《Go 语言编程实战》4.1 REST 资源建模与状态码

tenant（租户，付费与隔离的边界）
  └── project（项目，团队协作的容器）
        └── task（任务，最小工作单元）

GET    /api/v1/tenants/{tenantID}                         读租户
GET    /api/v1/tenants/{tenantID}/projects                列项目
POST   /api/v1/tenants/{tenantID}/projects                建项目
GET    /api/v1/projects/{projectID}/tasks                 列任务（分页）
POST   /api/v1/projects/{projectID}/tasks                 建任务
GET    /api/v1/projects/{projectID}/tasks/{taskID}        读任务
PATCH  /api/v1/projects/{projectID}/tasks/{taskID}        改任务
DELETE /api/v1/projects/{projectID}/tasks/{taskID}        删任务

mux := http.NewServeMux()
mux.HandleFunc("POST /api/v1/projects/{projectID}/tasks", handleCreateTask)
mux.HandleFunc("GET /api/v1/projects/{projectID}/tasks/{taskID}", handleGetTask)
mux.HandleFunc("DELETE /api/v1/projects/{projectID}/tasks/{taskID}", handleDeleteTask)

func handleGetTask(w http.ResponseWriter, r *http.Request) {
	projectID := r.PathValue("projectID") // 直接取，不用正则解析
	taskID := r.PathValue("taskID")
	_ = projectID
	_ = taskID
}

type APIError struct {
	Code    string `json:"code"`
	Message string `json:"message"`
}

func writeJSON(w http.ResponseWriter, status int, v any) {
	w.Header().Set("Content-Type", "application/json; charset=utf-8")
	w.WriteHeader(status)
	if v != nil {
		_ = json.NewEncoder(w).Encode(v)
	}
}

func writeError(w http.ResponseWriter, status int, code, msg string) {
	writeJSON(w, status, APIError{Code: code, Message: msg})
}

func handleCreateTask(w http.ResponseWriter, r *http.Request) {
	projectID := r.PathValue("projectID")
	var in struct {
		Title string `json:"title"`
	}
	if err := json.NewDecoder(r.Body).Decode(&in); err != nil {
		writeError(w, http.StatusBadRequest, "malformed_request", "invalid JSON body")
		return
	}
	if strings.TrimSpace(in.Title) == "" {
		writeError(w, http.StatusUnprocessableEntity, "validation_failed", "title is required")
		return
	}
	t := Task{ID: "tsk_01", ProjectID: projectID, Title: in.Title, Status: "todo", CreatedAt: time.Now().UTC()}
	w.Header().Set("Location", "/api/v1/projects/"+projectID+"/tasks/"+t.ID)
	writeJSON(w, http.StatusCreated, t)
}

POST   /api/v1/projects/prj_7/tasks                   -> 201  Location="/api/v1/projects/prj_7/tasks/tsk_01"  body={"id":"tsk_01","project_id":"prj_7","title":"写卷二第 4 章","status":"todo","created_at":"2026-10-10T02:18:42.043753Z"}
POST   /api/v1/projects/prj_7/tasks                   -> 422  body={"code":"validation_failed","message":"title is required"}
GET    /api/v1/projects/prj_7/tasks/tsk_01            -> 200  body={"id":"tsk_01",...}
GET    /api/v1/projects/prj_7/tasks/tsk_99            -> 404  body={"code":"not_found","message":"task not found"}
DELETE /api/v1/projects/prj_7/tasks/tsk_01            -> 204  body=
DELETE /api/v1/projects/prj_7/tasks/tsk_01            -> 404  body={"code":"not_found","message":"task not found"}
PUT    /api/v1/projects/prj_7/tasks/tsk_01            -> 405  Allow="DELETE, GET, HEAD, PATCH"

cases := []struct {
	name   string
	method string
	path   string
	body   string
	want   int
}{
	{"create ok", "POST", "/api/v1/projects/prj_7/tasks", `{"title":"x"}`, 201},
	{"create empty title", "POST", "/api/v1/projects/prj_7/tasks", `{"title":"  "}`, 422},
	{"get missing", "GET", "/api/v1/projects/prj_7/tasks/tsk_99", "", 404},
	{"method not allowed", "PUT", "/api/v1/projects/prj_7/tasks/tsk_01", "", 405},
}
for _, tc := range cases {
	t.Run(tc.name, func(t *testing.T) {
		var r *http.Request
		if tc.body == "" {
			r = httptest.NewRequest(tc.method, tc.path, nil)
		} else {
			r = httptest.NewRequest(tc.method, tc.path, strings.NewReader(tc.body))
		}
		rec := httptest.NewRecorder()
		mux.ServeHTTP(rec, r)
		if rec.Code != tc.want {
			t.Fatalf("got %d, want %d", rec.Code, tc.want)
		}
	})
}