<?php
class Database {
    private static $sharedDbh = null;
    private static $sharedDriver = 'mysql';
    private $dbh;
    private $stmt;
    private $error;
    private $driver = 'mysql';
    private static $migrated = false;

    public function __construct() {
        if (self::$sharedDbh !== null) {
            $this->dbh = self::$sharedDbh;
            $this->driver = self::$sharedDriver;
            return;
        }

        $connectionType = Config::get('DB_CONNECTION', 'mysql');
        $host = Config::get('DB_HOST', 'localhost');
        $user = Config::get('DB_USER', 'root');
        $pass = Config::get('DB_PASS', '');
        $dbname = Config::get('DB_NAME', '');

        $options = [
            PDO::ATTR_ERRMODE => PDO::ERRMODE_EXCEPTION,
            PDO::ATTR_DEFAULT_FETCH_MODE => PDO::FETCH_ASSOC
        ];

        // Explicit SQLite configuration or empty dbname in non-production
        if ($connectionType === 'sqlite' || (empty($dbname) && Config::get('APP_ENV') !== 'production')) {
            $this->connectSqlite($options);
            self::$sharedDbh = $this->dbh;
            self::$sharedDriver = $this->driver;
            return;
        }

        if (empty($dbname)) {
            throw new Exception("Keine Datenbank in .env konfiguriert.");
        }

        $dsn = 'mysql:host=' . $host . ';dbname=' . $dbname . ';charset=utf8mb4';

        try {
            $this->dbh = new PDO($dsn, $user, $pass, $options);
            $this->driver = 'mysql';
            self::$sharedDbh = $this->dbh;
            self::$sharedDriver = $this->driver;
        } catch (PDOException $e) {
            $this->error = $e->getMessage();
            // In local development (macOS / Darwin) or when explicitly configured, fall back to SQLite
            if (PHP_OS_FAMILY === 'Darwin' || Config::get('APP_ENV') !== 'production' || $connectionType === 'sqlite') {
                $this->connectSqlite($options);
                self::$sharedDbh = $this->dbh;
                self::$sharedDriver = $this->driver;
            } else {
                throw new Exception("Datenbank-Verbindungsfehler: " . $e->getMessage());
            }
        }

        $this->ensureSchema();
    }

    private function connectSqlite(array $options): void {
        $this->driver = 'sqlite';
        $dataDir = __DIR__ . '/../data';
        if (!is_dir($dataDir)) {
            mkdir($dataDir, 0755, true);
        }
        $sqlitePath = $dataDir . '/database.sqlite';
        $this->dbh = new PDO('sqlite:' . $sqlitePath, null, null, $options);
        $this->dbh->exec('PRAGMA busy_timeout = 5000;');
        $this->dbh->exec('PRAGMA journal_mode = WAL;');
        $this->dbh->exec('PRAGMA foreign_keys = ON;');
        $this->ensureSchema();
    }

    private function ensureSchema(): void {
        if (!self::$migrated) {
            self::$migrated = true;
            if (class_exists('MigrationService')) {
                MigrationService::run($this);
            }
        }
    }

    public function getDriver(): string {
        return $this->driver;
    }

    public function lastInsertId(): string {
        return $this->dbh->lastInsertId();
    }

    public function query($sql) {
        $this->stmt = $this->dbh->prepare($sql);
    }

    public function bind($param, $value, $type = null) {
        if (is_null($type)) {
            switch (true) {
                case is_int($value):  $type = PDO::PARAM_INT; break;
                case is_bool($value): $type = PDO::PARAM_BOOL; break;
                case is_null($value): $type = PDO::PARAM_NULL; break;
                default:              $type = PDO::PARAM_STR;
            }
        }
        $this->stmt->bindValue($param, $value, $type);
    }

    public function execute() {
        return $this->stmt->execute();
    }

    public function resultSet() {
        $this->execute();
        $result = $this->stmt->fetchAll();
        $this->stmt->closeCursor();
        return $result;
    }

    public function single() {
        $this->execute();
        $result = $this->stmt->fetch();
        $this->stmt->closeCursor();
        return $result;
    }
    
    public function rowCount() {
        return $this->stmt->rowCount();
    }
}