<?php
/**
 * @link http://www.yiiframework.com/
 * @copyright Copyright (c) 2008 Yii Software LLC
 * @license http://www.yiiframework.com/license/
 */

namespace yii\data;

use Yii;
use yii\base\Object;
use yii\web\Request;

/**
 * Pagination represents information relevant to pagination of data items.
 *
 * When data needs to be rendered in multiple pages, Pagination can be used to
 * represent information such as [[totalCount|total item count]], [[pageSize|page size]],
 * [[page|current page]], etc. These information can be passed to [[\yii\widgets\LinkPager|pagers]]
 * to render pagination buttons or links.
 *
 * The following example shows how to create a pagination object and feed it
 * to a pager.
 *
 * Controller action:
 *
 * ~~~
 * function actionIndex()
 * {
 *     $query = Article::find()->where(['status' => 1]);
 *     $countQuery = clone $query;
 *     $pages = new Pagination(['totalCount' => $countQuery->count()]);
 *     $models = $query->offset($pages->offset)
 *         ->limit($pages->limit)
 *         ->all();
 *
 *     return $this->render('index', [
 *          'models' => $models,
 *          'pages' => $pages,
 *     ]);
 * }
 * ~~~
 *
 * View:
 *
 * ~~~
 * foreach ($models as $model) {
 *     // display $model here
 * }
 *
 * // display pagination
 * echo LinkPager::widget([
 *     'pagination' => $pages,
 * ]);
 * ~~~
 *
 * @property integer $limit The limit of the data. This may be used to set the LIMIT value for a SQL statement
 * for fetching the current page of data. Note that if the page size is infinite, a value -1 will be returned.
 * This property is read-only.
 * @property integer $offset The offset of the data. This may be used to set the OFFSET value for a SQL
 * statement for fetching the current page of data. This property is read-only.
 * @property integer $page The zero-based current page number.
 * @property integer $pageCount Number of pages. This property is read-only.
 *
 * @author Qiang Xue <qiang.xue@gmail.com>
 * @since 2.0
 */
class Pagination extends Object
{
	const LINK_SELF = 'self';
	const LINK_NEXT = 'next';
	const LINK_PREV = 'prev';
	const LINK_FIRST = 'first';
	const LINK_LAST = 'last';

	/**
	 * @var string name of the parameter storing the current page index.
	 * @see params
	 */
	public $pageParam = 'page';
	/**
	 * @var string name of the parameter storing the page size.
	 * @see params
	 */
	public $pageSizeParam = 'per-page';
	/**
	 * @var boolean whether to always have the page parameter in the URL created by [[createUrl()]].
	 * If false and [[page]] is 0, the page parameter will not be put in the URL.
	 */
	public $forcePageParam = true;
	/**
	 * @var string the route of the controller action for displaying the paged contents.
	 * If not set, it means using the currently requested route.
	 */
	public $route;
	/**
	 * @var array parameters (name => value) that should be used to obtain the current page number
	 * and to create new pagination URLs. If not set, all parameters from $_GET will be used instead.
	 *
	 * In order to add hash to all links use `array_merge($_GET, ['#' => 'my-hash'])`.
	 *
	 * The array element indexed by [[pageParam]] is considered to be the current page number (defaults to 0);
	 * while the element indexed by [[pageSizeParam]] is treated as the page size (defaults to [[defaultPageSize]]).
	 */
	public $params;
	/**
	 * @var \yii\web\UrlManager the URL manager used for creating pagination URLs. If not set,
	 * the "urlManager" application component will be used.
	 */
	public $urlManager;
	/**
	 * @var boolean whether to check if [[page]] is within valid range.
	 * When this property is true, the value of [[page]] will always be between 0 and ([[pageCount]]-1).
	 * Because [[pageCount]] relies on the correct value of [[totalCount]] which may not be available
	 * in some cases (e.g. MongoDB), you may want to set this property to be false to disable the page
	 * number validation. By doing so, [[page]] will return the value indexed by [[pageParam]] in [[params]].
	 */
	public $validatePage = true;
	/**
	 * @var integer total number of items.
	 */
	public $totalCount = 0;
	/**
	 * @var integer the default page size. This property will be returned by [[pageSize]] when page size
	 * cannot be determined by [[pageSizeParam]] from [[params]].
	 */
	public $defaultPageSize = 20;
	/**
	 * @var array|boolean the page size limits. The first array element stands for the minimal page size, and the second
	 * the maximal page size. If this is false, it means [[pageSize]] should always return the value of [[defaultPageSize]].
	 */
	public $pageSizeLimit = [1, 50];
	/**
	 * @var integer number of items on each page.
	 * If it is less than 1, it means the page size is infinite, and thus a single page contains all items.
	 */
	private $_pageSize;


	/**
	 * @return integer number of pages
	 */
	public function getPageCount()
	{
		$pageSize = $this->getPageSize();
		if ($pageSize < 1) {
			return $this->totalCount > 0 ? 1 : 0;
		} else {
			$totalCount = $this->totalCount < 0 ? 0 : (int)$this->totalCount;
			return (int)(($totalCount + $pageSize - 1) / $pageSize);
		}
	}

	private $_page;

	/**
	 * Returns the zero-based current page number.
	 * @param boolean $recalculate whether to recalculate the current page based on the page size and item count.
	 * @return integer the zero-based current page number.
	 */
	public function getPage($recalculate = false)
	{
		if ($this->_page === null || $recalculate) {
			$page = (int)$this->getQueryParam($this->pageParam, 1) - 1;
			$this->setPage($page, true);
		}
		return $this->_page;
	}

	/**
	 * Sets the current page number.
	 * @param integer $value the zero-based index of the current page.
	 * @param boolean $validatePage whether to validate the page number. Note that in order
	 * to validate the page number, both [[validatePage]] and this parameter must be true.
	 */
	public function setPage($value, $validatePage = false)
	{
		if ($value === null) {
			$this->_page = null;
		} else {
			$value = (int)$value;
			if ($validatePage && $this->validatePage) {
				$pageCount = $this->getPageCount();
				if ($value >= $pageCount) {
					$value = $pageCount - 1;
				}
			}
			if ($value < 0) {
				$value = 0;
			}
			$this->_page = $value;
		}
	}

	/**
	 * Returns the number of items per page.
	 * By default, this method will try to determine the page size by [[pageSizeParam]] in [[params]].
	 * If the page size cannot be determined this way, [[defaultPageSize]] will be returned.
	 * @return integer the number of items per page.
	 * @see pageSizeLimit
	 */
	public function getPageSize()
	{
		if ($this->_pageSize === null) {
			if (empty($this->pageSizeLimit)) {
				$pageSize = $this->defaultPageSize;
				$this->setPageSize($pageSize);
			} else {
				$pageSize = (int)$this->getQueryParam($this->pageSizeParam, $this->defaultPageSize);
				$this->setPageSize($pageSize, true);
			}
		}
		return $this->_pageSize;
	}

	/**
	 * @param integer $value the number of items per page.
	 * @param boolean $validatePageSize whether to validate page size.
	 */
	public function setPageSize($value, $validatePageSize = false)
	{
		if ($value === null) {
			$this->_pageSize = null;
		} else {
			$value = (int)$value;
			if ($validatePageSize && count($this->pageSizeLimit) === 2 && isset($this->pageSizeLimit[0], $this->pageSizeLimit[1])) {
				if ($value < $this->pageSizeLimit[0]) {
					$value = $this->pageSizeLimit[0];
				} elseif ($value > $this->pageSizeLimit[1]) {
					$value = $this->pageSizeLimit[1];
				}
			}
			$this->_pageSize = $value;
		}
	}

	/**
	 * Creates the URL suitable for pagination with the specified page number.
	 * This method is mainly called by pagers when creating URLs used to perform pagination.
	 * @param integer $page the zero-based page number that the URL should point to.
	 * @param boolean $absolute whether to create an absolute URL. Defaults to `false`.
	 * @return string the created URL
	 * @see params
	 * @see forcePageParam
	 */
	public function createUrl($page, $absolute = false)
	{
		if (($params = $this->params) === null) {
			$request = Yii::$app->getRequest();
			$params = $request instanceof Request ? $request->getQueryParams() : [];
		}
		if ($page > 0 || $page >= 0 && $this->forcePageParam) {
			$params[$this->pageParam] = $page + 1;
		} else {
			unset($params[$this->pageParam]);
		}
		$pageSize = $this->getPageSize();
		if ($pageSize != $this->defaultPageSize) {
			$params[$this->pageSizeParam] = $pageSize;
		} else {
			unset($params[$this->pageSizeParam]);
		}
		$params[0] = $this->route === null ? Yii::$app->controller->getRoute() : $this->route;
		$urlManager = $this->urlManager === null ? Yii::$app->getUrlManager() : $this->urlManager;
		if ($absolute) {
			return $urlManager->createAbsoluteUrl($params);
		} else {
			return $urlManager->createUrl($params);
		}
	}

	/**
	 * @return integer the offset of the data. This may be used to set the
	 * OFFSET value for a SQL statement for fetching the current page of data.
	 */
	public function getOffset()
	{
		$pageSize = $this->getPageSize();
		return $pageSize < 1 ? 0 : $this->getPage() * $pageSize;
	}

	/**
	 * @return integer the limit of the data. This may be used to set the
	 * LIMIT value for a SQL statement for fetching the current page of data.
	 * Note that if the page size is infinite, a value -1 will be returned.
	 */
	public function getLimit()
	{
		$pageSize = $this->getPageSize();
		return $pageSize < 1 ? -1 : $pageSize;
	}

	/**
	 * Returns a whole set of links for navigating to the first, last, next and previous pages.
	 * @param boolean $absolute whether the generated URLs should be absolute.
	 * @return array the links for navigational purpose. The array keys specify the purpose of the links (e.g. [[LINK_FIRST]]),
	 * and the array values are the corresponding URLs.
	 */
	public function getLinks($absolute = false)
	{
		$currentPage = $this->getPage();
		$pageCount = $this->getPageCount();
		$links = [
			self::LINK_SELF => $this->createUrl($currentPage, $absolute),
		];
		if ($currentPage > 0) {
			$links[self::LINK_FIRST] = $this->createUrl(0, $absolute);
			$links[self::LINK_PREV] = $this->createUrl($currentPage - 1, $absolute);
		}
		if ($currentPage < $pageCount - 1) {
			$links[self::LINK_NEXT] = $this->createUrl($currentPage + 1, $absolute);
			$links[self::LINK_LAST] = $this->createUrl($pageCount - 1, $absolute);
		}
		return $links;
	}

	/**
	 * Returns the value of the specified query parameter.
	 * This method returns the named parameter value from [[params]]. Null is returned if the value does not exist.
	 * @param string $name the parameter name
	 * @param string $defaultValue the value to be returned when the specified parameter does not exist in [[params]].
	 * @return string the parameter value
	 */
	protected function getQueryParam($name, $defaultValue = null)
	{
		if (($params = $this->params) === null) {
			$request = Yii::$app->getRequest();
			$params = $request instanceof Request ? $request->getQueryParams() : [];
		}
		return isset($params[$name]) && is_scalar($params[$name]) ? $params[$name] : $defaultValue;
	}
}