Start using sinatra & ruby for backend

Signed-off-by: Syed Daanish <me@syedm.dev>

public/src/js/event_bus.js

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+/**
+ * @author Syed Daanish <me@syedm.dev>
+ * @file `event_bus.js`
+ */
+
+/**
+ * @name EventBus
+ * @access public
+ * @classdesc Handles event emission & listening
+ *            to connect with other modules.
+ * @exports EventBus
+ * @default
+ */
+export default class EventBus {
+  /**
+   * @constructs EventBus
+   * @function constructor
+   * @description Initializes the event bus
+   */
+  constructor() {
+    this.retreivable_events = {};
+    this.events = {};
+  }
+  /**
+   * @function on
+   * @description Sets up an event listener
+   * @param {string} event - Event name
+   * @param {Function} callback - Callback function to call
+   *                              (multiple functions can be added)
+   */
+  on(event, callback) {
+    if (!this.events[event]) {
+      this.events[event] = [];
+    }
+    this.events[event].push(callback);
+  }
+  /**
+   * @function emit
+   * @description Emits an event
+   * @param {string} event - Event name
+   * @param {...*} args - Arguments to pass to the callback
+   *                      functions (0 or more)
+   */
+  emit(event, ...args) {
+    if (this.events[event]) {
+      this.events[event].forEach((fn) => {
+        fn(...args);
+      });
+    }
+  }
+  /**
+   * @function onRetrievable
+   * @description Sets up a retrievable event listener
+   * @param {string} event - Event name
+   * @param {Function} callback - Callback function to call
+   *                              (can only be used once)
+   */
+  onRetrievable(event, callback) {
+    this.retreivable_events[event] = callback;
+  }
+  /**
+   * @function get
+   * @description Retrieves data from an event
+   * @param {string} event - Event name
+   * @param {...*} args - Arguments to pass to the callback
+   *                      function (only one)
+   * @returns {any|undefined} - Data from the event or undefined
+   */
+  get(event, ...args) {
+    if (this.retreivable_events[event]) {
+      return this.retreivable_events[event](...args);
+    }
+    return undefined;
+  }
+}