Initial OSS scaffold from Songs2VID (pre-strip)

lib/fonts-server.ts

@@ -0,0 +1,44 @@
+/** Server-only font filesystem helpers. Do not import from client components. */
+
+import fs from "fs/promises";
+import path from "path";
+import { CURATED_FONTS, type CuratedFontKey } from "./fonts";
+
+export function getFontsDir(): string {
+  return path.join(process.cwd(), "assets", "fonts");
+}
+
+/** Resolve a curated font file on disk (must exist under assets/fonts). */
+export function resolveCuratedFontPath(key: CuratedFontKey): string {
+  const meta = CURATED_FONTS.find((f) => f.key === key);
+  if (!meta) throw new Error("Unknown font");
+  // Whitelist filename only  never accept user-controlled path segments
+  const safe = meta.file.replace(/[^a-zA-Z0-9._-]/g, "");
+  if (safe !== meta.file) throw new Error("Invalid font asset name");
+  return path.join(getFontsDir(), safe);
+}
+
+/**
+ * Validate TTF / OTF magic bytes.
+ * TTF: 00 01 00 00 | true | typ1
+ * OTF: OTTO
+ */
+export async function assertFontFile(filePath: string): Promise<"ttf" | "otf"> {
+  const fh = await fs.open(filePath, "r");
+  try {
+    const buf = Buffer.alloc(4);
+    await fh.read(buf, 0, 4, 0);
+    const asStr = buf.toString("ascii");
+    if (asStr === "OTTO") return "otf";
+    if (asStr === "true" || asStr === "typ1") return "ttf";
+    if (buf[0] === 0x00 && buf[1] === 0x01 && buf[2] === 0x00 && buf[3] === 0x00) {
+      return "ttf";
+    }
+    if (asStr === "wOFF" || asStr === "wOF2") {
+      throw new Error("WOFF fonts are not supported. Upload a .ttf or .otf file.");
+    }
+    throw new Error("File is not a valid TTF or OTF font");
+  } finally {
+    await fh.close();
+  }
+}