// 未使用struct的代碼
fn print_user(name: String, age: u8, email: String) {
    println!("用戶: {}, 年齡: {}, 郵箱: {}", name, age, email);
}
fn main() {
    let name = String::from("張三");
    let age = 25;
    let email = String::from("zhangsan@example.com");
    // 問題：參數(shù)順序容易出錯！
    print_user(email, age, name); // 錯誤：郵箱和用戶名傳反了
}

struct User {
    name: String,
    age: u8,
    email: String,
}
fn print_user(user: &User) {
    println!(
        "用戶: {}, 年齡: {}, 郵箱: {}",
        user.name, user.age, user.email
    );
}
fn main() {
    let user = User {
        name: String::from("張三"),
        age: 25,
        email: String::from("zhangsan@example.com"),
    };
    print_user(&user); // 正確：字段通過結構體明確關聯(lián)
}

// 未使用enum的代碼
struct Message {
    kind: String,  // 用字符串標記類型："text", "image", "video"
    content: String,
}
fn process_message(msg: &Message) {
    if msg.kind == "text" {
        println!("收到文本: {}", msg.content);
    } else if msg.kind == "image" {
        println!("收到圖片: {}", msg.content);
    } else {
        // 潛在問題：可能遺漏某些類型！
        panic!("未知消息類型");
    }
}

enum Message {
    Text(String),
    Image { url: String, width: u32, height: u32 },
    Video(String),
}
fn process_message(msg: &Message) {
    match msg {
        Message::Text(text) => println!("收到文本: {}", text),
        Message::Image { url, width, height } => {
            println!("收到圖片: {} (尺寸: {}x{})", url, width, height)
        }
        Message::Video(url) => println!("收到視頻: {}", url),
    }
}
fn main() {
    let msg1 = Message::Text(String::from("你好！"));
    let msg2 = Message::Image {
        url: String::from("https://example.com/image.jpg"),
        width: 800,
        height: 600,
    };
    process_message(&msg1);
    process_message(&msg2);
}

// 定義數(shù)據(jù)包類型
enum Packet {
    Login(LoginData),
    Logout(LogoutData),
}
// 登錄包的數(shù)據(jù)結構
struct LoginData {
    username: String,
    password: String,
}
// 登出包的數(shù)據(jù)結構
struct LogoutData {
    timestamp: u64,
}
fn parse_packet(packet: Packet) {
    match packet {
        Packet::Login(data) => {
            println!(
                "登錄請求 - 用戶名: {}, 密碼: {}",
                data.username, data.password
            )
        }
        Packet::Logout(data) => {
            println!("登出時間: {}", data.timestamp)
        }
    }
}
fn main() {
    let login_packet = Packet::Login(LoginData {
        username: String::from("user123"),
        password: String::from("secret"),
    });
    let logout_packet = Packet::Logout(LogoutData {
        timestamp: 1629782400,
    });
    parse_packet(login_packet);
    parse_packet(logout_packet);
}

enum Message {
    Text(String),
    Image { url: String, width: u32, height: u32 },
    Video(String),
    Audio(String), // 新增變體
}
fn process_message(msg: &Message) {
    match msg {
        Message::Text(text) => println!("收到文本: {}", text),
        Message::Image { url, width, height } => {
            println!("收到圖片: {} (尺寸: {}x{})", url, width, height)
        }
        // 編譯器會報錯：未處理 `Message::Audio` 分支！
    }
}

// 定義一個“形狀”枚舉
enum Shape {
    Circle { radius: f64 },
    Rectangle { width: f64, height: f64 },
}
// 為枚舉實現(xiàn)方法
impl Shape {
    fn area(&self) -> f64 {
        match self {
            Shape::Circle { radius } => std::f64::consts::PI * radius * radius,
            Shape::Rectangle { width, height } => width * height,
        }
    }
}
fn main() {
    let circle = Shape::Circle { radius: 3.0 };
    let rect = Shape::Rectangle {
        width: 4.0,
        height: 5.0,
    };
    println!("圓形面積: {:.2}", circle.area()); // 輸出: 28.27
    println!("矩形面積: {:.2}", rect.area());   // 輸出: 20.00
}