feat(admin-web, functions): overhaul music library and add AI genre classification

- admin-web: Added an "All Music" library view with search, genre, and status filters.
- admin-web: Converted Jobs view to use expandable cards instead of a split pane.
- admin-web: Added ability to delete individual tracks from a job.
- functions: Added new `youtube-classify` edge function to automatically categorize tracks using Gemini LLM.
- functions: Integrated AI genre classification during initial playlist import if no manual genre is provided.
- worker: Added `/classify` endpoint for the worker to securely interface with Gemini.
- scripts: Updated deployment script to include `GEMINI_API_KEY`.

youtube-worker/server.js

@@ -4,6 +4,7 @@ import { readFile, unlink, mkdir } from "node:fs/promises";
 import { promisify } from "node:util";
 import { Innertube } from "youtubei.js";
 import { createClient } from "@supabase/supabase-js";
+import { GoogleGenAI, Type } from "@google/genai";
 
 const execFileAsync = promisify(execFile);
 
@@ -16,6 +17,7 @@ const STORAGE_BUCKET = process.env.STORAGE_BUCKET || "workout-audio";
 // SUPABASE_URL is the internal Docker network URL (e.g. http://kong:8000)
 // which browsers cannot reach.
 const SUPABASE_PUBLIC_URL = process.env.SUPABASE_PUBLIC_URL || SUPABASE_URL;
+const GEMINI_API_KEY = process.env.GEMINI_API_KEY || "";
 
 if (!SUPABASE_URL || !SUPABASE_SERVICE_ROLE_KEY) {
   console.error("Missing SUPABASE_URL or SUPABASE_SERVICE_ROLE_KEY");
@@ -107,6 +109,7 @@ async function handlePlaylist(req, res) {
       items.push({
         videoId: item.id,
         title: item.title?.toString() ?? "Untitled",
+        author: item.author?.name ?? null,
         durationSeconds: item.duration?.seconds ?? 0,
         thumbnailUrl: item.thumbnails?.[0]?.url ?? null,
       });
@@ -193,6 +196,182 @@ async function handleHealth(_req, res) {
   jsonResponse(res, 200, { status: "ok" });
 }
 
+// ── Genre classification ─────────────────────────────────────
+
+const VALID_GENRES = new Set([
+  "edm", "hip-hop", "pop", "rock", "latin", "house",
+  "drum-and-bass", "dubstep", "r-and-b", "country", "metal", "ambient",
+]);
+
+const CLASSIFY_SYSTEM_PROMPT = `You classify music tracks into exactly one genre for a fitness/workout app.
+
+Available genres (pick exactly one per track):
+- edm: Electronic dance music, techno, trance, electro
+- hip-hop: Hip-hop, rap, trap beats
+- pop: Pop music, mainstream hits
+- rock: Rock, alternative, indie rock, punk
+- latin: Reggaeton, salsa, bachata, latin pop
+- house: House music, deep house, tech house
+- drum-and-bass: Drum and bass, jungle, liquid DnB
+- dubstep: Dubstep, bass music, brostep
+- r-and-b: R&B, soul, neo-soul
+- country: Country, country pop, Americana
+- metal: Heavy metal, metalcore, hard rock
+- ambient: Ambient, chill, lo-fi, downtempo, meditation
+
+For each track, pick the single best-fit genre. If the track is clearly a
+workout/tabata/HIIT track, infer genre from musical style cues in the title.
+If truly ambiguous, default to "edm" for workout/tabata tracks.`;
+
+/**
+ * Fetch YouTube metadata (category + keywords) for a batch of video IDs.
+ * Runs in parallel batches of 10 to avoid rate limits.
+ * Returns Map<videoId, {category, keywords}>.
+ */
+async function fetchVideoMetadata(videoIds) {
+  const yt = await getYouTubeClient();
+  const metadata = new Map();
+  const BATCH_SIZE = 10;
+
+  for (let i = 0; i < videoIds.length; i += BATCH_SIZE) {
+    const batch = videoIds.slice(i, i + BATCH_SIZE);
+    const results = await Promise.allSettled(
+      batch.map(async (id) => {
+        const info = await yt.getBasicInfo(id);
+        return {
+          id,
+          category: info.basic_info?.category ?? null,
+          keywords: info.basic_info?.keywords ?? [],
+        };
+      })
+    );
+
+    for (const result of results) {
+      if (result.status === "fulfilled") {
+        const { id, category, keywords } = result.value;
+        metadata.set(id, { category, keywords });
+      }
+      // Rejected = skip that video's metadata silently
+    }
+  }
+
+  return metadata;
+}
+
+/**
+ * Classify tracks into genres using Gemini.
+ * Input: array of {videoId, title, author, category?, keywords?}
+ * Batches into groups of 50 to keep schema/prompt manageable.
+ * Returns: Record<videoId, genre>
+ */
+async function classifyWithGemini(tracks) {
+  if (!GEMINI_API_KEY) {
+    console.warn("GEMINI_API_KEY not set — skipping genre classification");
+    return {};
+  }
+
+  const ai = new GoogleGenAI({ apiKey: GEMINI_API_KEY });
+  const BATCH_SIZE = 50;
+  const allGenres = {};
+
+  for (let i = 0; i < tracks.length; i += BATCH_SIZE) {
+    const batch = tracks.slice(i, i + BATCH_SIZE);
+
+    // Build concise input for the prompt
+    const trackDescriptions = batch.map((t) => {
+      const parts = [`"${t.title}"`];
+      if (t.author) parts.push(`by ${t.author}`);
+      if (t.category) parts.push(`[${t.category}]`);
+      if (t.keywords?.length) parts.push(`tags: ${t.keywords.slice(0, 8).join(", ")}`);
+      return `${t.videoId}: ${parts.join(" — ")}`;
+    });
+
+    const userPrompt = `Classify each track into one genre. Return a JSON object mapping videoId to genre string.\n\n${trackDescriptions.join("\n")}`;
+
+    try {
+      const response = await ai.models.generateContent({
+        model: "gemini-3.1-flash-lite-preview",
+        contents: userPrompt,
+        config: {
+          systemInstruction: CLASSIFY_SYSTEM_PROMPT,
+          responseMimeType: "application/json",
+          responseSchema: {
+            type: Type.OBJECT,
+            properties: Object.fromEntries(
+              batch.map((t) => [
+                t.videoId,
+                {
+                  type: Type.STRING,
+                  description: "Genre classification",
+                  enum: [...VALID_GENRES],
+                },
+              ])
+            ),
+            required: batch.map((t) => t.videoId),
+          },
+          temperature: 0.1,
+        },
+      });
+
+      const parsed = JSON.parse(response.text);
+
+      // Validate each genre against the allowed set
+      for (const [videoId, genre] of Object.entries(parsed)) {
+        if (VALID_GENRES.has(genre)) {
+          allGenres[videoId] = genre;
+        } else {
+          console.warn(`Invalid genre "${genre}" for ${videoId} — skipping`);
+        }
+      }
+    } catch (batchErr) {
+      console.error(`Gemini batch ${i / BATCH_SIZE + 1} failed:`, batchErr.message);
+      // Continue with next batch — partial results are fine
+    }
+  }
+
+  return allGenres;
+}
+
+async function handleClassify(req, res) {
+  const { items } = await readBody(req);
+  if (!Array.isArray(items) || items.length === 0) {
+    return jsonResponse(res, 400, { error: "items array is required" });
+  }
+
+  console.log(`Classifying ${items.length} tracks...`);
+
+  try {
+    // Step 1: Fetch YouTube metadata for enrichment
+    const videoIds = items.map((i) => i.videoId);
+    console.log("Fetching YouTube metadata...");
+    const metadata = await fetchVideoMetadata(videoIds);
+    console.log(`Got metadata for ${metadata.size}/${items.length} videos`);
+
+    // Step 2: Merge metadata with input items
+    const enriched = items.map((item) => {
+      const meta = metadata.get(item.videoId);
+      return {
+        videoId: item.videoId,
+        title: item.title,
+        author: item.author ?? null,
+        category: meta?.category ?? null,
+        keywords: meta?.keywords ?? [],
+      };
+    });
+
+    // Step 3: Classify via Gemini
+    console.log("Calling Gemini for classification...");
+    const genres = await classifyWithGemini(enriched);
+    console.log(`Classified ${Object.keys(genres).length}/${items.length} tracks`);
+
+    jsonResponse(res, 200, { genres });
+  } catch (err) {
+    // Classification is best-effort — never block the import
+    console.error("Classification failed:", err.message);
+    jsonResponse(res, 200, { genres: {}, warning: err.message });
+  }
+}
+
 // ── Server ────────────────────────────────────────────────────
 
 const server = http.createServer(async (req, res) => {
@@ -206,6 +385,9 @@ const server = http.createServer(async (req, res) => {
     if (req.method === "POST" && req.url === "/download") {
       return await handleDownload(req, res);
     }
+    if (req.method === "POST" && req.url === "/classify") {
+      return await handleClassify(req, res);
+    }
     jsonResponse(res, 404, { error: "Not found" });
   } catch (err) {
     console.error(`${req.method} ${req.url} error:`, err.message);