<?php
/**
 * db.php — single PDO connection used everywhere.
 * Prepared statements only; real prepares (no emulation).
 */

function db(): PDO
{
    static $pdo = null;
    if ($pdo instanceof PDO) return $pdo;

    $dsn = 'mysql:host=' . DB_HOST . ';dbname=' . DB_NAME . ';charset=utf8mb4';
    $opt = [
        PDO::ATTR_ERRMODE            => PDO::ERRMODE_EXCEPTION,
        PDO::ATTR_DEFAULT_FETCH_MODE => PDO::FETCH_ASSOC,
        PDO::ATTR_EMULATE_PREPARES   => false,   // true server-side prepares
        PDO::ATTR_STRINGIFY_FETCHES  => false,
    ];
    try {
        $pdo = new PDO($dsn, DB_USER, DB_PASS, $opt);
    } catch (Throwable $e) {
        error_log('DB connect failed: ' . $e->getMessage());
        http_response_code(500);
        exit('Service temporarily unavailable.');
    }
    return $pdo;
}