[enh] add BMA watcher + reorganize code

src/lib/watcherLoop.ts

@@ -0,0 +1,50 @@
+export async function watcherLoop(
+  connect: () => Promise<void>,
+  onConnectionClosed: () => Promise<void>,
+  reconnectionDelays: number[],
+  onStart: () => Promise<void>,
+  onDisconnection: (waitingDelay: number) => Promise<void>,
+  onRestart: () => Promise<void>,
+  onRestartSuccess: () => Promise<void>,
+  onError: (e: Error) => Promise<void>,
+) {
+
+  let hasStarted = false
+
+  ;(async () => {
+
+    let connected = false
+    let i = 0
+    while (!connected) {
+      try {
+
+        if (hasStarted) {
+          await onRestart()
+        }
+
+        // Connection trial
+        await connect()
+
+        if (!hasStarted) {
+          hasStarted = true
+          await onStart()
+        } else {
+          await onRestartSuccess()
+        }
+
+        // We reset the delay of reconnection
+        i = 0
+
+        await onConnectionClosed()
+
+      } catch (e) {
+        await onError(e)
+      }
+      // Wait before reconnecting
+      const waitingDelay = reconnectionDelays[Math.min(reconnectionDelays.length - 1, i)]
+      await onDisconnection(waitingDelay)
+      await new Promise(resolve => setTimeout(resolve, waitingDelay))
+      i++
+    }
+  })()
+}