feat(cdp): port DevToolsActivePort discovery to Result

1 files changed, 91 insertions, 0 deletions

diff --git a/src/cdp/discovery.ts b/src/cdp/discovery.ts
new file mode 100644
index 0000000..1b33bee
--- /dev/null
+++ b/src/cdp/discovery.ts
@@ -0,0 +1,91 @@
+import { readFile } from "node:fs/promises";
+import { homedir } from "node:os";
+import { join } from "node:path";
+import { connect as netConnect } from "node:net";
+import { type Result, err, ok } from "../util/result";
+import { type CdpError, cdpError } from "./errors";
+
+const PORT_PROBE_DEADLINE_MS = 30_000;
+const PORT_PROBE_INTERVAL_MS = 1_000;
+
+const profileDirs = (): ReadonlyArray<string> => {
+  const home = homedir();
+  return [
+    join(home, "Library/Application Support/Google/Chrome"),
+    join(home, "Library/Application Support/Microsoft Edge"),
+    join(home, "Library/Application Support/Microsoft Edge Beta"),
+    join(home, "Library/Application Support/Microsoft Edge Dev"),
+    join(home, "Library/Application Support/Microsoft Edge Canary"),
+    join(home, ".config/google-chrome"),
+    join(home, ".config/chromium"),
+    join(home, ".config/chromium-browser"),
+    join(home, ".config/microsoft-edge"),
+    join(home, ".config/microsoft-edge-beta"),
+    join(home, ".config/microsoft-edge-dev"),
+    join(home, ".var/app/org.chromium.Chromium/config/chromium"),
+    join(home, ".var/app/com.google.Chrome/config/google-chrome"),
+    join(home, ".var/app/com.brave.Browser/config/BraveSoftware/Brave-Browser"),
+    join(home, ".var/app/com.microsoft.Edge/config/microsoft-edge"),
+    join(home, "AppData/Local/Google/Chrome/User Data"),
+    join(home, "AppData/Local/Chromium/User Data"),
+    join(home, "AppData/Local/Microsoft/Edge/User Data"),
+    join(home, "AppData/Local/Microsoft/Edge Beta/User Data"),
+    join(home, "AppData/Local/Microsoft/Edge Dev/User Data"),
+    join(home, "AppData/Local/Microsoft/Edge SxS/User Data"),
+  ];
+};
+
+const probePort = (port: number): Promise<Result<void, CdpError>> =>
+  new Promise((resolve) => {
+    const sock = netConnect({ host: "127.0.0.1", port });
+    const finish = (r: Result<void, CdpError>): void => {
+      sock.destroy();
+      resolve(r);
+    };
+    sock.setTimeout(1000, () => finish(err(cdpError("discovery_failed", "probe timeout"))));
+    sock.once("error", (e) => finish(err(cdpError("discovery_failed", e.message))));
+    sock.once("connect", () => {
+      sock.end();
+      resolve(ok(undefined));
+    });
+  });
+
+const waitForPort = async (port: number): Promise<Result<void, CdpError>> => {
+  const end = Date.now() + PORT_PROBE_DEADLINE_MS;
+  let lastMessage = "unknown";
+  while (Date.now() < end) {
+    const probe = await probePort(port);
+    if (probe.success) return probe;
+    lastMessage = probe.error.message;
+    await new Promise((r) => setTimeout(r, PORT_PROBE_INTERVAL_MS));
+  }
+  return err(cdpError(
+    "discovery_failed",
+    `Chrome's remote-debugging page is open, but DevTools is not live yet on 127.0.0.1:${port} — if Chrome opened a profile picker, choose your normal profile first, then tick the checkbox and click Allow if shown (last error: ${lastMessage})`,
+  ));
+};
+
+export const discoverWsUrl = async (): Promise<Result<string, CdpError>> => {
+  const dirs = profileDirs();
+  for (const base of dirs) {
+    const portFile = join(base, "DevToolsActivePort");
+    let raw: string;
+    try {
+      raw = await readFile(portFile, "utf8");
+    } catch {
+      continue;
+    }
+    const lines = raw.trim().split("\n");
+    if (lines.length < 2) continue;
+    const port = lines[0]?.trim();
+    const path = lines[1]?.trim();
+    if (!port || !path) continue;
+    const ready = await waitForPort(Number(port));
+    if (!ready.success) return ready;
+    return ok(`ws://127.0.0.1:${port}${path}`);
+  }
+  return err(cdpError(
+    "discovery_failed",
+    `DevToolsActivePort not found in ${dirs.join(", ")} — open chrome://inspect/#remote-debugging in your browser, tick the checkbox, click Allow, then retry. Or set BU_CDP_WS to a remote browser endpoint.`,
+  ));
+};