parser-combinator/src/lib/standard/json/jsonparser.js

Parser combinators

/*
 * Parsec
 * https://github.com/d-plaindoux/parsec
 *
 * Copyright (c) 2016 Didier Plaindoux
 * Licensed under the LGPL2 license.
 */

import genlex from '../../genlex/genlex.js';
import token from '../../genlex/token';
import {F} from '../../parsec/index';

//
// Facilities
//

var tkNumber = token.parser.number,
    tkString = token.parser.string,
    tkKeyword = token.parser.keyword;

function tkKey(s) {
    return tkKeyword.match(s);
}

// unit -> Parser ? Token
function arrayOrNothing() {
    var value = [],
        addValue = e => {
            value = value.concat(e);
        },
        getValue = () => value,
        item = F.lazy(expr).map(addValue);
    return item.then(tkKey(',').thenRight(item).optrep()).opt().map(getValue);
}

// unit -> Parser ? Token
function objectOrNothing() {
    var value = {},
        addValue = e => {
            value[e[0]] = e[1];
        },
        getValue = () => value,
        attribute = tkString
            .thenLeft(tkKey(':'))
            .then(F.lazy(expr))
            .map(addValue);
    return attribute
        .thenLeft(tkKey(',').then(attribute).optrep())
        .opt()
        .map(getValue);
}

// unit -> Parser ? Token
function expr() {
    return tkNumber
        .or(tkString)
        .or(tkKey('null').thenReturns(null))
        .or(tkKey('true').thenReturns(true))
        .or(tkKey('false').thenReturns(false))
        .or(tkKey('[').thenRight(F.lazy(arrayOrNothing)).thenLeft(tkKey(']')))
        .or(tkKey('{').thenRight(F.lazy(objectOrNothing)).thenLeft(tkKey('}')));
}

//const parse =
export default {
    parse: function(source) {
        var keywords = ['null', 'false', 'true', '{', '}', '[', ']', ':', ','],
            tokenizer = genlex
                .generator(keywords)
                .tokenBetweenSpaces(token.builder);

        return tokenizer.chain(expr().thenLeft(F.eos)).parse(source, 0);
    },
};