use ::ast::{self, WithLocation};
use super::environment;
use super::types::Ty;

#[derive(Debug)]
pub enum TypeError {
    Unimplemented,
}

type TypeEnvironment<'a> = environment::Environment<'a, String, Ty>;
pub type Result = ::std::result::Result<Ty, WithLocation<TypeError>>;

pub fn translate(program: &ast::Program) -> Result {
    trans_exp(TypeEnvironment::new(None), &*program.0)
}

fn trans_exp<'a>(venv: TypeEnvironment<'a>, exp: &WithLocation<ast::Expression>) -> Result {
    use ast::Expression::*;

    match &exp.value {
        &Let(ref decls, ref body) => {
            Err(WithLocation::new(TypeError::Unimplemented, exp.start, exp.end))
        },
        &UnaryOp(ref op, ref operand) => {
            Err(WithLocation::new(TypeError::Unimplemented, exp.start, exp.end))
        },
        &BinOp(ref op, ref left, ref right) => {
            Err(WithLocation::new(TypeError::Unimplemented, exp.start, exp.end))
        },
        &Number(_) => Ok(Ty::Int),
        &String(_) => Ok(Ty::String),
        &Name(ref name) => {
            Err(WithLocation::new(TypeError::Unimplemented, exp.start, exp.end))
        },
        &Nil => {
            Err(WithLocation::new(TypeError::Unimplemented, exp.start, exp.end))
        },
    }
}