/**
 * Asset manager.
 *
 * @copyright Dennis Eichhorn
 * @license   OMS License 1.0
 * @version   1.0.0
 * @since     1.0.0
 */
export class AssetManager
{
    /**
     * @constructor
     *
     * @since 1.0.0
     */
    constructor ()
    {
        this.assets = {};
        this.registerLoadedAssets();
    };

    /**
     * Register all loaded assets.
     *
     * @return {void}
     *
     * @since 1.0.0
     */
    registerLoadedAssets ()
    {
        const scripts = document.getElementsByTagName('script'),
            length    = !scripts ? 0 : scripts.length;

        this.assets = {};

        for (let i = 0; i < length; ++i) {
            this.assets[jsOMS.hash(scripts[i].src)] = scripts[i].src;
        }
    };

    /**
     * Load asset.
     *
     * @param {string}          path       Asset path
     * @param {string}          filetype   Filetype of the asset
     * @param {requestCallback} [callback] Callback after load
     *
     * @return {string|boolean}
     *
     * @since 1.0.0
     */
    load (path, filetype, callback)
    {
        let hash;

        if (!this.assets[(hash = jsOMS.hash(path))]) {
            let fileref = null;

            if (filetype === 'js') {
                fileref = document.createElement('script');
                fileref.setAttribute('type', 'text/javascript');
                fileref.setAttribute('src', path);

                if (typeof fileref !== 'undefined') {
                    const head = document.getElementsByTagName('head');

                    if (head) {
                        head[0].appendChild(fileref);
                    }
                }

                this.assets[hash] = path;
            } else if (filetype === 'css') {
                fileref = document.createElement('link');
                fileref.setAttribute('rel', 'stylesheet');
                fileref.setAttribute('type', 'text/css');
                fileref.setAttribute('href', path);

                if (typeof fileref !== 'undefined') {
                    const head = document.getElementsByTagName('head');

                    if (head) {
                        head[0].appendChild(fileref);
                    }
                }

                this.assets[hash] = path;
            } else if (filetype === 'img') {
                /** global: Image */
                this.assets[hash]     = new Image();
                this.assets[hash].src = path;
            }

            if (callback) {
                fileref.onreadystatechange ()
                {
                    if (this.readyState === 'complete') {
                        callback();
                    }
                };

                fileref.onload = callback();
            }

            return hash;
        }

        return false;
    };

    /**
     * Get asset.
     *
     * @param {string} key Key of the asset
     *
     * @return {null|string}
     *
     * @since 1.0.0
     */
    get (key)
    {
        key = jsOMS.hash(key);

        if (this.assets[key]) {
            return this.assets[key];
        }

        return null;
    };

    /**
     * Remove asset.
     *
     * @param {string} key Key of the asset
     *
     * @return {boolean}
     *
     * @since 1.0.0
     */
    remove (key)
    {
        key = jsOMS.hash(key);

        if (typeof this.assets[key] !== 'undefined') {
            delete this.assets[key];

            return true;
        }

        return false;
    };
};