Initial commit: KeySelector implementation

server/index.js

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+require('dotenv').config();
+const express = require('express');
+const cors = require('cors');
+const path = require('path');
+
+const recognizeRoute = require('./routes/recognize');
+const metadataRoute = require('./routes/metadata');
+const suggestionsRoute = require('./routes/suggestions');
+const coverRoute = require('./routes/cover');
+require('./workers/poll-quota'); // Start quota worker
+
+const app = express();
+const port = process.env.PORT || 3000;
+
+app.use(cors());
+app.use(express.json());
+
+// Serve static frontend
+app.use(express.static(path.join(__dirname, '../public')));
+app.use('/shared', express.static(path.join(__dirname, '../shared')));
+
+// API Routes
+app.use('/api/recognize', recognizeRoute);
+app.use('/api/metadata', metadataRoute);
+app.use('/api/suggestions', suggestionsRoute);
+app.use('/api/cover', coverRoute);
+
+app.listen(port, () => {
+  console.log(`KeySelector backend listening on port ${port}`);
+});

server/package.json

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+{
+  "name": "keyselector",
+  "version": "1.0.0",
+  "description": "Browser-basiertes DJ-Tool",
+  "main": "index.js",
+  "scripts": {
+    "start": "node index.js"
+  },
+  "dependencies": {
+    "cors": "^2.8.5",
+    "dotenv": "^16.3.1",
+    "express": "^4.18.2",
+    "node-fetch": "^3.3.2"
+  }
+}

server/routes/cover.js

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+const express = require('express');
+const fetch = require('node-fetch');
+const router = express.Router();
+
+// Fetch cover from iTunes API to avoid frontend CORS issues
+router.get('/', async (req, res) => {
+  const q = req.query.q;
+  if (!q) return res.status(400).json({ error: 'Missing q parameter' });
+  
+  try {
+    const url = `https://itunes.apple.com/search?term=${encodeURIComponent(q)}&media=music&entity=song&limit=1`;
+    const response = await fetch(url);
+    const data = await response.json();
+    
+    if (data.results && data.results[0] && data.results[0].artworkUrl100) {
+      const src = data.results[0].artworkUrl100.replace('100x100bb', '300x300bb');
+      return res.json({ url: src });
+    }
+    
+    res.json({ url: null });
+  } catch (err) {
+    console.error('iTunes cover fetch error', err);
+    res.status(500).json({ error: 'Server error fetching cover' });
+  }
+});
+
+module.exports = router;

server/routes/metadata.js

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+const express = require('express');
+const router = express.Router();
+
+// Mock metadata route
+router.get('/', async (req, res) => {
+  const track = req.query.track || 'Mock Track';
+  
+  // In production, this would call GetSongBPM and Last.fm
+  // to fetch BPM, Camelot Key, and genre/mood tags.
+  
+  res.json({
+    status: 'success',
+    data: {
+      key: '4B',
+      bpm: 120,
+      tags: ['Electronic', 'Synthpop']
+    }
+  });
+});
+
+module.exports = router;

server/routes/recognize.js

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+const express = require('express');
+const router = express.Router();
+
+// Mock recognize route
+router.post('/', async (req, res) => {
+  // In production, this would receive an audio buffer, fingerpint it,
+  // and call the AcoustID API.
+  
+  res.json({
+    status: 'success',
+    data: {
+      title: 'Mock Track',
+      artist: 'Mock Artist',
+      matchScore: '95%'
+    }
+  });
+});
+
+module.exports = router;

server/routes/suggestions.js

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+const express = require('express');
+const router = express.Router();
+// const { mixingRules } = require('../../shared/mixing-rules');
+
+// Mock suggestions route
+router.get('/', async (req, res) => {
+  const key = req.query.key;
+  const bpm = parseInt(req.query.bpm) || 120;
+  
+  // In production, this queries the PostgreSQL database populated with AcousticBrainz data
+  // to find tracks matching the compatible Camelot keys.
+  
+  res.json({
+    status: 'success',
+    data: [
+      { title: 'Suggestion 1', artist: 'Artist 1', key: '4A', bpm: bpm + 2 },
+      { title: 'Suggestion 2', artist: 'Artist 2', key: '3B', bpm: bpm - 1 }
+    ]
+  });
+});
+
+module.exports = router;

server/workers/poll-quota.js

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+// Simple worker to simulate quota polling
+const ntfyUrl = process.env.NTFY_URL;
+
+function checkQuota() {
+  // In production, check API quotas for Last.fm, GetSongBPM, AcoustID
+  // and send a push notification via ntfy if they run low.
+  console.log('[Worker] Checking API quotas...');
+}
+
+// Check daily
+setInterval(checkQuota, 24 * 60 * 60 * 1000);
+
+// Run once on startup
+setTimeout(checkQuota, 5000);