fix(tasks): 任务取消 - 禁止取消已开始的生成任务

backend/internal/service/task_cancellation_test.go

@@ -0,0 +1,47 @@
+package service
+
+import (
+	"context"
+	"testing"
+	"time"
+
+	"infinite-canvas/backend/internal/model"
+	"infinite-canvas/backend/internal/repository"
+
+	"gorm.io/driver/sqlite"
+	"gorm.io/gorm"
+)
+
+func TestCancelTaskRejectsRunningTask(t *testing.T) {
+	db, err := gorm.Open(sqlite.Open("file:"+newID()+"?mode=memory&cache=shared"), &gorm.Config{})
+	if err != nil {
+		t.Fatal(err)
+	}
+	if err := db.AutoMigrate(&model.Task{}); err != nil {
+		t.Fatal(err)
+	}
+	startedAt := time.Now()
+	task := model.Task{
+		ID:        "running-task",
+		UserID:    "user-1",
+		Status:    model.TaskStatusRunning,
+		Stage:     "调用生成模型",
+		StartedAt: &startedAt,
+	}
+	if err := db.Create(&task).Error; err != nil {
+		t.Fatal(err)
+	}
+
+	svc := &Service{repo: repository.New(db)}
+	if _, err := svc.CancelTask(context.Background(), task.UserID, task.ID); err == nil || err.Error() != "任务已开始生成，无法取消" {
+		t.Fatalf("CancelTask() error = %v", err)
+	}
+
+	stored, err := svc.repo.TaskForUser(task.UserID, task.ID)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if stored.Status != model.TaskStatusRunning || stored.CompletedAt != nil {
+		t.Fatalf("running task changed after cancellation attempt: status=%s completedAt=%v", stored.Status, stored.CompletedAt)
+	}
+}