<?php

class Cache {
    private static $instance = null;
    private $cache_path;
    private $duration;

    private function __construct() {
        $this->cache_path = CACHE_PATH;
        $this->duration = CACHE_DURATION;
        
        if (!file_exists($this->cache_path)) {
            mkdir($this->cache_path, 0755, true);
        }
    }

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

    public function set($key, $data) {
        if (!CACHE_ENABLED) return false;
        
        $cache_file = $this->getCacheFile($key);
        $cache_data = [
            'expires' => time() + $this->duration,
            'data' => $data
        ];
        
        return file_put_contents($cache_file, serialize($cache_data)) !== false;
    }

    public function get($key) {
        if (!CACHE_ENABLED) return false;
        
        $cache_file = $this->getCacheFile($key);
        
        if (!file_exists($cache_file)) {
            return false;
        }

        $cache_data = unserialize(file_get_contents($cache_file));
        
        if ($cache_data['expires'] < time()) {
            unlink($cache_file);
            return false;
        }
        
        return $cache_data['data'];
    }

    public function delete($key) {
        $cache_file = $this->getCacheFile($key);
        if (file_exists($cache_file)) {
            return unlink($cache_file);
        }
        return true;
    }

    public function clear() {
        $files = glob($this->cache_path . '/*');
        foreach ($files as $file) {
            if (is_file($file)) {
                unlink($file);
            }
        }
        return true;
    }

    private function getCacheFile($key) {
        return $this->cache_path . '/' . md5($key) . '.cache';
    }
}