extern crate modelica_parser;

use self::modelica_parser::*;

pub trait TranspileJS {
    fn repr_js(&self) -> Result<String, String>;
}


impl TranspileJS for ModelicaModel {
    fn repr_js(&self) -> Result<String, String> {
        let mut constants = vec![];
        for (c, e) in self.get_constant_vars() {
            if let Some(v) = e {
                constants.push(format!("var {} = {};", c, try!(v.repr_js())));
            }
        }
        let mut binds = vec![];
        let mut outputs = vec![];
        for eq in self.equations.iter() {
            if let Expr::Ident(ref symb) = eq.lhs {
                binds.push(format!("var {} = {};", symb, try!(eq.rhs.repr_js())));
                outputs.push(symb.to_string());
            } else {
                return Err("Expected an identifier on LHS (in this partial implementation)"
                    .to_string());
            }
        }
        Ok(format!(r#"function {slug}({args}) {{
                {constants}
                {binds}
                return [{outputs}];
        }}"#,
                   slug = "f",
                   args = self.get_free_vars().join(", "),
                   constants = constants.join("\n    "),
                   binds = binds.join("\n    "),
                   outputs = outputs.join(", ")))
    }
}

impl TranspileJS for Expr {
    fn repr_js(&self) -> Result<String, String> {
        use modelica_parser::Expr::*;
        match *self {
            Integer(e) => Ok(format!("{}", e)),
            Float(e) => Ok(format!("{}", e)),
            Boolean(true) => Ok(format!("true")),
            Boolean(false) => Ok(format!("false")),
            StringLiteral(ref s) => Ok(format!("\"{}\"", s)),
            Ident(ref e) => Ok(format!("{}", e)),
            Der(ref e) => Ok(format!("der({})", try!(e.repr_js()))),
            Sign(ref e) => Ok(format!("sign({})", try!(e.repr_js()))),
            MathUnaryExpr(func, ref e) => Ok(format!("{:?}({})", func, try!(e.repr_js()))),
            BinExpr(op, ref l, ref r) => {
                Ok(format!("({} {:?} {})", try!(l.repr_js()), op, try!(r.repr_js())))
            }
            Array(_) => Err("Array unimplemented".to_string()),
        }
    }
}