feat: add Claude proxy endpoint for auto pair generation

POST /api/claude/generate-pairs — proxies image + objects to Claude
Haiku and returns 30 structured pairs (text/yes_no/question, easy/medium)
as JSON. Keeps the Anthropic API key server-side via ANTHROPIC_API_KEY.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/index.js

@@ -40,6 +40,7 @@ app.use('/api/languages', auth, require('./routes/languages'));
 app.use('/api/user-names', auth, require('./routes/user-names'));
 app.use('/api/users-public', auth, require('./routes/users-public'));
 app.use('/api/users', auth, require('./routes/users'));
+app.use('/api/claude', auth, require('./routes/claude'));
 
 // 404
 app.use((req, res) => {

src/routes/claude.js

@@ -0,0 +1,71 @@
+const router = require('express').Router();
+
+const ANTHROPIC_API_URL = 'https://api.anthropic.com/v1/messages';
+
+// POST /api/claude/generate-pairs
+// Body: { imageUrl, objects: [{id, words: [{titel_de, titel_en}], selections: [{points:[{x,y}]}]}, ...], selectedObjectId }
+router.post('/generate-pairs', async (req, res, next) => {
+  try {
+    const apiKey = process.env.ANTHROPIC_API_KEY;
+    if (!apiKey) return res.status(500).json({ error: 'ANTHROPIC_API_KEY nicht konfiguriert' });
+
+    const { imageUrl, objects, selectedObjectId } = req.body;
+    if (!imageUrl) return res.status(400).json({ error: 'imageUrl fehlt' });
+    if (!Array.isArray(objects) || objects.length === 0) return res.status(400).json({ error: 'objects fehlt oder leer' });
+    if (!selectedObjectId) return res.status(400).json({ error: 'selectedObjectId fehlt' });
+
+    const objectsDesc = objects.map((obj, i) => {
+      const words = (obj.words || []).map(w => w.titel_de || w.titel_en).filter(Boolean).join(', ');
+      const isSelected = obj.id === selectedObjectId;
+      let posStr = '';
+      if (obj.selections?.[0]?.points?.length) {
+        const pts = obj.selections[0].points;
+        const cx = (pts.reduce((s, p) => s + p.x, 0) / pts.length * 100).toFixed(0);
+        const cy = (pts.reduce((s, p) => s + p.y, 0) / pts.length * 100).toFixed(0);
+        posStr = ` (ca. ${cx}% von links, ${cy}% von oben)`;
+      }
+      return `- Objekt ${i + 1}${isSelected ? ' [DIESES OBJEKT]' : ''}: ${words || '(unbenannt)'}${posStr}`;
+    }).join('\n');
+
+    const userPrompt = `Analysiere das Bild. Folgende Objekte sind markiert:\n${objectsDesc}\n\nErstelle Sprachlernmaterial für das Objekt [DIESES OBJEKT] auf Deutsch — natürliche Sätze wie in einem echten Gespräch.\n\nAntworte NUR mit gültigem JSON ohne Markdown:\n{"pairs":[...]}\n\nJedes Pair braucht: "type" und "difficulty". Feldregeln:\n- type "text": {"type":"text","difficulty":"...","positive":"Aussage."}\n- type "yes_no": {"type":"yes_no","difficulty":"...","question":"Frage?","answer":true}\n- type "question": {"type":"question","difficulty":"...","question":"Frage?","positive":"Positive Aussage.","negative":"Negative Aussage."}\n\nErstelle genau 30 Pairs:\n- 10 × type "text": 5 × difficulty "easy" (max 8 Wörter, für Kinder), 5 × "medium" (8–15 Wörter, für Teenager)\n- 10 × type "yes_no": 5 × "easy", 5 × "medium" — mix aus answer:true und answer:false\n- 10 × type "question": 5 × "easy", 5 × "medium"\n\nRegeln: Alle Sätze auf Deutsch. Sätze müssen natürlich klingen. Keine Wiederholungen.`;
+
+    const anthropicRes = await fetch(ANTHROPIC_API_URL, {
+      method: 'POST',
+      headers: {
+        'Content-Type': 'application/json',
+        'x-api-key': apiKey,
+        'anthropic-version': '2023-06-01',
+      },
+      body: JSON.stringify({
+        model: 'claude-haiku-4-5-20251001',
+        max_tokens: 8000,
+        system: 'Du bist ein Deutsch-Sprachlernassistent. Antworte AUSSCHLIESSLICH mit gültigem JSON, ohne Markdown-Codeblöcke, ohne Erklärungen.',
+        messages: [{ role: 'user', content: [
+          { type: 'image', source: { type: 'url', url: imageUrl } },
+          { type: 'text', text: userPrompt },
+        ]}],
+      }),
+    });
+
+    if (!anthropicRes.ok) {
+      const err = await anthropicRes.json().catch(() => ({}));
+      return res.status(anthropicRes.status).json({ error: err.error?.message || `Claude API Fehler ${anthropicRes.status}` });
+    }
+
+    const data = await anthropicRes.json();
+    let rawText = data.content[0].text.trim();
+
+    // Strip markdown code blocks if present
+    const mdMatch = rawText.match(/```(?:json)?\s*([\s\S]+?)\s*```/);
+    if (mdMatch) rawText = mdMatch[1];
+
+    const parsed = JSON.parse(rawText);
+    if (!Array.isArray(parsed.pairs)) return res.status(500).json({ error: 'Ungültiges JSON-Format von Claude' });
+
+    res.json({ pairs: parsed.pairs });
+  } catch (err) {
+    next(err);
+  }
+});
+
+module.exports = router;