package refund

import (
	"context"
	"strings"
	"time"

	"gorm.io/gorm"

	refundchannel "github.com/break/junhong_cmp_fiber/internal/application/refundchannel"
	"github.com/break/junhong_cmp_fiber/internal/model"
	"github.com/break/junhong_cmp_fiber/pkg/constants"
	"github.com/break/junhong_cmp_fiber/pkg/errors"
)

// refundMethodOption 描述一种可选退款方式及其不可用的原因。
type refundMethodOption struct {
	Method    string
	Name      string
	Available bool
	// Reason 在方式不可用时说明具体原因，供前端禁用并展示。
	Reason string
}

// refundMethodDecision 是一次退款方式判定的完整结果。
type refundMethodDecision struct {
	Options []refundMethodOption
	// FrozenActualReceivedAmount 是系统派生的权威实收金额（分），提交人不可填写或修改。
	FrozenActualReceivedAmount int64
	// Payment 是派生实收金额时使用的原成功支付记录，线上订单才有值。
	Payment *model.Payment
	// ChannelConfig 是原路退款实际使用的冻结商户当前凭证，非线上订单或原路不可用时为 nil。
	ChannelConfig *model.WechatConfig
}

// decideRefundMethods 派生权威实收金额并按来源实际支付方式生成可选退款方式。
//
// 派生来源：线上支付取该订单原成功支付记录金额；资产钱包、代理主钱包与后台线下套餐订单
// 取订单实际收款或实际扣款金额。无法确定或金额非正时拒绝，绝不允许提交人以自填金额替代。
func (s *Service) decideRefundMethods(ctx context.Context, order *model.Order) (*refundMethodDecision, error) {
	if order == nil || order.ID == 0 {
		return nil, errors.New(errors.CodeInvalidParam, "退款来源订单无效")
	}

	decision := &refundMethodDecision{}
	switch order.PaymentMethod {
	case model.PaymentMethodWechat, model.PaymentMethodAlipay:
		payment, err := s.loadPaidPackagePayment(ctx, order.ID)
		if err != nil {
			return nil, err
		}
		if payment.Amount <= 0 {
			return nil, errors.New(errors.CodeInvalidParam, "原成功支付记录金额非正，无法确定权威实收金额")
		}
		decision.Payment = payment
		decision.FrozenActualReceivedAmount = payment.Amount
		originalRoute, reason, config := s.originalRouteAvailability(ctx, order, payment)
		if originalRoute {
			decision.ChannelConfig = config
		}
		decision.Options = []refundMethodOption{
			{Method: constants.RefundMethodOriginalRoute, Name: constants.RefundMethodName(constants.RefundMethodOriginalRoute), Available: originalRoute, Reason: reason},
			{Method: constants.RefundMethodCustomerAccount, Name: constants.RefundMethodName(constants.RefundMethodCustomerAccount), Available: true},
		}
	case model.PaymentMethodWallet:
		amount, err := orderActualPaidAmount(order)
		if err != nil {
			return nil, err
		}
		decision.FrozenActualReceivedAmount = amount
		switch order.BuyerType {
		case model.BuyerTypeAgent:
			decision.Options = []refundMethodOption{
				{Method: constants.RefundMethodAgentWallet, Name: constants.RefundMethodName(constants.RefundMethodAgentWallet), Available: true},
			}
		case model.BuyerTypePersonal:
			decision.Options = []refundMethodOption{
				{Method: constants.RefundMethodAssetWallet, Name: constants.RefundMethodName(constants.RefundMethodAssetWallet), Available: true},
			}
		default:
			return nil, errors.New(errors.CodeInvalidParam, "钱包支付订单的买家类型不支持退款")
		}
	case model.PaymentMethodOffline:
		amount, err := orderActualPaidAmount(order)
		if err != nil {
			return nil, err
		}
		decision.FrozenActualReceivedAmount = amount
		decision.Options = []refundMethodOption{
			{Method: constants.RefundMethodCustomerAccount, Name: constants.RefundMethodName(constants.RefundMethodCustomerAccount), Available: true},
		}
	default:
		return nil, errors.New(errors.CodeInvalidParam, "该订单的支付方式不支持退款")
	}
	return decision, nil
}

// orderActualPaidAmount 取订单实际收款或实际扣款金额作为权威实收金额。
func orderActualPaidAmount(order *model.Order) (int64, error) {
	if order.ActualPaidAmount == nil || *order.ActualPaidAmount <= 0 {
		return 0, errors.New(errors.CodeInvalidParam, "订单实际收款金额缺失或非正，无法确定权威实收金额")
	}
	return *order.ActualPaidAmount, nil
}

// loadPaidPackagePayment 读取该订单原成功的线上支付记录。
func (s *Service) loadPaidPackagePayment(ctx context.Context, orderID uint) (*model.Payment, error) {
	var payment model.Payment
	err := s.db.WithContext(ctx).
		Where("order_id = ? AND order_type = ? AND status = ?", orderID, model.PaymentOrderTypePackage, model.PaymentRecordStatusPaid).
		Order("id DESC").
		First(&payment).Error
	if err != nil {
		if err == gorm.ErrRecordNotFound {
			return nil, errors.New(errors.CodeInvalidParam, "未找到该订单的原成功支付记录，无法确定权威实收金额")
		}
		return nil, errors.Wrap(errors.CodeDatabaseError, err, "查询退款关联支付记录失败")
	}
	return &payment, nil
}

// originalRouteAvailability 预检线上订单的原路退款可退性，并返回实际使用的商户凭证。
//
// 条件全部本地可判定：存在成功支付记录、可定位实际收款商户、该商户具备其服务商类型的
// 退款能力与必需凭证、且原交易未超出渠道可退时限。实际调用渠道后的结果才是退款资格的
// 最终判断；预检只用于在申请阶段禁用原路并说明原因。
func (s *Service) originalRouteAvailability(ctx context.Context, order *model.Order, payment *model.Payment) (bool, string, *model.WechatConfig) {
	if payment == nil {
		return false, "缺少原成功支付记录", nil
	}
	if strings.TrimSpace(payment.ThirdPartyTradeNo) == "" {
		return false, "原支付记录缺少渠道交易流水号", nil
	}
	if s.paymentMerchantRuntime == nil {
		return false, "商户凭证加载能力未配置", nil
	}

	var config *model.WechatConfig
	if payment.MerchantID != nil {
		merchant, err := s.paymentMerchantRuntime.LoadMerchant(ctx, *payment.MerchantID)
		if err != nil {
			return false, "实际收款商户不可用", nil
		}
		// 商户停用不阻断历史单的原路退款，因此只校验凭证完整性，不校验商户状态。
		config, err = merchantRefundConfig(merchant)
		if err != nil {
			return false, err.Error(), nil
		}
	} else {
		if payment.PaymentConfigID == nil {
			return false, "历史支付单缺少支付配置", nil
		}
		legacy, err := loadLegacyPaymentConfig(ctx, s.db, *payment.PaymentConfigID)
		if err != nil {
			return false, err.Error(), nil
		}
		config = legacy
	}

	if reason := channelRefundCredentialIssue(config); reason != "" {
		return false, reason, nil
	}
	if reason := channelRefundWindowIssue(config.ProviderType, payment.PaidAt); reason != "" {
		return false, reason, nil
	}
	return true, "", config
}

// channelRefundWindowIssue 判定原交易是否超出渠道可退时限。
// 富友按是否回传原交易日期区分：不回传仅支持 30 天内，回传可退 360 天内。
// 系统始终回传原交易日期，因此按 360 天判定；微信与支付宝不设本地时限。
func channelRefundWindowIssue(providerType string, paidAt *time.Time) string {
	if providerType != model.ProviderTypeFuiou {
		return ""
	}
	if paidAt == nil {
		return "富友原交易缺少支付时间，无法回传原交易日期"
	}
	if time.Since(*paidAt) > 360*24*time.Hour {
		return "富友原交易已超出渠道可退时限（360 天）"
	}
	return ""
}

// requestChannelRefundNo 按冻结商户生成渠道退款请求号，并在提交时冻结到审批尝试记录。
// 重提会生成新值；同一尝试的渠道重试复用该值，因此渠道侧以它作为幂等标识。
func requestChannelRefundNo(config *model.WechatConfig, now time.Time) string {
	return refundchannel.BuildChannelRefundRequestNo(merchantChannelPrefix(config), now)
}

// merchantChannelPrefix 取商户标识中的数字段作为请求号前缀。
// 富友要求前缀为其机构码；其余渠道只要求请求号在其长度与字符集约束内唯一。
func merchantChannelPrefix(config *model.WechatConfig) string {
	if config == nil {
		return "0000"
	}
	if config.ProviderType == model.ProviderTypeFuiou && strings.TrimSpace(config.FyInsCd) != "" {
		return config.FyInsCd
	}
	return config.WxMchID + config.AliAppID
}

// validateRefundMethod 校验提交的退款方式属于该订单的可选方式集合。
func validateRefundMethod(decision *refundMethodDecision, method string) error {
	method = strings.TrimSpace(method)
	if method == "" {
		return errors.New(errors.CodeInvalidParam, "退款方式不能为空")
	}
	for _, option := range decision.Options {
		if option.Method != method {
			continue
		}
		if !option.Available {
			return errors.New(errors.CodeInvalidParam, "该订单当前不支持此退款方式："+option.Reason)
		}
		return nil
	}
	return errors.New(errors.CodeInvalidParam, "该订单不支持此退款方式")
}

// validateCustomerAccountMaterial 校验客户收款信息方式的材料完整性。
// 客户收款信息与至少一个客户凭证附件必须同时存在；不得复用公司员工收款方式字典。
func validateCustomerAccountMaterial(method, customerAccountInfo string, voucherKeys []string) error {
	if method != constants.RefundMethodCustomerAccount {
		return nil
	}
	if strings.TrimSpace(customerAccountInfo) == "" {
		return errors.New(errors.CodeInvalidParam, "客户收款信息退款必须填写客户收款信息")
	}
	hasVoucher := false
	for _, key := range voucherKeys {
		if strings.TrimSpace(key) != "" {
			hasVoucher = true
			break
		}
	}
	if !hasVoucher {
		return errors.New(errors.CodeInvalidParam, "客户收款信息退款必须至少上传一个客户收款凭证")
	}
	return nil
}

// validateFrozenRefundAmount 校验退款金额为正分且不超过冻结实收金额。
func validateFrozenRefundAmount(amount, frozenActualReceivedAmount int64) error {
	if amount <= 0 {
		return errors.New(errors.CodeInvalidParam, "退款金额必须为正分")
	}
	if frozenActualReceivedAmount <= 0 {
		return errors.New(errors.CodeInvalidParam, "冻结实收金额缺失或非正，无法受理退款申请")
	}
	if amount > frozenActualReceivedAmount {
		return errors.New(errors.CodeInvalidParam, "退款金额不能超过冻结实收金额")
	}
	return nil
}

// buildAttemptFromDecision 依据方式判定结果构造一条不可变审批尝试记录。
func buildAttemptFromDecision(decision *refundMethodDecision, refund *model.RefundRequest, config *model.WechatConfig, now time.Time) *model.RefundRequestAttempt {
	attempt := &model.RefundRequestAttempt{
		RefundID:                   refund.ID,
		Method:                     refund.Method,
		RefundAmount:               refund.RequestedRefundAmount,
		FrozenActualReceivedAmount: decision.FrozenActualReceivedAmount,
		RefundReason:               refund.RefundReason,
		CustomerAccountInfo:        refund.CustomerAccountInfo,
		CustomerVoucherKeys:        refund.RefundVoucherKey,
		SubmittedByAccountID:       refund.Creator,
	}
	if refund.Method == constants.RefundMethodOriginalRoute {
		attempt.ChannelRefundRequestNo = requestChannelRefundNo(config, now)
	}
	return attempt
}