From 121f3bbe2902313efda2cb8d9a710d40af951a04 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Miroslav=20=C5=A0ediv=C3=BD?= <sedivy.miro@gmail.com>
Date: Thu, 15 Jul 2021 20:50:13 +0200
Subject: [PATCH] implement reconnecter class.

---
 src/component/utils/reconnecter.ts | 149 +++++++++++++++++++++++++++++
 1 file changed, 149 insertions(+)
 create mode 100644 src/component/utils/reconnecter.ts

diff --git a/src/component/utils/reconnecter.ts b/src/component/utils/reconnecter.ts
new file mode 100644
index 00000000..10aec3f3
--- /dev/null
+++ b/src/component/utils/reconnecter.ts
@@ -0,0 +1,149 @@
+import EventEmitter from 'eventemitter3'
+
+export interface ReconnecterAbstractEvents {
+  connect: () => void
+  disconnect: (error?: Error) => void
+}
+
+export abstract class ReconnecterAbstract extends EventEmitter<ReconnecterAbstractEvents> {
+  constructor() {
+    super()
+
+    if (this.constructor == ReconnecterAbstract) {
+      throw new Error("Abstract classes can't be instantiated.");
+    }
+  }
+
+  public async connect() {
+    throw new Error("Method 'connect()' must be implemented.");
+  }
+
+  public async disconnect() {
+    throw new Error("Method 'disconnect()' must be implemented.");
+  }
+}
+
+export interface ReconnecterEvents {
+  open: () => void
+  connect: () => void
+  disconnect: () => void
+  close: (error?: Error) => void
+}
+
+export interface ReconnecterConfig {
+  max_reconnects: number
+  timeout_ms: number
+  backoff_ms: number
+}
+
+export class Reconnecter extends EventEmitter<ReconnecterEvents> {
+  private _conn: ReconnecterAbstract
+  private _config: ReconnecterConfig
+  private _timeout: number | undefined
+
+  private _open = false
+  private _connected = false
+  private _total_reconnects = 0
+  private _last_connected: Date | undefined
+
+  constructor(conn: ReconnecterAbstract, config?: ReconnecterConfig) {
+    super()
+
+    this._conn = conn
+    this._config = {
+      max_reconnects: 10,
+      timeout_ms: 1500,
+      backoff_ms: 750,
+      ...config,
+    }
+
+    this._conn.on('connect', () => {
+      if (this._timeout) {
+        window.clearTimeout(this._timeout)
+        this._timeout = undefined
+      }
+
+      this._connected = true
+
+      if (this._open) {
+        this._last_connected = new Date()
+        this.emit('connect')
+      } else {
+        this._conn.disconnect()
+      }
+    })
+
+    this._conn.on('disconnect', () => {
+      if (this._timeout) {
+        window.clearTimeout(this._timeout)
+        this._timeout = undefined
+      }
+
+      this._connected = false
+
+      if (this._open) {
+        this.emit('disconnect')
+        this.reconnect()
+      }
+    })
+  }
+
+  public get isOpen(): boolean {
+    return this._open
+  }
+
+  public get isConnected(): boolean {
+    return this._connected
+  }
+
+  public get totalReconnects(): number {
+    return this._total_reconnects
+  }
+
+  public get lastConnected(): Date | undefined {
+    return this._last_connected
+  }
+
+  public open(): void {
+    if (this._open) {
+      throw new Error('connection is already open')
+    }
+
+    this._open = true
+    this.emit('open')
+
+    this._conn.connect()
+    this._timeout = window.setTimeout(() => {
+      this._conn.disconnect()
+      this.reconnect()
+    }, this._config.timeout_ms)
+  }
+
+  public close(error?: Error): void {
+    if (!this._open) {
+      throw new Error('connection is already closed')
+    }
+
+    this._open = false
+    this._last_connected = undefined
+    this.emit('close', error)
+
+    if (this._connected) {
+      this._conn.disconnect()
+    }
+  }
+
+  public reconnect(): void {
+    if (this._connected) {
+      throw new Error('connection is already connected')
+    }
+
+    this._total_reconnects++
+
+    if (this._config.max_reconnects < this._total_reconnects || this._total_reconnects < 0) {
+      setTimeout(this._conn.connect, this._config.backoff_ms)
+    } else {
+      this.close(new Error('reconnection failed'))
+    }
+  }
+}