//! JavaScript engine — lexer, parser, bytecode, register VM, GC, JIT (AArch64).

pub mod ast;
pub mod bytecode;
pub mod compiler;
pub mod lexer;
pub mod parser;
pub mod vm;

use std::fmt;

/// An error produced by the JavaScript engine.
#[derive(Debug)]
pub enum JsError {
    /// The engine does not yet support this feature or syntax.
    NotImplemented,
    /// A parse/syntax error in the source.
    SyntaxError(String),
    /// A runtime error during execution.
    RuntimeError(String),
}

impl fmt::Display for JsError {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        match self {
            JsError::NotImplemented => write!(f, "not implemented"),
            JsError::SyntaxError(msg) => write!(f, "SyntaxError: {}", msg),
            JsError::RuntimeError(msg) => write!(f, "RuntimeError: {}", msg),
        }
    }
}

/// Evaluate a JavaScript source string and return the completion value as a string.
///
/// Parses the source, compiles to bytecode, and executes in the VM.
pub fn evaluate(source: &str) -> Result<String, JsError> {
    let program = parser::Parser::parse(source).map_err(|e| JsError::SyntaxError(e.to_string()))?;
    let func = compiler::compile(&program)?;
    let mut engine = vm::Vm::new();
    let result = engine
        .execute(&func)
        .map_err(|e| JsError::RuntimeError(e.to_string()))?;
    Ok(result.to_string())
}