1 files changed, 127 insertions, 0 deletions

diff --git a/src/Event/EventEmitter.js b/src/Event/EventEmitter.js
new file mode 100644
index 0000000..3a6db25
--- /dev/null
+++ b/src/Event/EventEmitter.js
@@ -0,0 +1,127 @@
+export default class EventEmitter {
+
+    constructor() {
+        this._listeners = {};
+        this._once = {};
+    }
+
+    /**
+     * @param {String|String[]} event
+     * @param {Object} data
+     *
+     * @return {Promise<void>}
+     */
+    async emit(event, data) {
+        if(Array.isArray(event)) {
+            event.forEach((event) => {this.emit(event, data);});
+            return;
+        }
+
+        await this._notifyListeners(event, data);
+        await this._notifyOnce(event, data);
+    }
+
+    /**
+     * @param {String|String[]} event
+     * @param {Function} callback
+     *
+     * @return EventEmitter
+     */
+    on(event, callback) {
+        if(Array.isArray(event)) {
+            event.forEach((event) => {this.on(event, callback);});
+            return this;
+        }
+
+        if(!this._listeners.hasOwnProperty(event)) {
+            this._listeners[event] = [];
+        }
+
+        this._listeners[event].push(callback);
+
+        return this;
+    }
+
+    /**
+     * @param {String|String[]} event
+     * @param {Function} callback
+     *
+     * @return EventEmitter
+     */
+    off(event, callback) {
+        if(Array.isArray(event)) {
+            event.forEach((event) => {this.off(event, callback);});
+            return this;
+        }
+
+        if(!this._listeners.hasOwnProperty(event)) {
+            return this;
+        }
+
+        for(let i = 0; i < this._listeners[event].length; i++) {
+            if(this._listeners[event][i] === callback) {
+                this._listeners[event].splice(i, 1);
+                i--;
+            }
+        }
+
+        return this;
+    }
+
+    /**
+     * @param {String} event
+     * @param {Function} callback
+     *
+     * @return EventEmitter
+     */
+    once(event, callback) {
+        if(!this._once.hasOwnProperty(event)) {
+            this._once[event] = [];
+        }
+
+        this._once[event].push(callback);
+
+        return this;
+    }
+
+    /**
+     * @param {String} event
+     * @param {Object} data
+     * @return {Promise<void>}
+     * @private
+     */
+    async _notifyListeners(event, data) {
+        if(!this._listeners.hasOwnProperty(event)) {
+            return;
+        }
+
+        for(let callback of this._listeners[event]) {
+            try {
+                await callback(data);
+            } catch(e) {
+                console.error(e);
+            }
+        }
+    }
+
+    /**
+     * @param {String} event
+     * @param {Object} data
+     * @return {Promise<void>}
+     * @private
+     */
+    async _notifyOnce(event, data) {
+        if(!this._once.hasOwnProperty(event)) {
+            return;
+        }
+
+        let callback;
+        while(callback = this._once[event].pop()) {
+            try {
+                await callback(data);
+            } catch(e) {
+                console.error(e);
+            }
+        }
+    }
+}
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