import * as fs from "node:fs";
import * as path from "node:path";

export type Issue12ObserverEvent =
	| { kind: "worker_check_fired"; token: string }
	| { kind: "wake_sent"; messageId: string }
	| { kind: "assistant_provider"; messageId: string }
	| { kind: "agent_settled"; messageId: string }
	| { kind: "worker_check_rearmed"; token: string };

/**
 * Append one real-time observer fact. The proof observer calls this at the point it
 * sees the corresponding durable/session transition; the metrics extractor later
 * validates these facts against the archived wake records and raw parent session.
 */
export function appendIssue12ObserverEvent(file: string, event: Issue12ObserverEvent, now = Date.now()): void {
	fs.mkdirSync(path.dirname(file), { recursive: true, mode: 0o700 });
	fs.appendFileSync(file, `${JSON.stringify({ ...event, observedAt: new Date(now).toISOString() })}\n`, {
		encoding: "utf8",
		mode: 0o600,
	});
}