<?php

/**
 * This file is part of CodeIgniter 4 framework.
 *
 * (c) CodeIgniter Foundation <admin@codeigniter.com>
 *
 * For the full copyright and license information, please view
 * the LICENSE file that was distributed with this source code.
 */

namespace CodeIgniter\Typography;

/**
 * Typography Class
 */
class Typography
{
    /**
     * Block level elements that should not be wrapped inside <p> tags
     *
     * @var string
     */
    public $blockElements = 'address|blockquote|div|dl|fieldset|form|h\d|hr|noscript|object|ol|p|pre|script|table|ul';

    /**
     * Elements that should not have <p> and <br /> tags within them.
     *
     * @var string
     */
    public $skipElements = 'p|pre|ol|ul|dl|object|table|h\d';

    /**
     * Tags we want the parser to completely ignore when splitting the string.
     *
     * @var string
     */
    public $inlineElements = 'a|abbr|acronym|b|bdo|big|br|button|cite|code|del|dfn|em|i|img|ins|input|label|map|kbd|q|samp|select|small|span|strong|sub|sup|textarea|tt|var';

    /**
     * array of block level elements that require inner content to be within another block level element
     *
     * @var array
     */
    public $innerBlockRequired = ['blockquote'];

    /**
     * the last block element parsed
     *
     * @var string
     */
    public $lastBlockElement = '';

    /**
     * whether or not to protect quotes within { curly braces }
     *
     * @var bool
     */
    public $protectBracedQuotes = false;

    /**
     * Auto Typography
     *
     * This function converts text, making it typographically correct:
     *     - Converts double spaces into paragraphs.
     *     - Converts single line breaks into <br /> tags
     *     - Converts single and double quotes into correctly facing curly quote entities.
     *     - Converts three dots into ellipsis.
     *     - Converts double dashes into em-dashes.
     *  - Converts two spaces into entities
     *
     * @param bool $reduceLinebreaks whether to reduce more then two consecutive newlines to two
     */
    public function autoTypography(string $str, bool $reduceLinebreaks = false): string
    {
        if ($str === '') {
            return '';
        }

        // Standardize Newlines to make matching easier
        if (strpos($str, "\r") !== false) {
            $str = str_replace(["\r\n", "\r"], "\n", $str);
        }

        // Reduce line breaks.  If there are more than two consecutive linebreaks
        // we'll compress them down to a maximum of two since there's no benefit to more.
        if ($reduceLinebreaks === false) {
            $str = preg_replace("/\n\n+/", "\n\n", $str);
        }

        // HTML comment tags don't conform to patterns of normal tags, so pull them out separately, only if needed
        $htmlComments = [];
        if (strpos($str, '<!--') !== false && preg_match_all('#(<!\-\-.*?\-\->)#s', $str, $matches)) {
            for ($i = 0, $total = count($matches[0]); $i < $total; $i++) {
                $htmlComments[] = $matches[0][$i];
                $str            = str_replace($matches[0][$i], '{@HC' . $i . '}', $str);
            }
        }

        // match and yank <pre> tags if they exist.  It's cheaper to do this separately since most content will
        // not contain <pre> tags, and it keeps the PCRE patterns below simpler and faster
        if (strpos($str, '<pre') !== false) {
            $str = preg_replace_callback('#<pre.*?>.*?</pre>#si', [$this, 'protectCharacters'], $str);
        }

        // Convert quotes within tags to temporary markers.
        $str = preg_replace_callback('#<.+?>#si', [$this, 'protectCharacters'], $str);

        // Do the same with braces if necessary
        if ($this->protectBracedQuotes === false) {
            $str = preg_replace_callback('#\{.+?\}#si', [$this, 'protectCharacters'], $str);
        }

        // Convert "ignore" tags to temporary marker.  The parser splits out the string at every tag
        // it encounters.  Certain inline tags, like image tags, links, span tags, etc. will be
        // adversely affected if they are split out so we'll convert the opening bracket < temporarily to: {@TAG}
        $str = preg_replace('#<(/*)(' . $this->inlineElements . ')([ >])#i', '{@TAG}\\1\\2\\3', $str);

        /* Split the string at every tag. This expression creates an array with this prototype:
         *
         * 	[array]
         * 	{
         * 		[0] = <opening tag>
         * 		[1] = Content...
         * 		[2] = <closing tag>
         * 		Etc...
         * 	}
         */
        $chunks = preg_split('/(<(?:[^<>]+(?:"[^"]*"|\'[^\']*\')?)+>)/', $str, -1, PREG_SPLIT_DELIM_CAPTURE | PREG_SPLIT_NO_EMPTY);

        // Build our finalized string.  We cycle through the array, skipping tags, and processing the contained text
        $str     = '';
        $process = true;

        for ($i = 0, $c = count($chunks) - 1; $i <= $c; $i++) {
            // Are we dealing with a tag? If so, we'll skip the processing for this cycle.
            // Well also set the "process" flag which allows us to skip <pre> tags and a few other things.
            if (preg_match('#<(/*)(' . $this->blockElements . ').*?>#', $chunks[$i], $match)) {
                if (preg_match('#' . $this->skipElements . '#', $match[2])) {
                    $process = ($match[1] === '/');
                }

                if ($match[1] === '') {
                    $this->lastBlockElement = $match[2];
                }

                $str .= $chunks[$i];

                continue;
            }

            if ($process === false) {
                $str .= $chunks[$i];

                continue;
            }

            // Force a newline to make sure end tags get processed by _format_newlines()
            if ($i === $c) {
                $chunks[$i] .= "\n";
            }

            // Convert Newlines into <p> and <br /> tags
            $str .= $this->formatNewLines($chunks[$i]);
        }

        // No opening block level tag? Add it if needed.
        if (! preg_match('/^\s*<(?:' . $this->blockElements . ')/i', $str)) {
            $str = preg_replace('/^(.*?)<(' . $this->blockElements . ')/i', '<p>$1</p><$2', $str);
        }

        // Convert quotes, elipsis, em-dashes, non-breaking spaces, and ampersands
        $str = $this->formatCharacters($str);

        foreach ($htmlComments as $i => $htmlComment) {
            // remove surrounding paragraph tags, but only if there's an opening paragraph tag
            // otherwise HTML comments at the ends of paragraphs will have the closing tag removed
            // if '<p>{@HC1}' then replace <p>{@HC1}</p> with the comment, else replace only {@HC1} with the comment
            $str = preg_replace('#(?(?=<p>\{@HC' . $i . '\})<p>\{@HC' . $i . '\}(\s*</p>)|\{@HC' . $i . '\})#s', $htmlComment, $str);
        }

        // Final clean up
        $table = [
            // If the user submitted their own paragraph tags within the text
            // we will retain them instead of using our tags.
            '/(<p[^>*?]>)<p>/' => '$1', // <?php BBEdit syntax coloring bug fix
            // Reduce multiple instances of opening/closing paragraph tags to a single one
            '#(</p>)+#'      => '</p>',
            '/(<p>\W*<p>)+/' => '<p>',
            // Clean up stray paragraph tags that appear before block level elements
            '#<p></p><(' . $this->blockElements . ')#' => '<$1',
            // Clean up stray non-breaking spaces preceeding block elements
            '#(&nbsp;\s*)+<(' . $this->blockElements . ')#' => '  <$2',
            // Replace the temporary markers we added earlier
            '/\{@TAG\}/' => '<',
            '/\{@DQ\}/'  => '"',
            '/\{@SQ\}/'  => "'",
            '/\{@DD\}/'  => '--',
            '/\{@NBS\}/' => '  ',
            // An unintended consequence of the _format_newlines function is that
            // some of the newlines get truncated, resulting in <p> tags
            // starting immediately after <block> tags on the same line.
            // This forces a newline after such occurrences, which looks much nicer.
            "/><p>\n/" => ">\n<p>",
            // Similarly, there might be cases where a closing </block> will follow
            // a closing </p> tag, so we'll correct it by adding a newline in between
            '#</p></#' => "</p>\n</",
        ];

        // Do we need to reduce empty lines?
        if ($reduceLinebreaks === true) {
            $table['#<p>\n*</p>#'] = '';
        } else {
            // If we have empty paragraph tags we add a non-breaking space
            // otherwise most browsers won't treat them as true paragraphs
            $table['#<p></p>#'] = '<p>&nbsp;</p>';
        }

        return preg_replace(array_keys($table), $table, $str);
    }

    /**
     * Format Characters
     *
     * This function mainly converts double and single quotes
     * to curly entities, but it also converts em-dashes,
     * double spaces, and ampersands
     */
    public function formatCharacters(string $str): string
    {
        static $table;

        if (! isset($table)) {
            $table = [
                // nested smart quotes, opening and closing
                // note that rules for grammar (English) allow only for two levels deep
                // and that single quotes are _supposed_ to always be on the outside
                // but we'll accommodate both
                // Note that in all cases, whitespace is the primary determining factor
                // on which direction to curl, with non-word characters like punctuation
                // being a secondary factor only after whitespace is addressed.
                '/\'"(\s|$)/'     => '&#8217;&#8221;$1',
                '/(^|\s|<p>)\'"/' => '$1&#8216;&#8220;',
                '/\'"(\W)/'       => '&#8217;&#8221;$1',
                '/(\W)\'"/'       => '$1&#8216;&#8220;',
                '/"\'(\s|$)/'     => '&#8221;&#8217;$1',
                '/(^|\s|<p>)"\'/' => '$1&#8220;&#8216;',
                '/"\'(\W)/'       => '&#8221;&#8217;$1',
                '/(\W)"\'/'       => '$1&#8220;&#8216;',
                // single quote smart quotes
                '/\'(\s|$)/'     => '&#8217;$1',
                '/(^|\s|<p>)\'/' => '$1&#8216;',
                '/\'(\W)/'       => '&#8217;$1',
                '/(\W)\'/'       => '$1&#8216;',
                // double quote smart quotes
                '/"(\s|$)/'     => '&#8221;$1',
                '/(^|\s|<p>)"/' => '$1&#8220;',
                '/"(\W)/'       => '&#8221;$1',
                '/(\W)"/'       => '$1&#8220;',
                // apostrophes
                '/(\w)\'(\w)/' => '$1&#8217;$2',
                // Em dash and ellipses dots
                '/\s?\-\-\s?/' => '&#8212;',
                '/(\w)\.{3}/'  => '$1&#8230;',
                // double space after sentences
                '/(\W)  /' => '$1&nbsp; ',
                // ampersands, if not a character entity
                '/&(?!#?[a-zA-Z0-9]{2,};)/' => '&amp;',
            ];
        }

        return preg_replace(array_keys($table), $table, $str);
    }

    /**
     * Format Newlines
     *
     * Converts newline characters into either <p> tags or <br />
     */
    protected function formatNewLines(string $str): string
    {
        if ($str === '' || (strpos($str, "\n") === false && ! in_array($this->lastBlockElement, $this->innerBlockRequired, true))) {
            return $str;
        }

        // Convert two consecutive newlines to paragraphs
        $str = str_replace("\n\n", "</p>\n\n<p>", $str);

        // Convert single spaces to <br /> tags
        $str = preg_replace("/([^\n])(\n)([^\n])/", '\\1<br />\\2\\3', $str);

        // Wrap the whole enchilada in enclosing paragraphs
        if ($str !== "\n") {
            // We trim off the right-side new line so that the closing </p> tag
            // will be positioned immediately following the string, matching
            // the behavior of the opening <p> tag
            $str = '<p>' . rtrim($str) . '</p>';
        }

        // Remove empty paragraphs if they are on the first line, as this
        // is a potential unintended consequence of the previous code
        return preg_replace('/<p><\/p>(.*)/', '\\1', $str, 1);
    }

    /**
     * Protect Characters
     *
     * Protects special characters from being formatted later
     * We don't want quotes converted within tags so we'll temporarily convert them to {@DQ} and {@SQ}
     * and we don't want double dashes converted to emdash entities, so they are marked with {@DD}
     * likewise double spaces are converted to {@NBS} to prevent entity conversion
     */
    protected function protectCharacters(array $match): string
    {
        return str_replace(["'", '"', '--', '  '], ['{@SQ}', '{@DQ}', '{@DD}', '{@NBS}'], $match[0]);
    }

    /**
     * Convert newlines to HTML line breaks except within PRE tags
     */
    public function nl2brExceptPre(string $str): string
    {
        $newstr = '';

        for ($ex = explode('pre>', $str), $ct = count($ex), $i = 0; $i < $ct; $i++) {
            $newstr .= (($i % 2) === 0) ? nl2br($ex[$i]) : $ex[$i];

            if ($ct - 1 !== $i) {
                $newstr .= 'pre>';
            }
        }

        return $newstr;
    }
}