/**
 * Nimble
 * Copyright (c) 2011 Caolan McMahon
 *
 * Nimble is freely distributable under the MIT license.
 *
 * This source code is optimized for minification and gzip compression, not
 * readability. If you want reassurance, see the test suite.
 */

(function (exports) {

    var keys = Object.keys || function (obj) {
        var results = [];
        for (var k in obj) {
            if (obj.hasOwnProperty(k)) {
                results.push(k);
            }
        }
        return results;
    };

    var fallback = function (name, fallback) {
        var nativeFn = Array.prototype[name];
        return function (obj, iterator, memo) {
            var fn = obj ? obj[name]: 0;
            return fn && fn === nativeFn ?
                fn.call(obj, iterator, memo):
                fallback(obj, iterator, memo);
        };
    };

    var eachSync = fallback('forEach', function (obj, iterator) {
        var isObj = obj instanceof Object;
        var arr = isObj ? keys(obj): (obj || []);
        for (var i = 0, len = arr.length; i < len; i++) {
            var k = isObj ? arr[i]: i;
            iterator(obj[k], k, obj);
        }
    });

    var eachParallel = function (obj, iterator, callback) {
        var len = obj.length || keys(obj).length;
        if (!len) {
            return callback();
        }
        var completed = 0;
        eachSync(obj, function () {
            var cb = function (err) {
                if (err) {
                    callback(err);
                    callback = function () {};
                }
                else {
                    if (++completed === len) {
                        callback();
                    }
                }
            };
            var args = Array.prototype.slice.call(arguments);
            if (iterator.length) {
                args = args.slice(0, iterator.length - 1);
                args[iterator.length - 1] = cb;
            }
            else {
                args.push(cb);
            }
            iterator.apply(this, args);
        });
    };

    var eachSeries = function (obj, iterator, callback) {
        var keys_list = keys(obj);
        if (!keys_list.length) {
            return callback();
        }
        var completed = 0;
        var iterate = function () {
            var k = keys_list[completed];
            var args = [obj[k], k, obj].slice(0, iterator.length - 1);
            args[iterator.length - 1] = function (err) {
                if (err) {
                    callback(err);
                    callback = function () {};
                }
                else {
                    if (++completed === keys_list.length) {
                        callback();
                    }
                    else {
                        iterate();
                    }
                }
            };
            iterator.apply(this, args);
        };
        iterate();
    };

    var mapSync = fallback('map', function (obj, iterator) {
        var results = [];
        eachSync(obj, function (v, k, obj) {
            results[results.length] = iterator(v, k, obj);
        });
        return results;
    });

    var mapAsync = function (eachfn) {
        return function (obj, iterator, callback) {
            var results = [];
            eachfn(obj, function (value, i, obj, callback) {
                var cb = function (err, v) {
                    results[results.length] = v;
                    callback(err);
                };
                var args = [value, i, obj];
                if (iterator.length) {
                    args = args.slice(0, iterator.length - 1);
                    args[iterator.length - 1] = cb;
                }
                else {
                    args.push(cb);
                }
                iterator.apply(this, args);
            }, function (err) {
                callback(err, results);
            });
        };
    };

    var filterSync = fallback('filter', function (obj, iterator, callback) {
        var results = [];
        eachSync(obj, function (v, k, obj) {
            if (iterator(v, k, obj)) {
                results[results.length] = v;
            }
        });
        return results;
    });

    var filterParallel = function (obj, iterator, callback) {
        var results = [];
        eachParallel(obj, function (value, k, obj, callback) {
            var cb = function (err, a) {
                if (a) {
                    results[results.length] = value;
                }
                callback(err);
            };
            var args = [value, k, obj];
            if (iterator.length) {
                args = args.slice(0, iterator.length - 1);
                args[iterator.length - 1] = cb;
            }
            else {
                args.push(cb);
            }
            iterator.apply(this, args);
        }, function (err) {
            callback(err, results);
        });
    };

    var reduceSync = fallback('reduce', function (obj, iterator, memo) {
        eachSync(obj, function (v, i, obj) {
            memo = iterator(memo, v, i, obj);
        });
        return memo;
    });

    var reduceSeries = function (obj, iterator, memo, callback) {
        eachSeries(obj, function (value, i, obj, callback) {
            var cb = function (err, v) {
                memo = v;
                callback(err);
            };
            var args = [memo, value, i, obj];
            if (iterator.length) {
                args = args.slice(0, iterator.length - 1);
                args[iterator.length - 1] = cb;
            }
            else {
                args.push(cb);
            }
            iterator.apply(this, args);
        }, function (err) {
            callback(err, memo);
        });
    };

    exports.each = function (obj, iterator, callback) {
        return (callback ? eachParallel: eachSync)(obj, iterator, callback);
    };
    exports.map = function (obj, iterator, callback) {
        return (callback ? mapAsync(eachParallel): mapSync)(obj, iterator, callback);
    };
    exports.filter = function (obj, iterator, callback) {
        return (callback ? filterParallel: filterSync)(obj, iterator, callback);
    };
    exports.reduce = function (obj, iterator, memo, callback) {
        return (callback ? reduceSeries: reduceSync)(obj, iterator, memo, callback);
    };

    exports.parallel = function (fns, callback) {
        var results = new fns.constructor();
        eachParallel(fns, function (fn, k, cb) {
            fn(function (err) {
                var v = Array.prototype.slice.call(arguments, 1);
                results[k] = v.length <= 1 ? v[0]: v;
                cb(err);
            });
        }, function (err) {
            (callback || function () {})(err, results);
        });
    };

    exports.series = function (fns, callback) {
        var results = new fns.constructor();
        eachSeries(fns, function (fn, k, cb) {
            fn(function (err, result) {
                var v = Array.prototype.slice.call(arguments, 1);
                results[k] = v.length <= 1 ? v[0]: v;
                cb(err);
            });
        }, function (err) {
            (callback || function () {})(err, results);
        });
    };

}(typeof exports === 'undefined' ? this._ = this._ || {}: exports));