<?php
/**
 * Returns a shared PDO connection to the MySQL database.
 * Also ensures the `is_read` column exists (added after initial deploy).
 */
function get_db(): PDO {
    static $pdo = null;
    if ($pdo !== null) return $pdo;

    $host = getenv('DB_HOST') ?: 'db';
    $name = getenv('DB_NAME') ?: 'alwisp';
    $user = getenv('DB_USER') ?: '';
    $pass = getenv('DB_PASS') ?: '';

    $pdo = new PDO(
        "mysql:host=$host;dbname=$name;charset=utf8mb4",
        $user, $pass,
        [
            PDO::ATTR_ERRMODE            => PDO::ERRMODE_EXCEPTION,
            PDO::ATTR_DEFAULT_FETCH_MODE => PDO::FETCH_ASSOC,
        ]
    );

    // Auto-migrate: add is_read if the DB was initialised before this column existed
    $col_exists = $pdo->query(
        "SELECT COUNT(*) FROM INFORMATION_SCHEMA.COLUMNS
         WHERE TABLE_SCHEMA = DATABASE() AND TABLE_NAME = 'contacts' AND COLUMN_NAME = 'is_read'"
    )->fetchColumn();

    if (!$col_exists) {
        $pdo->exec("ALTER TABLE contacts ADD COLUMN is_read TINYINT(1) NOT NULL DEFAULT 0");
    }

    return $pdo;
}