ProtocolTest.java

/**
 * 協定解析器的測試（用 assert；也可以改寫成 JUnit）。
 *
 * 執行：javac *.java && java -ea ProtocolTest
 */
public class ProtocolTest {

    /** 「往返」性質：任何合法訊息 encode 之後再 parse，必須得到相等的物件。 */
    static void roundTrip(ChatMessage m) {
        String line = ChatMessage.encode(m);
        ChatMessage back = ChatMessage.parse(line);
        assert back.equals(m) : "往返失敗：" + m + " → \"" + line + "\" → " + back;
        System.out.println("  " + String.format("%-40s", line) + " ⇄ " + back);
    }

    static void expectError(String line) {
        try {
            ChatMessage m = ChatMessage.parse(line);
            assert false : "應該要失敗卻解析成功：" + line + " → " + m;
        } catch (ChatMessage.ProtocolException e) {
            System.out.println("  \"" + line + "\" → 拒絕：" + e.getMessage());
        }
    }

    public static void main(String[] args) throws java.io.IOException {
        System.out.println("=== 往返測試（record 自動有 equals，才能這樣比較）===");
        roundTrip(new ChatMessage.Login("angelia"));
        roundTrip(new ChatMessage.Join("general"));
        roundTrip(new ChatMessage.Say("general", "hello world, with spaces!"));
        roundTrip(new ChatMessage.Quit());
        roundTrip(new ChatMessage.Ok(""));
        roundTrip(new ChatMessage.Ok("welcome angelia"));
        roundTrip(new ChatMessage.Err(401, "login first"));
        roundTrip(new ChatMessage.Msg("general", "bob", "多位元組字元也沒問題：café 日本語"));
        roundTrip(new ChatMessage.Bye());

        System.out.println("=== 不合法的輸入必須被拒絕，而不是默默接受 ===");
        expectError("");
        expectError("DANCE");
        expectError("LOGIN");
        expectError("LOGIN two words");
        expectError("SAY general");
        expectError("ERR notanumber oops");
        expectError("MSG general bob");

        System.out.println("=== 指令不分大小寫 ===");
        assert ChatMessage.parse("login angelia").equals(new ChatMessage.Login("angelia"));

        System.out.println("=== 用 FakeChatClient 測 UI 邏輯（不需要網路）===");
        StringBuilder screen = new StringBuilder();
        ChatClient client = new FakeChatClient();
        client.addListener(new ChatClient.Listener() {         // 匿名類別實作監聽者介面
            public void onMessage(String room, String from, String text) {
                screen.append("[").append(room).append("] ").append(from).append(": ").append(text).append("\n");
            }
            public void onError(int code, String text) {
                screen.append("ERROR ").append(code).append(": ").append(text).append("\n");
            }
            public void onDisconnected() {
                screen.append("(disconnected)\n");
            }
        });
        client.connect("localhost", 5555, "angelia");
        client.say("general", "hi");                          // 還沒 join → 錯誤
        client.join("general");
        client.say("general", "hi again");
        client.disconnect();
        System.out.print(screen);
        assert screen.toString().equals(
                "ERROR 403: not in room general\n[general] angelia: hi again\n(disconnected)\n");
        try {
            client.say("general", "after disconnect");
        } catch (IllegalStateException e) {
            System.out.println("  斷線後操作 → IllegalStateException：" + e.getMessage());
        }
        System.out.println("全部通過。");
    }
}