index.js

'use strict';

var each = require('foreach');
module.exports = api;


/**
 * Convenience wrapper around the api.
 * Calls `.get` when called with an `object` and a `pointer`.
 * Calls `.set` when also called with `value`.
 * If only supplied `object`, returns a partially applied function, mapped to the object.
 *
 * @param obj
 * @param pointer
 * @param value
 * @returns {*}
 */

function api(obj, pointer, value) {
    // .set()
    if (arguments.length === 3) {
        return api.set(obj, pointer, value);
    }
    // .get()
    if (arguments.length === 2) {
        return api.get(obj, pointer);
    }
    // Return a partially applied function on `obj`.
    var wrapped = api.bind(api, obj);

    // Support for oo style
    for (var name in api) {
        if (api.hasOwnProperty(name)) {
            wrapped[name] = api[name].bind(wrapped, obj);
        }
    }
    return wrapped;
}


/**
 * Lookup a json pointer in an object
 *
 * @param obj
 * @param pointer
 * @returns {*}
 */
api.get = function get(obj, pointer) {
    var tok,
        refTokens = api.parse(pointer);
    while (refTokens.length) {
        tok = refTokens.shift();
        if (!obj.hasOwnProperty(tok)) {
            throw new Error('Invalid reference token: ' + tok);
        }
        obj = obj[tok];
    }
    return obj;
};

/**
 * Sets a value on an object
 *
 * @param obj
 * @param pointer
 * @param value
 */
api.set = function set(obj, pointer, value) {
    var refTokens = api.parse(pointer),
        tok,
        nextTok = refTokens[0];
    while (refTokens.length > 1) {
        tok = refTokens.shift();
        nextTok = refTokens[0];

        if (!obj.hasOwnProperty(tok)) {
            if (nextTok.match(/^\d+$/)) {
                obj[tok] = [];
            } else {
                obj[tok] = {};
            }
        }
        obj = obj[tok];
    }
    obj[nextTok] = value;
    return this;
};

/**
 * Removes an attribute
 *
 * @param obj
 * @param pointer
 */
api.remove = function (obj, pointer) {
    var refTokens = api.parse(pointer);
    var finalToken = refTokens.pop();
    if (finalToken === undefined) {
        throw new Error('Invalid JSON pointer for remove: "' + pointer + '"');
    }
    delete api.get(obj, api.compile(refTokens))[finalToken];
};

/**
 * Returns a (pointer -> value) dictionary for an object
 *
 * @param obj
 * @returns {{}}
 */
api.dict = function dict(obj) {
    var results = {},
        refTokens = [],

        mapObj = function (cur) {
            var type = Object.prototype.toString.call(cur);
            if (type === '[object Object]' || ( type === '[object Array]' && cur.length ) ) {
                each(cur, function (value, key) {
                    refTokens.push(String(key));
                    mapObj(value);
                    refTokens.pop();
                });
            } else {
                results[api.compile(refTokens)] = cur;
            }
        };

    mapObj(obj);
    return results;
};

/**
 * Iterates over an object
 * Iterator: function (value, pointer) {}
 *
 * @param obj
 * @param iterator
 */
api.walk = function walk(obj, iterator) {
    each(api.dict(obj), iterator);
};

/**
 * Tests if an object has a value for a json pointer
 *
 * @param obj
 * @param pointer
 * @returns {boolean}
 */
api.has = function has(obj, pointer) {
    try {
        api.get(obj, pointer);
    } catch (e) {
        return false;
    }
    return true;
};

/**
 * Escapes a reference token
 *
 * @param str
 * @returns {string}
 */
api.escape = function escape(str) {
    return str.replace(/~/g, '~0').replace(/\//g, '~1');
};

/**
 * Unescapes a reference token
 *
 * @param str
 * @returns {string}
 */
api.unescape = function unescape(str) {
    return str.replace(/~1/g, '/').replace(/~0/g, '~');
};

/**
 * Converts a json pointer into a array of reference tokens
 *
 * @param pointer
 * @returns {Array}
 */
api.parse = function parse(pointer) {
    if (pointer === '') { return []; }
    if (pointer.charAt(0) !== '/') { throw new Error('Invalid JSON pointer: ' + pointer); }
    return pointer.substring(1).split(/\//).map(api.unescape);
};

/**
 * Builds a json pointer from a array of reference tokens
 *
 * @param refTokens
 * @returns {string}
 */
api.compile = function compile(refTokens) {
    if (refTokens.length === 0) { return ''; }
    return '/' + refTokens.map(api.escape).join('/');
};