// cargo-deps: nom="4.0"
use std::fs;

#[macro_use]
extern crate nom;

#[derive(Debug)]
enum JsonValue {
    String(String),
    Number(f64),
    Array(Vec<JsonValue>),
    Object(Vec<(JsonValue, JsonValue)>),
    True,
    False,
    Null,
}

// XXX: If we add a second `nom::multispace0` after the `tag!("}")` for some reason the input can
// never be decided. I'm pretty sure we don't need it, however.
named!(
    object(&[u8]) -> JsonValue,
    delimited!(
        tuple!(nom::multispace0, tag!("{"), nom::multispace0),
        map!(
            separated_list!(
                tuple!(nom::multispace0, tag!(","), nom::multispace0),
                do_parse!(
                    key: string >>
                    tuple!(nom::multispace0, tag!(":"), nom::multispace0) >>
                    value: value >>
                (key, value))
            ),
            JsonValue::Object
        ),
        tuple!(nom::multispace0, tag!("}"))
    )
);

named!(
    array(&[u8]) -> JsonValue,
    ws!(delimited!(tag!("["),
               map!(separated_list!(tuple!(nom::multispace0, tag!(","), nom::multispace0), value), JsonValue::Array),
               tag!("]")))
);

named!(value(&[u8]) -> JsonValue, alt!(string | number | object | array | constant ));

// FIXME: Handle escapes!
named!(
    string_char(&[u8]) -> char,
    none_of!("\"")
);

named!(
    string(&[u8]) -> JsonValue,
    map!(delimited!(tag!("\""), many0!(string_char), tag!("\"")),
         |o| JsonValue::String(o.into_iter().collect()))
);

named!(
    number(&[u8]) -> JsonValue,
    map!(nom::double, JsonValue::Number)
);

named!(
    constant(&[u8]) -> JsonValue,
    alt!(
        tag!("true") => { |_| JsonValue::True } |
        tag!("false") => { |_| JsonValue::False } |
        tag!("null") => { |_| JsonValue::Null }
    )
);

fn main() {
    let contents = fs::read("sample.json").unwrap();
    let sample = nom::types::CompleteByteSlice(&contents);
    let (_, parsed_json) = object(&sample).unwrap();
    println!("{:#?}", parsed_json);
}