feat: add MinIO presign endpoints to scraper API and SvelteKit presign helper

ui/src/lib/server/minio.ts

@@ -0,0 +1,67 @@
+/**
+ * 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);
+}