package service

import (
	"errors"
	"fmt"
	"math"
	"regexp"
	"strings"
	"time"
	"wails-app/internal/dao"
	"wails-app/internal/global"
	parkingSessionService "wails-app/internal/modules/parking-session/service"
	"wails-app/internal/modules/payment/repository"

	"gorm.io/gorm"
)

// Internal payment constants and configuration values.
const (
	PaymentCash     = "cash"
	PaymentFree     = "free"
	PaymentPOS      = "pos"
	PaymentTicketQR = "ticket_qr"

	InputModeManualAmount = "manual_amount"
	InputModeConfirm      = "confirm"
	InputModeExternal     = "external"

	EntryCounter = "counter"
	EntryTicket  = "ticket"

	// Scene* are kept as source-compatible aliases for older callers. New code
	// should pass an Entry* value and treat it as the payment entry, not a
	// property of the payment method.
	SceneCounter = EntryCounter
	SceneTicket  = EntryTicket
)

var paymentCodePattern = regexp.MustCompile(`^[a-z][a-z0-9_]{1,31}$`)

var (
	ErrPaymentAlreadyProcessed = errors.New("payment already processed")
	ErrVehicleRecordNotFound   = errors.New("vehicle record not found")
)

type PaymentService struct {
	repo *repository.PaymentRepository
}

func NewPaymentService() *PaymentService {
	return &PaymentService{repo: &repository.PaymentRepository{}}
}

func (s *PaymentService) ListMethods() ([]dao.PaymentMethodConfig, error) {
	return s.repo.MethodList()
}

func (s *PaymentService) ListEntries() ([]dao.PaymentEntryConfig, error) {
	return s.repo.EntryList()
}

func (s *PaymentService) ListEnabledEntries() ([]dao.PaymentEntryConfig, error) {
	entries, err := s.repo.EntryList()
	if err != nil {
		return nil, err
	}
	result := make([]dao.PaymentEntryConfig, 0, len(entries))
	for _, entry := range entries {
		if entry.Enabled {
			result = append(result, entry)
		}
	}
	return result, nil
}

func (s *PaymentService) ListEnabledMethods(entryCode string) ([]dao.PaymentMethodConfig, error) {
	if entryCode != "" && entryCode != EntryCounter && entryCode != EntryTicket {
		// Custom entries are valid too; only reject an empty value at the API
		// boundary where an entry is required.
		if _, err := s.repo.GetEntryByCode(nil, entryCode); err != nil {
			return nil, errors.New("无效的支付入口")
		}
	}
	methods, err := s.repo.EnabledMethodList(global.GVA_DB, entryCode)
	if err == nil {
		return methods, nil
	}
	// Existing installations created before the split may not have the
	// relation tables yet. Keep their old scene data usable until startup
	// migration has completed.
	if strings.Contains(strings.ToLower(err.Error()), "no such table") {
		return s.listLegacyEnabledMethods(entryCode), nil
	}
	return nil, err
}

func (s *PaymentService) listLegacyEnabledMethods(entryCode string) []dao.PaymentMethodConfig {
	methods, err := s.repo.MethodList()
	if err != nil {
		return nil
	}
	result := make([]dao.PaymentMethodConfig, 0, len(methods))
	for _, method := range methods {
		if method.Enabled && containsScene(method.Scenes, entryCode) {
			result = append(result, method)
		}
	}
	return result
}

func normalizeCodes(codes []string) []string {
	seen := make(map[string]bool, len(codes))
	result := make([]string, 0, len(codes))
	for _, code := range codes {
		code = strings.ToLower(strings.TrimSpace(code))
		if code != "" && !seen[code] {
			seen[code] = true
			result = append(result, code)
		}
	}
	return result
}

func normalizeMethod(method *dao.PaymentMethodConfig) error {
	method.Code = strings.ToLower(strings.TrimSpace(method.Code))
	method.Name = strings.TrimSpace(method.Name)
	method.InputMode = strings.TrimSpace(method.InputMode)
	method.Description = strings.TrimSpace(method.Description)
	if !paymentCodePattern.MatchString(method.Code) {
		return errors.New("支付编码必须以小写字母开头，只能包含小写字母、数字和下划线，长度为2-32位")
	}
	if method.Name == "" || len([]rune(method.Name)) > 50 {
		return errors.New("支付方式名称不能为空且不能超过50个字符")
	}
	validModes := map[string]bool{InputModeManualAmount: true, InputModeConfirm: true, InputModeExternal: true}
	if !validModes[method.InputMode] {
		return errors.New("无效的金额处理方式")
	}
	method.EntryCodes = normalizeCodes(method.EntryCodes)
	// Scenes is only read during migration. Do not use it as a runtime
	// authorization source after payment entries have been configured.
	method.Scenes = normalizeCodes(method.Scenes)
	return nil
}

func (s *PaymentService) CreateMethod(method *dao.PaymentMethodConfig) error {
	if err := normalizeMethod(method); err != nil {
		return err
	}
	method.IsSystem = false
	err := global.GVA_DB.Transaction(func(tx *gorm.DB) error {
		if err := s.repo.CreateMethodTx(tx, method); err != nil {
			if strings.Contains(strings.ToLower(err.Error()), "unique") {
				return errors.New("支付编码已存在")
			}
			return fmt.Errorf("新增支付方式失败: %w", err)
		}
		if len(method.EntryCodes) > 0 {
			if err := s.validateMethodEntryCodes(tx, method.EntryCodes); err != nil {
				return err
			}
			return s.repo.ReplaceMethodEntries(tx, method.Code, method.EntryCodes)
		}
		return nil
	})
	return err
}

func (s *PaymentService) UpdateMethod(id uint, updates *dao.PaymentMethodConfig) error {
	current, err := s.repo.GetMethodByID(id)
	if err != nil {
		return errors.New("支付方式不存在")
	}
	updates.Code = current.Code
	updates.IsSystem = current.IsSystem
	updates.EntryCodes = nil
	if current.Code == PaymentCash {
		updates.InputMode = InputModeManualAmount
		updates.Enabled = true
	}
	if err := normalizeMethod(updates); err != nil {
		return err
	}
	updates.ID = current.ID
	return s.repo.UpdateMethod(updates)
}

func (s *PaymentService) SetMethodEnabled(id uint, enabled bool) error {
	method, err := s.repo.GetMethodByID(id)
	if err != nil {
		return errors.New("支付方式不存在")
	}
	if method.Code == PaymentCash && !enabled {
		return errors.New("人工支付是基础功能，不能停用")
	}
	return s.repo.SetMethodEnabled(id, enabled)
}

func (s *PaymentService) DeleteMethod(id uint) error {
	method, err := s.repo.GetMethodByID(id)
	if err != nil {
		return errors.New("支付方式不存在")
	}
	if method.IsSystem {
		return errors.New("系统内置支付方式不能删除")
	}
	return s.repo.DeleteMethod(method)
}

func normalizeEntry(entry *dao.PaymentEntryConfig) error {
	entry.Code = strings.ToLower(strings.TrimSpace(entry.Code))
	entry.Name = strings.TrimSpace(entry.Name)
	entry.Description = strings.TrimSpace(entry.Description)
	if !paymentCodePattern.MatchString(entry.Code) {
		return errors.New("支付入口编码必须以小写字母开头，只能包含小写字母、数字和下划线，长度为2-32位")
	}
	if entry.Name == "" || len([]rune(entry.Name)) > 50 {
		return errors.New("支付入口名称不能为空且不能超过50个字符")
	}
	entry.MethodCodes = normalizeCodes(entry.MethodCodes)
	if !containsScene(entry.MethodCodes, PaymentCash) {
		entry.MethodCodes = append([]string{PaymentCash}, entry.MethodCodes...)
	}
	return nil
}

func (s *PaymentService) validateEntryCodes(db *gorm.DB, codes []string) error {
	for _, code := range codes {
		method, err := s.repo.GetMethodByCode(db, code)
		if err != nil || method.IsLegacy {
			return fmt.Errorf("支付方式“%s”不存在或不可用", code)
		}
	}
	return nil
}

func (s *PaymentService) validateMethodEntryCodes(db *gorm.DB, codes []string) error {
	for _, code := range codes {
		if _, err := s.repo.GetEntryByCode(db, code); err != nil {
			return fmt.Errorf("支付入口“%s”不存在", code)
		}
	}
	return nil
}

func (s *PaymentService) CreateEntry(entry *dao.PaymentEntryConfig) error {
	if err := normalizeEntry(entry); err != nil {
		return err
	}
	if err := s.validateEntryCodes(global.GVA_DB, entry.MethodCodes); err != nil {
		return err
	}
	entry.IsSystem = false
	return global.GVA_DB.Transaction(func(tx *gorm.DB) error {
		if err := s.repo.CreateEntryTx(tx, entry); err != nil {
			if strings.Contains(strings.ToLower(err.Error()), "unique") {
				return errors.New("支付入口编码已存在")
			}
			return fmt.Errorf("新增支付入口失败: %w", err)
		}
		return s.repo.ReplaceEntryMethods(tx, entry.Code, entry.MethodCodes)
	})
}

func (s *PaymentService) UpdateEntry(id uint, updates *dao.PaymentEntryConfig) error {
	current, err := s.repo.GetEntryByID(id)
	if err != nil {
		return errors.New("支付入口不存在")
	}
	updates.Code = current.Code
	updates.IsSystem = current.IsSystem
	if err := normalizeEntry(updates); err != nil {
		return err
	}
	if err := s.validateEntryCodes(global.GVA_DB, updates.MethodCodes); err != nil {
		return err
	}
	updates.ID = current.ID
	return global.GVA_DB.Transaction(func(tx *gorm.DB) error {
		if err := s.repo.UpdateEntryTx(tx, updates); err != nil {
			return err
		}
		return s.repo.ReplaceEntryMethods(tx, current.Code, updates.MethodCodes)
	})
}

func (s *PaymentService) SetEntryEnabled(id uint, enabled bool) error {
	if _, err := s.repo.GetEntryByID(id); err != nil {
		return errors.New("支付入口不存在")
	}
	return s.repo.SetEntryEnabled(id, enabled)
}

func (s *PaymentService) DeleteEntry(id uint) error {
	entry, err := s.repo.GetEntryByID(id)
	if err != nil {
		return errors.New("支付入口不存在")
	}
	if entry.IsSystem {
		return errors.New("系统内置支付入口不能删除")
	}
	return s.repo.DeleteEntry(entry)
}

func containsScene(scenes []string, scene string) bool {
	for _, item := range scenes {
		if item == scene {
			return true
		}
	}
	return false
}

func (s *PaymentService) ValidateMethod(db *gorm.DB, code, entryCode string) (*dao.PaymentMethodConfig, error) {
	if code == PaymentFree {
		if entryCode != EntryCounter {
			return nil, errors.New("免密放行不能用于当前支付场景")
		}
		entry, err := s.repo.GetEntryByCode(db, entryCode)
		if err == nil && !entry.Enabled {
			return nil, fmt.Errorf("支付入口“%s”已停用", entry.Name)
		}
		if err != nil && !strings.Contains(strings.ToLower(err.Error()), "no such table") {
			return nil, errors.New("支付入口不存在")
		}
		return &dao.PaymentMethodConfig{Code: PaymentFree, Name: "免密放行", InputMode: InputModeConfirm, Enabled: true}, nil
	}
	entry, entryErr := s.repo.GetEntryByCode(db, entryCode)
	method, methodErr := s.repo.GetMethodByCode(db, code)
	if methodErr != nil {
		return nil, errors.New("支付方式不存在")
	}
	if !method.Enabled {
		return nil, fmt.Errorf("支付方式“%s”已停用", method.Name)
	}
	if entryErr != nil {
		if strings.Contains(strings.ToLower(entryErr.Error()), "no such table") && methodErr == nil {
			if containsScene(method.Scenes, entryCode) {
				return method, nil
			}
			return nil, fmt.Errorf("支付方式“%s”不适用于当前场景", method.Name)
		}
		return nil, errors.New("支付入口不存在")
	}
	if !entry.Enabled {
		return nil, fmt.Errorf("支付入口“%s”已停用", entry.Name)
	}
	allowed, err := s.repo.IsMethodAllowed(db, entryCode, code)
	if err != nil {
		if strings.Contains(strings.ToLower(err.Error()), "no such table") && containsScene(method.Scenes, entryCode) {
			return method, nil
		}
		return nil, err
	}
	if !allowed {
		return nil, fmt.Errorf("支付方式“%s”未配置到当前支付入口", method.Name)
	}
	return method, nil
}

func (s *PaymentService) ValidatePayment(db *gorm.DB, code, entryCode string, amount, paidAmount float64) (*dao.PaymentMethodConfig, float64, error) {
	method, err := s.ValidateMethod(db, code, entryCode)
	if err != nil {
		return nil, 0, err
	}
	if math.IsNaN(amount) || math.IsInf(amount, 0) || math.IsNaN(paidAmount) || math.IsInf(paidAmount, 0) || amount < 0 || paidAmount < 0 {
		return nil, 0, errors.New("支付金额必须是有限的非负数")
	}
	if code == PaymentFree {
		return method, 0, nil
	}
	if method.InputMode == InputModeManualAmount {
		if paidAmount < amount {
			return nil, 0, errors.New("实收金额不足")
		}
		return method, paidAmount, nil
	}
	return method, amount, nil
}

// ProcessPayment creates a payment_record and updates vehicle_record payment status
func (s *PaymentService) ProcessPayment(recordID uint, paymentMethod string, amount float64, paidAmount float64, operatorID uint) (*dao.PaymentRecord, error) {
	if global.GVA_DB == nil {
		return nil, errors.New("database not initialized")
	}
	var result *dao.PaymentRecord
	err := global.GVA_DB.Transaction(func(tx *gorm.DB) error {
		var err error
		result, err = s.ProcessPaymentTxAtEntry(tx, recordID, EntryCounter, paymentMethod, amount, paidAmount, operatorID)
		return err
	})
	if err != nil {
		return nil, err
	}
	return result, nil
}

// ProcessPaymentTx keeps the pre-split argument order for callers compiled
// against the old service. The final argument is now interpreted as the
// payment entry.
func (s *PaymentService) ProcessPaymentTx(db *gorm.DB, recordID uint, paymentMethod string, amount float64, paidAmount float64, operatorID uint, paymentEntry string) (*dao.PaymentRecord, error) {
	return s.ProcessPaymentTxAtEntry(db, recordID, paymentEntry, paymentMethod, amount, paidAmount, operatorID)
}

func (s *PaymentService) ProcessPaymentTxAtEntry(db *gorm.DB, recordID uint, paymentEntry string, paymentMethod string, amount float64, paidAmount float64, operatorID uint) (*dao.PaymentRecord, error) {
	if db == nil {
		return nil, errors.New("database not initialized")
	}
	method, paidAmount, err := s.ValidatePayment(db, paymentMethod, paymentEntry, amount, paidAmount)
	if err != nil {
		return nil, err
	}
	changeAmount := 0.0
	if method.InputMode == InputModeManualAmount && paidAmount > amount {
		changeAmount = paidAmount - amount
	}
	if recordID != 0 {
		sessionSvc := parkingSessionService.NewParkingSessionService()
		if _, err := sessionSvc.MarkPaidTx(db, recordID, paymentEntry, paymentMethod, amount); err != nil {
			switch {
			case errors.Is(err, parkingSessionService.ErrSessionNotFound):
				return nil, ErrVehicleRecordNotFound
			case errors.Is(err, parkingSessionService.ErrSessionAlreadyPaid),
				errors.Is(err, parkingSessionService.ErrSessionAlreadyClosed):
				return nil, fmt.Errorf("payment already processed: %w", ErrPaymentAlreadyProcessed)
			default:
				return nil, fmt.Errorf("failed to update payment status: %w", err)
			}
		}
	}

	now := time.Now()
	pr := &dao.PaymentRecord{
		RecordID:      recordID,
		PaymentEntry:  paymentEntry,
		PaymentMethod: paymentMethod,
		Amount:        amount,
		PaidAmount:    paidAmount,
		ChangeAmount:  changeAmount,
		OperatorID:    operatorID,
		PaidAt:        now,
	}

	if err := db.Create(pr).Error; err != nil {
		return nil, fmt.Errorf("创建支付记录失败: %w", err)
	}

	return pr, nil
}

// QueryPayments 查询收费记录列表
func (s *PaymentService) QueryPayments(q repository.PaymentListQuery) ([]repository.PaymentListResult, int64, error) {
	return s.repo.List(q)
}

// GetTodaySummary 获取当日收费汇总
func (s *PaymentService) GetTodaySummary() (repository.TodaySummary, error) {
	return s.repo.GetTodaySummary()
}