use myslip::parse::parsetree::parse_to_ast;
use myslip::sexp::{SExp::*, SLeaf::Nil};
use std::{io, io::Write};

fn main() {
    match repl() {
        Ok(()) => println!("bye :)"),
        Err(e) => {
            println!("Error: {}", e);
            main();
        },
    }
}

fn repl() -> Result<(), String> {

    let stdin = io::stdin();
    
    let mut input = String::new();

    let mut stdout = io::stdout();
    
    print!("> ");
    match stdout.flush() {
        Ok(_) => (),
        Err(_) => println!("Enter s-expression:"),
    };
    let mut success = stdin.read_line(&mut input);

    while success.is_ok() && input != "exit\n" {
        if let Ok(0) = success {
            print!("\n");
            break;
        }

        let expression = match parse_to_ast(&input) {
            Ok(SCons(a, b)) if *b == Atom(Nil) => Ok(*a),
            t => t
        }?;

        let ty = expression.type_check().map_err(|e| e.to_string())?;

        let result = expression.multistep()?;

        println!("{} : {}", result, ty);

        print!("> ");
        match stdout.flush() {
            Ok(_) => (),
            Err(_) => println!("Enter s-expression:"),
        };
        input.clear();
        success = stdin.read_line(&mut input);

    }

    match success {
        Ok(_) => Ok(()),
        Err(e) => Err(format!("read error: {e}")),
    }

}