'use strict';
/*@
Ox.cache <f> Memoize a function
    <script>
        Ox.test.fn = Ox.cache(function(n) { return n * Math.random(); });
    </script>
    > Ox.test.fn(10) == Ox.test.fn(10);
    true
    > Ox.test.fn(10) == Ox.test.fn.clear()(10);
    false
@*/
Ox.cache = function(fn, options) {
    options = Ox.extend({
        async: false,
        key: JSON.stringify
    }, options || {})
    var cache = {},
        ret = function() {
            var args = Ox.toArray(arguments),
                callback,
                key = options.key(args);
            function callback() {
                // cache all arguments passed to callback
                cache[key] = Ox.toArray(arguments);
                // call the original callback
                Ox.last(args).apply(this, arguments);
            }
            if (options.async) {
                if (!(key in cache)) {
                    // call function with patched callback
                    fn.apply(this, args.slice(0, -1).concat(callback));
                } else {
                    // call callback with cached arguments
                    callback.apply(this, cache[key])
                }
            } else {
                if (!(key in cache)) {
                    cache[key] = fn.apply(this, args);
                }
                return cache[key];
            }
        };
    ret.clear = function() {
        if (arguments.length == 0) {
            cache = {};
        } else {
            Ox.makeArray(arguments).forEach(function(key) {
                delete cache[key];
            });
        }
        return ret;
    }
    return ret;
};

/*@
Ox.identity <f> Returns its first argument
    This can be used as a default iterator
@*/
Ox.identity = function(val) {
    return val;
};

/*@
Ox.noop <f> Returns undefined and calls optional callback without arguments
    This can be used to combine a synchronous and an asynchronous code path.
@*/
// IE 8 doesn't like `Ox.void`
Ox.noop = function(callback) {
    Ox.isFunction(callback) && callback();
};