From 6bca176bb61f1f8b8128078117ebc8dce83a7bfd Mon Sep 17 00:00:00 2001
From: Marvin Hagemeister <marvin@deno.com>
Date: Mon, 6 Nov 2023 10:31:51 +0100
Subject: [PATCH] chore: refactor dev client (#2002)

(cherry picked from commit 4fa0a637f0e57a6e8040de69bdc753eb17cf8258)
---
 src/runtime/entrypoints/client.ts | 32 ++++++++++++++++++-------------
 src/server/context.ts             | 19 +++++++++++++++++-
 2 files changed, 37 insertions(+), 14 deletions(-)

diff --git a/src/runtime/entrypoints/client.ts b/src/runtime/entrypoints/client.ts
index 21d1a656143..d3d6f7769f4 100644
--- a/src/runtime/entrypoints/client.ts
+++ b/src/runtime/entrypoints/client.ts
@@ -1,4 +1,5 @@
 let ws: WebSocket;
+let revision = 0;
 
 let reconnectTimer: number;
 const backoff = [
@@ -36,7 +37,7 @@ function reconnect() {
     backoffIdx++;
 
     try {
-      connect(true);
+      connect();
       clearTimeout(reconnectTimer);
     } catch (_err) {
       reconnect();
@@ -44,23 +45,19 @@ function reconnect() {
   }, backoff[Math.min(backoffIdx, backoff.length - 1)]);
 }
 
-function connect(forceReload?: boolean) {
+function connect() {
   const url = new URL("/_frsh/alive", location.origin.replace("http", "ws"));
   ws = new WebSocket(
     url,
   );
 
   ws.addEventListener("open", () => {
-    if (forceReload) {
-      location.reload();
-    } else {
-      backoffIdx = 0;
-      console.log(
-        `%c Fresh %c Connected to development server.`,
-        "background-color: #86efac; color: black",
-        "color: inherit",
-      );
-    }
+    backoffIdx = 0;
+    console.log(
+      `%c Fresh %c Connected to development server.`,
+      "background-color: #86efac; color: black",
+      "color: inherit",
+    );
   });
 
   ws.addEventListener("close", () => {
@@ -75,7 +72,16 @@ connect();
 
 function handleMessage(e: MessageEvent) {
   const data = JSON.parse(e.data);
-  console.log(data);
+  switch (data.type) {
+    case "initial-state": {
+      if (revision === 0) {
+        revision = data.revision;
+      } else if (revision < data.revision) {
+        // Needs reload
+        location.reload();
+      }
+    }
+  }
 }
 
 function handleError(e: Event) {
diff --git a/src/server/context.ts b/src/server/context.ts
index 155d316f1e3..23d1e75ba8d 100644
--- a/src/server/context.ts
+++ b/src/server/context.ts
@@ -413,6 +413,7 @@ export class ServerContext {
   #plugins: Plugin[];
   #builder: Builder | Promise<BuildSnapshot> | BuildSnapshot;
   #routerOptions: RouterOptions;
+  #revision = 0;
 
   constructor(
     routes: Route[],
@@ -493,6 +494,13 @@ export class ServerContext {
     const isDev = this.#dev;
     const bundleAssetRoute = this.#bundleAssetRoute();
 
+    if (this.#dev) {
+      this.#revision = Date.now();
+    }
+
+    // deno-lint-ignore no-this-alias
+    const _self = this;
+
     return async function handler(
       req: Request,
       connInfo: ServeHandlerInfo = DEFAULT_CONN_INFO,
@@ -511,7 +519,16 @@ export class ServerContext {
           // the client to know when the server is back up. Once we
           // have HMR we'll actively start sending messages back
           // and forth.
-          const { response } = Deno.upgradeWebSocket(req);
+          const { response, socket } = Deno.upgradeWebSocket(req);
+
+          socket.addEventListener("open", () => {
+            socket.send(
+              JSON.stringify({
+                type: "initial-state",
+                revision: _self.#revision,
+              }),
+            );
+          });
 
           return response;
         } else if (url.pathname === DEV_CLIENT_URL) {