<?php

#
#
# Parsedown
# http://parsedown.org
#
# (c) Emanuil Rusev
# http://erusev.com
#
# For the full license information, view the LICENSE file that was distributed
# with this source code.
#
#

    class Parsedown {
        # Multiton

        static function instance( $name = 'default' ) {
            if ( isset( self::$instances[ $name ] ) ) {
                return self::$instances[ $name ];
            }

            $instance = new Parsedown();

            self::$instances[ $name ] = $instance;

            return $instance;
        }

        private static $instances = array();

        #
        # Setters
        #

        # Enables GFM line breaks.

        function set_breaks_enabled( $breaks_enabled ) {
            $this->breaks_enabled = $breaks_enabled;

            return $this;
        }

        private $breaks_enabled = false;

        #
        # Synopsis
        #

        # Markdown is intended to be easy-to-read by humans - those of us who read
        # line by line, left to right, top to bottom. In order to take advantage of
        # this, Parsedown tries to read in a similar way. It breaks texts into
        # lines, it iterates through them and it looks at how they start and relate
        # to each other.
        #
        # Methods

        #

        function parse( $text ) {
            # standardize line breaks
            $text = str_replace( "\r\n", "\n", $text );
            $text = str_replace( "\r", "\n", $text );

            # replace tabs with spaces
            $text = str_replace( "\t", '    ', $text );

            # remove surrounding line breaks
            $text = trim( $text, "\n" );

            # split text into lines
            $lines = explode( "\n", $text );

            # convert lines into html
            $text = $this->parse_block_elements( $lines );

            # remove trailing line breaks
            $text = chop( $text, "\n" );

            return $text;
        }

        #
        # Private

        private function parse_block_elements( array $lines, $context = '' ) {
            $blocks = array();

            $block = array(
                'type' => '',
            );

            foreach ( $lines as $line ) {
                # context

                switch ( $block['type'] ) {
                    case 'fenced':

                        if ( ! isset( $block['closed'] ) ) {
                            if ( preg_match( '/^[ ]*' . $block['fence'][0] . '{3,}[ ]*$/', $line ) ) {
                                $block['closed'] = true;
                            } else {
                                if ( $block['text'] !== '' ) {
                                    $block['text'] .= "\n";
                                }

                                $block['text'] .= $line;
                            }

                            continue 2;
                        }

                        break;

                    case 'markup':

                        if ( ! isset( $block['closed'] ) ) {
                            if ( strpos( $line, $block['start'] ) !== false ) { # opening tag
                                $block['depth'] ++;
                            }

                            if ( strpos( $line, $block['end'] ) !== false ) { # closing tag
                                if ( $block['depth'] > 0 ) {
                                    $block['depth'] --;
                                } else {
                                    $block['closed'] = true;
                                }
                            }

                            $block['text'] .= "\n" . $line;

                            continue 2;
                        }

                        break;
                }

                # ~

                $indentation = 0;

                while ( isset( $line[ $indentation ] ) and $line[ $indentation ] === ' ' ) {
                    $indentation ++;
                }

                $outdented_line = $indentation > 0 ? ltrim( $line ) : $line;

                # blank

                if ( $outdented_line === '' ) {
                    $block['interrupted'] = true;

                    continue;
                }

                # context

                switch ( $block['type'] ) {
                    case 'quote':

                        if ( ! isset( $block['interrupted'] ) ) {
                            $line = preg_replace( '/^[ ]*>[ ]?/', '', $line );

                            $block['lines'] [] = $line;

                            continue 2;
                        }

                        break;

                    case 'li':

                        if ( $block['indentation'] === $indentation and preg_match( '/^' . $block['marker'] . '[ ]+(.*)/', $outdented_line, $matches ) ) {
                            unset( $block['last'] );

                            $blocks [] = $block;

                            $block['last']  = true;
                            $block['lines'] = array( $matches[1] );

                            unset( $block['first'] );
                            unset( $block['interrupted'] );

                            continue 2;
                        }

                        if ( ! isset( $block['interrupted'] ) ) {
                            $line = preg_replace( '/^[ ]{0,' . $block['baseline'] . '}/', '', $line );

                            $block['lines'] [] = $line;

                            continue 2;
                        } elseif ( $line[0] === ' ' ) {
                            $block['lines'] [] = '';

                            $line = preg_replace( '/^[ ]{0,' . $block['baseline'] . '}/', '', $line );

                            $block['lines'] [] = $line;

                            unset( $block['interrupted'] );

                            continue 2;
                        }

                        break;
                }

                # indentation sensitive types

                switch ( $line[0] ) {
                    case ' ':

                        # code

                        if ( $indentation >= 4 ) {
                            $code_line = substr( $line, 4 );

                            if ( $block['type'] === 'code' ) {
                                if ( isset( $block['interrupted'] ) ) {
                                    $block['text'] .= "\n";

                                    unset( $block['interrupted'] );
                                }

                                $block['text'] .= "\n" . $code_line;
                            } else {
                                $blocks [] = $block;

                                $block = array(
                                    'type' => 'code',
                                    'text' => $code_line,
                                );
                            }

                            continue 2;
                        }

                        break;

                    case '#':

                        # atx heading (#)

                        if ( isset( $line[1] ) ) {
                            $blocks [] = $block;

                            $level = 1;

                            while ( isset( $line[ $level ] ) and $line[ $level ] === '#' ) {
                                $level ++;
                            }

                            $block = array(
                                'type'  => 'heading',
                                'text'  => trim( $line, '# ' ),
                                'level' => $level,
                            );

                            continue 2;
                        }

                        break;

                    case '-':
                    case '=':

                        # setext heading (===)

                        if ( $block['type'] === 'paragraph' and isset( $block['interrupted'] ) === false ) {
                            $chopped_line = chop( $line );

                            $i = 1;

                            while ( isset( $chopped_line[ $i ] ) ) {
                                if ( $chopped_line[ $i ] !== $line[0] ) {
                                    break 2;
                                }

                                $i ++;
                            }

                            $block['type'] = 'heading';

                            $block['level'] = $line[0] === '-' ? 2 : 1;

                            continue 2;
                        }

                        break;
                }

                # indentation insensitive types

                switch ( $outdented_line[0] ) {
                    case '<':

                        $position = strpos( $outdented_line, '>' );

                        if ( $position > 1 ) {
                            $substring = substr( $outdented_line, 1, $position - 1 );

                            $substring = chop( $substring );

                            if ( substr( $substring, - 1 ) === '/' ) {
                                $is_self_closing = true;

                                $substring = substr( $substring, 0, - 1 );
                            }

                            $position = strpos( $substring, ' ' );

                            if ( $position ) {
                                $name = substr( $substring, 0, $position );
                            } else {
                                $name = $substring;
                            }

                            if ( ! ctype_alpha( $name ) ) {
                                break;
                            }

                            if ( in_array( $name, self::$text_level_elements ) ) {
                                break;
                            }

                            $blocks [] = $block;

                            if ( isset( $is_self_closing ) ) {
                                $block = array(
                                    'type' => 'self-closing tag',
                                    'text' => $outdented_line,
                                );

                                unset( $is_self_closing );

                                continue 2;
                            }

                            $block = array(
                                'type'  => 'markup',
                                'text'  => $outdented_line,
                                'start' => '<' . $name . '>',
                                'end'   => '</' . $name . '>',
                                'depth' => 0,
                            );

                            if ( strpos( $outdented_line, $block['end'] ) ) {
                                $block['closed'] = true;
                            }

                            continue 2;
                        }

                        break;

                    case '>':

                        # quote

                        if ( preg_match( '/^>[ ]?(.*)/', $outdented_line, $matches ) ) {
                            $blocks [] = $block;

                            $block = array(
                                'type'  => 'quote',
                                'lines' => array(
                                    $matches[1],
                                ),
                            );

                            continue 2;
                        }

                        break;

                    case '[':

                        # reference

                        $position = strpos( $outdented_line, ']:' );

                        if ( $position ) {
                            $reference = array();

                            $label = substr( $outdented_line, 1, $position - 1 );
                            $label = strtolower( $label );

                            $substring = substr( $outdented_line, $position + 2 );
                            $substring = trim( $substring );

                            if ( $substring === '' ) {
                                break;
                            }

                            if ( $substring[0] === '<' ) {
                                $position = strpos( $substring, '>' );

                                if ( $position === false ) {
                                    break;
                                }

                                $reference['&raquo;'] = substr( $substring, 1, $position - 1 );

                                $substring = substr( $substring, $position + 1 );
                            } else {
                                $position = strpos( $substring, ' ' );

                                if ( $position === false ) {
                                    $reference['&raquo;'] = $substring;

                                    $substring = false;
                                } else {
                                    $reference['&raquo;'] = substr( $substring, 0, $position );

                                    $substring = substr( $substring, $position + 1 );
                                }
                            }

                            if ( $substring !== false ) {
                                if ( $substring[0] !== '"' and $substring[0] !== "'" and $substring[0] !== '(' ) {
                                    break;
                                }

                                $last_char = substr( $substring, - 1 );

                                if ( $last_char !== '"' and $last_char !== "'" and $last_char !== ')' ) {
                                    break;
                                }

                                $reference['#'] = substr( $substring, 1, - 1 );
                            }

                            $this->reference_map[ $label ] = $reference;

                            continue 2;
                        }

                        break;

                    case '`':
                    case '~':

                        # fenced code block

                        if ( preg_match( '/^([`]{3,}|[~]{3,})[ ]*(\S+)?[ ]*$/', $outdented_line, $matches ) ) {
                            $blocks [] = $block;

                            $block = array(
                                'type'  => 'fenced',
                                'text'  => '',
                                'fence' => $matches[1],
                            );

                            if ( isset( $matches[2] ) ) {
                                $block['language'] = $matches[2];
                            }

                            continue 2;
                        }

                        break;

                    case '*':
                    case '+':
                    case '-':
                    case '_':

                        # hr

                        if ( preg_match( '/^([-*_])([ ]{0,2}\1){2,}[ ]*$/', $outdented_line ) ) {
                            $blocks [] = $block;

                            $block = array(
                                'type' => 'rule',
                            );

                            continue 2;
                        }

                        # li

                        if ( preg_match( '/^([*+-][ ]+)(.*)/', $outdented_line, $matches ) ) {
                            $blocks [] = $block;

                            $baseline = $indentation + strlen( $matches[1] );

                            $block = array(
                                'type'        => 'li',
                                'indentation' => $indentation,
                                'baseline'    => $baseline,
                                'marker'      => '[*+-]',
                                'first'       => true,
                                'last'        => true,
                                'lines'       => array(),
                            );

                            $block['lines'] [] = preg_replace( '/^[ ]{0,4}/', '', $matches[2] );

                            continue 2;
                        }
                }

                # li

                if ( $outdented_line[0] <= '9' and preg_match( '/^(\d+[.][ ]+)(.*)/', $outdented_line, $matches ) ) {
                    $blocks [] = $block;

                    $baseline = $indentation + strlen( $matches[1] );

                    $block = array(
                        'type'        => 'li',
                        'indentation' => $indentation,
                        'baseline'    => $baseline,
                        'marker'      => '\d+[.]',
                        'first'       => true,
                        'last'        => true,
                        'ordered'     => true,
                        'lines'       => array(),
                    );

                    $block['lines'] [] = preg_replace( '/^[ ]{0,4}/', '', $matches[2] );

                    continue;
                }

                # paragraph

                if ( $block['type'] === 'paragraph' ) {
                    if ( isset( $block['interrupted'] ) ) {
                        $blocks [] = $block;

                        $block['text'] = $line;

                        unset( $block['interrupted'] );
                    } else {
                        if ( $this->breaks_enabled ) {
                            $block['text'] .= '  ';
                        }

                        $block['text'] .= "\n" . $line;
                    }
                } else {
                    $blocks [] = $block;

                    $block = array(
                        'type' => 'paragraph',
                        'text' => $line,
                    );
                }
            }

            $blocks [] = $block;

            unset( $blocks[0] );

            # $blocks &raquo; HTML

            $markup = '';

            foreach ( $blocks as $block ) {
                switch ( $block['type'] ) {
                    case 'paragraph':

                        $text = $this->parse_span_elements( $block['text'] );

                        if ( $context === 'li' and $markup === '' ) {
                            if ( isset( $block['interrupted'] ) ) {
                                $markup .= "\n" . '<p>' . $text . '</p>' . "\n";
                            } else {
                                $markup .= $text;

                                if ( isset( $blocks[2] ) ) {
                                    $markup .= "\n";
                                }
                            }
                        } else {
                            $markup .= '<p>' . $text . '</p>' . "\n";
                        }

                        break;

                    case 'quote':

                        $text = $this->parse_block_elements( $block['lines'] );

                        $markup .= '<blockquote>' . "\n" . $text . '</blockquote>' . "\n";

                        break;

                    case 'code':

                        $text = htmlspecialchars( $block['text'], ENT_NOQUOTES, 'UTF-8' );

                        $markup .= '<pre><code>' . $text . '</code></pre>' . "\n";

                        break;

                    case 'fenced':

                        $text = htmlspecialchars( $block['text'], ENT_NOQUOTES, 'UTF-8' );

                        $markup .= '<pre><code';

                        if ( isset( $block['language'] ) ) {
                            $markup .= ' class="language-' . $block['language'] . '"';
                        }

                        $markup .= '>' . $text . '</code></pre>' . "\n";

                        break;

                    case 'heading':

                        $text = $this->parse_span_elements( $block['text'] );

                        $markup .= '<h' . $block['level'] . '>' . $text . '</h' . $block['level'] . '>' . "\n";

                        break;

                    case 'rule':

                        $markup .= '<hr />' . "\n";

                        break;

                    case 'li':

                        if ( isset( $block['first'] ) ) {
                            $type = isset( $block['ordered'] ) ? 'ol' : 'ul';

                            $markup .= '<' . $type . '>' . "\n";
                        }

                        if ( isset( $block['interrupted'] ) and ! isset( $block['last'] ) ) {
                            $block['lines'] [] = '';
                        }

                        $text = $this->parse_block_elements( $block['lines'], 'li' );

                        $markup .= '<li>' . $text . '</li>' . "\n";

                        if ( isset( $block['last'] ) ) {
                            $type = isset( $block['ordered'] ) ? 'ol' : 'ul';

                            $markup .= '</' . $type . '>' . "\n";
                        }

                        break;

                    case 'markup':

                        $markup .= $block['text'] . "\n";

                        break;

                    default:

                        $markup .= $block['text'] . "\n";
                }
            }

            return $markup;
        }

        private function parse_span_elements(
            $text, $markers = array(
                "  \n",
                '![',
                '&',
                '*',
                '<',
                '[',
                '\\',
                '_',
                '`',
                'http',
                '~~'
            )
        ) {
            if ( isset( $text[1] ) === false or $markers === array() ) {
                return $text;
            }

            # ~

            $markup = '';

            while ( $markers ) {
                $closest_marker          = null;
                $closest_marker_index    = 0;
                $closest_marker_position = null;

                foreach ( $markers as $index => $marker ) {
                    $marker_position = strpos( $text, $marker );

                    if ( $marker_position === false ) {
                        unset( $markers[ $index ] );

                        continue;
                    }

                    if ( $closest_marker === null or $marker_position < $closest_marker_position ) {
                        $closest_marker          = $marker;
                        $closest_marker_index    = $index;
                        $closest_marker_position = $marker_position;
                    }
                }

                # ~

                if ( $closest_marker === null or isset( $text[ $closest_marker_position + 1 ] ) === false ) {
                    $markup .= $text;

                    break;
                } else {
                    $markup .= substr( $text, 0, $closest_marker_position );
                }

                $text = substr( $text, $closest_marker_position );

                # ~

                unset( $markers[ $closest_marker_index ] );

                # ~

                switch ( $closest_marker ) {
                    case "  \n":

                        $markup .= '<br />' . "\n";

                        $offset = 3;

                        break;

                    case '![':
                    case '[':

                        if ( strpos( $text, ']' ) and preg_match( '/\[((?:[^][]|(?R))*)\]/', $text, $matches ) ) {
                            $element = array(
                                '!' => $text[0] === '!',
                                'a' => $matches[1],
                            );

                            $offset = strlen( $matches[0] );

                            if ( $element['!'] ) {
                                $offset ++;
                            }

                            $remaining_text = substr( $text, $offset );

                            if ( $remaining_text[0] === '(' and preg_match( '/\([ ]*(.*?)(?:[ ]+[\'"](.+?)[\'"])?[ ]*\)/', $remaining_text, $matches ) ) {
                                $element['&raquo;'] = $matches[1];

                                if ( isset( $matches[2] ) ) {
                                    $element['#'] = $matches[2];
                                }

                                $offset += strlen( $matches[0] );
                            } elseif ( $this->reference_map ) {
                                $reference = $element['a'];

                                if ( preg_match( '/^\s*\[(.*?)\]/', $remaining_text, $matches ) ) {
                                    $reference = $matches[1] ? $matches[1] : $element['a'];

                                    $offset += strlen( $matches[0] );
                                }

                                $reference = strtolower( $reference );

                                if ( isset( $this->reference_map[ $reference ] ) ) {
                                    $element['&raquo;'] = $this->reference_map[ $reference ]['&raquo;'];

                                    if ( isset( $this->reference_map[ $reference ]['#'] ) ) {
                                        $element['#'] = $this->reference_map[ $reference ]['#'];
                                    }
                                } else {
                                    unset( $element );
                                }
                            } else {
                                unset( $element );
                            }
                        }

                        if ( isset( $element ) ) {
                            $element['&raquo;'] = str_replace( '&', '&amp;', $element['&raquo;'] );
                            $element['&raquo;'] = str_replace( '<', '&lt;', $element['&raquo;'] );

                            if ( $element['!'] ) {
                                $markup .= '<img alt="' . $element['a'] . '" src="' . $element['&raquo;'] . '"';

                                if ( isset( $element['#'] ) ) {
                                    $markup .= ' title="' . $element['#'] . '"';
                                }

                                $markup .= ' />';
                            } else {
                                $element['a'] = $this->parse_span_elements( $element['a'], $markers );

                                $markup .= '<a href="' . $element['&raquo;'] . '"';

                                if ( isset( $element['#'] ) ) {
                                    $markup .= ' title="' . $element['#'] . '"';
                                }

                                $markup .= '>' . $element['a'] . '</a>';
                            }

                            unset( $element );
                        } else {
                            $markup .= $closest_marker;

                            $offset = $closest_marker === '![' ? 2 : 1;
                        }

                        break;

                    case '&':

                        if ( preg_match( '/^&#?\w+;/', $text, $matches ) ) {
                            $markup .= $matches[0];

                            $offset = strlen( $matches[0] );
                        } else {
                            $markup .= '&amp;';

                            $offset = 1;
                        }

                        break;

                    case '*':
                    case '_':

                        if ( $text[1] === $closest_marker and preg_match( self::$strong_regex[ $closest_marker ], $text, $matches ) ) {
                            $markers[]  = $closest_marker;
                            $matches[1] = $this->parse_span_elements( $matches[1], $markers );

                            $markup .= '<strong>' . $matches[1] . '</strong>';
                        } elseif ( preg_match( self::$em_regex[ $closest_marker ], $text, $matches ) ) {
                            $markers[]  = $closest_marker;
                            $matches[1] = $this->parse_span_elements( $matches[1], $markers );

                            $markup .= '<em>' . $matches[1] . '</em>';
                        }

                        if ( isset( $matches ) and $matches ) {
                            $offset = strlen( $matches[0] );
                        } else {
                            $markup .= $closest_marker;

                            $offset = 1;
                        }

                        break;

                    case '<':

                        if ( strpos( $text, '>' ) !== false ) {
                            if ( $text[1] === 'h' and preg_match( '/^<(https?:[\/]{2}[^\s]+?)>/i', $text, $matches ) ) {
                                $element_url = $matches[1];
                                $element_url = str_replace( '&', '&amp;', $element_url );
                                $element_url = str_replace( '<', '&lt;', $element_url );

                                $markup .= '<a href="' . $element_url . '">' . $element_url . '</a>';

                                $offset = strlen( $matches[0] );
                            } elseif ( strpos( $text, '@' ) > 1 and preg_match( '/<(\S+?@\S+?)>/', $text, $matches ) ) {
                                $markup .= '<a href="mailto:' . $matches[1] . '">' . $matches[1] . '</a>';

                                $offset = strlen( $matches[0] );
                            } elseif ( preg_match( '/^<\/?\w.*?>/', $text, $matches ) ) {
                                $markup .= $matches[0];

                                $offset = strlen( $matches[0] );
                            } else {
                                $markup .= '&lt;';

                                $offset = 1;
                            }
                        } else {
                            $markup .= '&lt;';

                            $offset = 1;
                        }

                        break;

                    case '\\':

                        if ( in_array( $text[1], self::$special_characters ) ) {
                            $markup .= $text[1];

                            $offset = 2;
                        } else {
                            $markup .= '\\';

                            $offset = 1;
                        }

                        break;

                    case '`':

                        if ( preg_match( '/^(`+)[ ]*(.+?)[ ]*(?<!`)\1(?!`)/', $text, $matches ) ) {
                            $element_text = $matches[2];
                            $element_text = htmlspecialchars( $element_text, ENT_NOQUOTES, 'UTF-8' );

                            $markup .= '<code>' . $element_text . '</code>';

                            $offset = strlen( $matches[0] );
                        } else {
                            $markup .= '`';

                            $offset = 1;
                        }

                        break;

                    case 'http':

                        if ( preg_match( '/^https?:[\/]{2}[^\s]+\b\/*/ui', $text, $matches ) ) {
                            $element_url = $matches[0];
                            $element_url = str_replace( '&', '&amp;', $element_url );
                            $element_url = str_replace( '<', '&lt;', $element_url );

                            $markup .= '<a href="' . $element_url . '">' . $element_url . '</a>';

                            $offset = strlen( $matches[0] );
                        } else {
                            $markup .= 'http';

                            $offset = 4;
                        }

                        break;

                    case '~~':

                        if ( preg_match( '/^~~(?=\S)(.+?)(?<=\S)~~/', $text, $matches ) ) {
                            $matches[1] = $this->parse_span_elements( $matches[1], $markers );

                            $markup .= '<del>' . $matches[1] . '</del>';

                            $offset = strlen( $matches[0] );
                        } else {
                            $markup .= '~~';

                            $offset = 2;
                        }

                        break;
                }

                if ( isset( $offset ) ) {
                    $text = substr( $text, $offset );
                }

                $markers[ $closest_marker_index ] = $closest_marker;
            }

            return $markup;
        }

        #
        # Fields

        #

        private $reference_map = array();

        #
        # Read-only
        private static $strong_regex = array(
            '*' => '/^[*]{2}((?:[^*]|[*][^*]*[*])+?)[*]{2}(?![*])/s',
            '_' => '/^__((?:[^_]|_[^_]*_)+?)__(?!_)/us',
        );
        private static $em_regex = array(
            '*' => '/^[*]((?:[^*]|[*][*][^*]+?[*][*])+?)[*](?![*])/s',
            '_' => '/^_((?:[^_]|__[^_]*__)+?)_(?!_)\b/us',
        );
        private static $special_characters = array(
            '\\',
            '`',
            '*',
            '_',
            '{',
            '}',
            '[',
            ']',
            '(',
            ')',
            '>',
            '#',
            '+',
            '-',
            '.',
            '!',
        );
        private static $text_level_elements = array(
            'a',
            'br',
            'bdo',
            'abbr',
            'blink',
            'nextid',
            'acronym',
            'basefont',
            'b',
            'em',
            'big',
            'cite',
            'small',
            'spacer',
            'listing',
            'i',
            'rp',
            'sub',
            'code',
            'strike',
            'marquee',
            'q',
            'rt',
            'sup',
            'font',
            'strong',
            's',
            'tt',
            'var',
            'mark',
            'u',
            'xm',
            'wbr',
            'nobr',
            'ruby',
            'span',
            'time',
        );

    }
