pub mod error;

use error::Error;
use std::io;
use std::io::prelude::*;


pub type Result<T> = std::result::Result<T, Error>;


pub enum Input {
    String(String),
    End,
}


fn main() -> Result<()> {
    std::process::exit(match repl() {
        Ok(()) => 0,
        Err(ref e) => {
            eprintln!("{}", e);
            1
        }
    })
}


fn repl() -> Result<()> {
    println!("Hello, terminal!");

    loop {
        prompt()?;

        let input = read()?;
        match input {
            Input::String(string) => execute(string)?,
            Input::End => break,
        }
    }

    Ok(())
}


fn prompt() -> Result<()> {
    print!("$ ");
    io::stdout().flush()?;

    Ok(())
}


fn read() -> Result<Input> {
    let mut input = String::new();
    let n_bytes = io::stdin().read_line(&mut input)?;

    if n_bytes == 0 {
        Ok(Input::End)
    } else {
        Ok(Input::String(input))
    }
}


fn execute(input: String) -> Result<()> {
    println!("{}", input);

    Ok(())
}