/**
 * Server-side MinIO presign helper.
 * Calls the scraper API to get presigned URLs, then optionally rewrites
 * the MinIO host to the public-facing URL for browser use.
 *
 * Never import this from client-side code.
 */

import { env } from '$env/dynamic/private';
import { env as pubEnv } from '$env/dynamic/public';

const SCRAPER_URL = env.SCRAPER_API_URL ?? 'http://localhost:8080';
// Public MinIO URL — used to rewrite presigned URLs so the browser can reach MinIO directly.
// In docker-compose this would differ from the internal endpoint.
const MINIO_PUBLIC_URL = pubEnv.PUBLIC_MINIO_PUBLIC_URL ?? 'http://localhost:9000';

/**
 * Rewrites the MinIO host in a presigned URL to the public-facing URL.
 * The presigned URL is signed against the internal endpoint (e.g. minio:9000),
 * but the browser needs the public URL (e.g. localhost:9000 in dev, or a CDN in prod).
 * Rewriting the host preserves all query params (signature, expiry, etc).
 */
function rewriteHost(presignedUrl: string): string {
	try {
		const u = new URL(presignedUrl);
		const pub = new URL(MINIO_PUBLIC_URL);
		u.protocol = pub.protocol;
		u.hostname = pub.hostname;
		u.port = pub.port;
		return u.toString();
	} catch {
		return presignedUrl;
	}
}

/**
 * Returns a presigned URL for a chapter markdown file.
 * URL is valid for ~15 minutes (set by the scraper).
 * The returned URL points to the public MinIO endpoint and can be used
 * server-side (in a +page.server.ts load function) to fetch the markdown content.
 */
export async function presignChapter(slug: string, n: number): Promise<string> {
	const res = await fetch(`${SCRAPER_URL}/api/presign/chapter/${slug}/${n}`);
	if (!res.ok) throw new Error(`presign chapter ${slug}/${n}: ${res.status}`);
	const data = (await res.json()) as { url: string };
	return rewriteHost(data.url);
}

/**
 * Returns a presigned URL for an audio file.
 * URL is valid for ~1 hour. The URL is returned to the browser for direct streaming.
 */
export async function presignAudio(
	slug: string,
	n: number,
	voice?: string,
	speed?: number
): Promise<string> {
	const params = new URLSearchParams();
	if (voice) params.set('voice', voice);
	if (speed) params.set('speed', String(speed));
	const qs = params.toString() ? `?${params.toString()}` : '';
	const res = await fetch(`${SCRAPER_URL}/api/presign/audio/${slug}/${n}${qs}`);
	if (!res.ok) throw new Error(`presign audio ${slug}/${n}: ${res.status}`);
	const data = (await res.json()) as { url: string };
	return rewriteHost(data.url);
}