Add electron

backend/src/DataSource/MqttSource.ts

@@ -0,0 +1,58 @@
+import { Client, connect as mqttConnect } from 'mqtt'
+import { DataSource, DataSourceState } from './'
+
+export interface MqttOptions {
+  url: string
+}
+
+export class MqttSource implements DataSource<MqttOptions> {
+  private client: Client | undefined
+  private messageCallback?: (topic: string, message: Buffer) => void
+  private rootSubscription = '#'
+  public topicSeparator = '/'
+
+  public onMessage(messageCallback: (topic: string, message: Buffer) => void) {
+    this.messageCallback = messageCallback
+  }
+
+  public connect(options: MqttOptions): DataSourceState {
+    const state = new DataSourceState()
+
+    const client = mqttConnect(options.url, {
+      resubscribe: false
+    })
+
+    this.client = client
+
+    client.on('error', (error: Error) => {
+      state.setError(error)
+    })
+
+    client.on('close', () => {
+      state.setConnected(false)
+    })
+
+    client.on('reconnect', () => {
+      state.setConnecting()
+    })
+
+    client.on('connect', () => {
+      state.setConnected(true)
+      client.subscribe(this.rootSubscription, (err: Error) => {
+        if (err) {
+          throw new Error('mqtt subscription failed')
+        }
+      })
+    })
+
+    client.on('message', (topic, message) => {
+      this.messageCallback && this.messageCallback(topic, message)
+    })
+
+    return state
+  }
+
+  public disconnect() {
+    this.client && this.client.end()
+  }
+}