import { readFileSync } from 'fs';
import { resolve } from 'path';

export function load_config(file_path) {
	if (!file_path) {
		throw new Error('--config <path> is required');
	}
	let raw;
	try {
		raw = readFileSync(file_path, 'utf8');
	} catch (err) {
		throw new Error(`Cannot read config file at ${file_path}: ${err.message}`);
	}
	let parsed;
	try {
		parsed = JSON.parse(raw);
	} catch (err) {
		throw new Error(`Config file is not valid JSON: ${err.message}`);
	}

	if (!parsed.secrets) {
		throw new Error("Config file must have a 'secrets' field pointing to the secrets file");
	}

	// Resolve secrets path relative to the config file's directory
	const config_dir = resolve(file_path, '..');
	const secrets_path = resolve(config_dir, parsed.secrets);

	let secrets_raw;
	try {
		secrets_raw = readFileSync(secrets_path, 'utf8');
	} catch (err) {
		throw new Error(`Cannot read secrets file at ${secrets_path}: ${err.message}`);
	}
	let secrets;
	try {
		secrets = JSON.parse(secrets_raw);
	} catch (err) {
		throw new Error(`Secrets file is not valid JSON: ${err.message}`);
	}
	if (!secrets.users || typeof secrets.users !== 'object') {
		throw new Error("Secrets file must have a top-level 'users' object");
	}

	const mail_perms_path = parsed.mail_perms
		? resolve(config_dir, parsed.mail_perms)
		: null;

	return {
		users:          secrets.users,
		smtp:           parsed.smtp ?? null,
		mail_perms_path,
		bind:           parsed.bind ?? null,
		port:           parsed.port ?? null,
	};
}