package distribution

import (
	"errors"
	"sync"
	"time"

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

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

// distributionTablesPresent 探测分销财务表是否存在，仅首次访问查询 information_schema，
// 兼容尚未执行分销迁移的旧环境，避免每次支付/退款事务都做系统表查询。
var (
	distributionTablePresent   bool
	distributionTableCheckOnce sync.Once
)

func distributionTablesPresent(tx *gorm.DB) bool {
	distributionTableCheckOnce.Do(func() {
		distributionTablePresent = tx.Migrator().HasTable(&model.DistributionOrderFinancial{})
	})
	return distributionTablePresent
}

// resolveDistributionMode 只根据买卖双方站点判定模式，不查库、不猜规则。
// buySiteID / listingSiteID 为 0 表示主站。
func resolveDistributionMode(buySiteID, listingSiteID uint64) string {
	switch {
	case buySiteID == 0 && listingSiteID == 0:
		return ""
	case buySiteID == 0:
		return ModeTwoPartyDistributorReceive
	case listingSiteID == 0:
		return ModeTwoPartyPlatformReceive
	case buySiteID == listingSiteID:
		return ModeSiteSelfSell
	default:
		return ModeThreeParty
	}
}

func derefSiteID(id *uint64) uint64 {
	if id == nil || *id == 0 {
		return 0
	}
	return *id
}

func loadListingSiteID(tx *gorm.DB, listingID uint64) (uint64, error) {
	if listingID == 0 {
		return 0, nil
	}
	var listing model.RentalListing
	if err := tx.Select("id, distribution_site_id").First(&listing, listingID).Error; err != nil {
		if errors.Is(err, gorm.ErrRecordNotFound) {
			return 0, nil
		}
		return 0, err
	}
	return derefSiteID(listing.DistributionSiteID), nil
}

func loadActiveSiteByID(tx *gorm.DB, siteID uint64) (*model.DistributionSite, error) {
	var site model.DistributionSite
	if err := tx.Where("id = ? AND status = 'active'", siteID).First(&site).Error; err != nil {
		return nil, ErrSiteNotFound
	}
	return &site, nil
}

func loadActiveSellSiteByCode(tx *gorm.DB, siteCode string) (*model.DistributionSite, error) {
	var site model.DistributionSite
	if err := tx.Where("site_code = ? AND status = 'active' AND display_account_enabled = ?", siteCode, true).First(&site).Error; err != nil {
		return nil, ErrSiteNotFound
	}
	return &site, nil
}

func ensureAccountDisplayTx(tx *gorm.DB, siteID, listingID, accountID uint64) error {
	var relation model.DistributionSiteAccount
	if err := tx.Where("site_id = ? AND listing_id = ? AND account_id = ? AND display_status = 'enabled'", siteID, listingID, accountID).First(&relation).Error; err != nil {
		return ErrAccountDisplayNotFound
	}
	return nil
}

func findActiveRuleTx(tx *gorm.DB, siteID uint64, mode string, at time.Time) (*model.DistributionRuleVersion, error) {
	var rule model.DistributionRuleVersion
	err := tx.Where("mode = ? AND status = 'active' AND effective_from <= ? AND (effective_to IS NULL OR effective_to > ?)", mode, at, at).
		Where("site_id = ? OR site_id IS NULL", siteID).
		Order("CASE WHEN site_id IS NULL THEN 1 ELSE 0 END, effective_from DESC, id DESC").
		First(&rule).Error
	if err != nil {
		if errors.Is(err, gorm.ErrRecordNotFound) {
			return nil, ErrRuleNotFound
		}
		return nil, err
	}
	return &rule, nil
}

// ResolveOrderSourceTx 先按买卖站点判定模式，再查该 mode 的生效规则，不再在两方规则之间猜优先级。
func ResolveOrderSourceTx(tx *gorm.DB, siteCode string, listingID, accountID uint64, at time.Time) (*model.DistributionSite, *model.DistributionRuleVersion, error) {
	listingSiteID, err := loadListingSiteID(tx, listingID)
	if err != nil {
		return nil, nil, err
	}

	var buySite *model.DistributionSite
	buySiteID := uint64(0)
	if siteCode != "" {
		buySite, err = loadActiveSellSiteByCode(tx, siteCode)
		if err != nil {
			return nil, nil, err
		}
		if err := ensureAccountDisplayTx(tx, buySite.ID, listingID, accountID); err != nil {
			return nil, nil, err
		}
		buySiteID = buySite.ID
	}

	mode := resolveDistributionMode(buySiteID, listingSiteID)
	if mode == "" {
		return nil, nil, nil
	}

	var anchor *model.DistributionSite
	switch mode {
	case ModeTwoPartyDistributorReceive:
		anchor, err = loadActiveSiteByID(tx, listingSiteID)
		if err != nil {
			return nil, nil, err
		}
	default:
		if buySite == nil {
			return nil, nil, ErrSiteNotFound
		}
		anchor = buySite
	}

	rule, err := findActiveRuleTx(tx, anchor.ID, mode, at)
	if err != nil {
		return nil, nil, err
	}
	return anchor, rule, nil
}

func ruleFromVersion(rule model.DistributionRuleVersion) Rule {
	parsed := Rule{
		Mode:                    rule.Mode,
		PlatformReceiveRatio:    rule.PlatformReceiveRatio,
		PlatformSellRatio:       rule.PlatformSellRatio,
		DistributorReceiveRatio: rule.DistributorReceiveRatio,
		DistributorSellRatio:    rule.DistributorSellRatio,
		DistributorARatio:       rule.DistributorARatio,
		DistributorBRatio:       rule.DistributorBRatio,
		ServiceFeeValue:         rule.ServiceFeeValue,
		ServiceFeeUnit:          rule.ServiceFeeUnit,
		PaymentFeeBPS:           rule.PaymentFeeBPS,
		TaxEnabled:              rule.TaxEnabled,
		TaxRateBPS:              rule.TaxRateBPS,
	}
	normalizeRulePercents(&parsed)
	return parsed
}

// calculateForRule 按规则快照计算手续费、服务费和分成基数。
func calculateForRule(rule model.DistributionRuleVersion, input SettlementInput) (SettlementResult, error) {
	return CalculateSettlement(ruleFromVersion(rule), input)
}

// SnapshotPaidOrderTx 在支付确认事务内幂等写入财务和参与方快照。
// 利润 = 租金 − 号主 − 加价（通道手续费由主站承担，只记录），再按 35%/40%/25% 切；尾差记入 RoundingAdjustmentCent。
func SnapshotPaidOrderTx(tx *gorm.DB, orderID uint64, grossPaidCent int64) error {
	if !distributionTablesPresent(tx) {
		return nil
	}
	var order model.RentalOrder
	if err := tx.First(&order, orderID).Error; err != nil {
		return err
	}
	if order.DistributionSiteID == nil || order.DistributionRuleVersionID == nil {
		return nil
	}
	var rule model.DistributionRuleVersion
	if err := tx.First(&rule, *order.DistributionRuleVersionID).Error; err != nil {
		return err
	}
	grossRent := order.RentAmountCent
	if grossRent <= 0 {
		grossRent = grossPaidCent
	}
	markup := order.ShelfMarkupCent
	if markup < 0 {
		markup = 0
	}
	ownerRent := order.OwnerRentAmountCent
	if ownerRent < 0 {
		ownerRent = 0
	}
	result, err := calculateForRule(rule, SettlementInput{GrossPaidAmountCent: grossRent, OwnerRentAmountCent: ownerRent, MarkupAmountCent: markup})
	if err != nil {
		return err
	}
	splits := SplitSettlement(ruleFromVersion(rule), result.SplitBaseAmountCent, result.MarkupAmountCent)
	financial := model.DistributionOrderFinancial{OrderID: order.ID, SiteID: *order.DistributionSiteID, RuleVersionID: rule.ID, GrossPaidAmountCent: grossRent, NetPaidAmountCent: result.NetPaidAmountCent, PaymentFeeBPS: rule.PaymentFeeBPS, PaymentFeeCent: result.PaymentFeeCent, ServiceFeeValue: rule.ServiceFeeValue, ServiceFeeUnit: rule.ServiceFeeUnit, ServiceFeeCent: result.ServiceFeeCent, MarkupAmountCent: markup, TaxEnabled: rule.TaxEnabled, TaxRateBPS: rule.TaxRateBPS, TaxAmountCent: result.TaxAmountCent, SplitBaseAmountCent: result.SplitBaseAmountCent, RoundingAdjustmentCent: SplitRoundingCent(result.SplitBaseAmountCent, result.ServiceFeeCent, result.MarkupAmountCent, splits), SettlementStatus: "pending"}
	// 支付回调可能重复触发：保留已写入的释放与结算时间，避免把已释放的快照重置回待释放。
	var existing model.DistributionOrderFinancial
	if err := tx.Where("order_id = ?", order.ID).First(&existing).Error; err == nil {
		financial.ReleaseAt = existing.ReleaseAt
		financial.ReleasedAt = existing.ReleasedAt
		financial.SettledAt = existing.SettledAt
		financial.SettlementStatus = existing.SettlementStatus
	}
	if err := tx.Where("order_id = ?", order.ID).Assign(financial).FirstOrCreate(&financial).Error; err != nil {
		return err
	}
	var count int64
	if err := tx.Model(&model.DistributionOrderParty{}).Where("order_id = ?", order.ID).Count(&count).Error; err != nil {
		return err
	}
	if count > 0 {
		return nil
	}
	parties := make([]model.DistributionOrderParty, 0, len(splits))
	for _, split := range splits {
		partyType := PartyTypeSite
		if split.PartyRole == "platform_sell" || split.PartyRole == "platform_receive" {
			partyType = PartyTypePlatform
		}
		partyID := *order.DistributionSiteID
		if partyType == PartyTypePlatform {
			partyID = 0
		} else if split.PartyRole == "distributor_a" {
			// 三方模式下 distributor_a 为商品收号站
			var listing model.RentalListing
			if err := tx.Select("distribution_site_id").First(&listing, order.ListingID).Error; err == nil && listing.DistributionSiteID != nil {
				partyID = *listing.DistributionSiteID
			}
		}
		parties = append(parties, model.DistributionOrderParty{OrderID: order.ID, SiteID: *order.DistributionSiteID, PartyRole: split.PartyRole, PartyType: partyType, PartyID: partyID, Ratio: split.Ratio, IncomeAmountCent: split.AmountCent, ProfitAmountCent: split.AmountCent})
	}
	if len(parties) == 0 {
		return nil
	}
	return tx.Create(&parties).Error
}

// ApplyRefundTx 按累计成功退款或结账结算重算手续费、分成基数和各方分成，不覆盖订单创建时的规则版本。
func ApplyRefundTx(tx *gorm.DB, orderID uint64, refundAmountCent int64) error {
	if !distributionTablesPresent(tx) {
		return nil
	}
	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 nil
		}
		return err
	}
	if refundAmountCent < 0 {
		return ErrInvalidAmount
	}

	var rule model.DistributionRuleVersion
	if err := tx.First(&rule, financial.RuleVersionID).Error; err != nil {
		return err
	}

	var order model.RentalOrder
	if err := tx.First(&order, orderID).Error; err != nil {
		return err
	}

	// 判定实际租金退款和号主应得租金：
	// 1. 如果存在已达成一致的结账单（accepted 或 settled），以结账单中的实际消费租金与号主实际所得为准
	var checkout model.OrderCheckout
	hasAcceptedCheckout := false
	if err := tx.Where("order_id = ? AND status IN ('accepted', 'settled')", orderID).
		Order("id DESC").First(&checkout).Error; err == nil {
		hasAcceptedCheckout = true
	}

	rentRefundCent := refundAmountCent
	ownerRent := order.OwnerRentAmountCent
	if ownerRent < 0 {
		ownerRent = 0
	}

	if hasAcceptedCheckout {
		// 结账单中，实际有效租金为 checkout.RentAmountCent
		// 真实的租金退款为 订单初始租金 - 实际有效租金
		actualRentRefund := order.RentAmountCent - checkout.RentAmountCent
		if actualRentRefund < 0 {
			actualRentRefund = 0
		}
		rentRefundCent = actualRentRefund
		// 号主实际租金所得以结账单的实际租金收入为准
		ownerRent = checkout.OwnerRentAmountCent
		if ownerRent < 0 {
			ownerRent = 0
		}
	} else {
		// 无结账单场景（例如交接超时、提前取消退款、维权全额退款）：
		// refundAmountCent 是租客收到的总退款（含押金与租金），押金不计入分销毛收入
		// 先抵扣押金退款，剩余部分才属于租金退款
		depositRefund := order.DepositAmountCent
		if refundAmountCent < depositRefund {
			depositRefund = refundAmountCent
		}
		actualRentRefund := refundAmountCent - depositRefund
		if actualRentRefund < 0 {
			actualRentRefund = 0
		}
		rentRefundCent = actualRentRefund
		// 如果租金全额退款，号主应得租金为 0
		if rentRefundCent >= financial.GrossPaidAmountCent {
			ownerRent = 0
		}
	}

	if rentRefundCent > financial.GrossPaidAmountCent {
		rentRefundCent = financial.GrossPaidAmountCent
	}

	result, err := calculateForRule(rule, SettlementInput{
		GrossPaidAmountCent: financial.GrossPaidAmountCent,
		RefundAmountCent:    rentRefundCent,
		OwnerRentAmountCent: ownerRent,
		MarkupAmountCent:    financial.MarkupAmountCent,
	})
	if err != nil {
		return err
	}
	splits := SplitSettlement(ruleFromVersion(rule), result.SplitBaseAmountCent, result.MarkupAmountCent)
	// 已释放入账的订单保持 settled，避免自动释放任务重复入账；差额通过回冲流水追偿。
	settlementStatus := "pending"
	if financial.ReleasedAt != nil {
		settlementStatus = "settled"
	}
	releaseAt, err := computeReleaseAt(tx, order, financial)
	if err != nil {
		return err
	}
	if err := tx.Model(&financial).Updates(map[string]any{
		"refund_amount_cent":       rentRefundCent,
		"net_paid_amount_cent":     result.NetPaidAmountCent,
		"payment_fee_cent":         result.PaymentFeeCent,
		"service_fee_cent":         result.ServiceFeeCent,
		"split_base_amount_cent":   result.SplitBaseAmountCent,
		"rounding_adjustment_cent": SplitRoundingCent(result.SplitBaseAmountCent, result.ServiceFeeCent, result.MarkupAmountCent, splits),
		"settlement_status":        settlementStatus,
		"release_at":               releaseAt,
	}).Error; err != nil {
		return err
	}
	for _, split := range splits {
		var party model.DistributionOrderParty
		if err := tx.Clauses(clause.Locking{Strength: "UPDATE"}).
			Where("order_id = ? AND party_role = ?", orderID, split.PartyRole).First(&party).Error; err != nil {
			if errors.Is(err, gorm.ErrRecordNotFound) {
				continue
			}
			return err
		}
		if party.IncomeAmountCent == split.AmountCent && party.ProfitAmountCent == split.AmountCent {
			continue
		}
		// 已结算入账的分站份额被退款调减时，从收款站点钱包扣回差额（允许扣成负数，由后续收益抵扣）。
		settled, err := partySettled(tx, party.ID)
		if err != nil {
			return err
		}
		if split.AmountCent < party.IncomeAmountCent && party.PartyType == PartyTypeSite && settled {
			reversal := party.IncomeAmountCent - split.AmountCent
			if err := wallet.AppendEntries(tx, wallet.Entry{
				UserID:             0,
				DistributionSiteID: party.PartyID,
				OrderID:            &orderID,
				Direction:          "out",
				AmountCent:         reversal,
				BalanceType:        "available",
				BizType:            "distribution_reversal",
				BizNo:              order.OrderNo,
				Remark:             "结算入账后退款回冲",
				AllowNegative:      true,
			}); err != nil {
				return err
			}
		}
		if err := tx.Model(&model.DistributionOrderParty{}).
			Where("id = ?", party.ID).
			Updates(map[string]any{
				"income_amount_cent": split.AmountCent,
				"profit_amount_cent": split.AmountCent,
			}).Error; err != nil {
			return err
		}
	}
	return nil
}

// EnsureCompletedReleaseAtTx 在订单进入 completed 且尚未入账时写入 release_at。
// 无分销快照时为 no-op，供结账、仲裁、退款重算共用，避免完单后漏写导致永远无法自动释放。
func EnsureCompletedReleaseAtTx(tx *gorm.DB, orderID uint64) error {
	if !distributionTablesPresent(tx) {
		return nil
	}
	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 nil
		}
		return err
	}
	var order model.RentalOrder
	if err := tx.Select("id, status, settled_at").First(&order, orderID).Error; err != nil {
		return err
	}
	releaseAt, err := computeReleaseAt(tx, order, financial)
	if err != nil {
		return err
	}
	return tx.Model(&financial).Update("release_at", releaseAt).Error
}

// computeReleaseAt 按站点当前冷却天数计算释放时间；已入账快照保持原 release_at。
func computeReleaseAt(tx *gorm.DB, order model.RentalOrder, financial model.DistributionOrderFinancial) (*time.Time, error) {
	if financial.ReleasedAt != nil {
		return financial.ReleaseAt, nil
	}
	if !orderStatusAllowsRelease(order.Status) {
		return financial.ReleaseAt, nil
	}
	completedAt := order.SettledAt
	if completedAt == nil {
		now := time.Now()
		completedAt = &now
	}
	var site model.DistributionSite
	if err := tx.Select("id, settlement_hold_days").First(&site, financial.SiteID).Error; err != nil {
		return nil, err
	}
	due := completedAt.AddDate(0, 0, site.SettlementHoldDays)
	return &due, nil
}

// rewritePendingReleaseAt 站点冷却天数变更后，按新规则回写尚未入账的已完成订单释放时间。
func rewritePendingReleaseAt(tx *gorm.DB, siteID uint64) error {
	var financials []model.DistributionOrderFinancial
	if err := tx.Where("site_id = ? AND settlement_status = ? AND released_at IS NULL", siteID, "pending").
		Find(&financials).Error; err != nil {
		return err
	}
	for _, financial := range financials {
		var order model.RentalOrder
		if err := tx.Select("id, status, settled_at").First(&order, financial.OrderID).Error; err != nil {
			if errors.Is(err, gorm.ErrRecordNotFound) {
				continue
			}
			return err
		}
		if !orderStatusAllowsRelease(order.Status) {
			continue
		}
		releaseAt, err := computeReleaseAt(tx, order, financial)
		if err != nil {
			return err
		}
		if err := tx.Model(&model.DistributionOrderFinancial{}).Where("id = ?", financial.ID).
			Update("release_at", releaseAt).Error; err != nil {
			return err
		}
	}
	return nil
}

func orderStatusAllowsRelease(status string) bool {
	return status == "completed" || status == "closed"
}

// partySettled 判断参与方份额是否已经通过结算批次入账。
func partySettled(tx *gorm.DB, partyID uint64) (bool, error) {
	var count int64
	if err := tx.Model(&model.DistributionSettlementItem{}).
		Where("party_id = ? AND status = 'settled'", partyID).Count(&count).Error; err != nil {
		return false, err
	}
	return count > 0, nil
}