// Postgres connection + migration runner for the Platform DB.
//
// Migration pattern matches the one already established in the Lab image's
// backend/server.js (check-before-alter, idempotent) — here it's file-based rather than
// inline, since this is a fresh schema with a real migrations/ directory instead of a single
// growing CREATE TABLE IF NOT EXISTS block.

const fs = require('fs');
const path = require('path');
const { Pool } = require('pg');

const MIGRATIONS_DIR = path.join(__dirname, '../migrations');

let _pool = null;
function getPool() {
  if (_pool) return _pool;
  _pool = new Pool({
    connectionString: process.env.PLATFORM_DB_URL || 'postgres://postgres:postgres@localhost:5433/rootnode_platform',
  });
  return _pool;
}

// Applies every .sql file in migrations/ that hasn't run yet, in filename order.
// Tracked in schema_migrations so re-running is a no-op — same idempotency guarantee the
// existing SQLite migrations already rely on.
async function runMigrations() {
  const pool = getPool();
  await pool.query(`
    CREATE TABLE IF NOT EXISTS schema_migrations (
      version     TEXT PRIMARY KEY,
      applied_at  TIMESTAMPTZ NOT NULL DEFAULT now()
    )
  `);

  const applied = new Set(
    (await pool.query('SELECT version FROM schema_migrations')).rows.map(r => r.version)
  );

  const files = fs.readdirSync(MIGRATIONS_DIR).filter(f => f.endsWith('.sql')).sort();
  const ranNow = [];
  for (const file of files) {
    if (applied.has(file)) continue;
    const sql = fs.readFileSync(path.join(MIGRATIONS_DIR, file), 'utf8');
    const client = await pool.connect();
    try {
      await client.query('BEGIN');
      await client.query(sql);
      await client.query('INSERT INTO schema_migrations (version) VALUES ($1)', [file]);
      await client.query('COMMIT');
      ranNow.push(file);
    } catch (e) {
      await client.query('ROLLBACK');
      throw new Error(`Migration ${file} failed: ${e.message}`);
    } finally {
      client.release();
    }
  }
  return ranNow;
}

module.exports = { getPool, runMigrations };