<?php

/**
 * This file contains the iwp_paging class
 *
 * @version $Id$
 * 
 *
 * @package IWP
 * @subpackage IWP_API
 */

/**
 * IWP Paging Class
 * This class is used by different sections to calculate paging links
 *
 * @package IWP
 * @subpackage IWP_API
 */

class iwp_paging extends iwp_engine {
	/**
	 * Instance
	 * This static variable holds the current instance of this object being loaded.
	 * So using the getInstance function anywhere will return the very same instance.
	 *
	 * @var iwp_paging Instance
	 */
	public static $Instance;

	/**
	 * The amount of items per page
	 * @var integer
	 */
	public $ItemsPerPage = 0;

	/**
	 * The total number of pages
	 * @var integer
	 */
	public $PageCount = 0;

	/**
	 * The current page number
	 * @var integer
	 */
	public $CurrentPage = 0;

	/**
	 * The URL for the previous page
	 * @var string
	 */
	public $PreviousURL = '';

	/**
	 * The URL for the next page
	 * @var string
	 */
	public $NextURL = '';

	/**
	 * The URL for the first page
	 *
	 * @var string
	 */
	public $FirstURL = '';

	/**
	 * The URL for the last (final) page
	 *
	 * @var string
	 */
	public $LastURL = '';

	/**
	 * The array of all the pages and their links
	 * @var array
	 */
	public $PageList = array();

	/**
	 * The string to replace page numbers with in provided urls, the default is %d
	 * @var string
	 */
	public $ReplaceToken = '%d';

	/**
	 * getInstance
	 * This is a static function that sets up the class instance and stores it to the static variable. It will then return that instantiation in the future.
	 *
	 * @return iwp_paging Returns the instantiated object
	 **/
	public static function getInstance(){
		if(!isset(self::$Instance)){
			self::$Instance = new self();
		}
		return self::$Instance;
	}


	/**
	 * Constructor.
	 *
	 * For convenience, if the required parameters for SetPaging are passed, it will automatically be called.
	 *
	 * @param  Integer $totalItems
	 * @param  Integer $itemsPerPage
	 * @param  Integer $requestPage
	 * @param  String  $url
	 * @param  Integer $numPagesToShow
	 * @return Object  iwp_paging
	 */
	public function __construct($totalItems = null, $itemsPerPage = null, $requestPage = null, $url = null, $numPagesToShow = 5)
	{
		parent::__construct();

		if (isset($totalItems) && isset($itemsPerPage) && isset($requestPage) && isset($url)) {
			$this->SetPaging($totalItems, $itemsPerPage, $requestPage, $url, $numPagesToShow);
		}
	}

	/**
	 * The main paging function, taking in the arguments and making all the calculations for the paging. It sets the next & previous links. It sets the page count and the page list.
	 *
	 * @param integer $totalItems The total number of items across all pages
	 * @param integer $itemsPerPage The maximum number of items to have on 1 page
	 * @param integer $requestPage The current page number (not number of items)
	 * @param string $url The URL structure to add the page number to. It should have a placeholder in it for page numbers such as %d (customisable using the $ReplaceToken property)
	 * @param integer $numPagesToShow The number of pages that should be displayed in the list of pages
	 *
	 * @return void
	 */
	function SetPaging($totalItems, $itemsPerPage, $requestPage, $url, $numPagesToShow = 5) {

		$this->ItemsPerPage = $itemsPerPage;
		$numPages = (int) ceil($totalItems / $itemsPerPage);

		if($numPagesToShow > $numPages){
			$numPagesToShow = $numPages;
		}

		if ($numPages <= 1) {
			$this->CurrentPage = 1;
			$this->NextURL = '';
			$this->PreviousURL = '';
			$this->PageList = array();
			$this->PageCount = 0;
			$this->FirstURL = '';
			$this->LastURL = '';
		} else {

			$requestPage = (int)$requestPage;

			if($requestPage > $numPages){
				$requestPage = $numPages;
			}

			if($requestPage < 1){
				$requestPage = 1;
			}

			$this->CurrentPage = $requestPage;
			$this->FirstURL = str_replace($this->ReplaceToken, 1, $url);
			$this->LastURL  = str_replace($this->ReplaceToken, $numPages, $url);

			if(($this->CurrentPage+1) <= $numPages){
				$this->NextURL = str_replace($this->ReplaceToken, ($this->CurrentPage+1), $url);
			} else {
				$this->NextURL =  str_replace($this->ReplaceToken, $numPages, $url);
			}

			if ($this->CurrentPage > 1) {
				$this->PreviousURL = str_replace($this->ReplaceToken, ($this->CurrentPage-1) ,$url);
			} else {
				$this->PreviousURL = str_replace($this->ReplaceToken, 1, $url);
			}

			if ($numPages > $numPagesToShow) {
				$start_page = $this->CurrentPage - (floor($numPagesToShow / 2));
				if ($start_page < 1){
					$start_page = 1;
				}

				$end_page = $this->CurrentPage + (floor($numPagesToShow / 2));

				if ($end_page > $numPages){
					$end_page = $numPages;
				}
				if ($end_page < $numPagesToShow){
					$end_page = $numPagesToShow;
				}

				$pagestoshow = ($end_page - $start_page);
				if (($pagestoshow < $numPagesToShow) && ($numPages > $numPagesToShow)){
					$start_page = ($end_page - $numPagesToShow + 1);
				}
			} else {
				$start_page = 1;
				$end_page = $numPages;
			}

			for ($pageid = $start_page; $pageid <= $end_page; $pageid++) {
				if ($pageid > $numPages){
					break;
				}
				$this->PageList[$pageid] = str_replace($this->ReplaceToken, $pageid ,$url);
			}

			$this->PageCount = $numPages;
		}
	}

	/**
	 * Returns the starting limit as an integer. Useful so we don't have to do repeat calculations when
	 * manually querying the database and sending a starting limit. A iwp_paging::getEndLimit() was added
	 * to complement the usage of iwp_paging::getStartLimit().
	 *
	 * @return int
	 */
	public function getStartLimit()
	{
		$start = ($this->CurrentPage - 1) * $this->ItemsPerPage;

		if (!$start) {
			$start = 0;
		}

		return $start;
	}

	/**
	 * Retruns the ending limit as an integer. Somewhat redundant because it just returns the property,
	 * but it was added for consistency as a complement to iwp_paging::getStartLimit() as well as to
	 * a logical way to generate an limiter for a database query. If the API changes in iwp_paging, then
	 * changing the logic to generate the end limit will only have to be changed here.
	 *
	 * @return int
	 */
	public function getEndLimit()
	{
		$end = $this->ItemsPerPage;

		if (!$end) {
			$end = 10;
		}

		return $end;
	}
}