From f1283940b773113b503f7929a044ce4d03cab9aa Mon Sep 17 00:00:00 2001
From: Steve Sanderson <SteveSandersonMS@users.noreply.github.com>
Date: Wed, 4 Apr 2018 14:06:30 +0100
Subject: [PATCH] In live reloading, also reload if the server is being
 recycled. Plus rewrite LiveReloading.ts completely to be better organized.

---
 .../src/LiveReloading.ts                      | 100 +++++++++++++-----
 1 file changed, 72 insertions(+), 28 deletions(-)

diff --git a/src/Microsoft.AspNetCore.Blazor.Browser.JS/src/LiveReloading.ts b/src/Microsoft.AspNetCore.Blazor.Browser.JS/src/LiveReloading.ts
index b0fd3e4702..bff0583523 100644
--- a/src/Microsoft.AspNetCore.Blazor.Browser.JS/src/LiveReloading.ts
+++ b/src/Microsoft.AspNetCore.Blazor.Browser.JS/src/LiveReloading.ts
@@ -1,38 +1,78 @@
-export function enableLiveReloading(endpointUri: string) {
-  listenForReloadEvent(endpointUri);
+const pollIntervalMs = 500;
+const maxPollDurationMs = 10 * 1000;
+
+export function enableLiveReloading(endpointUri: string) {
+  new ReloadContext(endpointUri).start();
 }
 
-function listenForReloadEvent(endpointUri: string) {
-  if (!WebSocket) {
-    console.log('Browser does not support WebSocket, so live reloading will be disabled.');
-    return;
+class ReloadContext {
+  private _websocketUri: string;
+  private _didConnect = false;
+  private _pollUntilConnectedThenReload = false;
+  private _stopPollingAtTime: Date | null = null;
+
+  constructor(endpointUri: string) {
+    this._websocketUri = toAbsoluteWebSocketUri(endpointUri);
   }
 
-  // First, connect to the endpoint
-  const websocketUri = toAbsoluteWebSocketUri(endpointUri);
-  const source = new WebSocket(websocketUri);
-  let allowConnectionFailedErrorReporting = true;
-
-  source.onopen = e => {
-    allowConnectionFailedErrorReporting = false;
-  };
-
-  source.onerror = e => {
-    if (allowConnectionFailedErrorReporting) {
-      allowConnectionFailedErrorReporting = false;
-      console.error(`The client app was compiled with live reloading enabled, but could not open `
-        + ` a WebSocket connection to the server at ${websocketUri}\n`
-        + `To fix this inconsistency, either run the server in development mode, or compile the `
-        + `client app in Release configuration.`);
+  start() {
+    if (typeof WebSocket !== 'undefined') {
+      this._attemptToConnect(/* delay */ 0);
+    } else {
+      console.log('Browser does not support WebSocket, so live reloading will be disabled.');
     }
-  };
+  }
 
-  // If we're notified that we should reload, then do so
-  source.onmessage = e => {
-    if (e.data === 'reload') {
-      location.reload();
+  private _attemptToConnect(delayMs: number) {
+    setTimeout(() => {
+      const source = new WebSocket(this._websocketUri);
+      source.onopen = event => this._onOpen();
+      source.onmessage = event => this._onMessage(event.data);
+      source.onerror = event => this._onError();
+      source.onclose = event => this._onClose();
+    }, delayMs);
+  }
+
+  private _onOpen() {
+    this._didConnect = true;
+
+    if (this._pollUntilConnectedThenReload) {
+      reloadNow();
     }
-  };
+  }
+
+  private _onMessage(data: string) {
+    if (data === 'reload') {
+      reloadNow();
+    }
+  }
+
+  private _onClose() {
+    if (this._didConnect) {
+      // Looks like the server is being recycled (or possibly just shut down, but in the
+      // absence of a graceful shutdown we have no way to tell the difference)
+      // Wait until the server appears to be back, then reload
+      this._pollUntilConnectedThenReload = true;
+      this._stopPollingAtTime = new Date(new Date().valueOf() + maxPollDurationMs);
+      this._attemptToConnect(/* delay */ pollIntervalMs);
+    }
+  }
+
+  private _onError() {
+    if (!this._didConnect) {
+      if (this._pollUntilConnectedThenReload) {
+        if (new Date() < this._stopPollingAtTime!) {
+          // Continue polling
+          this._attemptToConnect(/* delay */ pollIntervalMs);
+        }
+      } else {
+        console.error(`The client app was compiled with live reloading enabled, but could not open `
+          + ` a WebSocket connection to the server at ${this._websocketUri}\n`
+          + `To fix this inconsistency, either run the server in development mode, or compile the `
+          + `client app in Release configuration.`);
+      }
+    }
+  }
 }
 
 function toAbsoluteWebSocketUri(uri: string) {
@@ -46,3 +86,7 @@ function toAbsoluteWebSocketUri(uri: string) {
   // Scheme must be ws: or wss:
   return uri.replace(/^http/, 'ws');
 }
+
+function reloadNow() {
+  location.reload();
+}
\ No newline at end of file