snakkimo-API/src/lib/deleteCascade.js

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 };