/**
 * Server-side PocketBase client.
 * Uses admin credentials — never import this from client-side code.
 * All methods talk directly to PocketBase REST API.
 */

import { env } from '$env/dynamic/private';
import { log } from '$lib/server/logger';

const PB_URL = env.POCKETBASE_URL ?? 'http://localhost:8090';
const PB_EMAIL = env.POCKETBASE_ADMIN_EMAIL ?? 'admin@libnovel.local';
const PB_PASSWORD = env.POCKETBASE_ADMIN_PASSWORD ?? 'changeme123';

// ─── Types ────────────────────────────────────────────────────────────────────

export interface Book {
	id: string;
	slug: string;
	title: string;
	author: string;
	cover: string;
	status: string;
	genres: string[] | string;
	summary: string;
	total_chapters: number;
	source_url: string;
	ranking: number;
	meta_updated: string;
}

export interface ChapterIdx {
	id: string;
	slug: string;
	number: number;
	title: string;
	date_label: string;
}

export interface Progress {
	session_id: string;
	slug: string;
	chapter: number;
	updated: string;
}

export interface User {
	id: string;
	username: string;
	password_hash: string;
	role: string;
	created: string;
}

// ─── Auth token cache ─────────────────────────────────────────────────────────

let _token = '';
let _tokenExp = 0;

async function getToken(): Promise<string> {
	if (_token && Date.now() < _tokenExp) return _token;

	log.debug('pocketbase', 'authenticating with admin credentials', { url: PB_URL, email: PB_EMAIL });

	const res = await fetch(`${PB_URL}/api/collections/_superusers/auth-with-password`, {
		method: 'POST',
		headers: { 'Content-Type': 'application/json' },
		body: JSON.stringify({ identity: PB_EMAIL, password: PB_PASSWORD })
	});

	if (!res.ok) {
		const body = await res.text().catch(() => '');
		log.error('pocketbase', 'admin auth failed', { status: res.status, url: PB_URL, body });
		throw new Error(`PocketBase auth failed: ${res.status} — ${body}`);
	}

	const data = await res.json();
	_token = data.token as string;
	_tokenExp = Date.now() + 12 * 60 * 60 * 1000; // 12 hours
	log.info('pocketbase', 'admin auth token refreshed', { url: PB_URL });
	return _token;
}

// ─── Generic helpers ──────────────────────────────────────────────────────────

async function pbGet<T>(path: string): Promise<T> {
	const token = await getToken();
	const res = await fetch(`${PB_URL}${path}`, {
		headers: { Authorization: `Bearer ${token}` }
	});
	if (!res.ok) {
		const body = await res.text().catch(() => '');
		log.error('pocketbase', 'GET failed', { path, status: res.status, body });
		throw new Error(`PocketBase GET ${path} failed: ${res.status} — ${body}`);
	}
	return res.json() as Promise<T>;
}

async function pbPost(path: string, body: unknown): Promise<Response> {
	const token = await getToken();
	return fetch(`${PB_URL}${path}`, {
		method: 'POST',
		headers: { Authorization: `Bearer ${token}`, 'Content-Type': 'application/json' },
		body: JSON.stringify(body)
	});
}

async function pbPatch(path: string, body: unknown): Promise<Response> {
	const token = await getToken();
	return fetch(`${PB_URL}${path}`, {
		method: 'PATCH',
		headers: { Authorization: `Bearer ${token}`, 'Content-Type': 'application/json' },
		body: JSON.stringify(body)
	});
}

interface PBList<T> {
	items: T[];
	totalItems: number;
}

async function listAll<T>(collection: string, filter = '', sort = ''): Promise<T[]> {
	const params = new URLSearchParams({ perPage: '500' });
	if (filter) params.set('filter', filter);
	if (sort) params.set('sort', sort);
	const data = await pbGet<PBList<T>>(
		`/api/collections/${collection}/records?${params.toString()}`
	);
	return data.items ?? [];
}

async function listOne<T>(collection: string, filter: string): Promise<T | null> {
	const params = new URLSearchParams({ perPage: '1', filter });
	const data = await pbGet<PBList<T>>(
		`/api/collections/${collection}/records?${params.toString()}`
	);
	return data.items[0] ?? null;
}

// ─── Books ────────────────────────────────────────────────────────────────────

export async function listBooks(): Promise<Book[]> {
	const books = await listAll<Book>('books', '', '+title');
	const nullTitles = books.filter((b) => b.title == null).length;
	if (nullTitles > 0) {
		log.warn('pocketbase', 'listBooks: books with null title', { count: nullTitles, total: books.length });
	}
	log.debug('pocketbase', 'listBooks', { total: books.length, nullTitles });
	return books;
}

export async function getBook(slug: string): Promise<Book | null> {
	return listOne<Book>('books', `slug="${slug}"`);
}

// ─── Chapter index ────────────────────────────────────────────────────────────

export async function listChapterIdx(slug: string): Promise<ChapterIdx[]> {
	return listAll<ChapterIdx>('chapters_idx', `slug="${slug}"`, '+number');
}

// ─── Reading progress ─────────────────────────────────────────────────────────

export async function getProgress(sessionId: string, slug: string): Promise<Progress | null> {
	return listOne<Progress>('progress', `session_id="${sessionId}"&&slug="${slug}"`);
}

export async function allProgress(sessionId: string): Promise<Progress[]> {
	return listAll<Progress>('progress', `session_id="${sessionId}"`, '-updated');
}

export async function setProgress(sessionId: string, slug: string, chapter: number): Promise<void> {
	const existing = await listOne<Progress & { id: string }>(
		'progress',
		`session_id="${sessionId}"&&slug="${slug}"`
	);

	const payload = {
		session_id: sessionId,
		slug,
		chapter,
		updated: new Date().toISOString()
	};

	if (existing) {
		const res = await pbPatch(`/api/collections/progress/records/${existing.id}`, payload);
		if (!res.ok) {
			const body = await res.text().catch(() => '');
			log.error('pocketbase', 'setProgress PATCH failed', { slug, chapter, status: res.status, body });
		}
	} else {
		const res = await pbPost('/api/collections/progress/records', payload);
		if (!res.ok) {
			const body = await res.text().catch(() => '');
			log.error('pocketbase', 'setProgress POST failed', { slug, chapter, status: res.status, body });
		}
	}
}

// ─── Users ────────────────────────────────────────────────────────────────────

import { scryptSync, randomBytes, timingSafeEqual } from 'node:crypto';

function hashPassword(password: string): string {
	const salt = randomBytes(16).toString('hex');
	const hash = scryptSync(password, salt, 64).toString('hex');
	return `${salt}:${hash}`;
}

function verifyPassword(password: string, stored: string): boolean {
	const [salt, hash] = stored.split(':');
	if (!salt || !hash) return false;
	const derived = scryptSync(password, salt, 64);
	const hashBuf = Buffer.from(hash, 'hex');
	if (derived.length !== hashBuf.length) return false;
	return timingSafeEqual(derived, hashBuf);
}

/**
 * Look up a user by username. Returns null if not found.
 */
export async function getUserByUsername(username: string): Promise<User | null> {
	return listOne<User>('app_users', `username="${username.replace(/"/g, '\\"')}"`);
}

/**
 * Create a new user with a hashed password. Throws if username already exists.
 */
export async function createUser(username: string, password: string, role = 'user'): Promise<User> {
	log.info('pocketbase', 'createUser: checking for existing username', { username });
	const existing = await getUserByUsername(username);
	if (existing) {
		log.warn('pocketbase', 'createUser: username already taken', { username });
		throw new Error('Username already taken');
	}
	const password_hash = hashPassword(password);
	log.info('pocketbase', 'createUser: inserting new user', { username, role });
	const res = await pbPost('/api/collections/app_users/records', {
		username,
		password_hash,
		role,
		created: new Date().toISOString()
	});
	if (!res.ok) {
		const body = await res.text().catch(() => '');
		log.error('pocketbase', 'createUser: PocketBase rejected record', {
			username,
			status: res.status,
			body
		});
		throw new Error(`Failed to create user: ${res.status} ${body}`);
	}
	log.info('pocketbase', 'createUser: user created', { username, role });
	return res.json() as Promise<User>;
}

/**
 * Verify username + password. Returns the user on success, null on failure.
 */
export async function loginUser(username: string, password: string): Promise<User | null> {
	log.debug('pocketbase', 'loginUser: lookup', { username });
	const user = await getUserByUsername(username);
	if (!user) {
		log.warn('pocketbase', 'loginUser: username not found', { username });
		return null;
	}
	const ok = verifyPassword(password, user.password_hash);
	if (!ok) {
		log.warn('pocketbase', 'loginUser: wrong password', { username });
		return null;
	}
	log.info('pocketbase', 'loginUser: success', { username, role: user.role });
	return user;
}