crafting-interpreters/rust/rox/src/lib.rs

//! Interpret the Lox language. Either compile (interpret for now though) some source code or run a
//! REPL.

use std::{
    fs::{self},
    io::{self, Write},
    path::Path,
};

use interpreter::{Interpreter, InterpreterError};
use parser::ParserError;
use resolver::{Resolver, ResolverError};
use thiserror::Error;
use tracing::error;

pub mod callable;
pub mod cli;
pub mod environment;
pub mod expression;
pub mod function;
pub mod interpreter;
pub mod keywords;
pub mod native_functions;
pub mod parser;
pub mod resolver;
pub mod scanner;
pub mod statement;
pub mod token;
pub mod tokenizer {
    pub mod comment;
    pub mod identifier;
    pub mod interface;
    pub mod lookahead;
    pub mod newline;
    pub mod number;
    pub mod single_char;
    pub mod string;
    pub mod whitespace;
}
pub mod value;

#[derive(Error, Debug)]
pub enum RoxError {
    #[error("parser failed: {0}")]
    ParseError(#[from] ParserError),
    #[error("resolver failed: {0}")]
    ResolverError(#[from] ResolverError),
    #[error("interpreter failed: {0}")]
    InterpreterError(#[from] InterpreterError),
}

/// Read the source code in a file and scan it to tokens.
pub fn compile(source: &Path) -> Result<(), io::Error> {
    let input = fs::read_to_string(source)?;
    let mut interpreter = Interpreter::default();

    run(&input, &mut interpreter);

    Ok(())
}

/// Run a Lox REPL until SIGINT.
pub fn repl() {
    let mut interpreter = Interpreter::default();
    loop {
        print!("> ");
        let _ = io::stdout().flush();

        let mut input = String::new();
        match io::stdin().read_line(&mut input) {
            Ok(_) => {}
            Err(e) => error!("{}", e),
        }
        let input = input.trim().to_string();
        run(&input, &mut interpreter);
    }
}

/// Evaluate a Lox input string and print errors or output.
fn run(input: &str, interpreter: &mut Interpreter) {
    if let Err(e) = run_rox(input, interpreter) {
        error!("{e}");
    }
}

fn run_rox(input: &str, interpreter: &mut Interpreter) -> Result<(), RoxError> {
    let tokens = scanner::tokenize(input);
    let mut resolver = Resolver::new(interpreter);

    let ast = parser::ast(tokens)?;
    resolver.resolve(&ast)?;
    interpreter.run(ast)?;

    Ok(())
}