pom 2.0.0-alpha

#![feature(conservative_impl_trait)]

extern crate pom;
use pom::char_class::hex_digit;
use pom::combinator::*;
use pom::Parser;

use std::str::{self, FromStr};
use std::char::{decode_utf16, REPLACEMENT_CHARACTER};
use std::collections::HashMap;


#[derive(Debug, PartialEq)]
pub enum JsonValue {
	Null,
	Bool(bool),
	Number(f64),
	String(String),
	Array(Vec<JsonValue>),
	Object(HashMap<String,JsonValue>)
}

fn space<'a>() -> Combinator<impl Parser<'a, u8, Output=()>> {
	one_of(b" \t\r\n").repeat(0..).discard()
}

fn number<'a>() -> Combinator<impl Parser<'a, u8, Output=f64>> {
	let integer = one_of(b"123456789") - one_of(b"0123456789").repeat(0..) | sym(b'0');
	let frac = sym(b'.') + one_of(b"0123456789").repeat(1..);
	let exp = one_of(b"eE") + one_of(b"+-").opt() + one_of(b"0123456789").repeat(1..);
	let number = sym(b'-').opt() + integer + frac.opt() + exp.opt();
	number.collect().convert(|v|f64::from_str(str::from_utf8(v).unwrap()))
}

fn string<'a>() -> Combinator<impl Parser<'a, u8, Output=String>> {
	let special_char = sym(b'\\') | sym(b'/') | sym(b'"')
		| sym(b'b').map(|_|b'\x08') | sym(b'f').map(|_|b'\x0C')
		| sym(b'n').map(|_|b'\n') | sym(b'r').map(|_|b'\r') | sym(b't').map(|_|b'\t');
	let escape_sequence = sym(b'\\') * special_char;
	let char_string = (none_of(b"\\\"") | escape_sequence).repeat(1..).convert(|bytes|String::from_utf8(bytes));
	let utf16_char = sym(b'\\') * sym(b'u') * is_a(hex_digit).repeat(4).convert(|digits|u16::from_str_radix(&String::from_utf8(digits).unwrap(), 16));
	let utf16_string = utf16_char.repeat(1..).map(|chars|decode_utf16(chars).map(|r| r.unwrap_or(REPLACEMENT_CHARACTER)).collect::<String>());
	let string = sym(b'"') * (char_string | utf16_string).repeat(0..) - sym(b'"');
	string.map(|strings|strings.concat())
}

fn array<'a>() -> Combinator<impl Parser<'a, u8, Output=Vec<JsonValue>>> {
	let elems = list(comb(value), sym(b',') + space());
	sym(b'[') * space() * elems - sym(b']')
}

fn object<'a>() -> Combinator<impl Parser<'a, u8, Output=HashMap<String, JsonValue>>> {
	let member = string() - space() - sym(b':') - space() + comb(value);
	let members = list(member, sym(b',') + space());
	let obj = sym(b'{') * space() * members - sym(b'}');
	obj.map(|members|members.into_iter().collect::<HashMap<_,_>>())
}

// fn value<'a>() -> Combinator<impl Parser<'a, u8, Output=JsonValue>> {
fn value<'a>(input: &'a [u8], start: usize) -> pom::Result<(JsonValue, usize)> {
	(( seq(b"null").map(|_|JsonValue::Null)
	| seq(b"true").map(|_|JsonValue::Bool(true))
	| seq(b"false").map(|_|JsonValue::Bool(false))
	| number().map(|num|JsonValue::Number(num))
	| string().map(|text|JsonValue::String(text))
	| array().map(|arr|JsonValue::Array(arr))
	| object().map(|obj|JsonValue::Object(obj))
	) - space()).0.parse(input, start)
}

pub fn json<'a>() -> Combinator<impl Parser<'a, u8, Output=JsonValue>> {
	space() * comb(value) - end()
}

#[allow(dead_code)]
fn main() {
	let test = br#"
	{
		"Image": {
			"Width":  800,
			"Height": 600,
			"Title":  "View from 15th Floor",
			"Thumbnail": {
				"Url":    "http://www.example.com/image/481989943",
				"Height": 125,
				"Width":  100
			},
			"Animated" : false,
			"IDs": [116, 943, 234, 38793]
		},
		"escaped characters": "\u2192\uD83D\uDE00\"\t\uD834\uDD1E"
	}"#;

	println!("{:?}", json().parse(test));
}