package services

import (
	"context"
	"errors"
	"time"

	"quyun/v2/app/errorx"
	"quyun/v2/database/models"
	"quyun/v2/pkg/consts"

	"github.com/sirupsen/logrus"
	"gorm.io/gorm"
	"gorm.io/gorm/clause"
)

// LedgerApplyResult is the result of a single ledger application, including the created ledger record
// and the updated tenant user balance snapshot.
type LedgerApplyResult struct {
	// Ledger is the created ledger record (or existing one if idempotent hit).
	Ledger *models.TenantLedger
	// TenantUser is the updated tenant user record reflecting the post-apply balances.
	TenantUser *models.TenantUser
}

// ledger provides tenant balance ledger operations (freeze/unfreeze/etc.) with idempotency and row-locking.
//
//	@provider
type ledger struct {
	db *gorm.DB
}

// Freeze moves funds from available balance to frozen balance and records a tenant ledger entry.
func (s *ledger) Freeze(ctx context.Context, tenantID, userID, orderID, amount int64, idempotencyKey, remark string, now time.Time) (*LedgerApplyResult, error) {
	return s.apply(ctx, s.db, tenantID, userID, orderID, consts.TenantLedgerTypeFreeze, amount, -amount, amount, idempotencyKey, remark, now)
}

// Unfreeze moves funds from frozen balance back to available balance and records a tenant ledger entry.
func (s *ledger) Unfreeze(ctx context.Context, tenantID, userID, orderID, amount int64, idempotencyKey, remark string, now time.Time) (*LedgerApplyResult, error) {
	return s.apply(ctx, s.db, tenantID, userID, orderID, consts.TenantLedgerTypeUnfreeze, amount, amount, -amount, idempotencyKey, remark, now)
}

// FreezeTx is the transaction-scoped variant of Freeze.
func (s *ledger) FreezeTx(ctx context.Context, tx *gorm.DB, tenantID, userID, orderID, amount int64, idempotencyKey, remark string, now time.Time) (*LedgerApplyResult, error) {
	return s.apply(ctx, tx, tenantID, userID, orderID, consts.TenantLedgerTypeFreeze, amount, -amount, amount, idempotencyKey, remark, now)
}

// UnfreezeTx is the transaction-scoped variant of Unfreeze.
func (s *ledger) UnfreezeTx(ctx context.Context, tx *gorm.DB, tenantID, userID, orderID, amount int64, idempotencyKey, remark string, now time.Time) (*LedgerApplyResult, error) {
	return s.apply(ctx, tx, tenantID, userID, orderID, consts.TenantLedgerTypeUnfreeze, amount, amount, -amount, idempotencyKey, remark, now)
}

// DebitPurchaseTx turns frozen funds into a finalized debit (reduces frozen balance) and records a ledger entry.
func (s *ledger) DebitPurchaseTx(ctx context.Context, tx *gorm.DB, tenantID, userID, orderID, amount int64, idempotencyKey, remark string, now time.Time) (*LedgerApplyResult, error) {
	return s.apply(ctx, tx, tenantID, userID, orderID, consts.TenantLedgerTypeDebitPurchase, amount, 0, -amount, idempotencyKey, remark, now)
}

// CreditRefundTx credits funds back to available balance and records a ledger entry.
func (s *ledger) CreditRefundTx(ctx context.Context, tx *gorm.DB, tenantID, userID, orderID, amount int64, idempotencyKey, remark string, now time.Time) (*LedgerApplyResult, error) {
	return s.apply(ctx, tx, tenantID, userID, orderID, consts.TenantLedgerTypeCreditRefund, amount, amount, 0, idempotencyKey, remark, now)
}

// CreditTopupTx credits funds to available balance and records a ledger entry.
func (s *ledger) CreditTopupTx(ctx context.Context, tx *gorm.DB, tenantID, userID, orderID, amount int64, idempotencyKey, remark string, now time.Time) (*LedgerApplyResult, error) {
	return s.apply(ctx, tx, tenantID, userID, orderID, consts.TenantLedgerTypeCreditTopup, amount, amount, 0, idempotencyKey, remark, now)
}

func (s *ledger) apply(
	ctx context.Context,
	tx *gorm.DB,
	tenantID, userID, orderID int64,
	ledgerType consts.TenantLedgerType,
	amount, deltaBalance, deltaFrozen int64,
	idempotencyKey, remark string,
	now time.Time,
) (*LedgerApplyResult, error) {
	if amount <= 0 {
		return nil, errorx.ErrInvalidParameter.WithMsg("amount must be > 0")
	}
	if now.IsZero() {
		now = time.Now()
	}

	logrus.WithFields(logrus.Fields{
		"tenant_id":        tenantID,
		"user_id":          userID,
		"order_id":         orderID,
		"type":             ledgerType,
		"amount":           amount,
		"idempotency_key":  idempotencyKey,
		"delta_balance":    deltaBalance,
		"delta_frozen":     deltaFrozen,
		"remark_non_empty": remark != "",
	}).Info("services.ledger.apply")

	var out LedgerApplyResult

	err := tx.WithContext(ctx).Transaction(func(tx *gorm.DB) error {
		if idempotencyKey != "" {
			var existing models.TenantLedger
			if err := tx.
				Where("tenant_id = ? AND user_id = ? AND idempotency_key = ?", tenantID, userID, idempotencyKey).
				First(&existing).Error; err == nil {
				var current models.TenantUser
				if err := tx.Where("tenant_id = ? AND user_id = ?", tenantID, userID).First(&current).Error; err != nil {
					return err
				}
				out.Ledger = &existing
				out.TenantUser = &current
				return nil
			} else if !errors.Is(err, gorm.ErrRecordNotFound) {
				return err
			}
		}

		var tu models.TenantUser
		if err := tx.
			Clauses(clause.Locking{Strength: "UPDATE"}).
			Where("tenant_id = ? AND user_id = ?", tenantID, userID).
			First(&tu).Error; err != nil {
			if errors.Is(err, gorm.ErrRecordNotFound) {
				return errorx.ErrRecordNotFound.WithMsg("tenant user not found")
			}
			return err
		}

		if idempotencyKey != "" {
			var existing models.TenantLedger
			if err := tx.
				Where("tenant_id = ? AND user_id = ? AND idempotency_key = ?", tenantID, userID, idempotencyKey).
				First(&existing).Error; err == nil {
				out.Ledger = &existing
				out.TenantUser = &tu
				return nil
			} else if !errors.Is(err, gorm.ErrRecordNotFound) {
				return err
			}
		}

		balanceBefore := tu.Balance
		frozenBefore := tu.BalanceFrozen
		balanceAfter := balanceBefore + deltaBalance
		frozenAfter := frozenBefore + deltaFrozen

		if balanceAfter < 0 {
			return errorx.ErrPreconditionFailed.WithMsg("余额不足")
		}
		if frozenAfter < 0 {
			return errorx.ErrPreconditionFailed.WithMsg("冻结余额不足")
		}

		if err := tx.Model(&models.TenantUser{}).
			Where("id = ?", tu.ID).
			Updates(map[string]any{
				"balance":        balanceAfter,
				"balance_frozen": frozenAfter,
				"updated_at":     now,
			}).Error; err != nil {
			return err
		}

		ledger := &models.TenantLedger{
			TenantID:       tenantID,
			UserID:         userID,
			OrderID:        orderID,
			Type:           ledgerType,
			Amount:         amount,
			BalanceBefore:  balanceBefore,
			BalanceAfter:   balanceAfter,
			FrozenBefore:   frozenBefore,
			FrozenAfter:    frozenAfter,
			IdempotencyKey: idempotencyKey,
			Remark:         remark,
			CreatedAt:      now,
			UpdatedAt:      now,
		}
		if err := tx.Create(ledger).Error; err != nil {
			if idempotencyKey != "" {
				var existing models.TenantLedger
				if e2 := tx.
					Where("tenant_id = ? AND user_id = ? AND idempotency_key = ?", tenantID, userID, idempotencyKey).
					First(&existing).Error; e2 == nil {
					out.Ledger = &existing
					out.TenantUser = &tu
					return nil
				}
			}
			return err
		}

		tu.Balance = balanceAfter
		tu.BalanceFrozen = frozenAfter
		tu.UpdatedAt = now

		out.Ledger = ledger
		out.TenantUser = &tu
		return nil
	})
	if err != nil {
		logrus.WithFields(logrus.Fields{
			"tenant_id":       tenantID,
			"user_id":         userID,
			"order_id":        orderID,
			"type":            ledgerType,
			"idempotency_key": idempotencyKey,
		}).WithError(err).Warn("services.ledger.apply.failed")
		return nil, err
	}

	logrus.WithFields(logrus.Fields{
		"tenant_id":       tenantID,
		"user_id":         userID,
		"order_id":        orderID,
		"type":            ledgerType,
		"ledger_id":       out.Ledger.ID,
		"idempotency_key": idempotencyKey,
		"balance_after":   out.TenantUser.Balance,
		"frozen_after":    out.TenantUser.BalanceFrozen,
	}).Info("services.ledger.apply.ok")

	return &out, nil
}