<?php
class DB {
    private static ?DB $instance = null;
    private PDO $pdo;

    private function __construct() {
        $this->pdo = new PDO(
            "mysql:host=" . DB_HOST . ";dbname=" . DB_NAME . ";charset=utf8mb4",
            DB_USER, DB_PASS,
            [
                PDO::ATTR_ERRMODE            => PDO::ERRMODE_EXCEPTION,
                PDO::ATTR_DEFAULT_FETCH_MODE => PDO::FETCH_ASSOC,
                PDO::ATTR_EMULATE_PREPARES   => false,
            ]
        );
    }

    public static function getInstance(): self {
        if (!self::$instance) self::$instance = new self();
        return self::$instance;
    }

    public function execute(string $sql, array $params = []): PDOStatement {
        $stmt = $this->pdo->prepare($sql);
        $stmt->execute($params);
        return $stmt;
    }

    public function fetchOne(string $sql, array $params = []): ?array {
        return $this->execute($sql, $params)->fetch() ?: null;
    }

    public function fetchAll(string $sql, array $params = []): array {
        return $this->execute($sql, $params)->fetchAll();
    }

    public function insert(string $sql, array $params = []): string {
        $this->execute($sql, $params);
        return $this->pdo->lastInsertId();
    }

    public function pdo(): PDO { return $this->pdo; }
}