<?php

class SyntaxHighlight_GeSHi {

    /**
     * Has GeSHi been initialised this session?
     */
    private static $initialised = false;

    /**
     * List of languages available to GeSHi
     */
    private static $languages = null;

    /**
     * Parser hook
     *
     * @param string $text
     * @param array $args
     * @param Parser $parser
     * @return string
     */
    public static function parserHook( $text, $args = array(), $parser ) {
        global $wgSyntaxHighlightDefaultLang, $wgUseSiteCSS, $wgUseTidy;
        wfProfileIn( __METHOD__ );
        self::initialise();
        $text = rtrim( $text );
        // Don't trim leading spaces away, just the linefeeds
        $text = preg_replace( '/^\n+/', '', $text );

        if( $wgUseTidy ) {
            // HTML Tidy will convert tabs to spaces incorrectly (bug 30930).
            // Preemptively replace the spaces in a more controlled fashion.
            $text = self::tabsToSpaces( $text );
        }

        // Validate language
        if( isset( $args['lang'] ) && $args['lang'] ) {
            $lang = $args['lang'];
        } else {
            // language is not specified. Check if default exists, if yes, use it.
            if ( !is_null( $wgSyntaxHighlightDefaultLang ) ) {
                $lang = $wgSyntaxHighlightDefaultLang;
            } else {
                $error = self::formatLanguageError( $text );
                wfProfileOut( __METHOD__ );
                return $error;
            }
        }
        $lang = strtolower( $lang );
        if( !preg_match( '/^[a-z_0-9-]*$/', $lang ) ) {
            $error = self::formatLanguageError( $text );
            wfProfileOut( __METHOD__ );
            return $error;
        }
        $geshi = self::prepare( $text, $lang );
        if( !$geshi instanceof GeSHi ) {
            $error = self::formatLanguageError( $text );
            wfProfileOut( __METHOD__ );
            return $error;
        }

        $enclose = self::getEncloseType( $args );

        // Line numbers
        if( isset( $args['line'] ) ) {
            $geshi->enable_line_numbers( GESHI_FANCY_LINE_NUMBERS );
        }
        // Highlighting specific lines
        if( isset( $args['highlight'] ) ) {
            $lines = self::parseHighlightLines( $args['highlight'] );
            if ( count($lines) ) {
                $geshi->highlight_lines_extra( $lines );
            }
        }
        // Starting line number
        if( isset( $args['start'] ) ) {
            $geshi->start_line_numbers_at( $args['start'] );
        }
        $geshi->set_header_type( $enclose );
        // Strict mode
        if( isset( $args['strict'] ) ) {
            $geshi->enable_strict_mode();
        }
        // Format
        $out = $geshi->parse_code();
        if ( $geshi->error == GESHI_ERROR_NO_SUCH_LANG ) {
            // Common error :D
            $error = self::formatLanguageError( $text );
            wfProfileOut( __METHOD__ );
            return $error;
        }
        $err = $geshi->error();
        if( $err ) {
            // Other unknown error!
            $error = self::formatError( $err );
            wfProfileOut( __METHOD__ );
            return $error;
        }
        // Armour for Parser::doBlockLevels()
        if( $enclose === GESHI_HEADER_DIV )
            $out = str_replace( "\n", '', $out );
        // Register CSS
        $parser->mOutput->addHeadItem( self::buildHeadItem( $geshi ), "source-{$lang}" );

        if( $wgUseSiteCss ) {
                    $parser->mOutput->addModuleStyles( 'ext.geshi.local' );
            }


        $encloseTag = $enclose === GESHI_HEADER_NONE ? 'span' : 'div';
        $attribs = Sanitizer::validateTagAttributes( $args, $encloseTag );

        //lang is valid in HTML context, but also used on GeSHi
        unset( $attribs['lang'] );

        if ( $enclose === GESHI_HEADER_NONE ) {
            $attribs = self::addAttribute( $attribs, 'class', 'mw-geshi ' . $lang . ' source-' . $lang );
        } else {
            if ( !isset( $attribs['dir'] ) ) {
                $attribs = self::addAttribute( $attribs, 'dir', 'ltr' );
            }

            $attribs = self::addAttribute( $attribs, 'class', 'mw-geshi' );
            $attribs = self::addAttribute( $attribs, 'style', 'text-align: left;' );
        }
        $out = Xml::tags( $encloseTag, $attribs, $out );

        wfProfileOut( __METHOD__ );
        return $out;
    }

    private static function addAttribute( $attribs, $name, $value ) {
        if( isset( $attribs[$name] ) ) {
            $attribs[$name] = $value . ' ' . $attribs[$name];
        } else {
            $attribs[$name] = $value;
        }
        return $attribs;
    }

    /**
     * Take an input specifying a list of lines to highlight, returning
     * a raw list of matching line numbers.
     *
     * Input is comma-separated list of lines or line ranges.
     *
     * @input string
     * @return array of ints
     */
    protected static function parseHighlightLines( $arg ) {
        $lines = array();
        $values = array_map( 'trim', explode( ',', $arg ) );
        foreach ( $values as $value ) {
            if ( ctype_digit($value) ) {
                $lines[] = (int) $value;
            } elseif ( strpos( $value, '-' ) !== false ) {
                list( $start, $end ) = array_map( 'trim', explode( '-', $value ) );
                if ( self::validHighlightRange( $start, $end ) ) {
                    for ($i = intval( $start ); $i <= $end; $i++ ) {
                        $lines[] = $i;
                    }
                } else {
                    wfDebugLog( 'geshi', "Invalid range: $value\n" );
                }
            } else {
                wfDebugLog( 'geshi', "Invalid line: $value\n" );
            }
        }
        return $lines;
    }

    /**
     * Validate a provided input range
     */
    protected static function validHighlightRange( $start, $end ) {
        // Since we're taking this tiny range and producing a an
        // array of every integer between them, it would be trivial
        // to DoS the system by asking for a huge range.
        // Impose an arbitrary limit on the number of lines in a
        // given range to reduce the impact.
        $arbitrarilyLargeConstant = 10000;
        return
            ctype_digit($start) &&
            ctype_digit($end) &&
            $start > 0 &&
            $start < $end &&
            $end - $start < $arbitrarilyLargeConstant;
    }

    static function getEncloseType( $args ) {
        // Since version 1.0.8 geshi can produce valid pre, but we need to check for it
        if ( defined('GESHI_HEADER_PRE_VALID') ) {
            $pre = GESHI_HEADER_PRE_VALID;
        } else {
            $pre = GESHI_HEADER_PRE;
        }

        // "Enclose" parameter
        $enclose = $pre;
        if ( isset( $args['enclose'] ) ) {
            if ( $args['enclose'] === 'div' ) {
                $enclose = GESHI_HEADER_DIV;
            } elseif ( $args['enclose'] === 'none' ) {
                $enclose = GESHI_HEADER_NONE;
            }
        }

        if( isset( $args['line'] ) && $pre === GESHI_HEADER_PRE ) {
            // Force <div> mode to maintain valid XHTML, see
            // http://sourceforge.net/tracker/index.php?func=detail&aid=1201963&group_id=114997&atid=670231
            $enclose = GESHI_HEADER_DIV;
        }

        return $enclose;
    }

    /**
     * Hook into Article::view() to provide syntax highlighting for
     * custom CSS and JavaScript pages
     *
     * @param string $text
     * @param Title $title
     * @param OutputPage $output
     * @return bool
     */
    public static function viewHook( $text, $title, $output ) {
        global $wgUseSiteCSS;
        // Determine the language
        $matches = array();
        preg_match( '!\.(css|js)$!u', $title->getText(), $matches );
        $lang = $matches[1] == 'css' ? 'css' : 'javascript';
        // Attempt to format
        $geshi = self::prepare( $text, $lang );
        if( $geshi instanceof GeSHi ) {
            $out = $geshi->parse_code();
            if( !$geshi->error() ) {
                // Done
                $output->addHeadItem( "source-$lang", self::buildHeadItem( $geshi ) );
                $output->addHTML( "<div dir=\"ltr\">{$out}</div>" );
                if( $wgUseSiteCss ) {
                                        $output->addModuleStyles( 'ext.geshi.local' );
                                }

            return false;
            }
        }
        // Bottle out
        return true;
    }

    /**
     * Initialise a GeSHi object to format some code, performing
     * common setup for all our uses of it
     *
     * @param string $text
     * @param string $lang
     * @return GeSHi
     */
    public static function prepare( $text, $lang ) {
        self::initialise();
        $geshi = new GeSHi( $text, $lang );
        if( $geshi->error() == GESHI_ERROR_NO_SUCH_LANG ) {
            return null;
        }
        $geshi->set_encoding( 'UTF-8' );
        $geshi->enable_classes();
        $geshi->set_overall_class( "source-$lang" );
        $geshi->enable_keyword_links( false );
        return $geshi;
    }


    /**
     * Format an 'unknown language' error message and append formatted
     * plain text to it.
     *
     * @param string $text
     * @return string HTML fragment
     */
    private static function formatLanguageError( $text ) {
        $error = self::formatError( htmlspecialchars( wfMsgForContent( 'syntaxhighlight-err-language' ) ), $text );
        return $error . '<pre>' . htmlspecialchars( $text ) . '</pre>';
    }

    /**
     * Format an error message
     *
     * @param string $error
     * @return string
     */
    private static function formatError( $error = '' ) {
        $html = '';
        if( $error ) {
            $html .= "<p>{$error}</p>";
        }
        $html .= '<p>' . htmlspecialchars( wfMsgForContent( 'syntaxhighlight-specify' ) )
            . ' <samp>&lt;source lang=&quot;html4strict&quot;&gt;...&lt;/source&gt;</samp></p>'
            . '<p>' . htmlspecialchars( wfMsgForContent( 'syntaxhighlight-supported' ) ) . '</p>'
            . self::formatLanguages();
        return "<div style=\"border: solid red 1px; padding: .5em;\">{$html}</div>";
    }

    /**
     * Format the list of supported languages
     *
     * @return string
     */
    private static function formatLanguages() {
        $langs = self::getSupportedLanguages();
        $list = array();
        if( count( $langs ) > 0 ) {
            foreach( $langs as $lang ) {
                $list[] = '<samp>' . htmlspecialchars( $lang ) . '</samp>';
            }
            return '<p class="mw-collapsible mw-collapsed" style="padding: 0em 1em;">' . implode( ', ', $list ) . '</p><br style="clear: all"/>';
        } else {
            return '<p>' . htmlspecialchars( wfMsgForContent( 'syntaxhighlight-err-loading' ) ) . '</p>';
        }
    }

    /**
     * Get the list of supported languages
     *
     * @return array
     */
    private static function getSupportedLanguages() {
        if( !is_array( self::$languages ) ) {
            self::initialise();
            self::$languages = array();
            foreach( glob( GESHI_LANG_ROOT . "/*.php" ) as $file ) {
                self::$languages[] = basename( $file, '.php' );
            }
            sort( self::$languages );
        }
        return self::$languages;
    }

    /**
     * Initialise messages and ensure the GeSHi class is loaded
     */
    private static function initialise() {
        if( !self::$initialised ) {
            if( !class_exists( 'GeSHi' ) ) {
                require( 'geshi/geshi.php' );
            }
            self::$initialised = true;
        }
        return true;
    }

    /**
     * Get the GeSHI's version information while Special:Version is read.
     */
    public static function hSpecialVersion_GeSHi( &$extensionTypes ) {
        global $wgExtensionCredits;
        self::initialise();
        $wgExtensionCredits['parserhook']['SyntaxHighlight_GeSHi']['version'] = GESHI_VERSION;
        return true;
    }

    /**
     * @see SyntaxHighlight_GeSHi::hSpecialVersion_GeSHi
     */
    public static function hOldSpecialVersion_GeSHi( &$sp, &$extensionTypes ) {
        return self::hSpecialVersion_GeSHi( $extensionTypes );
    }

    /**
     * Convert tabs to spaces
     *
     * @param string $text
     * @return string
     */
    private static function tabsToSpaces( $text ) {
        $lines = explode( "\n", $text );
        $lines = array_map( array( __CLASS__, 'tabsToSpacesLine' ), $lines );
        return implode( "\n", $lines );
    }

    /**
     * Convert tabs to spaces for a single line
     *
     * @param string $text
     * @return string
     */
    private static function tabsToSpacesLine( $line ) {
        $parts = explode( "\t", $line );
        $width = 8; // To match tidy's config & typical browser defaults
        $out = $parts[0];
        foreach( array_slice( $parts, 1 ) as $chunk ) {
            $spaces = $width - (strlen( $out ) % $width);
            $out .= str_repeat( ' ', $spaces );
            $out .= $chunk;
        }
        return $out;
    }
}