Forbid creating multiple tasks with the same ID

task/task.go

@@ -8,7 +8,8 @@ import (
 )
 
 var (
-	ErrNotExists = errors.New("task does not exist")
+	ErrAlreadyExists = errors.New("task already exists")
+	ErrNotExists     = errors.New("task does not exist")
 )
 
 type Task struct {

tests/worker/start_task_test.go

@@ -0,0 +1,63 @@
+package worker
+
+import (
+	"dirigeant/task"
+	"dirigeant/tests/helper"
+	"dirigeant/worker"
+	"fmt"
+	"net/http"
+	"net/http/httptest"
+	"testing"
+
+	"github.com/google/uuid"
+	"github.com/stretchr/testify/assert"
+)
+
+func TestStartTask__ShouldPersistTask(t *testing.T) {
+	api := &worker.Api{
+		Worker: &worker.Worker{
+			Tasks: make(map[uuid.UUID]*task.Task),
+		},
+	}
+	testTask := helper.PrintFileTask("print-task", helper.HostsFilePath)
+	request := helper.NewTaskPostRequest(testTask)
+	responseRecorder := httptest.NewRecorder()
+
+	api.HandleCreateTask(responseRecorder, request)
+
+	assert.Equal(t, http.StatusCreated, responseRecorder.Code, "Response status code should be 201 Created")
+	assert.Empty(t, responseRecorder.Body, "Response body should be empty")
+	assert.Equal(t, 1, len(api.Worker.Tasks), "Tasks map should contain 1 task")
+	assert.NotNil(t, api.Worker.Tasks[testTask.ID], "Persisted task ID should match the one from request")
+}
+
+func TestStartTask__ShouldReturnAnErrorIfCreatingTheSameTaskTwice(t *testing.T) {
+	api := &worker.Api{
+		Worker: &worker.Worker{
+			Tasks: make(map[uuid.UUID]*task.Task),
+		},
+	}
+	testTask := helper.PrintFileTask("print-task", helper.HostsFilePath)
+
+	// 1 - Create a task for the first time
+	firstRequest := helper.NewTaskPostRequest(testTask)
+	firstResponseRecorder := httptest.NewRecorder()
+
+	api.HandleCreateTask(firstResponseRecorder, firstRequest)
+
+	assert.Equal(t, http.StatusCreated, firstResponseRecorder.Code, "Response status code should be 201 Created")
+	assert.Empty(t, firstResponseRecorder.Body, "Response body should be empty")
+	assert.Equal(t, 1, len(api.Worker.Tasks), "Tasks map should contain 1 task")
+	assert.NotNil(t, api.Worker.Tasks[testTask.ID], "Persisted task ID should match the one from request")
+
+	// 2 - Create the same task for the second time
+	secondRequest := helper.NewTaskPostRequest(testTask)
+	secondResponseRecorder := httptest.NewRecorder()
+
+	api.HandleCreateTask(secondResponseRecorder, secondRequest)
+
+	assert.Equal(t, http.StatusConflict, secondResponseRecorder.Code, "Response status code should be 409 Conflict")
+	assert.Equal(t, fmt.Sprintf("Error when executing the task: %s", task.ErrAlreadyExists), secondResponseRecorder.Body.String(), "Response body should contain error message")
+	assert.Equal(t, 1, len(api.Worker.Tasks), "Tasks map should contain 1 task")
+	assert.NotNil(t, api.Worker.Tasks[testTask.ID], "Persisted task ID should match the one from request")
+}

worker/api.go

@@ -70,7 +70,12 @@ func (a *Api) HandleCreateTask(w http.ResponseWriter, r *http.Request) {
 	}
 
 	if err := a.Worker.StartTask(t); err != nil {
-		w.WriteHeader(http.StatusInternalServerError)
+		if errors.Is(err, task.ErrAlreadyExists) {
+			w.WriteHeader(http.StatusConflict)
+		} else {
+			w.WriteHeader(http.StatusInternalServerError)
+		}
+
 		fmt.Fprintf(w, "Error when executing the task: %v", err)
 		return
 	}

worker/worker.go

@@ -23,6 +23,10 @@ func (w *Worker) GetTask(id uuid.UUID) *task.Task {
 }
 
 func (w *Worker) StartTask(t task.Task) error {
+	if _, ok := w.Tasks[t.ID]; ok {
+		return task.ErrAlreadyExists
+	}
+
 	t.Cmd = exec.Command(t.Executable, t.Args...)
 	w.Tasks[t.ID] = &t