<?php
/**
 * CodeIgniter
 *
 * An open source application development framework for PHP
 *
 * This content is released under the MIT License (MIT)
 *
 * Copyright (c) 2014 - 2016, British Columbia Institute of Technology
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 *
 * @package      CodeIgniter
 * @author       EllisLab Dev Team
 * @copyright    Copyright (c) 2008 - 2014, EllisLab, Inc. (https://ellislab.com/)
 * @copyright    Copyright (c) 2014 - 2016, British Columbia Institute of Technology (http://bcit.ca/)
 * @license      http://opensource.org/licenses/MIT    MIT License
 * @link         https://codeigniter.com
 * @since        Version 1.0.0
 * @filesource
 */
defined('BASEPATH') OR exit('No direct script access allowed');

/**
 * Database Cache Class
 *
 * @category      Database
 * @author        EllisLab Dev Team
 * @link          https://codeigniter.com/user_guide/database/
 */
class CI_DB_Cache {

	/**
	 * CI Singleton
	 *
	 * @var    object
	 */
	public $CI;

	/**
	 * Database object
	 *
	 * Allows passing of DB object so that multiple database connections
	 * and returned DB objects can be supported.
	 *
	 * @var    object
	 */
	public $db;

	// --------------------------------------------------------------------

	/**
	 * Constructor
	 *
	 * @param    object &$db
	 *
	 * @return    void
	 */
	public function __construct(&$db) {
		// Assign the main CI object to $this->CI and load the file helper since we use it a lot
		$this->CI =& get_instance();
		$this->db =& $db;
		$this->CI->load->helper('file');

		$this->check_path();

	}

	// --------------------------------------------------------------------

	/**
	 * Set Cache Directory Path
	 *
	 * @param    string $path Path to the cache directory
	 *
	 * @return    bool
	 */
	public function check_path($path = '') {
		if($path === '') {
			if($this->db->cachedir === '') {
				return $this->db->cache_off();
			}

			$path = $this->db->cachedir;
		}

		// Add a trailing slash to the path if needed
		$path = realpath($path)
			? rtrim(realpath($path), DIRECTORY_SEPARATOR) . DIRECTORY_SEPARATOR
			: rtrim($path, '/') . '/';

		if(!is_dir($path)) {
			log_message('debug', 'DB cache path error: ' . $path);

			// If the path is wrong we'll turn off caching
			return $this->db->cache_off();
		}

		if(!is_really_writable($path)) {
			log_message('debug', 'DB cache dir not writable: ' . $path);

			// If the path is not really writable we'll turn off caching
			return $this->db->cache_off();
		}

		$this->db->cachedir = $path;
		return TRUE;
	}

	// --------------------------------------------------------------------

	/**
	 * Retrieve a cached query
	 *
	 * The URI being requested will become the name of the cache sub-folder.
	 * An MD5 hash of the SQL statement will become the cache file name.
	 *
	 * @param    string $sql
	 *
	 * @return    string
	 */
	public function read($sql) {
		$segment_one = ($this->CI->uri->segment(1) == FALSE) ? 'default' : $this->CI->uri->segment(1);
		$segment_two = ($this->CI->uri->segment(2) == FALSE) ? 'index' : $this->CI->uri->segment(2);


		// BEGIN --- modification for supporting multi-level cache folders

		if(is_array($this->CI->config->item('multi_level_cache_folders'))) {
			$uri_md5  = md5($segment_one . '+' . $segment_two);
			$layer    = $this->get_folder_layers($uri_md5);
			$filepath = $this->db->cachedir . $segment_one . '/' . $segment_two . '/' . trim(implode('/', $layer), '/') . '/' . $uri_md5;
		} else {
			$filepath = $this->db->cachedir . $segment_one . '/' . $segment_two . '/' . md5($sql);
		}

		// END --- modification for supporting multi-level cache folders

		$cachedata = FALSE;
		if(file_exists($filepath) && FALSE === ($cachedata = @file_get_contents($filepath))) {
			return FALSE;
		}

		return unserialize($cachedata);
	}

	// --------------------------------------------------------------------

	/**
	 * Write a query to a cache file
	 *
	 * @param    string $sql
	 * @param    object $object
	 *
	 * @return    bool
	 */
	public function write($sql, $object) {
		$segment_one = ($this->CI->uri->segment(1) == FALSE) ? 'default' : $this->CI->uri->segment(1);
		$segment_two = ($this->CI->uri->segment(2) == FALSE) ? 'index' : $this->CI->uri->segment(2);


		// BEGIN --- modification for supporting multi-level cache folders

		if(is_array($this->CI->config->item('multi_level_cache_folders'))) {
			$uri_md5  = md5($segment_one . '+' . $segment_two);
			$layer    = $this->get_folder_layers($uri_md5);
			$dir_path = $this->db->cachedir . $segment_one . '/' . $segment_two . '/' . trim(implode('/', $layer), '/') . '/';

			if(!is_dir($dir_path)) {
				$old = umask(0);
				mkdir($dir_path, 0777, TRUE);
				umask($old);
			}
		} else {
			$dir_path = $this->db->cachedir . $segment_one . '/' . $segment_two . '/';
		}

		$filename = md5($sql);

		// END --- modification for supporting multi-level cache folders

		if(write_file($dir_path . $filename, serialize($object)) === FALSE) {
			return FALSE;
		}

		chmod($dir_path . $filename, 0640);
		return TRUE;
	}

	// --------------------------------------------------------------------

	/**
	 * Delete cache files within a particular directory
	 *
	 * @param    string $segment_one
	 * @param    string $segment_two
	 *
	 * @return    void
	 */
	public function delete($segment_one = '', $segment_two = '') {
		if($segment_one === '') {
			$segment_one = ($this->CI->uri->segment(1) == FALSE) ? 'default' : $this->CI->uri->segment(1);
		}

		if($segment_two === '') {
			$segment_two = ($this->CI->uri->segment(2) == FALSE) ? 'index' : $this->CI->uri->segment(2);
		}

		if(is_array($this->CI->config->item('multi_level_cache_folders'))) {
			$uri_md5  = md5($segment_one . '+' . $segment_two);
			$layer    = $this->get_folder_layers($uri_md5);
			$dir_path = $this->db->cachedir . $segment_one . '/' . $segment_two . '/' . trim(implode('/', $layer), '/') . '/';
		} else {
			$dir_path = $this->db->cachedir . $segment_one . '/' . $segment_two . '/';
		}
		delete_files($dir_path, TRUE);
	}

	// --------------------------------------------------------------------

	/**
	 * Delete all existing cache files
	 *
	 * @return    void
	 */
	public function delete_all() {
		delete_files($this->db->cachedir, TRUE, TRUE);
	}

	/**
	 * @param $md5
	 *
	 * @return array
	 */
	private function get_folder_layers($md5) {
		$layer      = array();
		$last_key   = 0;
		$last_value = 0;

		foreach($this->CI->config->item('multi_level_cache_folders') AS $key => $value) {
			if($key != 0) {
				$key = $last_key + $last_value;
			}
			$layer[] = substr($md5, $key, $value);

			$last_key   = (int) $key;
			$last_value = (int) $value;
		}
		return $layer;
	}

}
