// db.js
// Handles PostgreSQL database connection and queries

const { Pool } = require('pg');
require('dotenv').config(); // Load environment variables from .env file

// Create a new pool instance using environment variables
// The pool manages multiple client connections
const pool = new Pool({
  user: process.env.DB_USER,
  host: process.env.DB_HOST,
  database: process.env.DB_DATABASE,
  password: process.env.DB_PASSWORD,
  port: process.env.DB_PORT,
  // Add connection pool settings for better performance
  max: 20, // Maximum number of clients
  idleTimeoutMillis: 30000, // How long a client is allowed to remain idle before being closed
  connectionTimeoutMillis: 2000, // How long to wait for a connection
  // Optional: Add SSL configuration if required by your database provider
  // ssl: {
  //   rejectUnauthorized: false // Adjust as needed
  // }
});

// Listen for errors on the pool
pool.on('error', (err) => {
  console.error('Unexpected error on idle client', err);
  process.exit(-1);
});

// Test the database connection on startup
pool.connect((err, client, release) => {
  if (err) {
    console.error('Error acquiring client for initial DB connection test:', err.stack);
    // Exit the process if the database connection fails on startup
    process.exit(1);
  } else {
    console.log('Successfully connected to PostgreSQL database.');
    // Release the client back to the pool
    release();
  }
});

// Export functions to interact with the database
module.exports = {
  query: (text, params) => pool.query(text, params),
  // Add transaction helper
  withTransaction: async (callback) => {
    const client = await pool.connect();
    try {
      await client.query('BEGIN');
      const result = await callback(client);
      await client.query('COMMIT');
      return result;
    } catch (e) {
      await client.query('ROLLBACK');
      throw e;
    } finally {
      client.release();
    }
  }
};