'use strict';

/*@
Ox.get <f> Get a remote file
    # fixme: remote? same-origin-policy? jsonp?
    (url, callback) -> <u> undefined
    url <s> Remote URL
    callback <f> Callback function
        data <s> The contents of the remote resource
@*/
Ox.get = function(url, callback) {
    var req = new XMLHttpRequest();
    req.open('GET', url, true);
    req.onreadystatechange = function() {
        if (req.readyState == 4) {
            if (req.status == 200) {
                callback(req.responseText);
            } else {
                throw new Error(
                    'Cannot get URL "' + url + '" (Status: ' + req.status + ')'
                );
            }
        }
    };
    req.send();                
};

/*@
Ox.getJSON <f> Get and parse one or more remote JSON files
    # fixme: remote? same-origin-policy? jsonp?
    (url, callback) -> <u> undefined
    url <s|[s]> One or more remote URLs
    callback <f> Callback function
        data <o> The parsed contents of the remote resource(s)
            For multiple URLs, keys are file names, values are contents
@*/
Ox.getJSON = (function() {
    function getJSON(url, callback) {
        Ox.get(url, function(data) {
            callback(JSON.parse(data));
        });
    }
    return function(url, callback) {
        var urls = Ox.toArray(url), data = {}, i = 0, n = urls.length;
        urls.forEach(function(url) {
            getJSON(url, function(data_) {
                data[url] = data_;
                ++i == n && callback(n == 1 ? data[url] : data);
            });
        });
    };
}());

/*@
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> Remote URL
    callback <f> Callback function
        data <s> The parsed contents of the remote resource
@*/
Ox.getJSONC = function(url, callback) {
    Ox.get(url, function(data) {
        callback(JSON.parse(Ox.minify(data)));
    });
};

/*@
Ox.loadFile <f> Loads a file (image, script or stylesheet)
    (file="script.js", callback)      -> <u> undefined
    (file="stylesheet.css", callback) -> <u> undefined
    (file="image.png", callback)      -> <u> undefined
    file     <s> Local path or remote URL
    callback <f> Callback function
        image <e> DOM element (if the file is an image)
@*/
Ox.loadFile = (function() {
    // fixme: this doesn't handle errors yet
    // fixme: rename to getFile?
    // fixme: what about array of files?
    var cache = {};
    return function (file, callback) {
        var element,
            head = document.head || document.getElementsByTagName( "head" )[0] || document.documentElement,
            request,
            type = file.split('.').pop(),
            isImage = type != 'css' && type != 'js';
        if (!cache[file]) {
            if (isImage) {
                element = new Image();
                element.onload = addFileToCache;
                element.src = file;
            } else {
                if (!findFileInHead()) {
                    element = document.createElement(
                        type == 'css' ? 'link' : 'script'
                    );
                    element[type == 'css' ? 'href' : 'src'] = file + '?' + Ox.random(1000000);
                    element.type = type == 'css' ? 'text/css' : 'text/javascript';
                    if (/MSIE/.test(navigator.userAgent)) {
                        // fixme: find a way to check if css/js have loaded in msie
                        setTimeout(addFileToCache, 2500);
                    } else {
                        if (type == 'css') {
                            element.rel = 'stylesheet';
                            waitForCSS();
                        } else {
                            element.onload = addFileToCache;
                        }                        
                    }
                    head.appendChild(element);
                } else {
                    addFileToCache();
                }
            }
        } else {
            callback();
        }
        function addFileToCache() {
            if (isImage) {
                // for an image, save the element itself,
                // so that it remains in the browser cache
                cache[file] = element;
                callback(element);
            } else {
                cache[file] = true;
                callback();
            }
        }
        function findFileInHead() {
            return Ox.makeArray(
                document.getElementsByTagName(type == 'css' ? 'link' : 'script')
            ).map(function(element) {
                return element[type == 'css' ? 'href' : 'src'] == file;
            }).reduce(function(prev, curr) {
                return prev || curr; 
            }, false);
        }
        function waitForCSS() {
            var error = false;
            try {
                element.sheet.cssRule;
            } catch(e) {
                error = true;
                setTimeout(function() {
                    waitForCSS();
                }, 25);
            }
            !error && addFileToCache();
        }
    };
}());

/*@
Ox.loadFiles <f> Loads multiple files (images, scripts or stylesheets)
    (files, callback) -> <u> undefined
    files <[s]|[[s]]> Array of files, or array of arrays of files
        Multiple files in the same array will be loaded simultaneously, but
        multiple arrays of files will be loaded in that order.
    callback <f> Callback function
        images <o> DOM elements (if any file was an image)
            Keys are the file names, values are the DOM elements
@*/
Ox.loadFiles = (function() {
    function loadFiles(files, callback) {
        files = Ox.toArray(files);
        var i = 0, n = files.length, images = {};
        Ox.toArray(files).forEach(function(file) {
            Ox.loadFile(file, function(image) {
                if (image) {
                    images[file] = image;
                }
                ++i == n && callback(images);
            });
        });
    }
    return function(files, callback) {
        var i = 0, n = files.length, images = {};
        files.forEach(function(file) {
            loadFiles(file, function(images_) {
                Ox.extend(images, images_)
                ++i == n && callback(Ox.len(images) ? images : void 0);
            });
        });
    };
}());