package service

import (
	"crypto/rand"
	"encoding/hex"
	"encoding/json"
	"errors"
	"fmt"
	"gorm.io/gorm"
	"math"
	"time"
	"wails-app/internal/dao"
	"wails-app/internal/global"
	"wails-app/internal/modules/digital-ticket/repository"
)

const (
	StateCreated        = "created"
	StatePendingPayment = "pending_payment"
	StatePaid           = "paid"
	StateExited         = "exited"
	StateExpired        = "expired"
)

var (
	ErrTicketStateChanged   = errors.New("digital ticket state changed")
	ErrInvalidTicketPayment = errors.New("invalid digital ticket payment amount")
)

type TicketService struct {
	repo *repository.TicketRepository
}

func NewTicketService() *TicketService {
	return &TicketService{repo: &repository.TicketRepository{}}
}

func genTicketNo() string {
	b := make([]byte, 16)
	rand.Read(b)
	return hex.EncodeToString(b)
}

func appendEvent(log string, event map[string]interface{}) string {
	var events []map[string]interface{}
	json.Unmarshal([]byte(log), &events)
	event["at"] = time.Now().Format(time.RFC3339)
	events = append(events, event)
	data, _ := json.Marshal(events)
	return string(data)
}

// Create 创建数字票（所有进场方式统一入口）
func (s *TicketService) Create(plateNumber, triggerMode string, recordID uint) (*dao.DigitalTicket, error) {
	return s.CreateTx(global.GVA_DB, plateNumber, triggerMode, recordID)
}

func (s *TicketService) CreateTx(db *gorm.DB, plateNumber, triggerMode string, recordID uint) (*dao.DigitalTicket, error) {
	log := appendEvent("[]", map[string]interface{}{"event": "created", "trigger": triggerMode})
	ticket := &dao.DigitalTicket{
		TicketNo: genTicketNo(), PlateNumber: plateNumber, TriggerMode: triggerMode,
		State: StatePendingPayment, VehicleRecordID: recordID, EntryTime: time.Now(), EventLog: log,
	}
	if err := s.repo.CreateTx(db, ticket); err != nil {
		return nil, err
	}
	return ticket, nil
}

// Transition 状态转换（校验合法性，原子更新）
func (s *TicketService) Transition(id uint, toState string, extra map[string]interface{}) error {
	return s.TransitionTx(global.GVA_DB, id, toState, extra)
}

func extraAmount(extra map[string]interface{}, key string) (float64, bool, error) {
	value, ok := extra[key]
	if !ok || value == nil {
		return 0, false, nil
	}
	switch number := value.(type) {
	case float64:
		return number, true, nil
	case float32:
		return float64(number), true, nil
	case int:
		return float64(number), true, nil
	case int8:
		return float64(number), true, nil
	case int16:
		return float64(number), true, nil
	case int32:
		return float64(number), true, nil
	case int64:
		return float64(number), true, nil
	case uint:
		return float64(number), true, nil
	case uint8:
		return float64(number), true, nil
	case uint16:
		return float64(number), true, nil
	case uint32:
		return float64(number), true, nil
	case uint64:
		return float64(number), true, nil
	case json.Number:
		parsed, err := number.Float64()
		return parsed, true, err
	default:
		return 0, true, fmt.Errorf("%s must be numeric", key)
	}
}

func validatePaymentExtra(extra map[string]interface{}) error {
	fee, hasFee, err := extraAmount(extra, "fee")
	if err != nil {
		return err
	}
	paid, hasPaid, err := extraAmount(extra, "paid_amount")
	if err != nil {
		return err
	}
	for _, amount := range []float64{fee, paid} {
		if math.IsNaN(amount) || math.IsInf(amount, 0) || amount < 0 {
			return ErrInvalidTicketPayment
		}
	}
	if hasFee && hasPaid && paid < fee {
		return errors.New("paid amount insufficient")
	}
	return nil
}

func (s *TicketService) TransitionTx(db *gorm.DB, id uint, toState string, extra map[string]interface{}) error {
	if db == nil {
		return errors.New("database not initialized")
	}
	ticket, err := s.repo.GetByIDTx(db, id)
	if err != nil {
		return errors.New("票不存在")
	}

	validTransitions := map[string][]string{
		StateCreated:        {StatePendingPayment},
		StatePendingPayment: {StatePaid, StateExpired},
		StatePaid:           {StateExited, StateExpired},
	}

	allowed := false
	for _, s := range validTransitions[ticket.State] {
		if s == toState {
			allowed = true
			break
		}
	}
	if !allowed {
		return fmt.Errorf("状态转换不合法: %s → %s", ticket.State, toState)
	}

	if toState == StatePaid {
		if err := validatePaymentExtra(extra); err != nil {
			return err
		}
	}

	updates := map[string]interface{}{}
	if toState == StatePaid {
		now := time.Now()
		updates["paid_at"] = now
	}
	if toState == StateExited {
		now := time.Now()
		updates["exit_time"] = now
	}
	// 只允许表中存在的字段写入数据库，其余仅记录到事件日志
	dbFields := map[string]bool{"payment_entry": true, "payment_method": true, "payment_order_no": true, "paid_amount": true, "fee": true}
	for k, v := range extra {
		if dbFields[k] {
			updates[k] = v
		}
	}

	event := map[string]interface{}{"event": toState}
	for k, v := range extra {
		event[k] = v
	}
	updates["event_log"] = appendEvent(ticket.EventLog, event)

	updated, err := s.repo.UpdateStateIfCurrentTx(db, id, ticket.State, toState, updates)
	if err != nil {
		return err
	}
	if !updated {
		return ErrTicketStateChanged
	}
	return nil
}

// MarkPaidAndExitedTx updates the ticket lifecycle in the caller's
// transaction. Payment entry and method are stored as payment metadata only;
// they do not define the ticket itself.
func (s *TicketService) MarkPaidAndExitedTx(db *gorm.DB, recordID uint, paymentEntry, paymentMethod, paymentOrderNo string, paidAmount, fee float64) error {
	if err := validatePaymentExtra(map[string]interface{}{"paid_amount": paidAmount, "fee": fee}); err != nil {
		return err
	}
	ticket, err := s.repo.GetByVehicleRecordIDTx(db, recordID)
	if err != nil {
		return errors.New("车辆对应的数字票不存在")
	}

	if ticket.State == StatePendingPayment {
		extra := map[string]interface{}{
			"payment_entry":    paymentEntry,
			"payment_method":   paymentMethod,
			"payment_order_no": paymentOrderNo,
			"paid_amount":      paidAmount,
			"fee":              fee,
		}
		if err := s.TransitionTx(db, ticket.ID, StatePaid, extra); err != nil {
			return err
		}
		ticket.State = StatePaid
	}

	if ticket.State == StatePaid {
		return s.TransitionTx(db, ticket.ID, StateExited, nil)
	}
	if ticket.State == StateExited {
		return nil
	}
	return fmt.Errorf("数字票状态不允许出场: %s", ticket.State)
}

func (s *TicketService) GetByTicketNo(no string) (*dao.DigitalTicket, error) {
	ticket, err := s.repo.GetByTicketNo(no)
	if err != nil {
		return nil, err
	}
	s.enrichTicket(ticket)
	return ticket, nil
}

func (s *TicketService) GetByTicketNoTx(db *gorm.DB, no string) (*dao.DigitalTicket, error) {
	return s.repo.GetByTicketNoTx(db, no)
}

func (s *TicketService) GetByVehicleRecordIDTx(db *gorm.DB, recordID uint) (*dao.DigitalTicket, error) {
	return s.repo.GetByVehicleRecordIDTx(db, recordID)
}

func (s *TicketService) List(q repository.TicketListQuery) ([]dao.DigitalTicket, int64, error) {
	list, total, err := s.repo.List(q)
	if err != nil {
		return nil, 0, err
	}
	for i := range list {
		s.enrichTicket(&list[i])
	}
	return list, total, nil
}

func (s *TicketService) Summary(q repository.TicketListQuery) (repository.TicketSummary, error) {
	return s.repo.Summary(q)
}

// enrichTicket keeps the ticket view useful before payment. A ticket is
// created at vehicle entry, while the definitive fee is calculated at payment
// or exit time. Pending tickets therefore need a live fee preview derived from
// their vehicle record and current parking duration.
func (s *TicketService) enrichTicket(ticket *dao.DigitalTicket) {
	if ticket == nil || ticket.VehicleRecordID == 0 || global.GVA_DB == nil {
		return
	}

	var record dao.VehicleRecord
	if err := global.GVA_DB.First(&record, ticket.VehicleRecordID).Error; err != nil {
		return
	}
	if record.PlateNumber != "" {
		ticket.PlateNumber = record.PlateNumber
	}

	var vehicle dao.Vehicle
	vehicleQuery := global.GVA_DB
	vehicleFound := false
	if record.PlateNumber != "" {
		vehicleQuery = vehicleQuery.Where("plate_number = ?", record.PlateNumber)
		vehicleFound = vehicleQuery.First(&vehicle).Error == nil
	} else if record.RFIDTag != "" {
		vehicleQuery = vehicleQuery.Where("rfid_tag = ?", record.RFIDTag)
		vehicleFound = vehicleQuery.First(&vehicle).Error == nil
	}
	if ticket.PlateNumber == "" && vehicleFound {
		ticket.PlateNumber = vehicle.PlateNumber
	}

	if ticket.State == StateCreated || ticket.State == StatePendingPayment {
		if !vehicleFound {
			return
		}
		stayTime := int64(math.Ceil(time.Since(record.EntryTime).Minutes()))
		if stayTime < 0 {
			stayTime = 0
		}
		// 预览保持宽容：未配置收费规则时费用显示 0，正式出场时由 CalculateFee 返回明确错误
		if fee, calcErr := CalculateFee(&vehicle, stayTime); calcErr == nil {
			ticket.Fee = fee
		}
		return
	}

	// Older rows may have a zero digital-ticket fee even though the vehicle
	// record was already settled. Keep the historical record's fee visible.
	if ticket.Fee == 0 && record.Fee != 0 {
		ticket.Fee = record.Fee
	}
}