<?php
/**
 * Veritabanı Sınıfı
 */

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

    private function __construct() {
        try {
            $dsn = "mysql:host=" . DB_HOST . ";dbname=" . DB_NAME . ";charset=" . DB_CHARSET;
            $options = [
                PDO::ATTR_ERRMODE => PDO::ERRMODE_EXCEPTION,
                PDO::ATTR_DEFAULT_FETCH_MODE => PDO::FETCH_ASSOC,
                PDO::ATTR_EMULATE_PREPARES => false,
            ];
            
            $this->connection = new PDO($dsn, DB_USER, DB_PASS, $options);
        } catch (PDOException $e) {
            if (DEBUG_MODE) {
                die("Veritabanı bağlantı hatası: " . $e->getMessage());
            } else {
                die("Veritabanı bağlantı hatası!");
            }
        }
    }

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

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

    // Query helper metodları
    public function query($sql, $params = []) {
        try {
            $stmt = $this->connection->prepare($sql);
            
            // Parametreleri bind et
            if (!empty($params)) {
                // Named parametreler (associative array)
                if (array_keys($params) !== range(0, count($params) - 1)) {
                    foreach ($params as $key => $value) {
                        $paramName = ':' . ltrim($key, ':');
                        $stmt->bindValue($paramName, $value);
                    }
                } else {
                    // Positional parametreler (indexed array)
                    $stmt->execute($params);
                    return $stmt;
                }
            }
            
            $stmt->execute();
            return $stmt;
        } catch (PDOException $e) {
            if (DEBUG_MODE) {
                die("Query hatası: " . $e->getMessage() . "<br>SQL: " . $sql . "<br>Params: " . print_r($params, true));
            }
            return false;
        }
    }

    public function fetchAll($sql, $params = []) {
        $stmt = $this->query($sql, $params);
        return $stmt ? $stmt->fetchAll() : [];
    }

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

    public function insert($table, $data) {
        $fields = implode(', ', array_keys($data));
        $placeholders = ':' . implode(', :', array_keys($data));
        
        $sql = "INSERT INTO {$table} ({$fields}) VALUES ({$placeholders})";
        $this->query($sql, $data);
        
        return $this->connection->lastInsertId();
    }

    public function update($table, $data, $where, $whereParams = []) {
        $set = [];
        $params = [];
        
        // SET kısmı için named parametreler
        foreach ($data as $key => $value) {
            $setKey = "set_" . $key;
            $set[] = "{$key} = :{$setKey}";
            $params[$setKey] = $value;
        }
        $set = implode(', ', $set);
        
        // WHERE kısmı için named parametreler (positional ? yerine)
        $whereSql = $where;
        if (!empty($whereParams)) {
            $paramIndex = 0;
            $whereSql = preg_replace_callback('/\?/', function() use (&$paramIndex, &$params, $whereParams) {
                $paramName = "where_param_" . $paramIndex;
                $params[$paramName] = $whereParams[$paramIndex];
                $paramIndex++;
                return ":{$paramName}";
            }, $where);
        }
        
        $sql = "UPDATE {$table} SET {$set} WHERE {$whereSql}";
        
        return $this->query($sql, $params);
    }

    public function delete($table, $where, $params = []) {
        // WHERE kısmı için named parametreler (positional ? yerine)
        $whereSql = $where;
        $namedParams = [];
        if (!empty($params) && strpos($where, '?') !== false) {
            $paramIndex = 0;
            $whereSql = preg_replace_callback('/\?/', function() use (&$paramIndex, &$namedParams, $params) {
                $paramName = "where_param_" . $paramIndex;
                $namedParams[$paramName] = $params[$paramIndex];
                $paramIndex++;
                return ":{$paramName}";
            }, $where);
            $params = $namedParams;
        }
        
        $sql = "DELETE FROM {$table} WHERE {$whereSql}";
        return $this->query($sql, $params);
    }
}