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

const pool = new Pool({
  connectionString: process.env.DATABASE_URL,
});

pool.on('error', (err) => {
  console.error('Unexpected Postgres pool error:', err);
});

// Apply schema.sql on startup (idempotent — uses CREATE TABLE IF NOT EXISTS).
async function init() {
  const schema = fs.readFileSync(path.join(__dirname, '..', 'db', 'schema.sql'), 'utf8');
  await pool.query(schema);
}

function query(text, params) {
  return pool.query(text, params);
}

// Run a function inside a transaction, passing it a dedicated client.
async function transaction(fn) {
  const client = await pool.connect();
  try {
    await client.query('BEGIN');
    const result = await fn(client);
    await client.query('COMMIT');
    return result;
  } catch (err) {
    await client.query('ROLLBACK');
    throw err;
  } finally {
    client.release();
  }
}

module.exports = { pool, query, transaction, init };