php paginator markup generator

Paginator.php

<?php

namespace utils\markup\paginator;


class Paginator{

    private $template;

    private $templateDefault = [
        'prev' => '<li><a href="*url*">&laquo;</a></li>',
        'prev_disabled' => '',
        'next' => '<li><a href="*url*">&raquo;</a></li>',
        'next_disabled' => '',
        'link' => '<li><a href="*url*">*pageNumber*</a></li>',
        'link_active' => '<li class="active"><a href="*url*" >*pageNumber*</a></li>',
        'gap' => '<li class="disabled">&hellip;</li>',
        'wrapper' => '<nav class="paginator"><ul class="paginator">*links*</ul></nav>'
    ];

    private $urlPrefix;
    private $totalPages;
    private $activePage;
    private $nextURL;
    private $prevURL;

    private $gap1Start;
    private $gap1End;
    private $gap2Start;
    private $gap2End;
    private $gap1Length;
    private $gap2Length;

    private $HTML = '';

    /**
     * Paginator constructor.
     * @param $activePage
     * @param $perPage
     * @param $itemsCount
     * @param string $urlPrefix
     * @param int $indent
     * @param array $template
     * @return self
     */
    public function __construct($activePage, $perPage, $itemsCount, $urlPrefix = '', $indent = 0, $template = [])
    {
        $this->urlPrefix = $urlPrefix ? $urlPrefix.'&page=' : '?page=';
        $this->totalPages = ceil($itemsCount / $perPage);
        $this->activePage = (int) $activePage;

        $this->prevURL = $this->urlPrefix . ($activePage - 1);
        $this->nextURL = $this->urlPrefix . ($activePage + 1);
        if ($indent) {
            //  1 2 3  ... 6 7 8 9 10 ... 18 19 20
            $this->gap1Start = $indent + 1;
            $this->gap1End = $this->activePage - $indent;
            $this->gap2Start = $this->activePage + $indent + 1;
            $this->gap2End = $this->totalPages - $indent + 1;
            $this->gap1Length = $this->gap1End - $this->gap1Start;
            $this->gap2Length = $this->gap2End - $this->gap2Start;
            if ($this->gap1Length < 2) $this->gap1End = $this->gap1Start;
            if ($this->gap2Length < 2) $this->gap2End = $this->gap2Start;
        } else {
            // if no indent, all links generated in last cycle (see gap2End)
            $this->gap1Length = $gap2Length = $gap1Start = $gap1End = $gap2Start = 0;
            $this->gap2End = 1;
        }

        $this->setTemplate($template);

        return $this;
    }

    /**
     * Объединяет templateDefault c переданным
     * @param array $template with html parts. Look for example at $this->templateDefault
     * @return self
     */
    public function setTemplate($template)
    {
        $this->template = array_merge($this->templateDefault, $template);
        return $this;
    }

    public function __toString()
    {
        $this->generate();
        return $this->HTML;
    }

    /**
     * send HTML to output
     * @return $this
     */
    public function renderHTML()
    {
        $this->generate();
        echo $this->HTML;
        return $this;
    }

    private function generate() {
        $links = '';
        if ($this->activePage > 1) { // previous
            $links .= str_replace('*url*', $this->prevURL, $this->template['prev']);
        } else {
            $links .= str_replace('*url*', $this->prevURL, $this->template['prev_disabled']);
        }

        for ($p = 1; $p < $this->gap1Start; $p++)
            $links .= $this->generateLink($p);
        if ($this->gap1Length > 1) $links .= $this->generateGap();
        for ($p = $this->gap1End; $p < $this->gap2Start && $p <= $this->totalPages; $p++)
            $links .= $this->generateLink($p);
        if ($this->gap2Length > 1) $links .= $this->generateGap();
        for ($p = $this->gap2End; $p <= $this->totalPages; $p++)
            $links .= $this->generateLink($p);

        if ($this->activePage < $this->totalPages) { // next
            $links .= str_replace('*url*', $this->nextURL, $this->template['next']);
        } else {
            $links .= str_replace('*url*', $this->nextURL, $this->template['next_disabled']);
        }
        $this->HTML = str_replace('*links*',  PHP_EOL . $links . PHP_EOL, $this->template['wrapper']);
    }

    private function generateLink($page)
    {
        if ($page === $this->activePage) {
            return str_replace(['*url*', '*pageNumber*'], [$this->urlPrefix . $page, $page], $this->template['link_active']) . PHP_EOL;
        } else {
            return str_replace(['*url*', '*pageNumber*'], [$this->urlPrefix . $page, $page], $this->template['link']) . PHP_EOL;
        }
    }

    private function generateGap()
    {
        return $this->template['gap'] . PHP_EOL;
    }

}