package employeecollection

import (
	"context"
	"strconv"
	"strings"
	"time"

	"github.com/bytedance/sonic"
	"gorm.io/gorm"

	employeecollectiondomain "github.com/break/junhong_cmp_fiber/internal/domain/employeecollection"
	"github.com/break/junhong_cmp_fiber/internal/model"
	"github.com/break/junhong_cmp_fiber/internal/model/dto"
	"github.com/break/junhong_cmp_fiber/pkg/constants"
	"github.com/break/junhong_cmp_fiber/pkg/errors"
	"github.com/break/junhong_cmp_fiber/pkg/middleware"
)

// billDateLayout 是账单筛选使用的自然日格式。
const billDateLayout = "2006-01-02"

// BillQuery 查询员工代收款账单列表、统计与详情。
// 列表与统计共用 applyBillScope 生成的同一个 *gorm.DB，禁止两处各写一套筛选。
type BillQuery struct {
	db *gorm.DB
}

// NewBillQuery 创建员工代收款账单查询。
func NewBillQuery(db *gorm.DB) *BillQuery {
	return &BillQuery{db: db}
}

// List 分页查询当前可见范围内的员工代收款账单。
func (q *BillQuery) List(ctx context.Context, request dto.EmployeeCollectionBillListRequest) (*dto.EmployeeCollectionBillListResponse, error) {
	query, err := q.applyBillScope(ctx, billFilterOfList(request))
	if err != nil {
		return nil, err
	}
	page, pageSize := normalizePage(request.Page, request.PageSize)
	var total int64
	if err := query.Count(&total).Error; err != nil {
		return nil, errors.Wrap(errors.CodeDatabaseError, err, "查询员工代收款账单总数失败")
	}
	var bills []model.EmployeeCollectionBill
	if err := query.Order("created_at DESC, id DESC").
		Offset((page - 1) * pageSize).Limit(pageSize).
		Find(&bills).Error; err != nil {
		return nil, errors.Wrap(errors.CodeDatabaseError, err, "查询员工代收款账单列表失败")
	}
	list := make([]*dto.EmployeeCollectionBillResponse, 0, len(bills))
	for index := range bills {
		item, err := ProjectBill(&bills[index])
		if err != nil {
			return nil, err
		}
		list = append(list, item)
	}
	return &dto.EmployeeCollectionBillListResponse{
		List: list, Total: total, Page: page, PageSize: pageSize,
	}, nil
}

// Statistics 汇总当前可见范围内的应收、已核销、未核销金额与待处理账单数。
// 使用与列表完全相同的可见性与筛选条件。
func (q *BillQuery) Statistics(
	ctx context.Context,
	request dto.EmployeeCollectionBillStatisticsRequest,
) (*dto.EmployeeCollectionBillStatisticsResponse, error) {
	query, err := q.applyBillScope(ctx, billFilterOfStatistics(request))
	if err != nil {
		return nil, err
	}
	var row struct {
		ReceivableTotal  int64
		ReceivedTotal    int64
		UnsettledTotal   int64
		PendingBillCount int64
	}
	if err := query.Select(
		`COALESCE(SUM(receivable_amount), 0) AS receivable_total,
		 COALESCE(SUM(received_amount), 0) AS received_total,
		 COALESCE(SUM(CASE WHEN status = ? THEN 0 ELSE receivable_amount - received_amount END), 0) AS unsettled_total,
		 COALESCE(SUM(CASE WHEN status IN (?, ?) THEN 1 ELSE 0 END), 0) AS pending_bill_count`,
		constants.EmployeeCollectionBillStatusClosed,
		constants.EmployeeCollectionBillStatusPending,
		constants.EmployeeCollectionBillStatusPartial,
	).Scan(&row).Error; err != nil {
		return nil, errors.Wrap(errors.CodeDatabaseError, err, "查询员工代收款账单统计失败")
	}
	return &dto.EmployeeCollectionBillStatisticsResponse{
		ReceivableTotal: row.ReceivableTotal, ReceivedTotal: row.ReceivedTotal,
		UnsettledTotal: row.UnsettledTotal, PendingBillCount: row.PendingBillCount,
	}, nil
}

// Detail 返回当前可见范围内的账单详情，包含退款冲销、分摊与申请审批历史。
// 不可见与不存在返回同一错误，不产生可枚举差异。
func (q *BillQuery) Detail(ctx context.Context, id uint) (*dto.EmployeeCollectionBillDetailResponse, error) {
	if q == nil || q.db == nil || id == 0 {
		return nil, errors.New(errors.CodeEmployeeCollectionBillNotFound)
	}
	scoped, err := applyBillVisibility(ctx, q.db.WithContext(ctx).Model(&model.EmployeeCollectionBill{}))
	if err != nil {
		return nil, err
	}
	var bill model.EmployeeCollectionBill
	if err := scoped.Where("id = ?", id).First(&bill).Error; err != nil {
		if err == gorm.ErrRecordNotFound {
			return nil, errors.New(errors.CodeEmployeeCollectionBillNotFound)
		}
		return nil, errors.Wrap(errors.CodeDatabaseError, err, "查询员工代收款账单详情失败")
	}
	billResponse, err := ProjectBill(&bill)
	if err != nil {
		return nil, err
	}
	refunds, err := q.billRefunds(ctx, bill.ID)
	if err != nil {
		return nil, err
	}
	allocations, applicationIDs, err := q.billAllocations(ctx, bill.ID)
	if err != nil {
		return nil, err
	}
	applications, err := q.billApplications(ctx, applicationIDs)
	if err != nil {
		return nil, err
	}
	return &dto.EmployeeCollectionBillDetailResponse{
		Bill: billResponse, Refunds: refunds, Allocations: allocations, Applications: applications,
	}, nil
}

// applyBillScope 生成同时应用可见性与筛选条件的账单查询。
// 列表、统计与关闭后的可见性校验都必须走这一处，避免筛选或数据范围分叉。
func (q *BillQuery) applyBillScope(ctx context.Context, filter billFilter) (*gorm.DB, error) {
	if q == nil || q.db == nil {
		return nil, errors.New(errors.CodeServiceUnavailable, "员工代收款账单查询尚未配置")
	}
	query, err := applyBillVisibility(ctx, q.db.WithContext(ctx).Model(&model.EmployeeCollectionBill{}))
	if err != nil {
		return nil, err
	}
	return applyBillFilters(query, filter)
}

// billFilter 账单列表与统计共用的筛选条件，屏蔽两种请求 DTO 的字段差异。
type billFilter struct {
	SourceType      *string
	SourceNo        *string
	Status          *int
	DebtorAccountID *uint
	CustomerID      *uint
	CreatedFrom     *string
	CreatedTo       *string
}

// billFilterOfList 投影账单列表请求的筛选字段。
func billFilterOfList(request dto.EmployeeCollectionBillListRequest) billFilter {
	return billFilter{
		SourceType: request.SourceType, SourceNo: request.SourceNo, Status: request.Status,
		DebtorAccountID: request.DebtorAccountID, CustomerID: request.CustomerID,
		CreatedFrom: request.CreatedFrom, CreatedTo: request.CreatedTo,
	}
}

// billFilterOfStatistics 投影账单统计请求的筛选字段。
func billFilterOfStatistics(request dto.EmployeeCollectionBillStatisticsRequest) billFilter {
	return billFilter{
		SourceType: request.SourceType, SourceNo: request.SourceNo, Status: request.Status,
		DebtorAccountID: request.DebtorAccountID, CustomerID: request.CustomerID,
		CreatedFrom: request.CreatedFrom, CreatedTo: request.CreatedTo,
	}
}

// applyBillVisibility 应用账单可见性：超级管理员见全部，其他账号仅见本人欠款账单。
func applyBillVisibility(ctx context.Context, query *gorm.DB) (*gorm.DB, error) {
	if middleware.GetUserTypeFromContext(ctx) == constants.UserTypeSuperAdmin {
		return query, nil
	}
	accountID := middleware.GetUserIDFromContext(ctx)
	if accountID == 0 {
		return nil, errors.New(errors.CodeUnauthorized)
	}
	return query.Where("debtor_account_id = ?", accountID), nil
}

// applyBillFilters 应用账单列表与统计共用的筛选条件。
func applyBillFilters(query *gorm.DB, request billFilter) (*gorm.DB, error) {
	if request.DebtorAccountID != nil && *request.DebtorAccountID > 0 {
		query = query.Where("debtor_account_id = ?", *request.DebtorAccountID)
	}
	if request.SourceType != nil {
		sourceType := strings.TrimSpace(*request.SourceType)
		switch sourceType {
		case "":
		case constants.EmployeeCollectionSourceTypeOrder, constants.EmployeeCollectionSourceTypeRecharge:
			query = query.Where("source_type = ?", sourceType)
		default:
			return nil, errors.New(errors.CodeInvalidParam, "不支持的账单来源类型")
		}
	}
	if request.SourceNo != nil {
		if sourceNo := strings.TrimSpace(*request.SourceNo); sourceNo != "" {
			query = query.Where("source_no = ?", sourceNo)
		}
	}
	if request.Status != nil {
		switch *request.Status {
		case constants.EmployeeCollectionBillStatusPending, constants.EmployeeCollectionBillStatusPartial,
			constants.EmployeeCollectionBillStatusSettled, constants.EmployeeCollectionBillStatusClosed:
			query = query.Where("status = ?", *request.Status)
		default:
			return nil, errors.New(errors.CodeInvalidParam, "不支持的账单状态")
		}
	}
	if request.CustomerID != nil && *request.CustomerID > 0 {
		customerID := strconv.FormatUint(uint64(*request.CustomerID), 10)
		query = query.Where("customer_snapshot->>'buyer_id' = ? OR customer_snapshot->>'shop_id' = ?", customerID, customerID)
	}
	if request.CreatedFrom != nil {
		from, err := parseBillDate(*request.CreatedFrom)
		if err != nil {
			return nil, err
		}
		if from != nil {
			query = query.Where("created_at >= ?", *from)
		}
	}
	if request.CreatedTo != nil {
		to, err := parseBillDate(*request.CreatedTo)
		if err != nil {
			return nil, err
		}
		if to != nil {
			query = query.Where("created_at < ?", to.AddDate(0, 0, 1))
		}
	}
	return query, nil
}

// parseBillDate 解析自然日筛选值；空值表示不筛选。
func parseBillDate(value string) (*time.Time, error) {
	trimmed := strings.TrimSpace(value)
	if trimmed == "" {
		return nil, nil
	}
	parsed, err := time.ParseInLocation(billDateLayout, trimmed, time.Local)
	if err != nil {
		return nil, errors.New(errors.CodeInvalidParam, "账单筛选日期格式必须为 YYYY-MM-DD")
	}
	return &parsed, nil
}

// billRefunds 读取账单的来源订单退款冲销关联。
func (q *BillQuery) billRefunds(ctx context.Context, billID uint) ([]*dto.EmployeeCollectionBillRefundResponse, error) {
	var refunds []model.EmployeeCollectionBillRefund
	if err := q.db.WithContext(ctx).Where("bill_id = ?", billID).Order("id ASC").Find(&refunds).Error; err != nil {
		return nil, errors.Wrap(errors.CodeDatabaseError, err, "查询账单退款冲销关联失败")
	}
	result := make([]*dto.EmployeeCollectionBillRefundResponse, 0, len(refunds))
	for index := range refunds {
		item := refunds[index]
		result = append(result, &dto.EmployeeCollectionBillRefundResponse{
			ID: item.ID, RefundID: item.RefundID, SourceOrderID: item.SourceOrderID,
			RefundAmount: item.RefundAmount, BillReceivableAmount: item.BillReceivableAmount,
			Outcome: item.Outcome, OutcomeName: constants.GetEmployeeCollectionRefundOutcomeName(item.Outcome),
			ReducedAmount: item.ReducedAmount, CreatedAt: item.CreatedAt,
		})
	}
	return result, nil
}

// billAllocations 读取账单分摊，并返回涉及的去重申请 ID。
func (q *BillQuery) billAllocations(ctx context.Context, billID uint) ([]*dto.EmployeeCollectionBillAllocationResponse, []uint, error) {
	var allocations []model.EmployeeCollectionApplicationAllocation
	if err := q.db.WithContext(ctx).Where("bill_id = ?", billID).Order("id ASC").Find(&allocations).Error; err != nil {
		return nil, nil, errors.Wrap(errors.CodeDatabaseError, err, "查询账单分摊失败")
	}
	applicationIDs := make([]uint, 0, len(allocations))
	seen := make(map[uint]struct{}, len(allocations))
	for index := range allocations {
		if _, exists := seen[allocations[index].ApplicationID]; !exists {
			seen[allocations[index].ApplicationID] = struct{}{}
			applicationIDs = append(applicationIDs, allocations[index].ApplicationID)
		}
	}
	applicationStatus := make(map[uint]int, len(applicationIDs))
	if len(applicationIDs) > 0 {
		var applications []model.EmployeeCollectionApplication
		if err := q.db.WithContext(ctx).Select("id", "status").
			Where("id IN ?", applicationIDs).Find(&applications).Error; err != nil {
			return nil, nil, errors.Wrap(errors.CodeDatabaseError, err, "查询账单分摊所属申请失败")
		}
		for index := range applications {
			applicationStatus[applications[index].ID] = applications[index].Status
		}
	}
	result := make([]*dto.EmployeeCollectionBillAllocationResponse, 0, len(allocations))
	for index := range allocations {
		item := allocations[index]
		status := applicationStatus[item.ApplicationID]
		result = append(result, &dto.EmployeeCollectionBillAllocationResponse{
			ID: item.ID, ApplicationID: item.ApplicationID,
			ApplicationStatus: status, ApplicationStatusName: constants.GetEmployeeCollectionApplicationStatusName(status),
			AttemptID: item.AttemptID, Amount: item.Amount,
			Status: item.Status, StatusName: constants.GetEmployeeCollectionAllocationStatusName(item.Status),
			ReleasedAt: item.ReleasedAt, CreatedAt: item.CreatedAt,
		})
	}
	return result, applicationIDs, nil
}

// billApplications 读取涉及该账单的申请及其审批尝试历史。
func (q *BillQuery) billApplications(ctx context.Context, applicationIDs []uint) ([]*dto.EmployeeCollectionBillApplicationResponse, error) {
	if len(applicationIDs) == 0 {
		return []*dto.EmployeeCollectionBillApplicationResponse{}, nil
	}
	var applications []model.EmployeeCollectionApplication
	if err := q.db.WithContext(ctx).Where("id IN ?", applicationIDs).Order("id ASC").Find(&applications).Error; err != nil {
		return nil, errors.Wrap(errors.CodeDatabaseError, err, "查询账单关联核销申请失败")
	}
	attemptsByApplication, approvalStatus, approvalOpinions, err := q.applicationAttempts(ctx, applicationIDs)
	if err != nil {
		return nil, err
	}
	result := make([]*dto.EmployeeCollectionBillApplicationResponse, 0, len(applications))
	for index := range applications {
		application := applications[index]
		vouchers := []string(application.PaymentVoucherKeys)
		if vouchers == nil {
			vouchers = []string{}
		}
		attempts, err := attemptResponses(
			application.ID, attemptsByApplication[application.ID], approvalStatus, approvalOpinions)
		if err != nil {
			return nil, err
		}
		result = append(result, &dto.EmployeeCollectionBillApplicationResponse{
			ID: application.ID, ApplicantAccountID: application.ApplicantAccountID,
			ActingOperatorID: application.ActingOperatorID, ActingReason: application.ActingReason,
			PaymentMethodID: application.PaymentMethodID, PaymentMethodCode: application.PaymentMethodCode,
			PaymentMethodName: application.PaymentMethodName, PaidAmount: application.PaidAmount,
			PayerName: application.PayerName, PaidAt: application.PaidAt,
			ExternalTransactionNo: application.ExternalTransactionNo, PaymentVoucherKeys: vouchers,
			Remark: application.Remark, Status: application.Status,
			StatusName:               constants.GetEmployeeCollectionApplicationStatusName(application.Status),
			LatestApprovalInstanceID: application.LatestApprovalInstanceID,
			DecidedAt:                application.DecidedAt, TerminalReason: application.TerminalReason,
			CreatedAt: application.CreatedAt,
			Attempts:  attempts,
		})
	}
	return result, nil
}

// applicationAttempts 读取申请的审批尝试记录、审批实例状态与审批意见。
func (q *BillQuery) applicationAttempts(
	ctx context.Context,
	applicationIDs []uint,
) (map[uint][]model.EmployeeCollectionApplicationAttempt, map[uint]int, map[uint]string, error) {
	var attempts []model.EmployeeCollectionApplicationAttempt
	if err := q.db.WithContext(ctx).Where("application_id IN ?", applicationIDs).
		Order("application_id ASC, attempt_no ASC").Find(&attempts).Error; err != nil {
		return nil, nil, nil, errors.Wrap(errors.CodeDatabaseError, err, "查询审批尝试记录失败")
	}
	approvalStatus, approvalOpinions, err := approvalStatusOfAttempts(ctx, q.db, attempts)
	if err != nil {
		return nil, nil, nil, err
	}
	grouped := make(map[uint][]model.EmployeeCollectionApplicationAttempt, len(applicationIDs))
	for index := range attempts {
		grouped[attempts[index].ApplicationID] = append(grouped[attempts[index].ApplicationID], attempts[index])
	}
	return grouped, approvalStatus, approvalOpinions, nil
}

// approvalStatusOfAttempts 批量读取审批尝试记录关联的通用审批实例状态与终态审批意见。
func approvalStatusOfAttempts(
	ctx context.Context,
	db *gorm.DB,
	attempts []model.EmployeeCollectionApplicationAttempt,
) (map[uint]int, map[uint]string, error) {
	instanceIDs := make([]uint, 0, len(attempts))
	for index := range attempts {
		if attempts[index].ApprovalInstanceID != nil {
			instanceIDs = append(instanceIDs, *attempts[index].ApprovalInstanceID)
		}
	}
	approvalStatus := make(map[uint]int, len(instanceIDs))
	approvalOpinions := make(map[uint]string, len(instanceIDs))
	if len(instanceIDs) == 0 {
		return approvalStatus, approvalOpinions, nil
	}
	columns := []string{"id", "status", "decision_snapshot"}
	var instances []model.ApprovalInstance
	if err := db.WithContext(ctx).Select(columns).
		Where("id IN ?", instanceIDs).Find(&instances).Error; err != nil {
		return nil, nil, errors.Wrap(errors.CodeDatabaseError, err, "查询审批实例状态失败")
	}
	for index := range instances {
		approvalStatus[instances[index].ID] = instances[index].Status
		if opinion := employeecollectiondomain.ExtractApprovalOpinion(instances[index].DecisionSnapshot); opinion != "" {
			approvalOpinions[instances[index].ID] = opinion
		}
	}
	return approvalStatus, approvalOpinions, nil
}

// attemptResponses 投影审批尝试记录，附件只返回对象键引用与审批实例引用。
func attemptResponses(
	applicationID uint,
	attempts []model.EmployeeCollectionApplicationAttempt,
	approvalStatus map[uint]int,
	approvalOpinions map[uint]string,
) ([]*dto.EmployeeCollectionBillAttemptResponse, error) {
	result := make([]*dto.EmployeeCollectionBillAttemptResponse, 0, len(attempts))
	for index := range attempts {
		attempt := attempts[index]
		if attempt.ApplicationID != applicationID {
			continue
		}
		vouchers := []string(attempt.PaymentVoucherKeys)
		if vouchers == nil {
			vouchers = []string{}
		}
		snapshot := make([]map[string]any, 0)
		if len(attempt.AllocationSnapshot) > 0 {
			if err := sonic.Unmarshal(attempt.AllocationSnapshot, &snapshot); err != nil {
				return nil, errors.Wrap(errors.CodeInternalError, err, "解析审批尝试分摊快照失败")
			}
		}
		var status *int
		statusName := ""
		opinion := ""
		if attempt.ApprovalInstanceID != nil {
			if value, ok := approvalStatus[*attempt.ApprovalInstanceID]; ok {
				status = &value
				statusName = constants.GetApprovalStatusName(value)
			}
			opinion = approvalOpinions[*attempt.ApprovalInstanceID]
		}
		result = append(result, &dto.EmployeeCollectionBillAttemptResponse{
			ID: attempt.ID, AttemptNo: attempt.AttemptNo,
			PaymentMethodID: attempt.PaymentMethodID, PaymentMethodCode: attempt.PaymentMethodCode,
			PaymentMethodName: attempt.PaymentMethodName, PaidAmount: attempt.PaidAmount,
			PayerName: attempt.PayerName, PaidAt: attempt.PaidAt,
			ExternalTransactionNo: attempt.ExternalTransactionNo, PaymentVoucherKeys: vouchers,
			Remark: attempt.Remark, SubmittedByAccountID: attempt.SubmittedByAccountID,
			ActingReason: attempt.ActingReason, AllocationSnapshot: snapshot,
			ApprovalInstanceID: attempt.ApprovalInstanceID,
			ApprovalStatus:     status, ApprovalStatusName: statusName,
			ApprovalOpinion: opinion, CreatedAt: attempt.CreatedAt,
		})
	}
	return result, nil
}

// ProjectBill 将账单事实投影为对外响应；关闭用例与查询共用同一投影。
func ProjectBill(bill *model.EmployeeCollectionBill) (*dto.EmployeeCollectionBillResponse, error) {
	if bill == nil {
		return nil, errors.New(errors.CodeEmployeeCollectionBillNotFound)
	}
	debtorSnapshot := make(map[string]any)
	if len(bill.DebtorSnapshot) > 0 {
		if err := sonic.Unmarshal(bill.DebtorSnapshot, &debtorSnapshot); err != nil {
			return nil, errors.Wrap(errors.CodeInternalError, err, "解析账单欠款人快照失败")
		}
	}
	customerSnapshot := make(map[string]any)
	if len(bill.CustomerSnapshot) > 0 {
		if err := sonic.Unmarshal(bill.CustomerSnapshot, &customerSnapshot); err != nil {
			return nil, errors.Wrap(errors.CodeInternalError, err, "解析账单客户快照失败")
		}
	}
	remaining := int64(0)
	if bill.Status != constants.EmployeeCollectionBillStatusClosed {
		remaining = bill.ReceivableAmount - bill.ReceivedAmount - bill.ReservedAmount
		if remaining < 0 {
			remaining = 0
		}
	}
	return &dto.EmployeeCollectionBillResponse{
		ID: bill.ID, SourceType: bill.SourceType,
		SourceTypeName: constants.GetEmployeeCollectionSourceTypeName(bill.SourceType),
		SourceID:       bill.SourceID, SourceNo: bill.SourceNo,
		DebtorAccountID: bill.DebtorAccountID, DebtorSnapshot: debtorSnapshot,
		CustomerSnapshot: customerSnapshot,
		ReceivableAmount: bill.ReceivableAmount, ReceivedAmount: bill.ReceivedAmount,
		ReservedAmount: bill.ReservedAmount, RemainingAmount: remaining,
		Status: bill.Status, StatusName: constants.GetEmployeeCollectionBillStatusName(bill.Status),
		ApprovalPending: bill.ReservedAmount > 0,
		ClosedReason:    bill.ClosedReason, ClosedAt: bill.ClosedAt,
		CreatedAt: bill.CreatedAt, UpdatedAt: bill.UpdatedAt,
	}, nil
}