feat: Event messages (#3345)

* feat: add createCallLink function

* feat: create Event class

* feat: add functionality for sending Events

* feat: add editEvent function

* refactor: send event location prop as wa does

* refactor: combine modules

* feat: add sendResponseToEvent function

* fix: createEventCallLink parameter

* docs: add documentation

* fix: eslint

* refactor: change timestamp to Date for the user's convenience

* refactor: rename 'Event' to 'ScheduledEvent' for more clarity

* style: fix typo in inner function

* refactor: remove unnecessary inner function

* refactor: rename 'sendResponseToEvent' to 'sendResponseToScheduledEvent' for more clarity

* fix: update the module name

src/structures/ScheduledEvent.js

@@ -0,0 +1,71 @@
+'use strict';
+
+/**
+ * ScheduledEvent send options
+ * @typedef {Object} ScheduledEventSendOptions
+ * @property {?string} description The scheduled event description
+ * @property {?Date} endTime The end time of the event
+ * @property {?string} location The location of the event
+ * @property {?string} callType The type of a WhatsApp call link to generate, valid values are: `video` | `voice`
+ * @property {boolean} [isEventCanceled = false] Indicates if a scheduled event should be sent as an already canceled
+ * @property {?Array<number>} messageSecret The custom message secret, can be used as an event ID. NOTE: it has to be a unique vector with a length of 32
+ */
+
+/** Represents a ScheduledEvent on WhatsApp */
+class ScheduledEvent {
+    /**
+     * @param {string} name
+     * @param {Date} startTime
+     * @param {ScheduledEventSendOptions} options
+     */
+    constructor(name, startTime, options = {}) {
+        /**
+         * The name of the event
+         * @type {string}
+         */
+        this.name = this._validateInputs('name', name).trim();
+
+        /**
+         * The start time of the event
+         * @type {number}
+         */
+        this.startTimeTs = Math.floor(startTime.getTime() / 1000);
+
+        /**
+         * The send options for the event
+         * @type {Object}
+         */
+        this.eventSendOptions = {
+            description: options.description?.trim(),
+            endTimeTs: options.endTime ? Math.floor(options.endTime.getTime() / 1000) : null,
+            location: options.location?.trim(),
+            callType: this._validateInputs('callType', options.callType),
+            isEventCanceled: options.isEventCanceled ?? false,
+            messageSecret: options.messageSecret
+        };
+    }
+
+    /**
+     * Inner function to validate input values
+     * @param {string} propName The property name to validate the value of
+     * @param {string | number} propValue The property value to validate
+     * @returns {string | number} The property value if a validation succeeded
+     */
+    _validateInputs(propName, propValue) {
+        if (propName === 'name' && !propValue) {
+            throw new class CreateScheduledEventError extends Error {
+                constructor(m) { super(m); }
+            }(`Empty '${propName}' parameter value is provided.`);
+        }
+
+        if (propName === 'callType' && propValue && !['video', 'voice'].includes(propValue)) {
+            throw new class CreateScheduledEventError extends Error {
+                constructor(m) { super(m); }
+            }(`Invalid '${propName}' parameter value is provided. Valid values are: 'voice' | 'video'.`);
+        }
+        
+        return propValue;
+    }
+}
+
+module.exports = ScheduledEvent;