1 files changed, 81 insertions, 0 deletions
diff --git a/src/hot_reload.js b/src/hot_reload.js
new file mode 100644
index 0000000..0777380
--- /dev/null
+++ b/src/hot_reload.js
@@ -0,0 +1,81 @@
+const WS_RETRY_MS = 1_000;
+
+function refetchCSS(file) {
+  const node = Array.from(document.head.childNodes).find(
+    (n) => n.href && n.href.includes(file),
+  );
+  if (!node) {
+    console.warn("Could not find node", file);
+    console.log(Array.from(document.head.childNodes));
+    return;
+  }
+  const url = new URL(node.href);
+  url.searchParams.set("v", parseInt(url.searchParams.get("v") || "0") + 1);
+
+  const n2 = node.cloneNode();
+  n2.href = url.toString();
+  document.head.appendChild(n2);
+  setTimeout(() => {
+    document.head.removeChild(node);
+  }, 100);
+}
+
+let __file_to_module = {};
+function refetchJS(file) {
+  if (file in __file_to_module) {
+    const o = __file_to_module[file];
+    if ("__cleanup" in o) {
+      o.__cleanup();
+    } else {
+      console.warn("no cleanup");
+    }
+  }
+  import(`/static/${file}?v=${Date.now()}`)
+    .then((m) => {
+      __file_to_module[file] = m;
+    })
+    .catch((e) => {
+      console.error(e);
+    });
+  return;
+}
+
+function connect() {
+  console.log("try to connect through websocket");
+  const ws = new WebSocket(`ws://${window.location.host}/dev-hr/ws`);
+
+  const file2timeout = new Map();
+  ws.addEventListener("message", (msg) => {
+    const file = msg.data; // the path to a changed file relative to `static/`.
+    if (file2timeout.has(file)) clearTimeout(file2timeout.get(file));
+    file2timeout.set(
+      file,
+      setTimeout(() => {
+        if (file.slice(-4) === ".css") refetchCSS(file);
+        else if (file.slice(-3) === ".js") refetchJS(file);
+        else console.warn("unknown file extension", file);
+      }, 100),
+    );
+  });
+
+  ws.addEventListener("open", () => {
+    console.log("websocket connected");
+  });
+
+  ws.addEventListener("close", () => {
+    console.log("websocket disconnected");
+    setTimeout(() => {
+      try {
+        connect();
+      } catch (e) {
+        console.error(e);
+      }
+    }, WS_RETRY_MS);
+  });
+
+  ws.addEventListener("error", (e) => {
+    console.error(e);
+    ws.close();
+  });
+}
+setTimeout(() => connect(), WS_RETRY_MS);