<?php

/**
 * @package KantPHP
 * @author  Zhenqiang Zhang <zhenqiang.zhang@hotmail.com>
 * @copyright (c) KantPHP Studio, All rights reserved.
 * @license http://www.opensource.org/licenses/BSD-3-Clause  The BSD 3-Clause License
 */
namespace Kant\Widget;

use Kant\Kant;
use Kant\Exception\InvalidConfigException;
use Kant\Helper\Html;
use Kant\Widget\Widget;
use Kant\Data\Pagination;

/**
 * LinkPager displays a list of hyperlinks that lead to different pages of target.
 *
 * LinkPager works with a [[Pagination]] object which specifies the total 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.
     * @see \Kant\Helper\Html::renderTagAttributes() for details on how attributes are being rendered.
     */
    public $options = [
        'class' => 'pagination'
    ];

    /**
     *
     * @var array HTML attributes for the link in a pager container tag.
     * @see \yii\helpers\Html::renderTagAttributes() for details on how attributes are being rendered.
     */
    public $linkOptions = [];

    /**
     *
     * @var string the CSS class for the each page button.
     * @since 2.0.7
     */
    public $pageCssClass = null;

    /**
     *
     * @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|boolean the label for the "next" page button. Note that this will NOT be HTML-encoded.
     *      If this property is false, the "next" page button will not be displayed.
     */
    public $nextPageLabel = '&raquo;';

    /**
     *
     * @var string|boolean the text label for the previous page button. Note that this will NOT be HTML-encoded.
     *      If this property is false, the "previous" page button will not be displayed.
     */
    public $prevPageLabel = '&laquo;';

    /**
     *
     * @var string|boolean the text label for the "first" page button. Note that this will NOT be HTML-encoded.
     *      If it's specified as true, page number will be used as label.
     *      Default is false that means the "first" page button will not be displayed.
     */
    public $firstPageLabel = false;

    /**
     *
     * @var string|boolean the text label for the "last" page button. Note that this will NOT be HTML-encoded.
     *      If it's specified as true, page number will be used as label.
     *      Default is false that means the "last" page button will not be displayed.
     */
    public $lastPageLabel = false;

    /**
     *
     * @var boolean whether to register link tags in the HTML header for prev, next, first and last page.
     *      Defaults to `false` to avoid conflicts when multiple pagers are used on one page.
     * @see http://www.w3.org/TR/html401/struct/links.html#h-12.1.2
     * @see registerLinkTags()
     */
    public $registerLinkTags = false;

    /**
     *
     * @var boolean Hide widget when only one page exist.
     */
    public $hideOnSinglePage = true;

    /**
     * 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()
    {
        if ($this->registerLinkTags) {
            $this->registerLinkTags();
        }
        echo $this->renderPageButtons();
    }

    /**
     * Registers relational link tags in the html header for prev, next, first and last page.
     * These links are generated using [[\yii\data\Pagination::getLinks()]].
     * 
     * @see http://www.w3.org/TR/html401/struct/links.html#h-12.1.2
     */
    protected function registerLinkTags()
    {
        $view = $this->getView();
        foreach ($this->pagination->getLinks() as $rel => $href) {
            $view->registerLinkTag([
                'rel' => $rel,
                'href' => $href
            ], $rel);
        }
    }

    /**
     * Renders the page buttons.
     * 
     * @return string the rendering result
     */
    protected function renderPageButtons()
    {
        $pageCount = $this->pagination->getPageCount();
        if ($pageCount < 2 && $this->hideOnSinglePage) {
            return '';
        }
        
        $buttons = [];
        $currentPage = $this->pagination->getPage();
        
        // first page
        $firstPageLabel = $this->firstPageLabel === true ? '1' : $this->firstPageLabel;
        if ($firstPageLabel !== false) {
            $buttons[] = $this->renderPageButton($firstPageLabel, 0, $this->firstPageCssClass, $currentPage <= 0, false);
        }
        
        // prev page
        if ($this->prevPageLabel !== false) {
            if (($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 ($this->nextPageLabel !== false) {
            if (($page = $currentPage + 1) >= $pageCount - 1) {
                $page = $pageCount - 1;
            }
            $buttons[] = $this->renderPageButton($this->nextPageLabel, $page, $this->nextPageCssClass, $currentPage >= $pageCount - 1, false);
        }
        
        // last page
        $lastPageLabel = $this->lastPageLabel === true ? $pageCount : $this->lastPageLabel;
        if ($lastPageLabel !== false) {
            $buttons[] = $this->renderPageButton($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)
    {
        $options = [
            'class' => empty($class) ? $this->pageCssClass : sprintf("%s %s", $this->pageCssClass, $class)
        ];
        if ($active) {
            Html::addCssClass($options, $this->activePageCssClass);
        }
        if ($disabled) {
            Html::addCssClass($options, $this->disabledPageCssClass);
            
            return Html::tag('li', Html::tag('span', $label), $options);
        }
        $linkOptions = $this->linkOptions;
        $linkOptions['data-page'] = $page;
        
        return Html::tag('li', Html::a($label, $this->pagination->createUrl($page), $linkOptions), $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
        ];
    }
}
