<?php
require_once __DIR__ . '/config.php';

try {
    $pdo = db();
    // Add sold_serial_id column
    $sql_add_column = "ALTER TABLE warranty_registrations ADD COLUMN sold_serial_id INT NULL AFTER serial_number";
    $pdo->exec($sql_add_column);

    // Add foreign key constraint
    $sql_add_fk = "ALTER TABLE warranty_registrations ADD CONSTRAINT fk_sold_serial FOREIGN KEY (sold_serial_id) REFERENCES sold_serials(id) ON DELETE SET NULL";
    $pdo->exec($sql_add_fk);

    echo "Table 'warranty_registrations' modified successfully." . PHP_EOL;

} catch (PDOException $e) {
    // Check if column already exists to avoid fatal error on re-run
    if (strpos($e->getMessage(), 'Duplicate column name') === false) {
        die("DB ERROR: " . $e->getMessage());
    }
    echo "Column 'sold_serial_id' already exists in 'warranty_registrations'." . PHP_EOL;
}