/**
 * Where an instance lives and what it is configured with.
 *
 *   %LOCALAPPDATA%\Vash\Broadcast\            (VASH_BROADCAST_HOME overrides)
 *     bin\vash-broadcast.exe                  the CLI, copied here by setup
 *     bin\vash-broadcast-worker.exe           the same program without a console window
 *     bin\vash-desktop.ps1                    desktop helper (windows, capture, OCR, input)
 *     downloads\                              verified archives, reused by every instance
 *     tourney.lock                            which instance runs osu!tourney + tosu now
 *     instances\<name>\
 *       config.json                           server, channel, token, ports, options
 *       obs\ osu\ tosu\ ffmpeg\               this instance's own copies of each program
 *       hls\ logs\ snapshots\                 recording scratch, logs, diagnostics
 *       state.json runtime.json               what the worker is doing; how to reach it
 *
 * Every program an instance runs lives under its own folder, so stopping one
 * instance can find and stop exactly its processes and nothing else.
 */
import { randomBytes } from 'node:crypto';
import { existsSync } from 'node:fs';
import { mkdir, readdir, readFile, rename, writeFile } from 'node:fs/promises';
import { homedir } from 'node:os';
import { join } from 'node:path';

export const VERSION = '0.1.0';

export function rootDir() {
	if (process.env.VASH_BROADCAST_HOME) return process.env.VASH_BROADCAST_HOME;
	if (process.platform === 'win32')
		return join(
			process.env.LOCALAPPDATA ?? join(homedir(), 'AppData', 'Local'),
			'Vash',
			'Broadcast'
		);
	return join(process.env.XDG_DATA_HOME ?? join(homedir(), '.local', 'share'), 'vash-broadcast');
}

export const INSTANCE_NAME = /^[a-z][a-z0-9-]{0,19}$/;

export function instanceDir(name: string) {
	if (!INSTANCE_NAME.test(name))
		throw new Error(
			`Instance names are 1–20 lowercase letters, digits or dashes, starting with a letter (got "${name}")`
		);
	return join(rootDir(), 'instances', name);
}

/** Paths inside an instance folder. */
export function layout(name: string) {
	const dir = instanceDir(name);
	const root = rootDir();
	return {
		root,
		dir,
		config: join(dir, 'config.json'),
		state: join(dir, 'state.json'),
		runtime: join(dir, 'runtime.json'),
		request: join(dir, 'request.json'),
		login: join(dir, 'login.json'),
		doctor: join(dir, 'doctor.json'),
		logs: join(dir, 'logs'),
		log: join(dir, 'logs', 'worker.log'),
		snapshots: join(dir, 'snapshots'),
		hls: join(dir, 'hls'),
		obs: join(dir, 'obs'),
		obsExe: join(dir, 'obs', 'bin', '64bit', 'obs64.exe'),
		obsConfig: join(dir, 'obs', 'config', 'obs-studio'),
		osu: join(dir, 'osu'),
		osuExe: join(dir, 'osu', 'osu!.exe'),
		tosu: join(dir, 'tosu'),
		tosuExe: join(dir, 'tosu', 'tosu.exe'),
		ffmpeg: join(dir, 'ffmpeg', process.platform === 'win32' ? 'ffmpeg.exe' : 'ffmpeg'),
		bin: join(root, 'bin'),
		cliExe: join(root, 'bin', 'vash-broadcast.exe'),
		workerExe: join(root, 'bin', 'vash-broadcast-worker.exe'),
		helperScript: join(root, 'bin', 'vash-desktop.ps1'),
		downloads: join(root, 'downloads'),
		lock: join(root, 'tourney.lock')
	};
}

export type Layout = ReturnType<typeof layout>;

export interface Ports {
	/** The worker's local control API (status, stop, snapshots). */
	control: number;
	/** obs-websocket of this instance's OBS. */
	obs: number;
	/** tosu's HTTP/websocket server. */
	tosu: number;
	/** RTMP ingest OBS streams into; the relay records and restreams it. */
	ingest: number;
	/** The one-time sign-in screen viewer. */
	viewer: number;
	/** Local overlay proxy for sites behind Cloudflare Access (OBS cannot send its headers). */
	proxy: number;
}

export interface InstanceConfig {
	version: 1;
	name: string;
	/** The Vash site, e.g. https://esports.vash.software */
	server: string;
	channel: string;
	/** The channel's agent token (Broadcast page → Agent token). */
	token: string;
	/** Cloudflare Access service token for sites behind Access (dev, staging). */
	access: { clientId: string; clientSecret: string } | null;
	ports: Ports;
	obsPassword: string;
	ingestKey: string;
	/** Where osu!.exe was copied from for this instance's separate tourney installation. */
	osuSource: string | null;
	/** osu!tourney's streamable height (tournament.cfg Height); the window is ~200 px taller. */
	tourneyHeight: number;
	/** 'amd' asks OBS for AMD AMF hardware encoding; 'x264' chooses software encoding on purpose. */
	encoder: 'amd' | 'x264';
	/** Start the worker when this Windows user signs in. */
	autostart: boolean;
}

const PORT_BASE = 47100;
const PORT_STEP = 10;

export function portsForSlot(slot: number): Ports {
	const base = PORT_BASE + slot * PORT_STEP;
	return {
		control: base,
		obs: base + 1,
		tosu: base + 2,
		ingest: base + 3,
		viewer: base + 4,
		proxy: base + 5
	};
}

/** The first port block no other instance uses. */
export function allocatePorts(taken: Ports[]): Ports {
	const used = new Set(taken.map((ports) => ports.control));
	for (let slot = 0; slot < 50; slot++) {
		const ports = portsForSlot(slot);
		if (!used.has(ports.control)) return ports;
	}
	throw new Error('No free port block for another instance');
}

export const secret = (bytes = 18) => randomBytes(bytes).toString('base64url');

export function validateServer(server: string) {
	let url: URL;
	try {
		url = new URL(server);
	} catch {
		throw new Error(`--server must be a URL like https://esports.vash.software (got "${server}")`);
	}
	if (url.protocol !== 'https:' && !['127.0.0.1', 'localhost'].includes(url.hostname))
		throw new Error('--server must use https:// (plain http only for localhost)');
	return url.origin;
}

const UUID = /^[0-9a-f]{8}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{12}$/;

export function validateConfig(value: unknown): InstanceConfig {
	const config = value as InstanceConfig;
	const problems: string[] = [];
	if (!config || typeof config !== 'object') throw new Error('config.json is not an object');
	if (config.version !== 1) problems.push('unknown config version');
	if (!INSTANCE_NAME.test(config.name ?? '')) problems.push('bad instance name');
	try {
		validateServer(config.server);
	} catch (err) {
		problems.push((err as Error).message);
	}
	if (!UUID.test(config.channel ?? '')) problems.push('channel must be the channel id (a UUID)');
	if (typeof config.token !== 'string' || !config.token) problems.push('missing agent token');
	for (const key of ['control', 'obs', 'tosu', 'ingest', 'viewer', 'proxy'] as const)
		if (!Number.isInteger(config.ports?.[key])) problems.push(`missing ${key} port`);
	if (!config.obsPassword || !config.ingestKey) problems.push('missing generated secrets');
	if (!(config.tourneyHeight >= 568 && config.tourneyHeight <= 2160))
		problems.push('tourneyHeight must be 568–2160');
	if (config.encoder !== 'amd' && config.encoder !== 'x264')
		problems.push('encoder must be amd or x264');
	if (problems.length) throw new Error(`Invalid instance config: ${problems.join('; ')}`);
	return config;
}

export async function loadConfig(name: string): Promise<InstanceConfig> {
	const path = layout(name).config;
	if (!existsSync(path))
		throw new Error(
			`Instance "${name}" is not set up. Run: vash-broadcast setup --instance ${name} …`
		);
	return validateConfig(JSON.parse(await readFile(path, 'utf8')));
}

export async function listInstances(): Promise<InstanceConfig[]> {
	const dir = join(rootDir(), 'instances');
	const names = await readdir(dir).catch(() => [] as string[]);
	const configs: InstanceConfig[] = [];
	for (const name of names) {
		if (!INSTANCE_NAME.test(name)) continue;
		try {
			configs.push(await loadConfig(name));
		} catch {
			/* half-set-up instance; ignore */
		}
	}
	return configs;
}

/** Writes JSON through a temporary file so readers never see half a file. */
export async function writeJson(path: string, value: unknown) {
	await mkdir(join(path, '..'), { recursive: true });
	const temp = `${path}.${process.pid}.tmp`;
	await writeFile(temp, JSON.stringify(value, null, '\t'));
	await rename(temp, path);
}

export async function readJson<T>(path: string): Promise<T | null> {
	try {
		return JSON.parse(await readFile(path, 'utf8')) as T;
	} catch {
		return null;
	}
}

export async function saveConfig(config: InstanceConfig) {
	await writeJson(layout(config.name).config, validateConfig(config));
}

/** Headers for a site behind Cloudflare Access. */
export function accessHeaders(config: InstanceConfig): Record<string, string> {
	return config.access
		? {
				'CF-Access-Client-Id': config.access.clientId,
				'CF-Access-Client-Secret': config.access.clientSecret
			}
		: {};
}