type Message struct {
    ID      int       `json:"id"`
    User    string    `json:"user"`
    Content string    `json:"content"`
    Time    time.Time `json:"time"`
}

func main() {
    messages := &[]Message{} // 模拟存储
    http.HandleFunc("/messages", func(w http.ResponseWriter, r *http.Request) {
        switch r.Method {
        case "GET":
            getMessages(w, *messages)
        case "POST":
            addMessage(w, r, messages)
        default:
            http.Error(w, "不支持的请求方法", http.StatusMethodNotAllowed)
        }
    })

    fmt.Println("服务启动在 :8080")
    http.ListenAndServe(":8080", nil)
}

func getMessages(w http.ResponseWriter, messages []Message) {
    w.Header().Set("Content-Type", "application/json")
    json.NewEncoder(w).Encode(messages)
}

func addMessage(w http.ResponseWriter, r *http.Request, messages *[]Message) {
    if err := r.ParseForm(); err != nil {
        http.Error(w, "解析表单失败", http.StatusBadRequest)
        return
    }

    user := r.FormValue("user")
    content := r.FormValue("content")

    if user == "" || content == "" {
        http.Error(w, "用户名和内容不能为空", http.StatusBadRequest)
        return
    }

    msg := Message{
        ID:      len(*messages) + 1,
        User:    user,
        Content: content,
        Time:    time.Now(),
    }
    *messages = append(*messages, msg)

    w.WriteHeader(http.StatusCreated)
    json.NewEncoder(w).Encode(msg)
}

func servePage(w http.ResponseWriter, r *http.Request) {
    html := `
<html>
<body>
  <h2>留言板</h2>
  <form onsubmit="addMessage(event)">
    用户名: <input type="text" id="user" required><br>
    留言: <textarea id="content" required></textarea><br>
    <button type="submit">提交</button>
  </form>
  <div id="list"></div>

  <script>
    function loadMessages() {
      fetch('/messages').then(r => r.json()).then(data => {
        document.getElementById('list').innerHTML = data.map(m =>
          '<p><b>'+m.user+'</b> ('+new Date(m.time).toLocaleString()+'): '+m.content+'</p>'
        ).join('');
      });
    }
    function addMessage(e) {
      e.preventDefault();
      const user = document.getElementById('user').value;
      const content = document.getElementById('content').value;
      fetch('/messages', {
        method: 'POST',
        headers: {'Content-Type': 'application/x-www-form-urlencoded'},
        body: 'user='+encodeURIComponent(user)+'&content='+encodeURIComponent(content)
      }).then(() => {
        document.getElementById('user').value = '';
        document.getElementById('content').value = '';
        loadMessages();
      });
    }
    loadMessages();
  </script>
</body>
</html>
`
    w.Write([]byte(html))
}