package usecase

import (
	"context"
	"errors"
	"testing"
	"time"

	"cmroubao/backend-api/internal/domain"
)

func TestTaskServiceCreateNormalizesAndHashesForIdempotency(t *testing.T) {
	repository := &fakeTaskRepository{}
	service := mustTaskService(t, repository)
	budget := "20.00"
	sourceRef := " source-1 "

	result, err := service.Create(context.Background(), CreateTaskCommand{
		CreatorSubject: " local-admin ",
		ActorUserID:    "00000000-0000-4000-8000-000000000099",
		IdempotencyKey: " create-1 ",
		SourceRef:      &sourceRef,
		Title:          " Demo title ",
		Description:    "description",
		SKU:            " SKU-1 ",
		ImageAssetID:   "00000000-0000-4000-8000-000000000001",
		Quantity:       2,
		MaxBudget:      &budget,
	})
	if err != nil {
		t.Fatalf("Create() error = %v", err)
	}
	if result.Task.Status != domain.TaskStatusPending ||
		result.Task.Title != "Demo title" ||
		result.Task.SKU != "SKU-1" ||
		result.Task.SourceRef == nil ||
		*result.Task.SourceRef != "source-1" ||
		result.Task.CreatedByUserID == nil ||
		*result.Task.CreatedByUserID !=
			"00000000-0000-4000-8000-000000000099" ||
		result.Task.MaxBudgetCents == nil ||
		*result.Task.MaxBudgetCents != 2000 {
		t.Fatalf("created task = %+v", result.Task)
	}
	if repository.key != "create-1" || len(repository.hash) != 64 {
		t.Fatalf(
			"idempotency key/hash = %q/%q",
			repository.key,
			repository.hash,
		)
	}
	if repository.event.Type != "TASK_CREATED" ||
		repository.event.TaskID != result.Task.ID ||
		repository.event.ActorUserID == nil ||
		*repository.event.ActorUserID !=
			"00000000-0000-4000-8000-000000000099" {
		t.Fatalf("event = %+v", repository.event)
	}
}

func TestTaskServiceCreateMapsValidationAndRepositoryErrors(t *testing.T) {
	repository := &fakeTaskRepository{createErr: ErrAssetUnavailable}
	service := mustTaskService(t, repository)
	_, err := service.Create(context.Background(), CreateTaskCommand{
		CreatorSubject: "local-admin",
		ActorUserID:    "00000000-0000-4000-8000-000000000099",
		IdempotencyKey: "create-1",
		Title:          "title",
		SKU:            "sku",
		ImageAssetID:   "00000000-0000-4000-8000-000000000001",
		Quantity:       1,
	})
	assertUsecaseError(t, err, ErrorKindConflict, "TASK_ASSET_UNAVAILABLE")

	_, err = service.Create(context.Background(), CreateTaskCommand{
		CreatorSubject: "local-admin",
		ActorUserID:    "00000000-0000-4000-8000-000000000099",
		IdempotencyKey: "create-2",
		Title:          "",
		SKU:            "",
		ImageAssetID:   "bad",
		Quantity:       0,
	})
	assertUsecaseError(t, err, ErrorKindInvalid, "TASK_VALIDATION_FAILED")
}

func TestTaskServiceListUsesStableOpaqueCursor(t *testing.T) {
	createdAt := time.Date(2026, 7, 26, 1, 2, 3, 4, time.UTC)
	repository := &fakeTaskRepository{
		listResult: []domain.PurchaseTask{
			{ID: "00000000-0000-4000-8000-000000000003", CreatedAt: createdAt},
			{ID: "00000000-0000-4000-8000-000000000002", CreatedAt: createdAt},
			{ID: "00000000-0000-4000-8000-000000000001", CreatedAt: createdAt},
		},
	}
	service := mustTaskService(t, repository)
	page, err := service.List(context.Background(), ListTasksQuery{
		CreatorSubject: "local-admin",
		Limit:          2,
	})
	if err != nil {
		t.Fatalf("List() error = %v", err)
	}
	if len(page.Items) != 2 || page.NextCursor == "" {
		t.Fatalf("page = %+v", page)
	}
	if repository.filter.Limit != 3 {
		t.Fatalf("repository limit = %d", repository.filter.Limit)
	}
	cursor, err := decodeTaskCursor(page.NextCursor)
	if err != nil {
		t.Fatalf("decodeTaskCursor() error = %v", err)
	}
	if cursor.ID != page.Items[1].ID || !cursor.CreatedAt.Equal(createdAt) {
		t.Fatalf("cursor = %+v", cursor)
	}
}

func TestTaskServiceCancelMapsStateConflict(t *testing.T) {
	repository := &fakeTaskRepository{cancelErr: ErrTaskStateConflict}
	service := mustTaskService(t, repository)
	_, err := service.Cancel(context.Background(), CancelTaskCommand{
		CreatorSubject: "local-admin",
		ActorUserID:    "00000000-0000-4000-8000-000000000099",
		TaskID:         "00000000-0000-4000-8000-000000000001",
		Reason:         "no longer needed",
	})
	assertUsecaseError(t, err, ErrorKindConflict, "TASK_STATE_CONFLICT")
	if repository.event.ActorUserID == nil ||
		*repository.event.ActorUserID !=
			"00000000-0000-4000-8000-000000000099" {
		t.Fatalf("cancel event = %+v", repository.event)
	}
}

type fakeClock struct{}

func (fakeClock) Now() time.Time {
	return time.Date(2026, 7, 26, 1, 2, 3, 4, time.UTC)
}

type sequenceIDs struct {
	next int
}

func (generator *sequenceIDs) NewID() (string, error) {
	generator.next++
	return "00000000-0000-4000-8000-" +
		pad12(generator.next), nil
}

func pad12(value int) string {
	result := "000000000000"
	digits := []byte{}
	for value > 0 {
		digits = append([]byte{byte('0' + value%10)}, digits...)
		value /= 10
	}
	if len(digits) == 0 {
		digits = []byte{'0'}
	}
	return result[:12-len(digits)] + string(digits)
}

type fakeTaskRepository struct {
	createErr  error
	cancelErr  error
	listResult []domain.PurchaseTask
	task       domain.PurchaseTask
	event      domain.TaskEvent
	key        string
	hash       string
	filter     TaskListFilter
}

func (repository *fakeTaskRepository) CreateTaskIdempotent(
	_ context.Context,
	task domain.PurchaseTask,
	event domain.TaskEvent,
	key string,
	hash string,
) (domain.PurchaseTask, bool, error) {
	repository.task = task
	repository.event = event
	repository.key = key
	repository.hash = hash
	return task, true, repository.createErr
}

func (repository *fakeTaskRepository) ListTasks(
	_ context.Context,
	filter TaskListFilter,
) ([]domain.PurchaseTask, error) {
	repository.filter = filter
	return repository.listResult, nil
}

func (repository *fakeTaskRepository) GetTaskDetail(
	context.Context,
	string,
	string,
) (domain.TaskDetail, error) {
	return domain.TaskDetail{}, errors.New("not implemented")
}

func (repository *fakeTaskRepository) CancelPendingTask(
	_ context.Context,
	_ string,
	_ string,
	_ string,
	_ time.Time,
	event domain.TaskEvent,
) (domain.PurchaseTask, error) {
	repository.event = event
	return domain.PurchaseTask{}, repository.cancelErr
}

func mustTaskService(
	t *testing.T,
	repository TaskRepository,
) *TaskService {
	t.Helper()
	service, err := NewTaskService(
		repository,
		fakeClock{},
		&sequenceIDs{},
	)
	if err != nil {
		t.Fatalf("NewTaskService() error = %v", err)
	}
	return service
}

func assertUsecaseError(
	t *testing.T,
	err error,
	kind ErrorKind,
	code string,
) {
	t.Helper()
	var typed *Error
	if !errors.As(err, &typed) {
		t.Fatalf("error = %v, want *Error", err)
	}
	if typed.Kind != kind || typed.Code != code {
		t.Fatalf("error = %+v, want kind=%s code=%s", typed, kind, code)
	}
}