use std::str::FromStr;

#[derive(PartialEq, Debug, Clone, Copy)]
pub enum Op {
    Add,
    Sub,
    Mul,
    Div,
    Modulo,
    Equals,
    Greater,
    GrEqTo,
    Less,
    LsEqTo,
    Define,
}

impl FromStr for Op {
    type Err = String;

    fn from_str(s: &str) -> Result<Self, Self::Err> {
        match s {
            "+" => Ok(Op::Add),
            "-" => Ok(Op::Sub),
            "*" => Ok(Op::Mul),
            "/" => Ok(Op::Div),
            "%" => Ok(Op::Modulo),
            "=" => Ok(Op::Equals),
            ">" => Ok(Op::Greater),
            ">=" => Ok(Op::GrEqTo),
            "<" => Ok(Op::Less),
            "<=" => Ok(Op::LsEqTo),
            "define" => Ok(Op::Define),
            x => Err(format!("{} is not an operator", x))
        }
    }
}

#[derive(PartialEq, Debug, Clone)]
pub enum Number {
    Int(isize),
    Float(f32)
}

#[derive(PartialEq, Debug, Clone)]
pub enum Type {
    Bool(bool),
    Number(Number),
    Str(String),
    Symbol(String),
    Operator(Op),
}

#[derive(PartialEq, Debug)]
pub enum SEXP {
    Atom(Type),
    Sexpr(Vec<SEXP>)
}

#[test]
fn construct() {
    let atom1 = SEXP::Atom(Type::Number(Number::Int(1)));
    let atom2 = SEXP::Atom(Type::Number(Number::Int(2)));
    let atom3 = SEXP::Atom(Type::Number(Number::Int(3)));
    let atom4 = SEXP::Atom(Type::Number(Number::Int(4)));
    let sexp = SEXP::Sexpr(vec!(atom1, atom2, atom3, atom4));
    match sexp {
        SEXP::Sexpr(ref x) => {
            assert_eq!(x[0], SEXP::Atom(Type::Number(Number::Int(1))));
        },
        _ => panic!("What")
    }
}

#[test]
fn mutability() {
    let atom1 = SEXP::Atom(Type::Number(Number::Int(1)));
    let atom2 = SEXP::Atom(Type::Number(Number::Int(2)));
    let atom3 = SEXP::Atom(Type::Number(Number::Int(3)));
    let atom4 = SEXP::Atom(Type::Number(Number::Int(4)));
    let mut sexp = SEXP::Sexpr(vec!(atom1, atom2, atom3, atom4));
    match sexp {
        SEXP::Sexpr(ref mut x) => match x[0] {
            SEXP::Atom(Type::Number(Number::Int(ref mut x))) => *x += 7,
            _ => panic!("What")
        },
        _ => panic!("What")
    }

    match sexp {
        SEXP::Sexpr(ref x) => {
            assert_eq!(x[0], SEXP::Atom(Type::Number(Number::Int(8))));
        },
        _ => panic!("What")
    }
}