class UserProfile {
    readonly userId: string;
    name: string;

    constructor(userId: string, name: string) {
        this.userId = userId; // 可以在構(gòu)造函數(shù)中賦值
        this.name = name;
    }

    updateName(newName: string) {
        this.name = newName; // 普通屬性可以修改
    }

    // 嘗試修改 readonly 屬性會(huì)導(dǎo)致編譯錯(cuò)誤
    // updateUserId(newUserId: string) {
    //     this.userId = newUserId; // Error: Cannot assign to 'userId' because it is a read-only property.
    // }
}

const user = new UserProfile("user-123", "Alice");
console.log(user.userId); // "user-123"
user.updateName("Bob");
console.log(user.name); // "Bob"

// user.userId = "user-456"; // Error: Cannot assign to 'userId' because it is a read-only property.

interface Point {
    readonly x: number;
    readonly y: number;
}

let p1: Point = { x: 10, y: 20 };
// p1.x = 5; // Error: Cannot assign to 'x' because it is a read-only property.

function movePoint(p: Point, dx: number, dy: number): Point {
    // 不能直接修改 p.x 和 p.y
    // 要返回一個(gè)新的 Point 對(duì)象
    return { x: p.x + dx, y: p.y + dy };
}

const p2 = movePoint(p1, 5, 5);
console.log(p1); // { x: 10, y: 20 } (原始對(duì)象未改變)
console.log(p2); // { x: 15, y: 25 } (返回了新對(duì)象)

interface Config {
    readonly serverUrl: string;
    readonly settings: {
        timeout: number;
        retries: number;
    };
}

const appConfig: Config = {
    serverUrl: "https://api.example.com",
    settings: {
        timeout: 5000,
        retries: 3,
    },
};

// appConfig.serverUrl = "https://new.api.example.com"; // Error: Cannot assign to 'serverUrl' because it is a read-only property.

appConfig.settings.timeout = 10000; // 這是允許的！
console.log(appConfig.settings.timeout); // 10000

interface MutableConfigs {
    port: number;
    debugMode: boolean;
    features: string[];
}

// 使用 Readonly<T> 將 MutableConfigs 的所有屬性變?yōu)橹蛔x
type ImmutableConfigs = Readonly<MutableConfigs>;

const initialConfigs: MutableConfigs = {
    port: 3000,
    debugMode: true,
    features: ["featureA", "featureB"]
};

// immutableAppConfig 的類型是 ImmutableConfigs
const immutableAppConfig: ImmutableConfigs = initialConfigs;

// immutableAppConfig.port = 8080; // Error: Cannot assign to 'port' because it is a read-only property.
// immutableAppConfig.debugMode = false; // Error: Cannot assign to 'debugMode' because it is a read-only property.

// 同樣，Readonly<T> 也是淺不可變的
// immutableAppConfig.features.push("featureC"); // 這仍然是允許的，因?yàn)?features 是一個(gè)數(shù)組對(duì)象
// console.log(immutableAppConfig.features); // ["featureA", "featureB", "featureC"]

// 如果要使數(shù)組也只讀，可以這樣定義：
interface TrulyImmutableConfigs {
    readonly port: number;
    readonly debugMode: boolean;
    readonly features: ReadonlyArray<string>; // 使用 ReadonlyArray<T>
}

const trulyImmutableAppConfig: TrulyImmutableConfigs = {
    port: 8000,
    debugMode: false,
    features: ["logging", "monitoring"]
};

// trulyImmutableAppConfig.features.push("newFeature"); // Error: Property 'push' does not exist on type 'readonly string[]'.
// trulyImmutableAppConfig.features[0] = "newLogging"; // Error: Index signature in type 'readonly string[]' only permits reading.

function processConfig(config: Readonly<MutableConfigs>): void {
    console.log(`Processing config for port: ${config.port}`);
    // config.port = 8081; // Error: Cannot assign to 'port' because it is a read-only property.
}

processConfig(initialConfigs);

let readOnlyNumbers: ReadonlyArray<number> = [1, 2, 3, 4, 5];

// readOnlyNumbers.push(6); // Error: Property 'push' does not exist on type 'readonly number[]'.
// readOnlyNumbers[0] = 0; // Error: Index signature in type 'readonly number[]' only permits reading.

// 可以使用不會(huì)修改原數(shù)組的方法
const doubledNumbers = readOnlyNumbers.map(n => n * 2);
console.log(doubledNumbers); // [2, 4, 6, 8, 10]
console.log(readOnlyNumbers); // [1, 2, 3, 4, 5] (原始數(shù)組未改變)