import * as mssqlQueries from '../../providers/mssql/queries/healthcheck.js';
import * as sqliteQueries from '../../providers/sqlite3/queries/healthcheck.js';
import makeRunner from '../runner.js';

export default function check(provider) {
  const isSqlite = provider?.dialect === 'sqlite3';
  const queries = isSqlite ? sqliteQueries : mssqlQueries;

  /**
   * Executes a database health check:
   * 1. Ensures the healthcheck table has one row (creates with sequence 0 if not).
   * 2. Selects that row for update with minimal, reasonable locking within a transaction.
   * 3. Updates the sequence by 1 in a separate statement within the transaction.
   *
   * @param {object} [tx] - Optional transaction to run within.
   * @returns {Promise<{ok: boolean, sequence: number}>} The health check result.
   *
   * @example
   * const result = await store.healthcheck.check();
   * // => { ok: true, sequence: 1 }
   */
  return async (tx) => {
    const runTx = async (runner) => {
      // 1. Ensure table has one row, if not create that row with number 0
      await runner.query(queries.ENSURE_ROW);

      // 2. Select for update on that row with minimal, reasonable locking
      const selected = await runner.query(queries.SELECT_FOR_UPDATE);
      const row = selected.rows[0];
      if (!row) {
        throw new Error('Healthcheck row not found');
      }

      // 3. Updating the number by 1 and do an update (not in one statement, but in a tx)
      const currentSeq = Number(row.sequence ?? 0);
      const nextSeq = currentSeq + 1;

      await runner.query(queries.UPDATE_SEQUENCE, {
        id: row.id,
        sequence: nextSeq,
      });

      return {
        ok: true,
        sequence: nextSeq,
      };
    };

    if (tx) {
      return runTx(makeRunner(provider, tx));
    }
    if (typeof provider?.transaction === 'function') {
      return provider.transaction((runner) => runTx(makeRunner(provider, runner)));
    }
    return runTx(makeRunner(provider));
  };
}