'use strict';

/*@
Ox.get <f> Get a remote resource
    (url, callback) -> <u> undefined
    url <s> Remote URL
    callback <f> Callback function
        data <s|null> The contents of the remote resource, or `null` on error
        error <o|null> Error, or `null` on success
            code <n> Status code
            text <s> Status text
@*/
Ox.get = function(url, callback) {
    var request = new XMLHttpRequest();
    request.open('GET', url, true);
    request.onreadystatechange = function() {
        if (request.readyState == 4) {
            if (request.status == 200) {
                callback(request.responseText, null);
            } else {
                callback(null, {
                    code: request.status,
                    text: request.statusText
                });
            }
        }
    };
    request.send();                
};

/*@
Ox.getAsync <f> Runs an asynchonous loader for an array of URLs
    (urls, get, callback) -> <u> undefined
    urls <s|a> URL or array of URLs or arrays of such arrays 
        Multiple URLs in the same array will be processed simultaneously, but
        multiple arrays of URLs will be processed in that order.
    get <f> Asynchronous function that loads a URL (for example Ox.get)
        url <s> URL
        callback <f> Callback function
            result <s|null> Result, or `null` on error
            error <o|null> Error, or `null` on success
                code <n> Status code
                text <s> Status text
    callback <f> Callback function
        results <o|{}> Results, or empty on error
            Keys are file names, values are results
        errors <o|{}> Errors, or empty on success
            Keys are file names, values are error objects
@*/
Ox.getAsync = function(urls, get, callback) {
    urls = Ox.makeArray(urls);
    var errors = {}, i = 0, n = urls.length, results = {};
    function done() {
        callback && callback(filter(results), filter(errors));
    }
    function extend(object, value, urls) {
        value !== null && Ox.extend.apply(null, [object].concat(
            urls.length === 1 ? [urls[0], value] : [value]
        ));
    }
    function filter(object) {
        return n == 1 ? object[urls[0]] : Ox.filter(object, function(value) {
            return value !== null;
        });
    }
    function getParallel() {
        urls.forEach(function(url) {
            get(url, function(result, error) {
                results[url] = result;
                errors[url] = error;
                ++i == n && done();
            });
        });
    }
    function getSerial() {
        var url = urls.shift();
        Ox.getAsync(url, get, function(result, error) {
            extend(results, result, url);
            extend(errors, error, url);
            urls.length ? getSerial() : done();
        });
    }
    urls.some(Ox.isArray) ? getSerial() : getParallel();
};

(function() {

    var cache = {},
        head = document.head
            || document.getElementsByTagName('head')[0]
            || document.documentElement;

    function getFile(type, url, callback) {
        var element, tagValue, typeValue, urlKey;
        if (!cache[url]) {
            if (!type) {
                type = url.split('.').pop();
                type = type == 'css' ? 'stylesheet'
                    : type == 'js' ? 'script' : 'image';
            }
            if (type == 'image') {
                element = new Image();
                element.onerror = onError;
                element.onload = onLoad;
                element.src = url;
            } else {
                tagValue = type == 'script' ? 'script' : 'link';
                typeValue = type == 'script' ? 'text/javascript' : 'text/css';
                urlKey = type == 'script' ? 'src' : 'href';
                if (Ox.some(
                    document.getElementsByTagName(tagValue),
                    function(element) {
                        return element[urlKey] == url;
                    }
                )) {
                    onLoad();
                } else {
                    element = document.createElement(tagValue);
                    element.onerror = onError;
                    element.onload = element.onreadystatechange = onLoad;
                    element.type = typeValue;
                    element[urlKey] = url;
                    if (type == 'stylesheet') {
                        element.rel = 'stylesheet';
                    }
                    head.appendChild(element);
                }
            }
        } else {
            callback(cache[url], null);
        }
        function onError() {
            callback(null, {code: 404, text: 'Not Found'});
        }
        function onLoad() {
            if (
                !this || !this.readyState
                || this.readyState == 'loaded' || this.readyState == 'complete'
            ) {
                // for an image, keep a reference to the element
                // to keep the image in the browser cache
                cache[url] = type == 'image' ? this : true;
                callback(cache[url], null);
            }
        }
    }

    function getFiles(type, urls, callback) {
        Ox.getAsync(urls, function(url, callback) {
            getFile(type, url, callback);
        }, callback);
    }

    /*@
    Ox.getFile <f> Loads a file (image, script or stylesheet)
        (file, callback) -> <u> undefined
        file <s|a> Local path or remote URL, or array of those, or array of such arrays
            Multiple files in the same array will be processed simultaneously,
            but multiple arrays of files will be processed in that order.
        callback <f> Callback function
            image <h> DOM element (if the file is an image)
    @*/
    Ox.getFile = function(url, callback) {
        getFiles(null, url, callback);
    };

    /*@
    Ox.getImage <f> Loads an image
        (file, callback) -> <u> undefined
        file <s|a> Local path or remote URL, or array of those, or array of such arrays
            Multiple files in the same array will be processed simultaneously,
            but multiple arrays of files will be processed in that order.
        callback <f> Callback function
            image <h> DOM element
    @*/
    Ox.getImage = function(url, callback) {
        getFiles('image', url, callback);
    };

    /*@
    Ox.getScript <f> Loads a script
        (file, callback) -> <u> undefined
        file <s|a> Local path or remote URL, or array of those, or array of such arrays
            Multiple files in the same array will be processed simultaneously,
            but multiple arrays of files will be processed in that order.
        callback <f> Callback function
    @*/
    Ox.getScript = function() {
        getFiles('script', url, callback);
    };

    /*@
    Ox.getStylesheet <f> Loads a stylesheet
        (file, callback) -> <u> undefined
        file <s|a> Local path or remote URL, or array of those, or array of such arrays
            Multiple files in the same array will be processed simultaneously,
            but multiple arrays of files will be processed in that order.
        callback <f> Callback function
    @*/
    Ox.getStylesheet = function() {
        getFiles('stylesheet', url, callback);
    };

}());

/*@
Ox.getJSON <f> Get and parse one or more remote JSON files
    (url, callback) -> <u> undefined
    url <s|a> One or more remote URLs
    callback <f> Callback function
        data <*|o|null> The parsed content of the remote resource(s)
            For multiple URLs, keys are file names, values are parsed contents
        error <o|null> Error(s)
            For multiple URLs, keys are file names, values are error objects
@*/
Ox.getJSON = function(url, callback, isJSONC) {
    var urls = Ox.makeArray(url);
    Ox.getAsync(urls, function(url, callback) {
        Ox.get(url, function(data, error) {
            callback(JSON.parse(
                isJSONC ? Ox.minify(data || '') : data
            ), error);
        });
    }, callback);
};

/*@
Ox.getJSONC <f> Get and parse a remote JSONC file
    JSONC is JSON with JavaScript line or block comments
    (url, callback) -> <u> undefined
    url <s|a> One or more remote URLs
    callback <f> Callback function
        data <*|o|null> The parsed content of the remote resource(s)
            For multiple URLs, keys are file names, values are parsed contents
        error <o|null> Error(s)
            For multiple URLs, keys are file names, values are error objects
@*/
Ox.getJSONC = function(url, callback) {
    Ox.getJSON(url, callback, true);
};

/*@
Ox.getJSONP <f> Get and parse one or more remote JSONP files
    (url, callback) -> <u> undefined
    url <s|a> One or more remote URLs
        {callback} gets replaced with jsonp callback function name
    callback <f> Callback function
        data <*|o|null> The parsed content of the remote resource(s)
            For multiple URLs, keys are file names, values are parsed contents
        error <o|null> Error(s)
            For multiple URLs, keys are file names, values are error objects
@*/
Ox.getJSONP = function(url, callback) {
    var urls = Ox.makeArray(url);
    Ox.getAsync(urls, function(url, callback) {
        var id = 'callback' + Ox.uid();
        Ox.getJSONP[id] = function(data) {
            delete Ox.getJSONP[id];
            callback(data, null);
        };
        Ox.$('body').append(Ox.$('<script>').attr({
            'src': url.replace('{callback}', 'Ox.getJSONP.' + id),
            'type': 'text/javascript'
        }));
    }, callback);
};