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

namespace yii\widgets;

use Yii;
use yii\base\InvalidConfigException;
use yii\helpers\Html;
use yii\base\Widget;
use yii\data\Pagination;

/**
 * LinkPager displays a list of hyperlinks that lead to different pages of target.
 *
 * LinkPager works with a [[Pagination]] object which specifies the totally number
 * of pages and the current page number.
 *
 * Note that LinkPager only generates the necessary HTML markups. In order for it
 * to look like a real pager, you should provide some CSS styles for it.
 * With the default configuration, LinkPager should look good using Twitter Bootstrap CSS framework.
 *
 * @author Qiang Xue <qiang.xue@gmail.com>
 * @since 2.0
 */
class LinkPager extends Widget
{
	/**
	 * @var Pagination the pagination object that this pager is associated with.
	 * You must set this property in order to make LinkPager work.
	 */
	public $pagination;
	/**
	 * @var array HTML attributes for the pager container tag.
	 */
	public $options = ['class' => 'pagination'];
	/**
	 * @var string the CSS class for the "first" page button.
	 */
	public $firstPageCssClass = 'first';
	/**
	 * @var string the CSS class for the "last" page button.
	 */
	public $lastPageCssClass = 'last';
	/**
	 * @var string the CSS class for the "previous" page button.
	 */
	public $prevPageCssClass = 'prev';
	/**
	 * @var string the CSS class for the "next" page button.
	 */
	public $nextPageCssClass = 'next';
	/**
	 * @var string the CSS class for the active (currently selected) page button.
	 */
	public $activePageCssClass = 'active';
	/**
	 * @var string the CSS class for the disabled page buttons.
	 */
	public $disabledPageCssClass = 'disabled';
	/**
	 * @var integer maximum number of page buttons that can be displayed. Defaults to 10.
	 */
	public $maxButtonCount = 10;
	/**
	 * @var string the label for the "next" page button. Note that this will NOT be HTML-encoded.
	 * If this property is null, the "next" page button will not be displayed.
	 */
	public $nextPageLabel = '&raquo;';
	/**
	 * @var string the text label for the previous page button. Note that this will NOT be HTML-encoded.
	 * If this property is null, the "previous" page button will not be displayed.
	 */
	public $prevPageLabel = '&laquo;';
	/**
	 * @var string the text label for the "first" page button. Note that this will NOT be HTML-encoded.
	 * If this property is null, the "first" page button will not be displayed.
	 */
	public $firstPageLabel;
	/**
	 * @var string the text label for the "last" page button. Note that this will NOT be HTML-encoded.
	 * If this property is null, the "last" page button will not be displayed.
	 */
	public $lastPageLabel;


	/**
	 * Initializes the pager.
	 */
	public function init()
	{
		if ($this->pagination === null) {
			throw new InvalidConfigException('The "pagination" property must be set.');
		}
	}

	/**
	 * Executes the widget.
	 * This overrides the parent implementation by displaying the generated page buttons.
	 */
	public function run()
	{
		echo $this->renderPageButtons();
	}

	/**
	 * Renders the page buttons.
	 * @return string the rendering result
	 */
	protected function renderPageButtons()
	{
		$buttons = [];

		$pageCount = $this->pagination->getPageCount();
		$currentPage = $this->pagination->getPage();

		// first page
		if ($this->firstPageLabel !== null) {
			$buttons[] = $this->renderPageButton($this->firstPageLabel, 0, $this->firstPageCssClass, $currentPage <= 0, false);
		}

		// prev page
		if ($this->prevPageLabel !== null) {
			if (($page = $currentPage - 1) < 0) {
				$page = 0;
			}
			$buttons[] = $this->renderPageButton($this->prevPageLabel, $page, $this->prevPageCssClass, $currentPage <= 0, false);
		}

		// internal pages
		list($beginPage, $endPage) = $this->getPageRange();
		for ($i = $beginPage; $i <= $endPage; ++$i) {
			$buttons[] = $this->renderPageButton($i + 1, $i, null, false, $i == $currentPage);
		}

		// next page
		if ($this->nextPageLabel !== null) {
			if (($page = $currentPage + 1) >= $pageCount - 1) {
				$page = $pageCount - 1;
			}
			$buttons[] = $this->renderPageButton($this->nextPageLabel, $page, $this->nextPageCssClass, $currentPage >= $pageCount - 1, false);
		}

		// last page
		if ($this->lastPageLabel !== null) {
			$buttons[] = $this->renderPageButton($this->lastPageLabel, $pageCount - 1, $this->lastPageCssClass, $currentPage >= $pageCount - 1, false);
		}

		return Html::tag('ul', implode("\n", $buttons), $this->options);
	}

	/**
	 * Renders a page button.
	 * You may override this method to customize the generation of page buttons.
	 * @param string $label the text label for the button
	 * @param integer $page the page number
	 * @param string $class the CSS class for the page button.
	 * @param boolean $disabled whether this page button is disabled
	 * @param boolean $active whether this page button is active
	 * @return string the rendering result
	 */
	protected function renderPageButton($label, $page, $class, $disabled, $active)
	{
		$options = ['class' => $class === '' ? null : $class];
		if ($active) {
			Html::addCssClass($options, $this->activePageCssClass);
		}
		if ($disabled) {
			Html::addCssClass($options, $this->disabledPageCssClass);
			return Html::tag('li', Html::tag('span', $label), $options);
		}
		return Html::tag('li', Html::a($label, $this->pagination->createUrl($page), ['data-page' => $page]), $options);
	}

	/**
	 * @return array the begin and end pages that need to be displayed.
	 */
	protected function getPageRange()
	{
		$currentPage = $this->pagination->getPage();
		$pageCount = $this->pagination->getPageCount();

		$beginPage = max(0, $currentPage - (int)($this->maxButtonCount / 2));
		if (($endPage = $beginPage + $this->maxButtonCount - 1) >= $pageCount) {
			$endPage = $pageCount - 1;
			$beginPage = max(0, $endPage - $this->maxButtonCount + 1);
		}
		return [$beginPage, $endPage];
	}
}
