party.OrderID] {
				continue
			}
			eligible = append(eligible, party)
		}
		if len(eligible) == 0 {
			return nil
		}

		batch, err := ensureAutoBatch(tx, siteID, now)
		if err != nil {
			return err
		}
		var total int64
		orderSet := make(map[uint64]struct{}, len(eligible))
		for _, party := range eligible {
			item := model.DistributionSettlementItem{
				BatchID: batch.ID, OrderID: party.OrderID, PartyID: party.ID,
				AmountCent: party.IncomeAmountCent, Status: "settled",
			}
			if err := tx.Create(&item).Error; err != nil {
				if isDuplicateSettlementItem(err) {
					// 唯一键命中说明另一条路径（手工批次或并发自动释放）已为该参与方建过明细，
					// 跳过它，避免重复入账。
					continue
				}
				return err
			}
			total += party.IncomeAmountCent
			orderSet[party.OrderID] = struct{}{}
		}
		if total > 0 {
			if err := wallet.AppendEntries(tx, wallet.Entry{
				UserID:             0,
				DistributionSiteID: siteID,
				Direction:          "in",
				AmountCent:         total,
				BalanceType:        "available",
				BizType:            "distribution_settlement",
				BizNo:              batch.BatchNo,
				Remark:             fmt.Sprintf("分销自动结算释放 %s", batch.BatchNo),
			}); err != nil {
				return err
			}
		}
		if err := tx.Model(&model.DistributionSettlementBatch{}).Where("id = ?", batch.ID).
			Updates(map[string]any{
				"total_amount_cent": gorm.Expr("total_amount_cent + ?", total),
				"status":            "settled",
				"settled_at":        now,
			}).Error; err != nil {
			return err
		}
		orderList := make([]uint64, 0, len(orderSet))
		for orderID := range orderSet {
			orderList = append(orderList, orderID)
		}
		if err := markFinancialsSettledIfSitePartiesDone(tx, orderList, now); err != nil {
			return err
		}
		releasedOrders = len(orderList)
		return nil
	})
	if err != nil {
		return 0, err
	}
	return releasedOrders, nil
}

// isDuplicateSettlementItem 判断错误是否为结算明细唯一键冲突。
// GORM 未开启 TranslateError 时 MySQL 1062 不会映射为 ErrDuplicatedKey，因此同时检查错误链与错误文本。
func isDuplicateSettlementItem(err error) bool {
	if err == nil {
		return false
	}
	if errors.Is(err, gorm.ErrDuplicatedKey) {
		return true
	}
	return strings.Contains(err.Error(), "1062")
}

// releasableOrder 复核订单是否仍满足释放条件，并返回财务快照。
// 订单在扫描后可能进入退款或维权流程，因此事务内需要重新校验。
func releasableOrder(tx *gorm.DB, orderID uint64, now time.Time) (bool, error) {
	var financial model.DistributionOrderFinancial
	if err := tx.Clauses(clause.Locking{Strength: "UPDATE"}).
		Where("order_id = ?", orderID).First(&financial).Error; err != nil {
		if errors.Is(err, gorm.ErrRecordNotFound) {
			return false, nil
		}
		return false, err
	}
	if financial.SettlementStatus != "pending" || financial.ReleaseAt == nil || financial.ReleaseAt.After(now) {
		return false, nil
	}
	var order model.RentalOrder
	if err := tx.Select("id, status, refund_status").First(&order, orderID).Error; err != nil {
		return false, err
	}
	if !orderStatusAllowsRelease(order.Status) || slices.Contains(autoReleaseBlockedRefundStatuses, order.RefundStatus) {
		return false, nil
	}
	var openDisputes int64
	if err := tx.Table("disputes").
		Where("order_id = ? AND status IN ?", orderID, autoReleaseBlockedDisputeStatuses).
		Count(&openDisputes).Error; err != nil {
		return false, err
	}
	return openDisputes == 0, nil
}

// ensureAutoBatch 复用当天的自动批次（不论 pending/settled），没有则创建，保证对账按站点按天聚合。
func ensureAutoBatch(tx *gorm.DB, siteID uint64, now time.Time) (*model.DistributionSettlementBatch, error) {
	startOfDay := time.Date(now.Year(), now.Month(), now.Day(), 0, 0, 0, 0, now.Location())
	var batch model.DistributionSettlementBatch
	err := tx.Clauses(clause.Locking{Strength: "UPDATE"}).
		Where("site_id = ? AND batch_no LIKE ? AND period_start = ?", siteID, autoBatchPrefix+"%", startOfDay).
		Order("id ASC").First(&batch).Error
	if err == nil {
		return &batch, nil
	}
	if !errors.Is(err, gorm.ErrRecordNotFound) {
		return nil, err
	}
	batch = model.DistributionSettlementBatch{
		SiteID:      siteID,
		BatchNo:     fmt.Sprintf("%s%s%d", autoBatchPrefix, now.Format("20060102150405.000000000"), siteID),
		PeriodStart: startOfDay,
		PeriodEnd:   startOfDay.AddDate(0, 0, 1),
		Status:      "pending",
	}
	if err := tx.Create(&batch).Error; err != nil {
		return nil, err
	}
	return &batch, nil
}