<?php
/**
 * Database Configuration
 * Production fitness tracking app database connection
 */

class Database {
    private static $instance = null;
    private $connection;

    private function __construct() {
        try {
            require_once __DIR__ . '/Config.php';
            AppConfig::loadEnvironment();
            mysqli_report(MYSQLI_REPORT_ERROR | MYSQLI_REPORT_STRICT);

            $this->connection = new mysqli(
                AppConfig::required('DB_HOST'),
                AppConfig::required('DB_USERNAME'),
                AppConfig::required('DB_PASSWORD'),
                AppConfig::required('DB_DATABASE'),
                AppConfig::integer('DB_PORT', 3306)
            );
            $this->connection->set_charset('utf8mb4');
            $this->connection->query("SET time_zone = '+00:00'");
        } catch (Throwable $e) {
            error_log('Database initialization failed: ' . $e->getMessage());
            throw new RuntimeException('Database connection failed', 0, $e);
        }
    }

    /**
     * Singleton instance getter
     */
    public static function getInstance() {
        if (self::$instance === null) {
            self::$instance = new self();
        }
        return self::$instance;
    }

    /**
     * Get connection
     */
    public function getConnection() {
        return $this->connection;
    }

    /**
     * Prepare and execute query
     */
    public function prepare($query) {
        return $this->connection->prepare($query);
    }

    /**
     * Escape string
     */
    public function escape($string) {
        return $this->connection->real_escape_string($string);
    }

    /**
     * Close connection
     */
    public function close() {
        if ($this->connection) {
            $this->connection->close();
        }
    }

    /**
     * Begin transaction
     */
    public function beginTransaction() {
        $this->connection->begin_transaction();
    }

    /**
     * Commit transaction
     */
    public function commit() {
        $this->connection->commit();
    }

    /**
     * Rollback transaction
     */
    public function rollback() {
        $this->connection->rollback();
    }

    /**
     * Get last inserted ID
     */
    public function getLastInsertId() {
        return $this->connection->insert_id;
    }

    /**
     * Get affected rows
     */
    public function getAffectedRows() {
        return $this->connection->affected_rows;
    }
}

// Prevent cloning
final class SingletonDatabase extends Database {
    private function __clone() {}
    public function __wakeup() {
        throw new LogicException('Database singleton cannot be unserialized');
    }
}
?>