/*
Copyright (c) 2009, Yahoo! Inc. All rights reserved.
Code licensed under the BSD License:
http://developer.yahoo.net/yui/license.txt
version: 3.0.0b1
build: 1163
*/
YUI.add('get', function(Y) {

(function() {

/**
 * Provides a mechanism to fetch remote resources and
 * insert them into a document.
 * @module yui
 * @submodule get
 */

var ua         = Y.UA, 
    L          = Y.Lang,
    // PREFIX     = Y.guid(),
    TYPE_JS    = "text/javascript",
    TYPE_CSS   = "text/css",
    STYLESHEET = "stylesheet";

/**
 * Fetches and inserts one or more script or link nodes into the document 
 * @class Get
 * @static
 */
Y.Get = function() {

    /**
     * hash of queues to manage multiple requests
     * @property queues
     * @private
     */
    var queues={}, 
        
    /**
     * queue index used to generate transaction ids
     * @property qidx
     * @type int
     * @private
     */
        qidx=0, 
        
    /**
     * interal property used to prevent multiple simultaneous purge 
     * processes
     * @property purging
     * @type boolean
     * @private
     */
        purging=false,

    
    /** 
     * Generates an HTML element, this is not appended to a document
     * @method _node
     * @param type {string} the type of element
     * @param attr {string} the attributes
     * @param win {Window} optional window to create the element in
     * @return {HTMLElement} the generated node
     * @private
     */
    _node = function(type, attr, win) {
        var w = win || Y.config.win, d=w.document, n=d.createElement(type),
            i;

        for (i in attr) {
            if (attr[i] && attr.hasOwnProperty(i)) {
                n.setAttribute(i, attr[i]);
            }
        }

        return n;
    },

    /**
     * Generates a link node
     * @method _linkNode
     * @param url {string} the url for the css file
     * @param win {Window} optional window to create the node in
     * @param attributes optional attributes collection to apply to the new node
     * @return {HTMLElement} the generated node
     * @private
     */
    _linkNode = function(url, win, attributes) {
        var o = {
            id:   Y.guid(),
            type: TYPE_CSS,
            rel:  STYLESHEET,
            href: url
        };
        if (attributes) {
            Y.mix(o, attributes);
        }
        return _node("link", o, win);
    },

    /**
     * Generates a script node
     * @method _scriptNode
     * @param url {string} the url for the script file
     * @param win {Window} optional window to create the node in
     * @param attributes optional attributes collection to apply to the new node
     * @return {HTMLElement} the generated node
     * @private
     */
    _scriptNode = function(url, win, attributes) {
        var o = {
            id:   Y.guid(),
            type: TYPE_JS,
            src:  url
        };

        if (attributes) {
            Y.mix(o, attributes);
        }

        return _node("script", o, win);
    },

    /**
     * Removes the nodes for the specified queue
     * @method _purge
     * @private
     */
    _purge = function(tId) {
        var q=queues[tId], n, l, d, h, s, i;
        if (q) {
            n = q.nodes; 
            l = n.length;
            d = q.win.document;
            h = d.getElementsByTagName("head")[0];

            if (q.insertBefore) {
                s = _get(q.insertBefore, tId);
                if (s) {
                    h = s.parentNode;
                }
            }

            for (i=0; i<l; i=i+1) {
                h.removeChild(n[i]);
            }
        }
        q.nodes = [];
    },

    /**
     * Returns the data payload for callback functions
     * @method _returnData
     * @private
     */
    _returnData = function(q, msg, result) {
        return {
                tId: q.tId,
                win: q.win,
                data: q.data,
                nodes: q.nodes,
                msg: msg,
                statusText: result,
                purge: function() {
                    _purge(this.tId);
                }
            };
    },

    /**
     * The transaction is finished
     * @method _end
     * @param id {string} the id of the request
     * @private
     */
    _end = function(id, msg, result) {
        var q = queues[id], sc;
        if (q && q.onEnd) {
            sc = q.context || q;
            q.onEnd.call(sc, _returnData(q, msg, result));
        }
    },

    /*
     * The request failed, execute fail handler with whatever
     * was accomplished.  There isn't a failure case at the
     * moment unless you count aborted transactions
     * @method _fail
     * @param id {string} the id of the request
     * @private
     */
    _fail = function(id, msg) {

        Y.log("get failure: " + msg, "warn", "get");

        var q = queues[id], sc;
        if (q.timer) {
            q.timer.cancel();
        }

        // execute failure callback
        if (q.onFailure) {
            sc = q.context || q;
            q.onFailure.call(sc, _returnData(q, msg));
        }

        _end(id, msg, 'failure');
    },

    _get = function(nId, tId) {
        var q = queues[tId],
            n = (L.isString(nId)) ? q.win.document.getElementById(nId) : nId;
        if (!n) {
            _fail(tId, "target node not found: " + nId);
        }

        return n;
    },

    /**
     * The request is complete, so executing the requester's callback
     * @method _finish
     * @param id {string} the id of the request
     * @private
     */
    _finish = function(id) {
        Y.log("Finishing transaction " + id, "info", "get");
        var q = queues[id], msg, sc;
        if (q.timer) {
            q.timer.cancel();
        }
        q.finished = true;

        if (q.aborted) {
            msg = "transaction " + id + " was aborted";
            _fail(id, msg);
            return;
        }

        // execute success callback
        if (q.onSuccess) {
            sc = q.context || q;
            q.onSuccess.call(sc, _returnData(q));
        }

        _end(id, msg, 'OK');
    },

    /**
     * Timeout detected
     * @method _timeout
     * @param id {string} the id of the request
     * @private
     */
    _timeout = function(id) {
        Y.log("Timeout " + id, "info", "get");
        var q = queues[id], sc;
        if (q.onTimeout) {
            sc = q.context || q;
            q.onTimeout.call(sc, _returnData(q));
        }

        _end(id, 'timeout', 'timeout');
    },
    

    /**
     * Loads the next item for a given request
     * @method _next
     * @param id {string} the id of the request
     * @param loaded {string} the url that was just loaded, if any
     * @private
     */
    _next = function(id, loaded) {

        Y.log("_next: " + id + ", loaded: " + (loaded || "nothing"), "info", "get");

        var q = queues[id], msg, w, d, h, n, url, s;

        if (q.timer) {
            // Y.log('cancel timer');
            q.timer.cancel();
        }

        if (q.aborted) {
            msg = "transaction " + id + " was aborted";
            _fail(id, msg);
            return;
        }

        if (loaded) {
            q.url.shift(); 
            if (q.varName) {
                q.varName.shift(); 
            }
        } else {
            // This is the first pass: make sure the url is an array
            q.url = (L.isString(q.url)) ? [q.url] : q.url;
            if (q.varName) {
                q.varName = (L.isString(q.varName)) ? [q.varName] : q.varName;
            }
        }

        w = q.win; 
        d = w.document; 
        h = d.getElementsByTagName("head")[0];

        if (q.url.length === 0) {
            _finish(id);
            return;
        } 

        url = q.url[0];

        // if the url is undefined, this is probably a trailing comma problem in IE
        if (!url) {
            q.url.shift(); 
            Y.log('skipping empty url');
            return _next(id);
        }

        Y.log("attempting to load " + url, "info", "get");

        if (q.timeout) {
            // Y.log('create timer');
            q.timer = L.later(q.timeout, q, _timeout, id);
        }

        if (q.type === "script") {
            n = _scriptNode(url, w, q.attributes);
        } else {
            n = _linkNode(url, w, q.attributes);
        }

        // track this node's load progress
        _track(q.type, n, id, url, w, q.url.length);

        // add the node to the queue so we can return it to the user supplied callback
        q.nodes.push(n);

        // add it to the head or insert it before 'insertBefore'
        if (q.insertBefore) {
            s = _get(q.insertBefore, id);
            if (s) {
                s.parentNode.insertBefore(n, s);
            }
        } else {
            h.appendChild(n);
        }
        
        Y.log("Appending node: " + url, "info", "get");

        // FireFox does not support the onload event for link nodes, so there is
        // no way to make the css requests synchronous. This means that the css 
        // rules in multiple files could be applied out of order in this browser
        // if a later request returns before an earlier one.  Safari too.
        if ((ua.webkit || ua.gecko) && q.type === "css") {
            _next(id, url);
        }
    },

    /**
     * Removes processed queues and corresponding nodes
     * @method _autoPurge
     * @private
     */
    _autoPurge = function() {

        if (purging) {
            return;
        }

        purging = true;

        var i, q;

        for (i in queues) {
            if (queues.hasOwnProperty(i)) {
                q = queues[i];
                if (q.autopurge && q.finished) {
                    _purge(q.tId);
                    delete queues[i];
                }
            }
        }

        purging = false;
    },

    /**
     * Saves the state for the request and begins loading
     * the requested urls
     * @method queue
     * @param type {string} the type of node to insert
     * @param url {string} the url to load
     * @param opts the hash of options for this request
     * @private
     */
    _queue = function(type, url, opts) {

        opts = opts || {};

        var id = "q" + (qidx++), q,
            thresh = opts.purgethreshold || Y.Get.PURGE_THRESH;

        if (qidx % thresh === 0) {
            _autoPurge();
        }

        queues[id] = Y.merge(opts, {
            tId: id,
            type: type,
            url: url,
            finished: false,
            nodes: []
        });

        q           = queues[id];
        q.win       = q.win || Y.config.win;
        q.context   = q.context || q;
        q.autopurge = ("autopurge" in q) ? q.autopurge : 
                      (type === "script") ? true : false;

        if (opts.charset) {
            q.attributes = q.attributes || {};
            q.attributes.charset = opts.charset;
        }

        L.later(0, q, _next, id);

        return {
            tId: id
        };
    },

    /**
     * Detects when a node has been loaded.  In the case of
     * script nodes, this does not guarantee that contained
     * script is ready to use.
     * @method _track
     * @param type {string} the type of node to track
     * @param n {HTMLElement} the node to track
     * @param id {string} the id of the request
     * @param url {string} the url that is being loaded
     * @param win {Window} the targeted window
     * @param qlength the number of remaining items in the queue,
     * including this one
     * @param trackfn {Function} function to execute when finished
     * the default is _next
     * @private
     */
    _track = function(type, n, id, url, win, qlength, trackfn) {
        var f = trackfn || _next;

        // IE supports the readystatechange event for script and css nodes
        // Opera only for script nodes.  Opera support onload for script
        // nodes, but this doesn't fire when there is a load failure.
        // The onreadystatechange appears to be a better way to respond
        // to both success and failure.
        if (ua.ie) {
            n.onreadystatechange = function() {
                var rs = this.readyState;
                if ("loaded" === rs || "complete" === rs) {
                    Y.log(id + " onreadstatechange " + url, "info", "get");
                    n.onreadystatechange = null;
                    f(id, url);
                }
            };

        // webkit prior to 3.x is no longer supported
        } else if (ua.webkit) {

            if (type === "script") {
                // Safari 3.x supports the load event for script nodes (DOM2)
                n.addEventListener("load", function() {
                    Y.log(id + " DOM2 onload " + url, "info", "get");
                    f(id, url);
                });
            } 

        // FireFox and Opera support onload (but not DOM2 in FF) handlers for
        // script nodes.  Opera, but not FF, supports the onload event for link
        // nodes.
        } else { 

            n.onload = function() {
                Y.log(id + " onload " + url, "info", "get");
                f(id, url);
            };

            n.onerror = function(e) {
                _fail(id, e + ": " + url);
            };
        }
    };

    return {

        /**
         * The number of request required before an automatic purge.
         * Can be configured via the 'purgethreshold' config
         * property PURGE_THRESH
         * @static
         * @type int
         * @default 20
         * @private
         */
        PURGE_THRESH: 20,

        /**
         * Called by the the helper for detecting script load in Safari
         * @method _finalize
         * @static
         * @param id {string} the transaction id
         * @private
         */
        _finalize: function(id) {
            Y.log(id + " finalized ", "info", "get");
            L.later(0, null, _finish, id);
        },

        /**
         * Abort a transaction
         * @method abort
         * @static
         * @param o {string|object} Either the tId or the object returned from
         * script() or css()
         */
        abort: function(o) {
            var id = (L.isString(o)) ? o : o.tId,
                q = queues[id];
            if (q) {
                Y.log("Aborting " + id, "info", "get");
                q.aborted = true;
            }
        }, 

        /**
         * Fetches and inserts one or more script nodes into the head
         * of the current document or the document in a specified window.
         *
         * @method script
         * @static
         * @param url {string|string[]} the url or urls to the script(s)
         * @param opts {object} Options: 
         * <dl>
         * <dt>onSuccess</dt>
         * <dd>
         * callback to execute when the script(s) are finished loading
         * The callback receives an object back with the following
         * data:
         * <dl>
         * <dt>win</dt>
         * <dd>the window the script(s) were inserted into</dd>
         * <dt>data</dt>
         * <dd>the data object passed in when the request was made</dd>
         * <dt>nodes</dt>
         * <dd>An array containing references to the nodes that were
         * inserted</dd>
         * <dt>purge</dt>
         * <dd>A function that, when executed, will remove the nodes
         * that were inserted</dd>
         * <dt>
         * </dl>
         * </dd>
         * <dt>onTimeout</dt>
         * <dd>
         * callback to execute when a timeout occurs.
         * The callback receives an object back with the following
         * data:
         * <dl>
         * <dt>win</dt>
         * <dd>the window the script(s) were inserted into</dd>
         * <dt>data</dt>
         * <dd>the data object passed in when the request was made</dd>
         * <dt>nodes</dt>
         * <dd>An array containing references to the nodes that were
         * inserted</dd>
         * <dt>purge</dt>
         * <dd>A function that, when executed, will remove the nodes
         * that were inserted</dd>
         * <dt>
         * </dl>
         * </dd>
         * <dt>onEnd</dt>
         * <dd>a function that executes when the transaction finishes, regardless of the exit path</dd>
         * <dt>onFailure</dt>
         * <dd>
         * callback to execute when the script load operation fails
         * The callback receives an object back with the following
         * data:
         * <dl>
         * <dt>win</dt>
         * <dd>the window the script(s) were inserted into</dd>
         * <dt>data</dt>
         * <dd>the data object passed in when the request was made</dd>
         * <dt>nodes</dt>
         * <dd>An array containing references to the nodes that were
         * inserted successfully</dd>
         * <dt>purge</dt>
         * <dd>A function that, when executed, will remove any nodes
         * that were inserted</dd>
         * <dt>
         * </dl>
         * </dd>
         * <dt>context</dt>
         * <dd>the execution context for the callbacks</dd>
         * <dt>win</dt>
         * <dd>a window other than the one the utility occupies</dd>
         * <dt>autopurge</dt>
         * <dd>
         * setting to true will let the utilities cleanup routine purge 
         * the script once loaded
         * </dd>
         * <dt>purgethreshold</dt>
         * <dd>
         * The number of transaction before autopurge should be initiated
         * </dd>
         * <dt>data</dt>
         * <dd>
         * data that is supplied to the callback when the script(s) are
         * loaded.
         * </dd>
         * <dt>insertBefore</dt>
         * <dd>node or node id that will become the new node's nextSibling</dd>
         * </dl>
         * <dt>charset</dt>
         * <dd>Node charset, default utf-8 (deprecated, use the attributes config)</dd>
         * <dt>attributes</dt>
         * <dd>An object literal containing additional attributes to add to the link tags</dd>
         * <dt>timeout</dt>
         * <dd>Number of milliseconds to wait before aborting and firing the timeout event</dd>
         * <pre>
         * &nbsp;&nbsp;Y.Get.script(
         * &nbsp;&nbsp;["http://yui.yahooapis.com/2.5.2/build/yahoo/yahoo-min.js",
         * &nbsp;&nbsp;&nbsp;"http://yui.yahooapis.com/2.5.2/build/event/event-min.js"], &#123;
         * &nbsp;&nbsp;&nbsp;&nbsp;onSuccess: function(o) &#123;
         * &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;this.log("won't cause error because Y is the context");
         * &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Y.log(o.data); // foo
         * &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Y.log(o.nodes.length === 2) // true
         * &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;// o.purge(); // optionally remove the script nodes immediately
         * &nbsp;&nbsp;&nbsp;&nbsp;&#125;,
         * &nbsp;&nbsp;&nbsp;&nbsp;onFailure: function(o) &#123;
         * &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Y.log("transaction failed");
         * &nbsp;&nbsp;&nbsp;&nbsp;&#125;,
         * &nbsp;&nbsp;&nbsp;&nbsp;onTimeout: function(o) &#123;
         * &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Y.log("transaction timed out");
         * &nbsp;&nbsp;&nbsp;&nbsp;&#125;,
         * &nbsp;&nbsp;&nbsp;&nbsp;data: "foo",
         * &nbsp;&nbsp;&nbsp;&nbsp;timeout: 10000, // 10 second timeout
         * &nbsp;&nbsp;&nbsp;&nbsp;context: Y, // make the YUI instance
         * &nbsp;&nbsp;&nbsp;&nbsp;// win: otherframe // target another window/frame
         * &nbsp;&nbsp;&nbsp;&nbsp;autopurge: true // allow the utility to choose when to remove the nodes
         * &nbsp;&nbsp;&nbsp;&nbsp;purgetheshold: 1 // purge previous transaction before next transaction
         * &nbsp;&nbsp;&#125;);
         * </pre>
         * @return {tId: string} an object containing info about the transaction
         */
        script: function(url, opts) { 
            return _queue("script", url, opts); 
        },

        /**
         * Fetches and inserts one or more css link nodes into the 
         * head of the current document or the document in a specified
         * window.
         * @method css
         * @static
         * @param url {string} the url or urls to the css file(s)
         * @param opts Options: 
         * <dl>
         * <dt>onSuccess</dt>
         * <dd>
         * callback to execute when the css file(s) are finished loading
         * The callback receives an object back with the following
         * data:
         * <dl>win</dl>
         * <dd>the window the link nodes(s) were inserted into</dd>
         * <dt>data</dt>
         * <dd>the data object passed in when the request was made</dd>
         * <dt>nodes</dt>
         * <dd>An array containing references to the nodes that were
         * inserted</dd>
         * <dt>purge</dt>
         * <dd>A function that, when executed, will remove the nodes
         * that were inserted</dd>
         * <dt>
         * </dl>
         * </dd>
         * <dt>context</dt>
         * <dd>the execution context for the callbacks</dd>
         * <dt>win</dt>
         * <dd>a window other than the one the utility occupies</dd>
         * <dt>data</dt>
         * <dd>
         * data that is supplied to the callbacks when the nodes(s) are
         * loaded.
         * </dd>
         * <dt>insertBefore</dt>
         * <dd>node or node id that will become the new node's nextSibling</dd>
         * <dt>charset</dt>
         * <dd>Node charset, default utf-8 (deprecated, use the attributes config)</dd>
         * <dt>attributes</dt>
         * <dd>An object literal containing additional attributes to add to the link tags</dd>
         * </dl>
         * <pre>
         *      Y.Get.css("http://yui.yahooapis.com/2.3.1/build/menu/assets/skins/sam/menu.css");
         * </pre>
         * <pre>
         * &nbsp;&nbsp;Y.Get.css(
         * &nbsp;&nbsp;["http://yui.yahooapis.com/2.3.1/build/menu/assets/skins/sam/menu.css",
         * &nbsp;&nbsp;&nbsp;"http://yui.yahooapis.com/2.3.1/build/logger/assets/skins/sam/logger.css"], &#123;
         * &nbsp;&nbsp;&nbsp;&nbsp;insertBefore: 'custom-styles' // nodes will be inserted before the specified node
         * &nbsp;&nbsp;&#125;);
         * </pre>
         * @return {tId: string} an object containing info about the transaction
         */
        css: function(url, opts) {
            return _queue("css", url, opts); 
        }
    };
}();

})();


}, '3.0.0b1' );
