import { json, error } from '@sveltejs/kit';
import type { RequestHandler } from './$types';
import { getBook, listChapterIdx, getProgress, isBookSaved } from '$lib/server/pocketbase';
import { log } from '$lib/server/logger';
import { env } from '$env/dynamic/private';

const SCRAPER_URL = env.SCRAPER_API_URL ?? 'http://localhost:8080';

interface PreviewChapter {
	number: number;
	title: string;
	url: string;
}

/**
 * GET /api/book/[slug]
 * Returns book metadata, chapter list, progress, and library status.
 * Falls back to a live scraper preview if the book is not in PocketBase.
 *
 * Response shape mirrors BookDetailResponse in the iOS APIClient.
 */
export const GET: RequestHandler = async ({ params, locals }) => {
	const { slug } = params;

	// Try PocketBase first
	let book = await getBook(slug).catch((e) => {
		log.error('api/book', 'getBook failed', { slug, err: String(e) });
		return null;
	});

	if (book) {
		let chapters, progress, saved;
		try {
			[chapters, progress, saved] = await Promise.all([
				listChapterIdx(slug),
				getProgress(locals.sessionId, slug, locals.user?.id),
				isBookSaved(locals.sessionId, slug, locals.user?.id)
			]);
		} catch (e) {
			log.error('api/book', 'failed to load book detail data', { slug, err: String(e) });
			error(500, 'Failed to load book');
		}

		return json({
			book,
			chapters,
			preview_chapters: null,
			in_lib: true,
			saved,
			last_chapter: progress?.chapter ?? null
		});
	}

	// Fall back to live scraper preview
	try {
		const res = await fetch(`${SCRAPER_URL}/api/book-preview/${encodeURIComponent(slug)}`);
		if (!res.ok) {
			log.warn('api/book', 'book-preview returned error', { slug, status: res.status });
			error(404, `Book "${slug}" not found`);
		}
		const preview: {
			in_lib: boolean;
			meta: {
				slug: string;
				title: string;
				author: string;
				cover: string;
				status: string;
				genres: string[];
				summary: string;
				total_chapters: number;
				source_url: string;
			};
			chapters: PreviewChapter[];
		} = await res.json();

		const previewBook = {
			id: '',
			slug: preview.meta.slug || slug,
			title: preview.meta.title,
			author: preview.meta.author,
			cover: preview.meta.cover,
			status: preview.meta.status,
			genres: preview.meta.genres ?? [],
			summary: preview.meta.summary,
			total_chapters: preview.meta.total_chapters,
			source_url: preview.meta.source_url,
			ranking: 0,
			meta_updated: ''
		};

		return json({
			book: previewBook,
			chapters: [],
			preview_chapters: preview.chapters,
			in_lib: preview.in_lib,
			saved: false,
			last_chapter: null
		});
	} catch (e) {
		if (e instanceof Error && 'status' in e) throw e;
		log.error('api/book', 'book-preview fetch failed', { slug, err: String(e) });
		error(404, `Book "${slug}" not found`);
	}
};