/*
	SPDX-FileCopyrightText: © 2025 Hornwitser <code@hornwitser.no>
	SPDX-License-Identifier: AGPL-3.0-or-later
*/
import { readFile, unlink, writeFile } from "node:fs/promises";
import type { ApiSchedule, ApiSubscription, ApiUserType } from "~/shared/types/api";
import type { Id } from "~/shared/types/common";

export interface ServerSession {
	id: number,
	account: ServerUser,
};

interface StoredSession {
	id: number,
	accountId: number,
}

export interface ServerUser {
	id: Id,
	updatedAt: string,
	deleted?: boolean,
	type: ApiUserType,
	name?: string,
	interestedEventIds?: number[],
	interestedEventSlotIds?: number[],
	timezone?: string,
	locale?: string,
}

// For this demo I'm just storing the runtime data in JSON files. When making
// this into proper application this should be replaced with an actual database.

const schedulePath = "data/schedule.json";
const subscriptionsPath = "data/subscriptions.json";
const usersPath = "data/users.json";
const nextUserIdPath = "data/next-user-id.json";
const sessionsPath = "data/sessions.json";
const nextSessionIdPath = "data/next-session-id.json";

async function remove(path: string) {
	try {
		await unlink(path);
	} catch (err: any) {
		if (err.code !== "ENOENT") {
			throw err;
		}
	}
}

export async function deleteDatabase() {
	await remove(schedulePath);
	await remove(subscriptionsPath);
	await remove(usersPath);
	await remove(sessionsPath);
}

async function readJson<T>(filePath: string, fallback: T) {
	let data: T extends () => infer R ? R : T;
	try {
		data = JSON.parse(await readFile(filePath, "utf-8"));
	} catch (err: any) {
		if (err.code !== "ENOENT")
			throw err;
		data = typeof fallback === "function" ? fallback() : fallback;
	}
	return data;
}

export async function readSchedule() {
	return readJson(schedulePath, (): ApiSchedule => ({
		id: 111,
		updatedAt: new Date().toISOString(),
	}));
}

export async function writeSchedule(schedule: ApiSchedule) {
	await writeFile(schedulePath, JSON.stringify(schedule, undefined, "\t") + "\n", "utf-8");
}

export async function readSubscriptions() {
	let subscriptions = await readJson<ApiSubscription[]>(subscriptionsPath, []);
	if (subscriptions.length && "keys" in subscriptions[0]) {
		// Discard old format
		subscriptions = [];
	}
	return subscriptions;
}

export async function writeSubscriptions(subscriptions: ApiSubscription[]) {
	await writeFile(subscriptionsPath, JSON.stringify(subscriptions, undefined, "\t") + "\n", "utf-8");
}

export async function readNextUserId() {
	return await readJson(nextUserIdPath, 0);
}

export async function writeNextUserId(nextId: number) {
	await writeFile(nextUserIdPath, String(nextId), "utf-8");
}

export async function nextUserId() {
	let nextId = await readJson(nextUserIdPath, 0);
	if (nextId === 0) {
		nextId = Math.max(...(await readUsers()).map(user => user.id), -1) + 1;
	}
	await writeFile(nextUserIdPath, String(nextId + 1), "utf-8");
	return nextId;
}

export async function readUsers() {
	return await readJson(usersPath, (): ServerUser[] => []);
}

export async function writeUsers(users: ServerUser[]) {
	await writeFile(usersPath, JSON.stringify(users, undefined, "\t") + "\n", "utf-8");
}

export async function readNextSessionId() {
	return await readJson(nextSessionIdPath, 0);
}

export async function writeNextSessionId(nextId: number) {
	await writeFile(nextSessionIdPath, String(nextId), "utf-8");
}

export async function nextSessionId() {
	const nextId = await readJson(nextSessionIdPath, 0);
	await writeFile(nextSessionIdPath, String(nextId + 1), "utf-8");
	return nextId;
}

export async function readSessions() {
	const users = await readUsers();
	const sessions: ServerSession[] = [];
	for (const stored of await readJson<StoredSession[]>(sessionsPath, [])) {
		const user = users.find(user => user.id === stored.accountId);
		if (user) {
			sessions.push({
				id: stored.id,
				account: user,
			});
		}
	}
	return sessions;
}

export async function writeSessions(sessions: ServerSession[]) {
	const stored: StoredSession[] = sessions.map(
		session => ({
			id: session.id,
			accountId: session.account.id,
		}),
	);
	await writeFile(sessionsPath, JSON.stringify(stored, undefined, "\t") + "\n", "utf-8");
}