1 files changed, 254 insertions, 0 deletions
diff --git a/present/js/controllers/plugins.js b/present/js/controllers/plugins.js
new file mode 100644
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--- /dev/null
+++ b/present/js/controllers/plugins.js
@@ -0,0 +1,254 @@
+import { loadScript } from '../utils/loader.js'
+
+/**
+ * Manages loading and registering of reveal.js plugins.
+ */
+export default class Plugins {
+
+	constructor( reveal ) {
+
+		this.Reveal = reveal;
+
+		// Flags our current state (idle -> loading -> loaded)
+		this.state = 'idle';
+
+		// An id:instance map of currently registered plugins
+		this.registeredPlugins = {};
+
+		this.asyncDependencies = [];
+
+	}
+
+	/**
+	 * Loads reveal.js dependencies, registers and
+	 * initializes plugins.
+	 *
+	 * Plugins are direct references to a reveal.js plugin
+	 * object that we register and initialize after any
+	 * synchronous dependencies have loaded.
+	 *
+	 * Dependencies are defined via the 'dependencies' config
+	 * option and will be loaded prior to starting reveal.js.
+	 * Some dependencies may have an 'async' flag, if so they
+	 * will load after reveal.js has been started up.
+	 */
+	load( plugins, dependencies ) {
+
+		this.state = 'loading';
+
+		plugins.forEach( this.registerPlugin.bind( this ) );
+
+		return new Promise( resolve => {
+
+			let scripts = [],
+				scriptsToLoad = 0;
+
+			dependencies.forEach( s => {
+				// Load if there's no condition or the condition is truthy
+				if( !s.condition || s.condition() ) {
+					if( s.async ) {
+						this.asyncDependencies.push( s );
+					}
+					else {
+						scripts.push( s );
+					}
+				}
+			} );
+
+			if( scripts.length ) {
+				scriptsToLoad = scripts.length;
+
+				const scriptLoadedCallback = (s) => {
+					if( s && typeof s.callback === 'function' ) s.callback();
+
+					if( --scriptsToLoad === 0 ) {
+						this.initPlugins().then( resolve );
+					}
+				};
+
+				// Load synchronous scripts
+				scripts.forEach( s => {
+					if( typeof s.id === 'string' ) {
+						this.registerPlugin( s );
+						scriptLoadedCallback( s );
+					}
+					else if( typeof s.src === 'string' ) {
+						loadScript( s.src, () => scriptLoadedCallback(s) );
+					}
+					else {
+						console.warn( 'Unrecognized plugin format', s );
+						scriptLoadedCallback();
+					}
+				} );
+			}
+			else {
+				this.initPlugins().then( resolve );
+			}
+
+		} );
+
+	}
+
+	/**
+	 * Initializes our plugins and waits for them to be ready
+	 * before proceeding.
+	 */
+	initPlugins() {
+
+		return new Promise( resolve => {
+
+			let pluginValues = Object.values( this.registeredPlugins );
+			let pluginsToInitialize = pluginValues.length;
+
+			// If there are no plugins, skip this step
+			if( pluginsToInitialize === 0 ) {
+				this.loadAsync().then( resolve );
+			}
+			// ... otherwise initialize plugins
+			else {
+
+				let initNextPlugin;
+
+				let afterPlugInitialized = () => {
+					if( --pluginsToInitialize === 0 ) {
+						this.loadAsync().then( resolve );
+					}
+					else {
+						initNextPlugin();
+					}
+				};
+
+				let i = 0;
+
+				// Initialize plugins serially
+				initNextPlugin = () => {
+
+					let plugin = pluginValues[i++];
+
+					// If the plugin has an 'init' method, invoke it
+					if( typeof plugin.init === 'function' ) {
+						let promise = plugin.init( this.Reveal );
+
+						// If the plugin returned a Promise, wait for it
+						if( promise && typeof promise.then === 'function' ) {
+							promise.then( afterPlugInitialized );
+						}
+						else {
+							afterPlugInitialized();
+						}
+					}
+					else {
+						afterPlugInitialized();
+					}
+
+				}
+
+				initNextPlugin();
+
+			}
+
+		} )
+
+	}
+
+	/**
+	 * Loads all async reveal.js dependencies.
+	 */
+	loadAsync() {
+
+		this.state = 'loaded';
+
+		if( this.asyncDependencies.length ) {
+			this.asyncDependencies.forEach( s => {
+				loadScript( s.src, s.callback );
+			} );
+		}
+
+		return Promise.resolve();
+
+	}
+
+	/**
+	 * Registers a new plugin with this reveal.js instance.
+	 *
+	 * reveal.js waits for all registered plugins to initialize
+	 * before considering itself ready, as long as the plugin
+	 * is registered before calling `Reveal.initialize()`.
+	 */
+	registerPlugin( plugin ) {
+
+		// Backwards compatibility to make reveal.js ~3.9.0
+		// plugins work with reveal.js 4.0.0
+		if( arguments.length === 2 && typeof arguments[0] === 'string' ) {
+			plugin = arguments[1];
+			plugin.id = arguments[0];
+		}
+		// Plugin can optionally be a function which we call
+		// to create an instance of the plugin
+		else if( typeof plugin === 'function' ) {
+			plugin = plugin();
+		}
+
+		let id = plugin.id;
+
+		if( typeof id !== 'string' ) {
+			console.warn( 'Unrecognized plugin format; can\'t find plugin.id', plugin );
+		}
+		else if( this.registeredPlugins[id] === undefined ) {
+			this.registeredPlugins[id] = plugin;
+
+			// If a plugin is registered after reveal.js is loaded,
+			// initialize it right away
+			if( this.state === 'loaded' && typeof plugin.init === 'function' ) {
+				plugin.init( this.Reveal );
+			}
+		}
+		else {
+			console.warn( 'reveal.js: "'+ id +'" plugin has already been registered' );
+		}
+
+	}
+
+	/**
+	 * Checks if a specific plugin has been registered.
+	 *
+	 * @param {String} id Unique plugin identifier
+	 */
+	hasPlugin( id ) {
+
+		return !!this.registeredPlugins[id];
+
+	}
+
+	/**
+	 * Returns the specific plugin instance, if a plugin
+	 * with the given ID has been registered.
+	 *
+	 * @param {String} id Unique plugin identifier
+	 */
+	getPlugin( id ) {
+
+		return this.registeredPlugins[id];
+
+	}
+
+	getRegisteredPlugins() {
+
+		return this.registeredPlugins;
+
+	}
+
+	destroy() {
+
+		Object.values( this.registeredPlugins ).forEach( plugin => {
+			if( typeof plugin.destroy === 'function' ) {
+				plugin.destroy();
+			}
+		} );
+
+		this.registeredPlugins = {};
+		this.asyncDependencies = [];
+
+	}
+
+}