import { readFileSync, writeFileSync, existsSync } from 'fs';

export function load_mail_perms(file_path) {
	let allowed = [];

	if (file_path && existsSync(file_path)) {
		try {
			const parsed = JSON.parse(readFileSync(file_path, 'utf8'));
			if (!Array.isArray(parsed.allowed)) {
				throw new Error("'allowed' must be an array");
			}
			allowed = parsed.allowed;
		} catch (err) {
			throw new Error(`Cannot load mail permissions from ${file_path}: ${err.message}`);
		}
	}

	function write() {
		if (!file_path) {
			return;
		}
		writeFileSync(file_path, JSON.stringify({ allowed }, null, '\t') + '\n', 'utf8');
	}

	function check(user, to, topic) {
		return allowed.some(e => e.user === user && e.to === to && (e.topic === topic || e.topic === null));
	}

	function add(user, to, topic) {
		if (!check(user, to, topic)) {
			allowed.push({ user, to, topic });
			write();
		}
	}

	function remove(user, to, topic) {
		const before = allowed.length;
		allowed = allowed.filter(e => !(e.user === user && e.to === to && e.topic === topic));
		if (allowed.length !== before) {
			write();
		}
	}

	function list() {
		return [...allowed];
	}

	return { check, add, remove, list };
}