package service

import (
	"errors"
	"sync"
	"testing"

	"github.com/stretchr/testify/require"
	"gorm.io/gorm"
	"wails-app/internal/dao"
	"wails-app/internal/global"
)

func createPendingTicketForEdgeTest(t *testing.T, svc *TicketService, plate string) *dao.DigitalTicket {
	t.Helper()
	record := &dao.VehicleRecord{PlateNumber: plate, PaymentStatus: "unpaid"}
	require.NoError(t, global.GVA_DB.Create(record).Error)
	ticket, err := svc.Create(plate, "test", record.ID)
	require.NoError(t, err)
	return ticket
}

func TestDigitalTicketRejectsNegativePaymentAmounts(t *testing.T) {
	svc := setupTicketServiceTest(t)
	ticket := createPendingTicketForEdgeTest(t, svc, "NEGATIVE-TICKET")

	err := svc.TransitionTx(global.GVA_DB, ticket.ID, StatePaid, map[string]interface{}{
		"fee": -1.0, "paid_amount": 0.0,
	})
	require.ErrorIs(t, err, ErrInvalidTicketPayment)

	var current dao.DigitalTicket
	require.NoError(t, global.GVA_DB.First(&current, ticket.ID).Error)
	require.Equal(t, StatePendingPayment, current.State)

	err = svc.MarkPaidAndExitedTx(global.GVA_DB, ticket.VehicleRecordID, "counter", "cash", "", -1, 0)
	require.ErrorIs(t, err, ErrInvalidTicketPayment)
}

func TestDigitalTicketAllowsZeroFeePayment(t *testing.T) {
	svc := setupTicketServiceTest(t)
	ticket := createPendingTicketForEdgeTest(t, svc, "ZERO-TICKET")

	require.NoError(t, svc.TransitionTx(global.GVA_DB, ticket.ID, StatePaid, map[string]interface{}{
		"fee": 0.0, "paid_amount": 0.0, "payment_entry": "counter", "payment_method": "cash",
	}))

	var current dao.DigitalTicket
	require.NoError(t, global.GVA_DB.First(&current, ticket.ID).Error)
	require.Equal(t, StatePaid, current.State)
	require.Zero(t, current.Fee)
	require.Zero(t, current.PaidAmount)
}

func TestDigitalTicketRejectsDuplicatePayment(t *testing.T) {
	svc := setupTicketServiceTest(t)
	ticket := createPendingTicketForEdgeTest(t, svc, "DUPLICATE-TICKET")
	extra := map[string]interface{}{"fee": 10.0, "paid_amount": 10.0, "payment_order_no": "ORDER-1"}

	require.NoError(t, svc.TransitionTx(global.GVA_DB, ticket.ID, StatePaid, extra))
	require.Error(t, svc.TransitionTx(global.GVA_DB, ticket.ID, StatePaid, extra))

	var current dao.DigitalTicket
	require.NoError(t, global.GVA_DB.First(&current, ticket.ID).Error)
	require.Equal(t, StatePaid, current.State)
	require.Equal(t, "ORDER-1", current.PaymentOrderNo)
}

func TestDigitalTicketConcurrentPaymentHasSingleWinner(t *testing.T) {
	svc := setupTicketServiceTest(t)
	ticket := createPendingTicketForEdgeTest(t, svc, "CONCURRENT-TICKET")

	const attempts = 8
	start := make(chan struct{})
	results := make(chan error, attempts)
	var wg sync.WaitGroup
	for i := 0; i < attempts; i++ {
		wg.Add(1)
		go func() {
			defer wg.Done()
			<-start
			results <- svc.TransitionTx(global.GVA_DB, ticket.ID, StatePaid, map[string]interface{}{
				"fee": 10.0, "paid_amount": 10.0,
			})
		}()
	}
	close(start)
	wg.Wait()
	close(results)

	successes := 0
	for err := range results {
		if err == nil {
			successes++
		}
	}
	require.Equal(t, 1, successes)

	var current dao.DigitalTicket
	require.NoError(t, global.GVA_DB.First(&current, ticket.ID).Error)
	require.Equal(t, StatePaid, current.State)
}

func TestDigitalTicketTransitionRollbackRestoresState(t *testing.T) {
	svc := setupTicketServiceTest(t)
	ticket := createPendingTicketForEdgeTest(t, svc, "ROLLBACK-TICKET")
	rollbackErr := errors.New("force rollback")

	err := global.GVA_DB.Transaction(func(tx *gorm.DB) error {
		if err := svc.TransitionTx(tx, ticket.ID, StatePaid, map[string]interface{}{
			"fee": 10.0, "paid_amount": 10.0,
		}); err != nil {
			return err
		}
		return rollbackErr
	})
	require.ErrorIs(t, err, rollbackErr)

	var current dao.DigitalTicket
	require.NoError(t, global.GVA_DB.First(&current, ticket.ID).Error)
	require.Equal(t, StatePendingPayment, current.State)
	require.Empty(t, current.PaymentOrderNo)
}