/**
 * Minimal Herdr socket client — one request, one reply, socket closed.
 *
 * Only what this extension needs (cell geometry and pane lookups). Frame
 * streaming is not used: images here are static, so they go through the
 * terminal's own graphics protocol rather than herdr's video path.
 */

import { connect } from "node:net";
import { homedir } from "node:os";
import { join } from "node:path";

export function herdrSocketPath(): string {
	const explicit = process.env.HERDR_SOCKET_PATH?.trim();
	if (explicit) return explicit;
	const session = process.env.HERDR_SESSION?.trim();
	const base = join(homedir(), ".config", "herdr");
	return session ? join(base, "sessions", session, "herdr.sock") : join(base, "herdr.sock");
}

export function isHerdrPane(): boolean {
	return process.env.HERDR_ENV === "1" && Boolean(process.env.HERDR_PANE_ID);
}

interface Envelope {
	result?: Record<string, unknown>;
	error?: { code?: string; message?: string };
}

export function herdrRequest(
	method: string,
	params: Record<string, unknown>,
	timeoutMs = 3_000,
): Promise<Record<string, unknown>> {
	return new Promise((resolve, reject) => {
		const sock = connect(herdrSocketPath());
		let buf = "";
		let settled = false;

		const done = (fn: () => void) => {
			if (settled) return;
			settled = true;
			clearTimeout(timer);
			sock.destroy();
			fn();
		};

		const timer = setTimeout(
			() => done(() => reject(new Error(`herdr ${method} timed out`))),
			timeoutMs,
		);

		sock.on("connect", () => {
			sock.write(`${JSON.stringify({ id: `wl-${method}`, method, params })}\n`);
		});
		sock.on("data", (chunk) => {
			buf += chunk.toString("utf-8");
			const nl = buf.indexOf("\n");
			if (nl < 0) return;
			let envelope: Envelope;
			try {
				envelope = JSON.parse(buf.slice(0, nl)) as Envelope;
			} catch {
				done(() => reject(new Error(`herdr ${method}: invalid JSON`)));
				return;
			}
			done(() => {
				if (envelope.error) {
					reject(new Error(envelope.error.message ?? `herdr ${method} failed`));
					return;
				}
				resolve(envelope.result ?? {});
			});
		});
		sock.on("error", (err) => done(() => reject(err)));
		sock.on("close", () => done(() => reject(new Error(`herdr ${method}: closed early`))));
	});
}