/*@
Ox.filter <f> Filters a collection by a given condition
    Unlike `Array.prototype.filter`, `Ox.filter` works for arrays, objects and
    strings.
    > Ox.filter([2, 1, 0], function(v, i) { return v == i; })
    [1]
    > Ox.filter({a: 'c', b: 'b', c: 'a'}, function(v, k) { return v == k; })
    {b: 'b'}
    > Ox.filter(' foo bar ', function(v) { return v != ' '; })
    'foobar'
@*/
export function filter(collection, iterator, that) {
    var ret, type = Ox.typeOf(collection);
    iterator = iterator || Ox.identity;
    if (type == 'object' || type == 'storage') {
        ret = {};
        Ox.forEach(collection, function(value, key) {
            if (iterator.call(that, value, key, collection)) {
                ret[key] = value;
            }
        });
    } else {
        ret = Ox.slice(collection).filter(iterator, that);
        if (type == 'string') {
            ret = ret.join('');
        }
    }
    return ret;
};

/*@
Ox.indexOf <f> Returns the first index of a collection element that passes a test
    > Ox.indexOf([1, 2, 3], function(val) { return val % 2 == 0; })
    1
    > Ox.indexOf({a: 1, b: 2, c: 3}, function(val) { return val % 2 == 0; })
    'b'
    > Ox.indexOf('FooBar', function(val) { return val == val.toUpperCase(); })
    0
    > Ox.indexOf([1, 2, 3], function(val) { return val == 0; })
    -1
@*/
export function indexOf(collection, test) {
    var index = Ox.forEach(collection, function(value) {
        return !test(value); // break if test succeeds
    });
    return Ox.isObject(collection) ? Object.keys(collection)[index] || null
        : index == collection.length ? -1 : index;
};