BlockLevelPass.php

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<?php

class BlockLevelPass {
    private $DTopen = false;
    private $inPre = false;
    private $lastSection = '';
    private $linestart;
    private $text;

    # State constants for the definition list colon extraction
    const COLON_STATE_TEXT = 0;
    const COLON_STATE_TAG = 1;
    const COLON_STATE_TAGSTART = 2;
    const COLON_STATE_CLOSETAG = 3;
    const COLON_STATE_TAGSLASH = 4;
    const COLON_STATE_COMMENT = 5;
    const COLON_STATE_COMMENTDASH = 6;
    const COLON_STATE_COMMENTDASHDASH = 7;

    public static function doBlockLevels( $text, $lineStart ) {
        $pass = new self( $text, $lineStart );
        return $pass->execute();
    }

    private function __construct( $text, $lineStart ) {
        $this->text = $text;
        $this->lineStart = $lineStart;
    }

    private function closeParagraph() {
        $result = '';
        if ( $this->lastSection !== '' ) {
            $result = '</' . $this->lastSection . ">\n";
        }
        $this->inPre = false;
        $this->lastSection = '';
        return $result;
    }

    private function getCommon( $st1, $st2 ) {
        $shorter = min( strlen( $st1 ), strlen( $st2 ) );

        for ( $i = 0; $i < $shorter; ++$i ) {
            if ( $st1[$i] !== $st2[$i] ) {
                break;
            }
        }
        return $i;
    }

    private function openList( $char ) {
        $result = $this->closeParagraph();

        if ( '*' === $char ) {
            $result .= "<ul><li>";
        } elseif ( '#' === $char ) {
            $result .= "<ol><li>";
        } elseif ( ':' === $char ) {
            $result .= "<dl><dd>";
        } elseif ( ';' === $char ) {
            $result .= "<dl><dt>";
            $this->DTopen = true;
        } else {
            $result = '<!-- ERR 1 -->';
        }

        return $result;
    }

    private function nextItem( $char ) {
        if ( '*' === $char || '#' === $char ) {
            return "</li>\n<li>";
        } elseif ( ':' === $char || ';' === $char ) {
            $close = "</dd>\n";
            if ( $this->DTopen ) {
                $close = "</dt>\n";
            }
            if ( ';' === $char ) {
                $this->DTopen = true;
                return $close . '<dt>';
            } else {
                $this->DTopen = false;
                return $close . '<dd>';
            }
        }
        return '<!-- ERR 2 -->';
    }

    private function closeList( $char ) {
        if ( '*' === $char ) {
            $text = "</li></ul>";
        } elseif ( '#' === $char ) {
            $text = "</li></ol>";
        } elseif ( ':' === $char ) {
            if ( $this->DTopen ) {
                $this->DTopen = false;
                $text = "</dt></dl>";
            } else {
                $text = "</dd></dl>";
            }
        } else {
            return '<!-- ERR 3 -->';
        }
        return $text;
    }

    private function execute() {
        $text = $this->text;
        # Parsing through the text line by line.  The main thing
        # happening here is handling of block-level elements p, pre,
        # and making lists from lines starting with * # : etc.
        $textLines = StringUtils::explode( "\n", $text );

        $lastPrefix = $output = '';
        $this->DTopen = $inBlockElem = false;
        $prefixLength = 0;
        $pendingPTag = false;
        $inBlockquote = false;

        foreach ( $textLines as $inputLine ) {
            # Fix up $lineStart
            if ( !$this->lineStart ) {
                $output .= $inputLine;
                $this->lineStart = true;
                continue;
            }
            # * = ul
            # # = ol
            # ; = dt
            # : = dd

            $lastPrefixLength = strlen( $lastPrefix );
            $preCloseMatch = preg_match( '/<\\/pre/i', $inputLine );
            $preOpenMatch = preg_match( '/<pre/i', $inputLine );
            # If not in a <pre> element, scan for and figure out what prefixes are there.
            if ( !$this->inPre ) {
                # Multiple prefixes may abut each other for nested lists.
                $prefixLength = strspn( $inputLine, '*#:;' );
                $prefix = substr( $inputLine, 0, $prefixLength );

                # eh?
                # ; and : are both from definition-lists, so they're equivalent
                #  for the purposes of determining whether or not we need to open/close
                #  elements.
                $prefix2 = str_replace( ';', ':', $prefix );
                $t = substr( $inputLine, $prefixLength );
                $this->inPre = (bool)$preOpenMatch;
            } else {
                # Don't interpret any other prefixes in preformatted text
                $prefixLength = 0;
                $prefix = $prefix2 = '';
                $t = $inputLine;
            }

            # List generation
            if ( $prefixLength && $lastPrefix === $prefix2 ) {
                # Same as the last item, so no need to deal with nesting or opening stuff
                $output .= $this->nextItem( substr( $prefix, -1 ) );
                $pendingPTag = false;

                if ( substr( $prefix, -1 ) === ';' ) {
                    # The one nasty exception: definition lists work like this:
                    # ; title : definition text
                    # So we check for : in the remainder text to split up the
                    # title and definition, without b0rking links.
                    $term = $t2 = '';
                    if ( $this->findColonNoLinks( $t, $term, $t2 ) !== false ) {
                        $t = $t2;
                        $output .= $term . $this->nextItem( ':' );
                    }
                }
            } elseif ( $prefixLength || $lastPrefixLength ) {
                # We need to open or close prefixes, or both.

                # Either open or close a level...
                $commonPrefixLength = $this->getCommon( $prefix, $lastPrefix );
                $pendingPTag = false;

                # Close all the prefixes which aren't shared.
                while ( $commonPrefixLength < $lastPrefixLength ) {
                    $output .= $this->closeList( $lastPrefix[$lastPrefixLength - 1] );
                    --$lastPrefixLength;
                }

                # Continue the current prefix if appropriate.
                if ( $prefixLength <= $commonPrefixLength && $commonPrefixLength > 0 ) {
                    $output .= $this->nextItem( $prefix[$commonPrefixLength - 1] );
                }

                # Open prefixes where appropriate.
                if ( $lastPrefix && $prefixLength > $commonPrefixLength ) {
                    $output .= "\n";
                }
                while ( $prefixLength > $commonPrefixLength ) {
                    $char = substr( $prefix, $commonPrefixLength, 1 );
                    $output .= $this->openList( $char );

                    if ( ';' === $char ) {
                        # @todo FIXME: This is dupe of code above
                        if ( $this->findColonNoLinks( $t, $term, $t2 ) !== false ) {
                            $t = $t2;
                            $output .= $term . $this->nextItem( ':' );
                        }
                    }
                    ++$commonPrefixLength;
                }
                if ( !$prefixLength && $lastPrefix ) {
                    $output .= "\n";
                }
                $lastPrefix = $prefix2;
            }

            # If we have no prefixes, go to paragraph mode.
            if ( 0 == $prefixLength ) {
                # No prefix (not in list)--go to paragraph mode
                # @todo consider using a stack for nestable elements like span, table and div
                $openMatch = preg_match(
                    '/(?:<table|<h1|<h2|<h3|<h4|<h5|<h6|<pre|<tr|'
                        . '<p|<ul|<ol|<dl|<li|<\\/tr|<\\/td|<\\/th)/iS',
                    $t
                );
                $closeMatch = preg_match(
                    '/(?:<\\/table|<\\/h1|<\\/h2|<\\/h3|<\\/h4|<\\/h5|<\\/h6|'
                        . '<td|<th|<\\/?blockquote|<\\/?div|<hr|<\\/pre|<\\/p|<\\/mw:|'
                        . Parser::MARKER_PREFIX
                        . '-pre|<\\/li|<\\/ul|<\\/ol|<\\/dl|<\\/?center)/iS',
                    $t
                );

                if ( $openMatch || $closeMatch ) {
                    $pendingPTag = false;
                    # @todo bug 5718: paragraph closed
                    $output .= $this->closeParagraph();
                    if ( $preOpenMatch && !$preCloseMatch ) {
                        $this->inPre = true;
                    }
                    $bqOffset = 0;
                    while ( preg_match( '/<(\\/?)blockquote[\s>]/i', $t,
                        $bqMatch, PREG_OFFSET_CAPTURE, $bqOffset )
                    ) {
                        $inBlockquote = !$bqMatch[1][0]; // is this a close tag?
                        $bqOffset = $bqMatch[0][1] + strlen( $bqMatch[0][0] );
                    }
                    $inBlockElem = !$closeMatch;
                } elseif ( !$inBlockElem && !$this->inPre ) {
                    if ( ' ' == substr( $t, 0, 1 )
                        && ( $this->lastSection === 'pre' || trim( $t ) != '' )
                        && !$inBlockquote
                    ) {
                        # pre
                        if ( $this->lastSection !== 'pre' ) {
                            $pendingPTag = false;
                            $output .= $this->closeParagraph() . '<pre>';
                            $this->lastSection = 'pre';
                        }
                        $t = substr( $t, 1 );
                    } else {
                        # paragraph
                        if ( trim( $t ) === '' ) {
                            if ( $pendingPTag ) {
                                $output .= $pendingPTag . '<br />';
                                $pendingPTag = false;
                                $this->lastSection = 'p';
                            } else {
                                if ( $this->lastSection !== 'p' ) {
                                    $output .= $this->closeParagraph();
                                    $this->lastSection = '';
                                    $pendingPTag = '<p>';
                                } else {
                                    $pendingPTag = '</p><p>';
                                }
                            }
                        } else {
                            if ( $pendingPTag ) {
                                $output .= $pendingPTag;
                                $pendingPTag = false;
                                $this->lastSection = 'p';
                            } elseif ( $this->lastSection !== 'p' ) {
                                $output .= $this->closeParagraph() . '<p>';
                                $this->lastSection = 'p';
                            }
                        }
                    }
                }
            }
            # somewhere above we forget to get out of pre block (bug 785)
            if ( $preCloseMatch && $this->inPre ) {
                $this->inPre = false;
            }
            if ( $pendingPTag === false ) {
                $output .= $t;
                if ( $prefixLength === 0 ) {
                    $output .= "\n";
                }
            }
        }
        while ( $prefixLength ) {
            $output .= $this->closeList( $prefix2[$prefixLength - 1] );
            --$prefixLength;
            if ( !$prefixLength ) {
                $output .= "\n";
            }
        }
        if ( $this->lastSection !== '' ) {
            $output .= '</' . $this->lastSection . '>';
            $this->lastSection = '';
        }

        return $output;
    }

    private function findColonNoLinks( $str, &$before, &$after ) {
        $colonPos = strpos( $str, ':' );
        if ( $colonPos === false ) {
            # Nothing to find!
            return false;
        }

        $ltPos = strpos( $str, '<' );
        if ( $ltPos === false || $ltPos > $colonPos ) {
            # Easy; no tag nesting to worry about
            $before = substr( $str, 0, $colonPos );
            $after = substr( $str, $colonPos + 1 );
            return $colonPos;
        }

        # Ugly state machine to walk through avoiding tags.
        $state = self::COLON_STATE_TEXT;
        $level = 0;
        $len = strlen( $str );
        for ( $i = 0; $i < $len; $i++ ) {
            $c = $str[$i];

            switch ( $state ) {
            case self::COLON_STATE_TEXT:
                switch ( $c ) {
                case "<":
                    # Could be either a <start> tag or an </end> tag
                    $state = self::COLON_STATE_TAGSTART;
                    break;
                case ":":
                    if ( $level === 0 ) {
                        # We found it!
                        $before = substr( $str, 0, $i );
                        $after = substr( $str, $i + 1 );
                        return $i;
                    }
                    # Embedded in a tag; don't break it.
                    break;
                default:
                    # Skip ahead looking for something interesting
                    $colonPos = strpos( $str, ':', $i );
                    if ( $colonPos === false ) {
                        # Nothing else interesting
                        return false;
                    }
                    $ltPos = strpos( $str, '<', $i );
                    if ( $level === 0 ) {
                        if ( $ltPos === false || $colonPos < $ltPos ) {
                            # We found it!
                            $before = substr( $str, 0, $colonPos );
                            $after = substr( $str, $colonPos + 1 );
                            return $i;
                        }
                    }
                    if ( $ltPos === false ) {
                        # Nothing else interesting to find; abort!
                        # We're nested, but there's no close tags left. Abort!
                        break 2;
                    }
                    # Skip ahead to next tag start
                    $i = $ltPos;
                    $state = self::COLON_STATE_TAGSTART;
                }
                break;
            case self::COLON_STATE_TAG:
                # In a <tag>
                switch ( $c ) {
                case ">":
                    $level++;
                    $state = self::COLON_STATE_TEXT;
                    break;
                case "/":
                    # Slash may be followed by >?
                    $state = self::COLON_STATE_TAGSLASH;
                    break;
                default:
                    # ignore
                }
                break;
            case self::COLON_STATE_TAGSTART:
                switch ( $c ) {
                case "/":
                    $state = self::COLON_STATE_CLOSETAG;
                    break;
                case "!":
                    $state = self::COLON_STATE_COMMENT;
                    break;
                case ">":
                    # Illegal early close? This shouldn't happen D:
                    $state = self::COLON_STATE_TEXT;
                    break;
                default:
                    $state = self::COLON_STATE_TAG;
                }
                break;
            case self::COLON_STATE_CLOSETAG:
                # In a </tag>
                if ( $c === ">" ) {
                    $level--;
                    if ( $level < 0 ) {
                        wfDebug( __METHOD__ . ": Invalid input; too many close tags\n" );
                        return false;
                    }
                    $state = self::COLON_STATE_TEXT;
                }
                break;
            case self::COLON_STATE_TAGSLASH:
                if ( $c === ">" ) {
                    # Yes, a self-closed tag <blah/>
                    $state = self::COLON_STATE_TEXT;
                } else {
                    # Probably we're jumping the gun, and this is an attribute
                    $state = self::COLON_STATE_TAG;
                }
                break;
            case self::COLON_STATE_COMMENT:
                if ( $c === "-" ) {
                    $state = self::COLON_STATE_COMMENTDASH;
                }
                break;
            case self::COLON_STATE_COMMENTDASH:
                if ( $c === "-" ) {
                    $state = self::COLON_STATE_COMMENTDASHDASH;
                } else {
                    $state = self::COLON_STATE_COMMENT;
                }
                break;
            case self::COLON_STATE_COMMENTDASHDASH:
                if ( $c === ">" ) {
                    $state = self::COLON_STATE_TEXT;
                } else {
                    $state = self::COLON_STATE_COMMENT;
                }
                break;
            default:
                throw new MWException( "State machine error in " . __METHOD__ );
            }
        }
        if ( $level > 0 ) {
            wfDebug( __METHOD__ . ": Invalid input; not enough close tags (level $level, state $state)\n" );
            return false;
        }
        return false;
    }
}