package refund

import (
	"context"
	stderrors "errors"
	"strings"
	"time"

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

	"github.com/break/junhong_cmp_fiber/internal/infrastructure/audit"
	"github.com/break/junhong_cmp_fiber/internal/model"
	"github.com/break/junhong_cmp_fiber/internal/model/dto"
	"github.com/break/junhong_cmp_fiber/pkg/auditcontext"
	"github.com/break/junhong_cmp_fiber/pkg/constants"
	"github.com/break/junhong_cmp_fiber/pkg/errors"
	"github.com/break/junhong_cmp_fiber/pkg/middleware"
)

// latestAttemptRemark 读取该退款单最近一次审批尝试冻结的申请人备注。
// 重提时未填写备注则沿用该值，使申请人不必重复填写；读取失败按未填写处理（备注不参与金额与状态判定）。
func (s *Service) latestAttemptRemark(ctx context.Context, refund *model.RefundRequest) string {
	if refund == nil || refund.ID == 0 {
		return ""
	}
	var attempt model.RefundRequestAttempt
	err := s.db.WithContext(ctx).
		Select("id", "remark").
		Where("refund_id = ?", refund.ID).
		Order("attempt_no DESC, id DESC").
		First(&attempt).Error
	if err != nil {
		if err != gorm.ErrRecordNotFound {
			s.logMaterialFailure(ctx, refund.ID, "applicant_remark", err)
		}
		return ""
	}
	return strings.TrimSpace(attempt.Remark)
}

// OrderOptions 按来源订单查询可选退款方式。
//
// 判定复用创建与重提使用的方式判定实现（decideRefundMethods），其中原路可退的凭证判定
// 复用执行前预检所用的同一凭证判定来源（refundchannel.RefundCredentialIssue），
// MUST NOT 引入第二套判定或独立开关。审批提交只消费已冻结材料，本查询不产生任何副作用。
//
// 判定所需事实缺失（无原成功支付记录、金额非正、支付方式不支持退款）时返回不可用原因而非报错；
// 数据库或能力未配置等基础设施故障仍按错误返回。查询受订单数据范围约束，越权与订单不存在不可区分。
func (s *Service) OrderOptions(ctx context.Context, req *dto.RefundOrderOptionsRequest) (*dto.RefundOrderOptionsResponse, error) {
	if req == nil || req.OrderID == 0 {
		return nil, errors.New(errors.CodeInvalidParam, "订单ID不能为空")
	}
	order, err := s.orderStore.GetByID(ctx, req.OrderID)
	if err != nil {
		// 数据范围外的订单与不存在的订单返回同一结果，避免形成可枚举差异。
		return nil, errors.New(errors.CodeNotFound, "订单不存在")
	}

	response := &dto.RefundOrderOptionsResponse{
		OrderID:          order.ID,
		OrderNo:          order.OrderNo,
		OrderPaymentType: order.PaymentMethod,
		Methods:          []dto.RefundMethodOptionResponse{},
		RefundCapability: dto.RefundCapabilityResponse{},
	}
	decision, err := s.decideRefundMethods(ctx, order)
	if err != nil {
		var appErr *errors.AppError
		if stderrors.As(err, &appErr) && appErr.Code == errors.CodeInvalidParam {
			// 判定事实缺失：以不可用原因返回，不让只读查询报错。
			response.UnavailableReason = appErr.Message
			response.RefundCapability = dto.RefundCapabilityResponse{Available: false, Unavailable: appErr.Message}
			return response, nil
		}
		return nil, err
	}
	response.Methods = make([]dto.RefundMethodOptionResponse, 0, len(decision.Options))
	for _, option := range decision.Options {
		response.Methods = append(response.Methods, dto.RefundMethodOptionResponse{
			Method: option.Method, MethodName: option.Name,
			Available: option.Available, Unavailable: option.Reason,
		})
	}
	response.RefundCapability = refundCapabilityProjection(decision.Options)
	if decision.Payment != nil {
		response.OriginalChannelTradeNo = strings.TrimSpace(decision.Payment.ThirdPartyTradeNo)
		response.MerchantID = decision.Payment.MerchantID
		response.MerchantName = strings.TrimSpace(decision.Payment.MerchantNameSnapshot)
	}
	return response, nil
}

// refundCapabilityProjection 从方式判定结果投影原路退款能力校验结果。
// 订单不含原路方式时能力不可用，原因取该订单方式矩阵的说明，避免展示与方式集合不一致的结论。
func refundCapabilityProjection(options []refundMethodOption) dto.RefundCapabilityResponse {
	for _, option := range options {
		if option.Method != constants.RefundMethodOriginalRoute {
			continue
		}
		return dto.RefundCapabilityResponse{Available: option.Available, Unavailable: option.Reason}
	}
	return dto.RefundCapabilityResponse{Available: false, Unavailable: "该订单的退款方式矩阵不包含原路退款"}
}

// RegisterOfflineSettlement 登记或更正线下退款处理流水号。
//
// 仅客户收款信息退款（线下到账方式）允许登记；重复调用即更正，历史值由审计留存。
// 登记在同一事务内写审计（操作者、时间、前后值），且 MUST NOT 改变退款状态、实收金额、
// 套餐失效与佣金回溯规则（ENG-TX-001：事实与要求成功必达的审计同事务）。
func (s *Service) RegisterOfflineSettlement(ctx context.Context, id uint, req *dto.OfflineSettlementRequest) (*dto.RefundResponse, error) {
	userID := middleware.GetUserIDFromContext(ctx)
	if userID == 0 {
		return nil, errors.New(errors.CodeUnauthorized, "未授权访问")
	}
	if id == 0 || req == nil {
		return nil, errors.New(errors.CodeInvalidParam, "退款申请ID不能为空")
	}
	if s.auditWriter == nil {
		return nil, errors.New(errors.CodeServiceUnavailable, "退款统一审计接缝未配置")
	}
	settlementNo := strings.TrimSpace(req.OfflineSettlementNo)
	if settlementNo == "" {
		return nil, errors.New(errors.CodeInvalidParam, "线下退款处理流水号不能为空")
	}
	if len(settlementNo) > 128 {
		return nil, errors.New(errors.CodeInvalidParam, "线下退款处理流水号长度不能超过 128")
	}
	refund, err := s.refundStore.GetByIDForOperation(ctx, id)
	if err != nil {
		// 数据范围外的退款申请与不存在返回同一结果。
		return nil, errors.New(errors.CodeNotFound, "退款申请不存在")
	}
	if refund.Method != constants.RefundMethodCustomerAccount {
		return nil, errors.New(errors.CodeInvalidStatus, "仅客户收款信息退款方式可登记线下退款处理流水号")
	}
	ctx = auditcontext.With(ctx, auditcontext.Context{CorrelationID: refund.RefundNo})
	settledAt := time.Now().UTC()
	err = s.db.WithContext(ctx).Transaction(func(tx *gorm.DB) error {
		var current model.RefundRequest
		if err := tx.WithContext(ctx).Clauses(clause.Locking{Strength: "UPDATE"}).First(&current, id).Error; err != nil {
			if err == gorm.ErrRecordNotFound {
				return errors.New(errors.CodeNotFound, "退款申请不存在")
			}
			return errors.Wrap(errors.CodeDatabaseError, err, "锁定退款申请失败")
		}
		if current.Method != constants.RefundMethodCustomerAccount {
			return errors.New(errors.CodeInvalidStatus, "仅客户收款信息退款方式可登记线下退款处理流水号")
		}
		beforeState := refundSettlementState(&current)
		result := tx.WithContext(ctx).Model(&model.RefundRequest{}).
			Where("id = ?", id).
			Updates(map[string]any{
				"offline_settlement_no": settlementNo,
				"offline_settled_at":    settledAt,
				"offline_settled_by":    userID,
				"updater":               userID,
				"updated_at":            settledAt,
			})
		if result.Error != nil {
			return errors.Wrap(errors.CodeDatabaseError, result.Error, "登记线下退款处理流水号失败")
		}
		if result.RowsAffected != 1 {
			return errors.New(errors.CodeConflict, "退款申请状态已变化")
		}
		if err := tx.WithContext(ctx).First(&current, id).Error; err != nil {
			return errors.Wrap(errors.CodeDatabaseError, err, "查询退款申请登记后快照失败")
		}
		primary := audit.RefundResource(&current, constants.AuditResourceRelationPrimary, constants.AuditResourceRoleRefundTarget)
		primary.BeforeData = beforeState
		primary.AfterData = refundSettlementState(&current)
		primary.SubjectVisibility = constants.AuditSubjectResult
		primary.SubjectSummary = "登记线下退款处理流水号"
		if err := s.auditWriter.Append(ctx, tx, audit.AppendInput{
			ActionCode: constants.AuditActionRefundOfflineSettled, Summary: "登记线下退款处理流水号",
			ScopeType: constants.AuditScopePlatform, Result: constants.AuditResultSuccess,
			CorrelationID: current.RefundNo,
			Metadata:      map[string]any{"operator_id": userID, "settled_at": settledAt},
			Resources:     []audit.ResourceInput{primary},
		}); err != nil {
			return err
		}
		refund = &current
		return nil
	})
	if err != nil {
		return nil, err
	}
	return buildRefundResponse(refund), nil
}

// refundSettlementState 投影线下退款处理流水号的审计前后值。
// 只包含本用例改动的字段，MUST NOT 夹带状态、实收金额等未改动事实，使审计前后值即登记差异。
func refundSettlementState(refund *model.RefundRequest) map[string]any {
	state := map[string]any{
		"offline_settlement_no": refund.OfflineSettlementNo,
		"offline_settled_by":    refund.OfflineSettledBy,
	}
	if refund.OfflineSettledAt != nil {
		state["offline_settled_at"] = refund.OfflineSettledAt
	}
	return state
}