rlox/src/interpreter.rs

use std::io::Write;

use crate::error::LoxError;
use crate::lexer::{scan_tokens, Token};
use crate::parser::parser::parse_tokens;

pub fn interpreter_main() {
    let args: Vec<String> = std::env::args().collect();

    match args.len() {
        1 => run_repl(),
        2 => run_file(&args[1]),
        _ => {
            eprintln!("Usage: rlox [script]");
            std::process::exit(64);
        }
    }
}

fn run_file(script_path: &str) {
    let source_code = std::fs::read_to_string(script_path).unwrap_or_else(|err| {
        eprintln!("Reading script file {} failed: {}", script_path, err);
        std::process::exit(66);
    });

    if let Err(err) = run(&source_code) {
        eprintln!("{}", err);
        std::process::exit(65);
    }
}

fn run_repl() {
    let stdin = std::io::stdin();

    'outer: loop {
        let mut input_buf = String::new();

        print!("> ");
        std::io::stdout().flush().unwrap();

        'inner: loop {
            stdin.read_line(&mut input_buf).unwrap_or_else(|err| {
                eprintln!("Could not read from stdin: {}", err);
                std::process::exit(66);
            });

            let num_open_braces = (input_buf.matches('{').count() as i64) - (input_buf.matches('}').count() as i64);
            let num_open_parens = (input_buf.matches('(').count() as i64) - (input_buf.matches(')').count() as i64);
            let num_open_brackets = (input_buf.matches('[').count() as i64) - (input_buf.matches(']').count() as i64);

            // all braces/parens/brackets closed => break
            if num_open_braces == 0 && num_open_parens == 0 && num_open_brackets == 0 {
                break 'inner;
            }

            // any braces/parens/brackets more closing than opening => break (will be parse error)
            if num_open_braces < 0 || num_open_parens < 0 || num_open_brackets < 0 {
                break 'inner;
            }

            print!("< ");
            std::io::stdout().flush().unwrap();
        }

        input_buf = input_buf.trim().to_owned();

        if input_buf.is_empty() || input_buf == "exit" || input_buf == "quit" {
            break 'outer;
        }

        match run(&input_buf) {
            Ok(()) => {}
            Err(err) => eprintln!("{}", err),
        }
    }
}

fn run(code_string: &str) -> Result<(), LoxError> {
    let tokens: Vec<Token> = scan_tokens(code_string)?;

    /* let token_str = tokens
        .iter()
        .map(|token| format!("{token}"))
        .collect::<Vec<String>>()
        .join(" ");

    println!("{token_str}"); */

    let expr = parse_tokens(tokens)?;

    println!("{expr}");

    Ok(())
}