import { readFile, unlink, writeFile } from "node:fs/promises";
import type { ApiAccount, ApiSchedule, ApiSubscription } from "~/shared/types/api";
import { generateDemoSchedule, generateDemoAccounts } from "./generate-demo-schedule";

export interface ServerSession {
	id: number,
	accountId: number,
};

// 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 accountsPath = "data/accounts.json";
const nextAccountIdPath = "data/next-account-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 deleteDatbase() {
	await remove(schedulePath);
	await remove(subscriptionsPath);
	await remove(accountsPath);
	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, generateDemoSchedule);
}

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 nextAccountId() {
	let nextId = await readJson(nextAccountIdPath, 0);
	if (nextId === 0) {
		nextId = Math.max(...(await readAccounts()).map(account => account.id), -1) + 1;
	}
	await writeFile(nextAccountIdPath, String(nextId + 1), "utf-8");
	return nextId;
}

export async function readAccounts() {
	return await readJson(accountsPath, generateDemoAccounts);
}

export async function writeAccounts(accounts: ApiAccount[]) {
	await writeFile(accountsPath, JSON.stringify(accounts, undefined, "\t") + "\n", "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() {
	return await readJson<ServerSession[]>(sessionsPath, []);
}

export async function writeSessions(sessions: ServerSession[]) {
	await writeFile(sessionsPath, JSON.stringify(sessions, undefined, "\t") + "\n", "utf-8");
}