Gateway: optional canvas host

src/canvas-host/server.ts

@@ -0,0 +1,247 @@
+import fs from "node:fs/promises";
+import http, { type Server } from "node:http";
+import os from "node:os";
+import path from "node:path";
+
+import chokidar from "chokidar";
+import express from "express";
+import { type WebSocket, WebSocketServer } from "ws";
+import type { BridgeBindMode } from "../config/config.js";
+import { pickPrimaryTailnetIPv4 } from "../infra/tailnet.js";
+import { detectMime } from "../media/mime.js";
+import type { RuntimeEnv } from "../runtime.js";
+import { ensureDir, resolveUserPath } from "../utils.js";
+
+export type CanvasHostOpts = {
+  runtime: RuntimeEnv;
+  rootDir?: string;
+  port?: number;
+  bind?: BridgeBindMode;
+  allowInTests?: boolean;
+};
+
+export type CanvasHostServer = {
+  port: number;
+  rootDir: string;
+  close: () => Promise<void>;
+};
+
+const WS_PATH = "/__clawdis/ws";
+
+export function injectCanvasLiveReload(html: string): string {
+  const snippet = `
+<script>
+(() => {
+  try {
+    const proto = location.protocol === "https:" ? "wss" : "ws";
+    const ws = new WebSocket(proto + "://" + location.host + ${JSON.stringify(WS_PATH)});
+    ws.onmessage = (ev) => {
+      if (String(ev.data || "") === "reload") location.reload();
+    };
+  } catch {}
+})();
+</script>
+`.trim();
+
+  const idx = html.toLowerCase().lastIndexOf("</body>");
+  if (idx >= 0) {
+    return `${html.slice(0, idx)}\n${snippet}\n${html.slice(idx)}`;
+  }
+  return `${html}\n${snippet}\n`;
+}
+
+function normalizeUrlPath(rawPath: string): string {
+  const decoded = decodeURIComponent(rawPath || "/");
+  const normalized = path.posix.normalize(decoded);
+  return normalized.startsWith("/") ? normalized : `/${normalized}`;
+}
+
+async function resolveFilePath(rootReal: string, urlPath: string) {
+  const normalized = normalizeUrlPath(urlPath);
+  const rel = normalized.replace(/^\/+/, "");
+  if (rel.split("/").some((p) => p === "..")) return null;
+
+  let candidate = path.join(rootReal, rel);
+  if (normalized.endsWith("/")) {
+    candidate = path.join(candidate, "index.html");
+  }
+
+  try {
+    const st = await fs.stat(candidate);
+    if (st.isDirectory()) {
+      candidate = path.join(candidate, "index.html");
+    }
+  } catch {
+    // ignore
+  }
+
+  const rootPrefix = rootReal.endsWith(path.sep)
+    ? rootReal
+    : `${rootReal}${path.sep}`;
+  try {
+    const lstat = await fs.lstat(candidate);
+    if (lstat.isSymbolicLink()) return null;
+    const real = await fs.realpath(candidate);
+    if (!real.startsWith(rootPrefix)) return null;
+    return real;
+  } catch {
+    return null;
+  }
+}
+
+function resolveBindHost(bind: BridgeBindMode | undefined): string | null {
+  const mode = bind ?? "lan";
+  if (mode === "loopback") return "127.0.0.1";
+  if (mode === "lan") return "0.0.0.0";
+  if (mode === "auto") return "0.0.0.0";
+  if (mode === "tailnet") return pickPrimaryTailnetIPv4() ?? null;
+  return "0.0.0.0";
+}
+
+function isDisabledByEnv() {
+  if (process.env.CLAWDIS_SKIP_CANVAS_HOST === "1") return true;
+  if (process.env.NODE_ENV === "test") return true;
+  if (process.env.VITEST) return true;
+  return false;
+}
+
+export async function startCanvasHost(
+  opts: CanvasHostOpts,
+): Promise<CanvasHostServer> {
+  if (isDisabledByEnv() && opts.allowInTests !== true) {
+    return { port: 0, rootDir: "", close: async () => {} };
+  }
+
+  const rootDir = resolveUserPath(
+    opts.rootDir ?? path.join(os.homedir(), "clawd", "canvas"),
+  );
+  await ensureDir(rootDir);
+  const rootReal = await fs.realpath(rootDir);
+
+  const bindHost = resolveBindHost(opts.bind);
+  if (!bindHost) {
+    throw new Error(
+      "canvasHost.bind is tailnet, but no tailnet interface was found; refusing to start canvas host",
+    );
+  }
+
+  const app = express();
+  app.disable("x-powered-by");
+
+  app.get(/.*/, async (req, res) => {
+    try {
+      const url = new URL(req.url ?? "/", "http://localhost");
+      if (url.pathname === WS_PATH) {
+        res.status(426).send("upgrade required");
+        return;
+      }
+
+      const filePath = await resolveFilePath(rootReal, url.pathname);
+      if (!filePath) {
+        if (url.pathname === "/" || url.pathname.endsWith("/")) {
+          res
+            .status(404)
+            .type("text/html")
+            .send(
+              `<!doctype html><meta charset="utf-8" /><title>Clawdis Canvas</title><pre>Missing file.\nCreate ${rootDir}/index.html</pre>`,
+            );
+          return;
+        }
+        res.status(404).send("not found");
+        return;
+      }
+
+      const lower = filePath.toLowerCase();
+      const mime =
+        lower.endsWith(".html") || lower.endsWith(".htm")
+          ? "text/html"
+          : (detectMime({ filePath }) ?? "application/octet-stream");
+
+      res.setHeader("Cache-Control", "no-store");
+      if (mime === "text/html") {
+        const html = await fs.readFile(filePath, "utf8");
+        res.type("text/html; charset=utf-8").send(injectCanvasLiveReload(html));
+        return;
+      }
+
+      res.type(mime).send(await fs.readFile(filePath));
+    } catch (err) {
+      opts.runtime.error(`canvasHost request failed: ${String(err)}`);
+      res.status(500).send("error");
+    }
+  });
+
+  const server: Server = http.createServer(app);
+  const wss = new WebSocketServer({ server, path: WS_PATH });
+  const sockets = new Set<WebSocket>();
+  wss.on("connection", (ws) => {
+    sockets.add(ws);
+    ws.on("close", () => sockets.delete(ws));
+  });
+
+  let debounce: NodeJS.Timeout | null = null;
+  const broadcastReload = () => {
+    for (const ws of sockets) {
+      try {
+        ws.send("reload");
+      } catch {
+        // ignore
+      }
+    }
+  };
+  const scheduleReload = () => {
+    if (debounce) clearTimeout(debounce);
+    debounce = setTimeout(() => {
+      debounce = null;
+      broadcastReload();
+    }, 75);
+    debounce.unref?.();
+  };
+
+  const watcher = chokidar.watch(rootReal, {
+    ignoreInitial: true,
+    awaitWriteFinish: { stabilityThreshold: 75, pollInterval: 10 },
+    ignored: [
+      /(^|[\\/])\../, // dotfiles
+      /(^|[\\/])node_modules([\\/]|$)/,
+    ],
+  });
+  watcher.on("all", () => scheduleReload());
+
+  const listenPort =
+    typeof opts.port === "number" && Number.isFinite(opts.port) && opts.port > 0
+      ? opts.port
+      : 0;
+  await new Promise<void>((resolve, reject) => {
+    const onError = (err: NodeJS.ErrnoException) => {
+      server.off("listening", onListening);
+      reject(err);
+    };
+    const onListening = () => {
+      server.off("error", onError);
+      resolve();
+    };
+    server.once("error", onError);
+    server.once("listening", onListening);
+    server.listen(listenPort, bindHost);
+  });
+
+  const addr = server.address();
+  const boundPort = typeof addr === "object" && addr ? addr.port : 0;
+  opts.runtime.log(
+    `canvas host listening on http://${bindHost}:${boundPort} (root ${rootDir})`,
+  );
+
+  return {
+    port: boundPort,
+    rootDir,
+    close: async () => {
+      if (debounce) clearTimeout(debounce);
+      await watcher.close().catch(() => {});
+      await new Promise<void>((resolve) => wss.close(() => resolve()));
+      await new Promise<void>((resolve, reject) =>
+        server.close((err) => (err ? reject(err) : resolve())),
+      );
+    },
+  };
+}