1 files changed, 84 insertions, 0 deletions
diff --git a/src/cdp/endpoint.ts b/src/cdp/endpoint.ts
new file mode 100644
index 0000000..1be5322
--- /dev/null
+++ b/src/cdp/endpoint.ts
@@ -0,0 +1,84 @@
+/**
+ * Which browser this harness should drive.
+ *
+ * Upstream only ever drives a browser on localhost. This fork adds a remote
+ * target so pi can drive a shared Chrome on another host (see FORK.md).
+ *
+ * Resolution is pure — no I/O — so the status command can report the configured
+ * intent without touching the network, and the daemon can resolve the same way
+ * in its own process.
+ */
+
+/** Default remote CDP endpoint: castle's Chrome, exposed on the wire network. */
+export const DEFAULT_REMOTE_CDP = "10.88.0.25:9223";
+
+/** Values of BU_CDP_HTTP that mean "ignore the default, use this machine". */
+const LOCAL_ALIASES = new Set(["local", "localhost", "off", "none", "0", "no"]);
+
+export type CdpTarget =
+  | {
+      readonly kind: "remote";
+      readonly host: string;
+      readonly port: number;
+      /** "env" was asked for explicitly; "default" is this fork's built-in. */
+      readonly source: "env" | "default";
+    }
+  | { readonly kind: "local"; readonly source: "env" }
+  | { readonly kind: "invalid"; readonly raw: string; readonly reason: string };
+
+/**
+ * Precedence:
+ *   BU_CDP_HTTP="host:port"  -> that remote, and a failure to reach it is fatal
+ *   BU_CDP_HTTP=local|off|…  -> upstream behaviour, this machine's own browser
+ *   unset                    -> DEFAULT_REMOTE_CDP, falling back to local when
+ *                               it isn't reachable
+ *
+ * The asymmetry is deliberate. An explicit endpoint is an instruction, so
+ * silently driving a different browser instead would be wrong. The built-in
+ * default is only a preference, so a laptop away from the wire network still
+ * gets the local browser the extension was originally written for.
+ */
+export const resolveCdpTarget = (env: NodeJS.ProcessEnv = process.env): CdpTarget => {
+  const raw = env["BU_CDP_HTTP"]?.trim();
+
+  if (raw === undefined || raw === "") {
+    const parsed = parseHostPort(DEFAULT_REMOTE_CDP);
+    // Unreachable in practice: the constant above is validated by its own test.
+    if (!parsed) return { kind: "local", source: "env" };
+    return { kind: "remote", host: parsed.host, port: parsed.port, source: "default" };
+  }
+
+  if (LOCAL_ALIASES.has(raw.toLowerCase())) return { kind: "local", source: "env" };
+
+  const parsed = parseHostPort(raw);
+  if (!parsed) {
+    return {
+      kind: "invalid",
+      raw,
+      reason: `expected "host:port" or one of ${[...LOCAL_ALIASES].join(", ")}`,
+    };
+  }
+  return { kind: "remote", host: parsed.host, port: parsed.port, source: "env" };
+};
+
+const parseHostPort = (value: string): { host: string; port: number } | null => {
+  const sep = value.lastIndexOf(":");
+  if (sep === -1) return null;
+  const host = value.slice(0, sep).trim();
+  const port = Number(value.slice(sep + 1).trim());
+  if (!host) return null;
+  if (!Number.isInteger(port) || port <= 0 || port >= 65536) return null;
+  return { host, port };
+};
+
+/** One-line description for /browser-status and error messages. */
+export const describeCdpTarget = (target: CdpTarget): string => {
+  switch (target.kind) {
+    case "remote":
+      return `${target.host}:${target.port}` + (target.source === "default" ? " (built-in default)" : " (BU_CDP_HTTP)");
+    case "local":
+      return "this machine's own browser (BU_CDP_HTTP=local)";
+    case "invalid":
+      return `invalid BU_CDP_HTTP "${target.raw}" — ${target.reason}`;
+  }
+};