use std::{fs::File, io::{ErrorKind, Read}};

fn main() {
    // let f = File::open("hello.txt");

    // let f = match f {
    //     Ok(file) => {
    //         println!("file is exist！");
    //         file
    //     }
    //     Err(err) => match err.kind() {
    //         std::io::ErrorKind::NotFound => match File::create("hello.txt") {
    //             Ok(fc) => fc,
    //             Err(e) => panic!("Error creating file: {:?}", e),
    //         },
    //         other_error => panic!("Error opeing the file: {:?}", other_error),
    //     },
    // };

    // let f = File::open("hello.txt").unwrap_or_else(|error|{
    //     if error.kind() == std::io::ErrorKind::NotFound {
    //         File::create("hello.txt").unwrap_or_else(|error| {
    //             panic!("Error creating file: {:?}", error);
    //         })
    //     } else {
    //         panic!("Error opeing the file: {:?}", error);
    //     }
    // });

    // let f = File::open("hello.txt").unwrap();

    // let f = File::open("hello.txt").expect("无法打开文件");

    fn read_username_from_file() -> Result<String, std::io::Error>{
        let f = File::open("hello.txt");

        let mut f = match f {
            Ok(file) => file,
            Err(e) => return Err(e),
        };

        let mut s = String::new();

        match f.read_to_string(&mut s) {
            Ok(_) => Ok(s),
            Err(e) => Err(e),            
        }
    }


    let result = read_username_from_file();

    fn read_username_from_file1() -> Result<String, std::io::Error>{
      let mut f = File::open("hello.txt")?;

      let mut s = String::new();

      f.read_to_string(&mut s)?;

      Ok(s)
    }


    fn read_username_from_file2() -> Result<String, std::io::Error>{
      let mut s = String::new();
      File::open("hello.txt")?.read_to_string(&mut s)?;

      Ok(s)
    }

    pub struct Guess {
      value: i32,
    }

    impl Guess {
      pub fn new(value: i32) -> Guess {
        if value < 1 || value > 100 {
          panic!("the secret number will be between 1 adn 100, got {}", value);
        }
        Guess { value }
      }

      pub fn value(&self) -> i32 {
        self.value
      }
    }

    loop {
      // mut 代表变量可变
      let mut guess: String = String::new();

      // 读取用户输入行，放入可变变量guess中
      // std库：标准库
      // &：引用
      std::io::stdin().read_line(&mut guess).expect("无法读取行");

      let guess: i32 = match guess.trim().parse(){
          Ok(num) => num,
          Err(_) => continue,
      };
  
      let guess = Guess::new(guess);
    }

}