feat: Deep-Delete für Pairs und Bilder (Fragen/Statements/Audios/Objekte kaskadieren)

DELETE /pairs/:id räumt jetzt unreferenzierte Fragen/Statements samt
Audio-Dateien (DB + S3) mit auf. DELETE /pictures/:id löscht zusätzlich
die nur mit diesem Bild verknüpften Objekte inkl. deren Pairs.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

src/lib/deleteCascade.js

@@ -0,0 +1,77 @@
+const { query } = require('../db');
+const { deleteFile, keyFromUrl } = require('../s3');
+
+// Audios (DB-Rows + S3-Dateien) einer Quelle entfernen.
+async function deleteAudiosFor(sourceTable, sourceId) {
+  const audios = await query(
+    `SELECT id, audio_link FROM audios WHERE source_table = $1 AND source_id = $2`,
+    [sourceTable, sourceId]
+  );
+  for (const a of audios.rows) {
+    const key = keyFromUrl(a.audio_link);
+    if (key) await deleteFile(key).catch(() => {});
+    await query('DELETE FROM audios WHERE id = $1', [a.id]);
+  }
+}
+
+// Pair inkl. Frage, Statements und deren Audios löschen.
+// Frage/Statements bleiben stehen, wenn ein anderes Pair sie noch referenziert.
+// Objekte werden nicht angefasst (object_pairs kaskadiert per FK).
+async function deletePairDeep(pairId) {
+  const existing = await query(
+    `SELECT question_id, positive_statement_id, negative_statement_id FROM pairs WHERE id = $1`,
+    [pairId]
+  );
+  if (!existing.rows.length) return false;
+  const { question_id, positive_statement_id, negative_statement_id } = existing.rows[0];
+
+  await query('DELETE FROM pairs WHERE id = $1', [pairId]);
+
+  if (question_id) {
+    const ref = await query('SELECT 1 FROM pairs WHERE question_id = $1 LIMIT 1', [question_id]);
+    if (!ref.rows.length) {
+      await deleteAudiosFor('questions', question_id);
+      await query('DELETE FROM questions WHERE id = $1', [question_id]);
+    }
+  }
+
+  const stmtIds = [...new Set([positive_statement_id, negative_statement_id].filter(Boolean))];
+  for (const stmtId of stmtIds) {
+    const ref = await query(
+      'SELECT 1 FROM pairs WHERE positive_statement_id = $1 OR negative_statement_id = $1 LIMIT 1',
+      [stmtId]
+    );
+    if (!ref.rows.length) {
+      await deleteAudiosFor('statements', stmtId);
+      await query('DELETE FROM statements WHERE id = $1', [stmtId]);
+    }
+  }
+
+  return true;
+}
+
+// Alle Objekte eines Bildes löschen (inkl. deren Pairs), sofern das Objekt
+// ausschließlich mit diesem Bild verknüpft ist.
+async function deletePictureObjectsDeep(pictureId) {
+  const objects = await query(
+    `SELECT object_id FROM object_pictures WHERE picture_id = $1`,
+    [pictureId]
+  );
+  for (const { object_id } of objects.rows) {
+    const other = await query(
+      `SELECT 1 FROM object_pictures WHERE object_id = $1 AND picture_id <> $2 LIMIT 1`,
+      [object_id, pictureId]
+    );
+    if (other.rows.length) continue;
+
+    const pairs = await query(
+      `SELECT pair_id FROM object_pairs WHERE object_id = $1`,
+      [object_id]
+    );
+    for (const { pair_id } of pairs.rows) await deletePairDeep(pair_id);
+
+    await query('DELETE FROM objects WHERE id = $1', [object_id]);
+  }
+}
+
+module.exports = { deletePairDeep, deletePictureObjectsDeep };