<?php

namespace App\Core;

use PDO;
use PDOException;

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

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

    public function getConnection(): PDO
    {
        if ($this->connection === null) {
            $this->connect();
        }
        return $this->connection;
    }

    private function connect(): void
    {
        try {
            $dsn = sprintf(
                'mysql:host=%s;port=%d;dbname=%s;charset=utf8mb4',
                DB_HOST,
                DB_PORT,
                DB_NAME
            );

            $options = [
                PDO::ATTR_ERRMODE => PDO::ERRMODE_EXCEPTION,
                PDO::ATTR_DEFAULT_FETCH_MODE => PDO::FETCH_ASSOC,
                PDO::ATTR_EMULATE_PREPARES => false,
                PDO::MYSQL_ATTR_INIT_COMMAND => "SET NAMES utf8mb4 COLLATE utf8mb4_unicode_ci"
            ];

            $this->connection = new PDO($dsn, DB_USER, DB_PASS, $options);

        } catch (PDOException $e) {
            error_log('Database connection failed: ' . $e->getMessage());
            throw new \Exception('Database connection failed');
        }
    }

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

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

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

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

    public function update(string $table, array $data, string $where, array $whereParams = []): int
    {
        $setParts = [];
        foreach (array_keys($data) as $column) {
            $setParts[] = "{$column} = :{$column}";
        }
        $setClause = implode(', ', $setParts);
        
        $sql = "UPDATE {$table} SET {$setClause} WHERE {$where}";
        
        $params = array_merge($data, $whereParams);
        $stmt = $this->query($sql, $params);
        
        return $stmt->rowCount();
    }

    public function delete(string $table, string $where, array $params = []): int
    {
        $sql = "DELETE FROM {$table} WHERE {$where}";
        $stmt = $this->query($sql, $params);
        return $stmt->rowCount();
    }

    public function beginTransaction(): bool
    {
        return $this->getConnection()->beginTransaction();
    }

    public function commit(): bool
    {
        return $this->getConnection()->commit();
    }

    public function rollback(): bool
    {
        return $this->getConnection()->rollback();
    }

    public function inTransaction(): bool
    {
        return $this->getConnection()->inTransaction();
    }

    public function quote(string $value): string
    {
        return $this->getConnection()->quote($value);
    }
}