import { mkdir, readFile, writeFile } from "node:fs/promises";
import os from "node:os";
import path from "node:path";
import { randomUUID } from "node:crypto";

export type TelemetryBootstrap = {
	distinctId: string;
	appVersion: string;
	platform: NodeJS.Platform;
};

export function defaultDataDir(
	platform: NodeJS.Platform,
	env: Record<string, string | undefined>,
	homeDir: string,
): string | null {
	void platform;
	if (env.AO_DATA_DIR) return env.AO_DATA_DIR;
	if (!homeDir) return null;
	return path.join(homeDir, ".ao", "data");
}

export async function loadOrCreateTelemetryInstallId(dataDir: string): Promise<string> {
	const file = path.join(dataDir, "telemetry_install_id");
	try {
		const existing = (await readFile(file, "utf8")).trim();
		if (existing) return existing;
	} catch {
		// Create the id on first use.
	}
	await mkdir(dataDir, { recursive: true });
	const distinctId = `ins_${randomUUID()}`;
	await writeFile(file, `${distinctId}\n`, { mode: 0o600 });
	return distinctId;
}

export async function buildTelemetryBootstrap(
	env: Record<string, string | undefined>,
	appVersion: string,
	platform: NodeJS.Platform,
	homeDir = os.homedir(),
): Promise<TelemetryBootstrap | null> {
	const dataDir = defaultDataDir(platform, env, homeDir);
	if (!dataDir) return null;
	return {
		distinctId: await loadOrCreateTelemetryInstallId(dataDir),
		appVersion,
		platform,
	};
}