From ba147ca9b2eae544e802c8216936065d2d86a8d8 Mon Sep 17 00:00:00 2001 From: Waylan Limberg Date: Tue, 11 Nov 2008 19:18:41 -0500 Subject: Replaced old core parser with new BlockParser and copied old core into extension. --- markdown.py | 641 ++++++++++++++++-------------------------- markdown_extensions/legacy.py | 469 ++++++++++++++++++++++++++++++ 2 files changed, 709 insertions(+), 401 deletions(-) create mode 100644 markdown_extensions/legacy.py diff --git a/markdown.py b/markdown.py index b534151..b40093f 100755 --- a/markdown.py +++ b/markdown.py @@ -98,24 +98,6 @@ INLINE_PLACEHOLDER_PREFIX = STX+"klzzwxh:" INLINE_PLACEHOLDER = INLINE_PLACEHOLDER_PREFIX + "%s" + ETX AMP_SUBSTITUTE = STX+"amp"+ETX -def wrapRe(raw_re) : return re.compile("^%s$" % raw_re, re.DOTALL) -CORE_RE = { - 'header': wrapRe(r'(#{1,6})[ \t]*(.*?)[ \t]*(#*)'), # # A title - 'reference-def': wrapRe(r'(\ ?\ ?\ ?)\[([^\]]*)\]:\s*([^ ]*)(.*)'), - # [Google]: http://www.google.com/ - 'containsline': wrapRe(r'([-]*)$|^([=]*)'), # -----, =====, etc. - 'ol': wrapRe(r'[ ]{0,3}[\d]*\.\s+(.*)'), # 1. text - 'ul': wrapRe(r'[ ]{0,3}[*+-]\s+(.*)'), # "* text" - 'isline1': wrapRe(r'(\**)'), # *** - 'isline2': wrapRe(r'(\-*)'), # --- - 'isline3': wrapRe(r'(\_*)'), # ___ - 'tabbed': wrapRe(r'((\t)|( ))(.*)'), # an indented line - 'quoted': wrapRe(r'[ ]{0,2}> ?(.*)'), # a quoted block ("> ...") - 'containsline': re.compile(r'^([-]*)$|^([=]*)$', re.M), - 'attr': re.compile("\{@([^\}]*)=([^\}]*)}") # {@id=123} -} -"""Basic and reusable regular expressions.""" - """ AUXILIARY GLOBAL FUNCTIONS @@ -163,11 +145,13 @@ def isBlockLevel(tag): """Check if the tag is a block level HTML tag.""" return BLOCK_LEVEL_ELEMENTS.match(tag) +ATTR_RE = re.compile("\{@([^\}]*)=([^\}]*)}") # {@id=123} + def handleAttributes(text, parent): """Set values of an element based on attribute definitions ({@id=123}).""" def attributeCallback(match): parent.set(match.group(1), match.group(2)) - return CORE_RE['attr'].sub(attributeCallback, text) + return ATTR_RE.sub(attributeCallback, text) def dequote(string): """Remove quotes from around a string.""" @@ -211,369 +195,286 @@ inline elements such as **bold** or *italics*, but rather just catches blocks, lists, quotes, etc. """ -class MarkdownParser: - """Parser Markdown into a ElementTree.""" +class BlockProcessor: + """ Base class for block processors. """ + def __init__(self, parser=None): + self.parser = parser - def __init__(self): - pass + def lastChild(self, parent): + """ Return the last child of an etree element. """ + if len(parent): + return parent[-1] + else: + return None - def parseDocument(self, lines): - """Parse a markdown string into an ElementTree.""" - # Create a ElementTree from the lines - root = etree.Element("div") - buffer = [] + def detab(self, text): + """ Remove a tab from the front of each line of the given text. """ + newtext = [] + lines = text.split('\n') for line in lines: - if line.startswith("#"): - self.parseChunk(root, buffer) - buffer = [line] + if line.startswith(' '*4): + newtext.append(line[4:]) + elif not line.strip(): + newtext.append('') else: - buffer.append(line) - - self.parseChunk(root, buffer) - - return etree.ElementTree(root) + break + return '\n'.join(newtext), '\n'.join(lines[len(newtext):]) - def parseChunk(self, parent_elem, lines, inList=0, looseList=0): - """Process a chunk of markdown-formatted text and attach the parse to - an ElementTree node. + def looseDetab(self, text): + """ Remove a tab from front of lines but allowing dedented lines. """ + lines = text.split('\n') + for i in range(len(lines)): + if lines[i].startswith(' '*4): + lines[i] = lines[i][4:] + return '\n'.join(lines) - Process a section of a source document, looking for high - level structural elements like lists, block quotes, code - segments, html blocks, etc. Some those then get stripped - of their high level markup (e.g. get unindented) and the - lower-level markup is processed recursively. + def test(self, parent, block): + """ Return boolean. Must be overriden by subclasses. """ + pass - Keyword arguments: + def run(self, parent, blocks): + """ Run processor. Must be overridden by subclasses. """ - * parent_elem: The ElementTree element to which the content will be - added. - * lines: a list of lines - * inList: a level - Returns: None +class ListIndentProcessor(BlockProcessor): + """ Process children of list items. """ - """ - # Loop through lines until none left. - while lines: - # Skipping empty line - if not lines[0]: - lines = lines[1:] - continue + def test(self, parent, block): + return block.startswith(' '*4) and parent[-1] and \ + (parent[-1].tag == "ul" or parent[-1].tag == "ol") - # Check if this section starts with a list, a blockquote or - # a code block. If so, process them. - processFn = { 'ul': self.__processUList, - 'ol': self.__processOList, - 'quoted': self.__processQuote, - 'tabbed': self.__processCodeBlock} - for regexp in ['ul', 'ol', 'quoted', 'tabbed']: - m = CORE_RE[regexp].match(lines[0]) - if m: - processFn[regexp](parent_elem, lines, inList) - return - - # We are NOT looking at one of the high-level structures like - # lists or blockquotes. So, it's just a regular paragraph - # (though perhaps nested inside a list or something else). If - # we are NOT inside a list, we just need to look for a blank - # line to find the end of the block. If we ARE inside a - # list, however, we need to consider that a sublist does not - # need to be separated by a blank line. Rather, the following - # markup is legal: - # - # * The top level list item - # - # Another paragraph of the list. This is where we are now. - # * Underneath we might have a sublist. - # - - if inList: - start, lines = self.__linesUntil(lines, (lambda line: - CORE_RE['ul'].match(line) - or CORE_RE['ol'].match(line) - or not line.strip())) - self.parseChunk(parent_elem, start, inList-1, - looseList=looseList) - inList = inList-1 - - else: # Ok, so it's just a simple block - test = lambda line: not line.strip() or line[0] == '>' - paragraph, lines = self.__linesUntil(lines, test) - if len(paragraph) and paragraph[0].startswith('#'): - self.__processHeader(parent_elem, paragraph) - elif len(paragraph) and CORE_RE["isline3"].match(paragraph[0]): - self.__processHR(parent_elem) - lines = paragraph[1:] + lines - elif paragraph: - self.__processParagraph(parent_elem, paragraph, - inList, looseList) - - if lines and not lines[0].strip(): - lines = lines[1:] # skip the first (blank) line - - def __processHR(self, parentElem): - hr = etree.SubElement(parentElem, "hr") - - def __processHeader(self, parentElem, paragraph): - m = CORE_RE['header'].match(paragraph[0]) - if m: - level = len(m.group(1)) - h = etree.SubElement(parentElem, "h%d" % level) - h.text = m.group(2).strip() + def run(self, parent, blocks): + block = blocks.pop(0) + sibling = self.lastChild(parent) + if len(sibling) and sibling[-1].tag == 'li': + self.parser.parseBlocks(sibling[-1], [self.looseDetab(block)]) else: - message(CRITICAL, "We've got a problem header!") + li = etree.SubElement(sibling, 'li') + self.parser.parseBlocks(li, [self.looseDetab(block)]) - def __processParagraph(self, parentElem, paragraph, inList, looseList): - if ( parentElem.tag == 'li' - and not (looseList or parentElem.getchildren())): +class CodeBlockProcessor(BlockProcessor): + """ Process code blocks. """ - # If this is the first paragraph inside "li", don't - # put

around it - append the paragraph bits directly - # onto parentElem - el = parentElem + def test(self, parent, block): + return block.startswith(' '*4) + + def run(self, parent, blocks): + sibling = self.lastChild(parent) + block = blocks.pop(0) + theRest = '' + if sibling and sibling.tag == "pre" and len(sibling) \ + and sibling[0].tag == "code": + code = sibling[0] + block, theRest = self.detab(block) + code.text = '%s\n%s\n' % (code.text, block.rstrip()) else: - # Otherwise make a "p" element - el = etree.SubElement(parentElem, "p") - - dump = [] - - # Searching for hr or header - for line in paragraph: - # it's hr - if CORE_RE["isline3"].match(line): - el.text = "\n".join(dump) - self.__processHR(el) - dump = [] - # it's header - elif line.startswith("#"): - el.text = "\n".join(dump) - self.__processHeader(parentElem, [line]) - dump = [] - else: - dump.append(line) - if dump: - text = "\n".join(dump) - el.text = text - - def __processUList(self, parentElem, lines, inList): - self.__processList(parentElem, lines, inList, listexpr='ul', tag='ul') - - def __processOList(self, parentElem, lines, inList): - self.__processList(parentElem, lines, inList, listexpr='ol', tag='ol') - - def __processList(self, parentElem, lines, inList, listexpr, tag): - """ - Given a list of document lines starting with a list item, - finds the end of the list, breaks it up, and recursively - processes each list item and the remainder of the text file. - - Keyword arguments: - - * parentElem: A ElementTree element to which the content will be added - * lines: a list of lines - * inList: a level + pre = etree.SubElement(parent, 'pre') + code = etree.SubElement(pre, 'code') + block, theRest = self.detab(block) + code.text = '%s\n' % block.rstrip() + if theRest: + blocks.insert(0, theRest) - Returns: None - """ - ul = etree.SubElement(parentElem, tag) # ul might actually be '

    ' - - looseList = 0 - - # Make a list of list items - items = [] - item = -1 +class BlockQuoteProcessor(BlockProcessor): - i = 0 # a counter to keep track of where we are - for line in lines: - loose = 0 - if not line.strip(): - # If we see a blank line, this _might_ be the end of the list - i += 1 - loose = 1 - - # Find the next non-blank line - for j in range(i, len(lines)): - if lines[j].strip(): - next = lines[j] - break - else: - # There is no more text => end of the list - break + RE = re.compile(r'^[ ]{0,3}>[ ](.*)') - # Check if the next non-blank line is still a part of the list + def test(self, parent, block): + return bool(self.RE.match(block)) - if ( CORE_RE[listexpr].match(next) or - CORE_RE['tabbed'].match(next) ): - # get rid of any white space in the line - items[item].append(line.strip()) - looseList = loose or looseList - continue - else: - break # found end of the list - - # Now we need to detect list items (at the current level) - # while also detabing child elements if necessary - - for expr in ['ul', 'ol', 'tabbed']: - m = CORE_RE[expr].match(line) - if m: - if expr in ['ul', 'ol']: # We are looking at a new item - #if m.group(1) : - # Removed the check to allow for a blank line - # at the beginning of the list item - items.append([m.group(1)]) - item += 1 - elif expr == 'tabbed': # This line needs to be detabbed - items[item].append(m.group(4)) #after the 'tab' - i += 1 - break - else: - items[item].append(line) # Just regular continuation - i += 1 # added on 2006.02.25 + def run(self, parent, blocks): + block = '\n'.join([self.clean(line) for line in + blocks.pop(0).split('\n')]) + sibling = self.lastChild(parent) + if sibling and sibling.tag == "blockquote": + quote = sibling else: - i += 1 - - # Add the ElementTree elements - for item in items: - li = etree.SubElement(ul, "li") - self.parseChunk(li, item, inList + 1, looseList = looseList) + quote = etree.SubElement(parent, 'blockquote') + self.parser.parseBlocks(quote, [block]) - # Process the remaining part of the section - self.parseChunk(parentElem, lines[i:], inList) - - def __linesUntil(self, lines, condition): - """ - A utility function to break a list of lines upon the - first line that satisfied a condition. The condition - argument should be a predicate function. - - """ - i = -1 - for line in lines: - i += 1 - if condition(line): - break + def clean(self, line): + """ Remove ``>`` from begining of a line. """ + m = self.RE.match(line) + if m: + return m.group(1) + elif line.strip() == ">": + return "" + else: + return line + +class OListProcessor(BlockProcessor): + """ Process ordered list blocks. """ + + TAG = 'ol' + RE = re.compile(r'^[ ]{0,3}\d+\.[ ](.*)') + + def test(self, parent, block): + return bool(self.RE.match(block)) + + def run(self, parent, blocks): + items = self.get_items(blocks.pop(0)) + sibling = self.lastChild(parent) + if sibling and sibling.tag == self.TAG: + lst = sibling + # make sure previous item is in a p. + if len(lst) and lst[-1].text and not len(lst[-1]): + p = etree.SubElement(lst[-1], 'p') + p.text = lst[-1].text + lst[-1].text = '' + # parse first block differently as it gets wrapped in a p. + li = etree.SubElement(lst, 'li') + self.parser.state = 'looselist' + firstitem = items.pop(0) + self.parser.parseBlocks(li, [firstitem]) + self.parser.resetState() else: - i += 1 - return lines[:i], lines[i:] + lst = etree.SubElement(parent, self.TAG) + self.parser.state = 'list' + for item in items: + li = etree.SubElement(lst, 'li') + self.parser.parseBlocks(li, [item]) + self.parser.resetState() - def __processQuote(self, parentElem, lines, inList): - """ - Given a list of document lines starting with a quote finds - the end of the quote, unindents it and recursively - processes the body of the quote and the remainder of the - text file. + def get_items(self, block): + """ Break a block into list items. """ + items = [] + for line in block.split('\n'): + m = self.RE.match(line) + if m: + items.append(m.group(1)) + else: + items[-1] = '\n'.join([items[-1], line]) + return items - Keyword arguments: - * parentElem: ElementTree element to which the content will be added - * lines: a list of lines - * inList: a level +class UListProcessor(OListProcessor): + """ Process unordered list blocks. """ - Returns: None + TAG = 'ul' + RE = re.compile(r'^[ ]{0,3}[*+-][ ](.*)') - """ - dequoted = [] - i = 0 - blank_line = False # allow one blank line between paragraphs - for line in lines: - m = CORE_RE['quoted'].match(line) - if m: - dequoted.append(m.group(1)) - i += 1 - blank_line = False - elif not blank_line and line.strip() != '': - dequoted.append(line) - i += 1 - elif not blank_line and line.strip() == '': - dequoted.append(line) - i += 1 - blank_line = True - else: - break - blockquote = etree.SubElement(parentElem, "blockquote") +class HashHeaderProcessor(BlockProcessor): + """ Process Hash Headers. """ - self.parseChunk(blockquote, dequoted, inList) - self.parseChunk(parentElem, lines[i:], inList) + RE = re.compile(r'^(#{1,6})(.*?)#*$') - def __processCodeBlock(self, parentElem, lines, inList): - """ - Given a list of document lines starting with a code block - finds the end of the block, puts it into the ElementTree verbatim - wrapped in ("
    ") and recursively processes the
-        the remainder of the text file.
+    def test(self, parent, block):
+        return block.startswith('#')
 
-        Keyword arguments:
+    def run(self, parent, blocks):
+        lines = blocks.pop(0).split('\n')
+        line1 = lines.pop(0)
+        m = self.RE.match(line1)
+        if m:
+            h = etree.SubElement(parent, 'h%d' % len(m.group(1)))
+            h.text = m.group(2).strip()
+        else:
+            lines.insert(0, line1)
+        if len(lines):
+            blocks.insert(0, '\n'.join(lines))
 
-        * parentElem: ElementTree element to which the content will be added
-        * lines: a list of lines
-        * inList: a level
 
-        Returns: None
+class SHeaderProcessor(BlockProcessor):
+    """ Process Setext-style Headers. """
 
-        """
-        detabbed, theRest = self.detectTabbed(lines)
-        pre = etree.SubElement(parentElem, "pre")
-        code = etree.SubElement(pre, "code")
-        text = "\n".join(detabbed).rstrip()+"\n"
-        code.text = AtomicString(text)
-        self.parseChunk(parentElem, theRest, inList)
+    RE = re.compile(r'^.*?\n[=-]{3,}', re.MULTILINE)
 
-    def detectTabbed(self, lines):
-        """ Find indented text and remove indent before further proccesing.
+    def test(self, parent, block):
+        return bool(self.RE.match(block))
 
-        Keyword arguments:
+    def run(self, parent, blocks):
+        lines = blocks.pop(0).split('\n')
+        if lines[1].startswith('='):
+            level = 1
+        else:
+            level = 2
+        h = etree.SubElement(parent, 'h%d' % level)
+        h.text = lines[0].strip()
+        if len(lines) > 2:
+            blocks.insert(0, '\n'.join(lines[2:]))
 
-        * lines: an array of strings
-        * fn: a function that returns a substring of a string
-           if the string matches the necessary criteria
 
-        Returns: a list of post processes items and the unused
-        remainder of the original list
+class HRProcessor(BlockProcessor):
+    """ Process Horizontal Rules. """
 
-        """
-        items = []
-        item = -1
-        i = 0 # to keep track of where we are
+    RE = re.compile(r'([*_-][ ]?){3,}')
 
-        def detab(line):
-            match = CORE_RE['tabbed'].match(line)
-            if match:
-               return match.group(4)
+    def test(self, parent, block):
+        return bool(self.RE.search(block))
 
+    def run(self, parent, blocks):
+        # Check for lines in block before hr.
+        lines = blocks.pop(0).split('\n')
+        prelines = []
         for line in lines:
-            if line.strip(): # Non-blank line
-                line = detab(line)
-                if line:
-                    items.append(line)
-                    i += 1
-                    continue
-                else:
-                    return items, lines[i:]
+            m = self.RE.match(line)
+            if m:
+                break
+            else:
+                prelines.append(line)
+        if len(prelines):
+            self.parser.parseBlocks(parent, ['\n'.join(prelines)])
+        # create hr
+        hr = etree.SubElement(parent, 'hr')
+        # check for lines in block after hr.
+        lines = lines[len(prelines)+1:]
+        if len(lines):
+            blocks.insert(0, '\n'.join(lines))
+
+
+class PBlockProcessor(BlockProcessor):
+    """ Process Paragraph blocks. """
+
+    def test(self, parent, block):
+        return True
+
+    def run(self, parent, blocks):
+        block = blocks.pop(0)
+        if block.strip():
+            if self.parser.state == 'list':
+                parent.text = block
+            else:
+                p = etree.SubElement(parent, 'p')
+                p.text = block
 
-            else: # Blank line: _maybe_ we are done.
-                i += 1 # advance
 
-                # Find the next non-blank line
-                for j in range(i, len(lines)):
-                    if lines[j].strip():
-                        next_line = lines[j]; break
-                else:
-                    break # There is no more text; we are done.
+class BlockParser:
+    """ Parse Markdown blocks into an ElementTree object. """
 
-                # Check if the next non-blank line is tabbed
-                if detab(next_line): # Yes, more work to do.
-                    items.append("")
-                    continue
-                else:
-                    break # No, we are done.
-        else:
-            i += 1
+    def __init__(self):
+        self.blockprocessors = OrderedDict()
+        self.blockprocessors['indent'] = ListIndentProcessor(self)
+        self.blockprocessors['code'] = CodeBlockProcessor(self)
+        self.blockprocessors['hashheader'] = HashHeaderProcessor(self)
+        self.blockprocessors['sheader'] = SHeaderProcessor(self)
+        self.blockprocessors['hr'] = HRProcessor(self)
+        self.blockprocessors['olist'] = OListProcessor(self)
+        self.blockprocessors['ulist'] = UListProcessor(self)
+        self.blockprocessors['quote'] = BlockQuoteProcessor(self)
+        self.blockprocessors['paragraph'] = PBlockProcessor(self)
+        self.resetState()
+
+    def resetState(self):
+        self.state = ''
 
-        return items, lines[i:]
+    def parseDocument(self, lines):
+        """ Parse a markdown string into an ElementTree. """
+        # Create a ElementTree from the lines
+        root = etree.Element("div")
+        blocks = '\n'.join(lines).split('\n\n')
+        self.parseBlocks(root, blocks)
+        return etree.ElementTree(root)
+
+    def parseBlocks(self, parent, blocks):
+        """ Process blocks of markdown text and attach to given etree node. """
+        while blocks:
+           for processor in self.blockprocessors.values():
+               if processor.test(parent, blocks[0]):
+                   processor.run(parent, blocks)
+                   break
 
 
 """
@@ -725,75 +626,15 @@ class HtmlBlockPreprocessor(Preprocessor):
         return new_text.split("\n")
 
 
-class HeaderPreprocessor(Preprocessor):
-
-    """Replace underlined headers with hashed headers.
-
-    (To avoid the need for lookahead later.)
-
-    """
-
-    def run (self, lines):
-        i = -1
-        while i+1 < len(lines):
-            i = i+1
-            if not lines[i].strip():
-                continue
-
-            if lines[i].startswith("#"):
-                lines.insert(i+1, "\n")
-
-            if (i+1 <= len(lines)
-                  and lines[i+1]
-                  and lines[i+1][0] in ['-', '=']):
-
-                underline = lines[i+1].strip()
-
-                if underline == "="*len(underline):
-                    lines[i] = "# " + lines[i].strip()
-                    lines[i+1] = ""
-                elif underline == "-"*len(underline):
-                    lines[i] = "## " + lines[i].strip()
-                    lines[i+1] = ""
-
-        return lines
-
-
-class LinePreprocessor(Preprocessor):
-    """Convert HR lines to "___" format."""
-    blockquote_re = re.compile(r'^(> )+')
-
-    def run (self, lines):
-        for i in range(len(lines)):
-            prefix = ''
-            m = self.blockquote_re.search(lines[i])
-            if m:
-                prefix = m.group(0)
-            if self._isLine(lines[i][len(prefix):]):
-                lines[i] = prefix + "___"
-        return lines
-
-    def _isLine(self, block):
-        """Determine if a block should be replaced with an 
    """
-        if block.startswith("    "):
-            return False  # a code block
-        text = "".join([x for x in block if not x.isspace()])
-        if len(text) <= 2:
-            return False
-        for pattern in ['isline1', 'isline2', 'isline3']:
-            m = CORE_RE[pattern].match(text)
-            if (m and m.group(1)):
-                return True
-        else:
-            return False
+class ReferencePreprocessor(Preprocessor):
+    """ Remove reference definitions from text and store for later use. """
 
+    RE = re.compile(r'^(\ ?\ ?\ ?)\[([^\]]*)\]:\s*([^ ]*)(.*)$', re.DOTALL)
 
-class ReferencePreprocessor(Preprocessor):
-    """Remove reference definitions from the text and store them for later use."""
     def run (self, lines):
         new_text = [];
         for line in lines:
-            m = CORE_RE['reference-def'].match(line)
+            m = self.RE.match(line)
             if m:
                 id = m.group(2).strip().lower()
                 t = m.group(4).strip()  # potential title
@@ -1776,7 +1617,7 @@ class Markdown:
         * safe_mode: Disallow raw html. One of "remove", "replace" or "escape".
 
         """
-        self.parser = MarkdownParser()
+        self.parser = BlockParser()
         self.safeMode = safe_mode
         self.registeredExtensions = []
         self.docType = ""
@@ -1784,8 +1625,6 @@ class Markdown:
 
         self.preprocessors = OrderedDict()
         self.preprocessors["html_block"] =  HtmlBlockPreprocessor(self)
-        self.preprocessors["header"] = HeaderPreprocessor(self)
-        self.preprocessors["line"] =  LinePreprocessor(self)
         self.preprocessors["reference"] = ReferencePreprocessor(self)
         # footnote preprocessor will be inserted with " ?(.*)'), # a quoted block ("> ...")
+    'containsline':    re.compile(r'^([-]*)$|^([=]*)$', re.M),
+    'attr':            re.compile("\{@([^\}]*)=([^\}]*)}") # {@id=123}
+}
+
+class MarkdownParser:
+    """Parser Markdown into a ElementTree."""
+
+    def __init__(self):
+        pass
+
+    def parseDocument(self, lines):
+        """Parse a markdown string into an ElementTree."""
+        # Create a ElementTree from the lines
+        root = etree.Element("div")
+        buffer = []
+        for line in lines:
+            if line.startswith("#"):
+                self.parseChunk(root, buffer)
+                buffer = [line]
+            else:
+                buffer.append(line)
+
+        self.parseChunk(root, buffer)
+
+        return etree.ElementTree(root)
+
+    def parseChunk(self, parent_elem, lines, inList=0, looseList=0):
+        """Process a chunk of markdown-formatted text and attach the parse to
+        an ElementTree node.
+
+        Process a section of a source document, looking for high
+        level structural elements like lists, block quotes, code
+        segments, html blocks, etc.  Some those then get stripped
+        of their high level markup (e.g. get unindented) and the
+        lower-level markup is processed recursively.
+
+        Keyword arguments:
+
+        * parent_elem: The ElementTree element to which the content will be
+                       added.
+        * lines: a list of lines
+        * inList: a level
+
+        Returns: None
+
+        """
+        # Loop through lines until none left.
+        while lines:
+            # Skipping empty line
+            if not lines[0]:
+                lines = lines[1:]
+                continue
+
+            # Check if this section starts with a list, a blockquote or
+            # a code block.  If so, process them.
+            processFn = { 'ul':     self.__processUList,
+                          'ol':     self.__processOList,
+                          'quoted': self.__processQuote,
+                          'tabbed': self.__processCodeBlock}
+            for regexp in ['ul', 'ol', 'quoted', 'tabbed']:
+                m = CORE_RE[regexp].match(lines[0])
+                if m:
+                    processFn[regexp](parent_elem, lines, inList)
+                    return
+
+            # We are NOT looking at one of the high-level structures like
+            # lists or blockquotes.  So, it's just a regular paragraph
+            # (though perhaps nested inside a list or something else).  If
+            # we are NOT inside a list, we just need to look for a blank
+            # line to find the end of the block.  If we ARE inside a
+            # list, however, we need to consider that a sublist does not
+            # need to be separated by a blank line.  Rather, the following
+            # markup is legal:
+            #
+            # * The top level list item
+            #
+            #     Another paragraph of the list.  This is where we are now.
+            #     * Underneath we might have a sublist.
+            #
+
+            if inList:
+                start, lines  = self.__linesUntil(lines, (lambda line:
+                                 CORE_RE['ul'].match(line)
+                                 or CORE_RE['ol'].match(line)
+                                                  or not line.strip()))
+                self.parseChunk(parent_elem, start, inList-1,
+                                looseList=looseList)
+                inList = inList-1
+
+            else: # Ok, so it's just a simple block
+                test = lambda line: not line.strip() or line[0] == '>'
+                paragraph, lines = self.__linesUntil(lines, test)
+                if len(paragraph) and paragraph[0].startswith('#'):
+                    self.__processHeader(parent_elem, paragraph)
+                elif len(paragraph) and CORE_RE["isline3"].match(paragraph[0]):
+                    self.__processHR(parent_elem)
+                    lines = paragraph[1:] + lines
+                elif paragraph:
+                    self.__processParagraph(parent_elem, paragraph,
+                                          inList, looseList)
+
+            if lines and not lines[0].strip():
+                lines = lines[1:]  # skip the first (blank) line
+
+    def __processHR(self, parentElem):
+        hr = etree.SubElement(parentElem, "hr")
+
+    def __processHeader(self, parentElem, paragraph):
+        m = CORE_RE['header'].match(paragraph[0])
+        if m:
+            level = len(m.group(1))
+            h = etree.SubElement(parentElem, "h%d" % level)
+            h.text = m.group(2).strip()
+        else:
+            message(CRITICAL, "We've got a problem header!")
+
+    def __processParagraph(self, parentElem, paragraph, inList, looseList):
+
+        if ( parentElem.tag == 'li'
+                and not (looseList or parentElem.getchildren())):
+
+            # If this is the first paragraph inside "li", don't
+            # put 
     around it - append the paragraph bits directly
+            # onto parentElem
+            el = parentElem
+        else:
+            # Otherwise make a "p" element
+            el = etree.SubElement(parentElem, "p")
+
+        dump = []
+
+        # Searching for hr or header
+        for line in paragraph:
+            # it's hr
+            if CORE_RE["isline3"].match(line):
+                el.text = "\n".join(dump)
+                self.__processHR(el)
+                dump = []
+            # it's header
+            elif line.startswith("#"):
+                el.text = "\n".join(dump)
+                self.__processHeader(parentElem, [line])
+                dump = []
+            else:
+                dump.append(line)
+        if dump:
+            text = "\n".join(dump)
+            el.text = text
+
+    def __processUList(self, parentElem, lines, inList):
+        self.__processList(parentElem, lines, inList, listexpr='ul', tag='ul')
+
+    def __processOList(self, parentElem, lines, inList):
+        self.__processList(parentElem, lines, inList, listexpr='ol', tag='ol')
+
+    def __processList(self, parentElem, lines, inList, listexpr, tag):
+        """
+        Given a list of document lines starting with a list item,
+        finds the end of the list, breaks it up, and recursively
+        processes each list item and the remainder of the text file.
+
+        Keyword arguments:
+
+        * parentElem: A ElementTree element to which the content will be added
+        * lines: a list of lines
+        * inList: a level
+
+        Returns: None
+
+        """
+        ul = etree.SubElement(parentElem, tag) # ul might actually be '
      '
+
+        looseList = 0
+
+        # Make a list of list items
+        items = []
+        item = -1
+
+        i = 0  # a counter to keep track of where we are
+        for line in lines:
+            loose = 0
+            if not line.strip():
+                # If we see a blank line, this _might_ be the end of the list
+                i += 1
+                loose = 1
+
+                # Find the next non-blank line
+                for j in range(i, len(lines)):
+                    if lines[j].strip():
+                        next = lines[j]
+                        break
+                else:
+                    # There is no more text => end of the list
+                    break
+
+                # Check if the next non-blank line is still a part of the list
+
+                if ( CORE_RE[listexpr].match(next) or
+                     CORE_RE['tabbed'].match(next) ):
+                    # get rid of any white space in the line
+                    items[item].append(line.strip())
+                    looseList = loose or looseList
+                    continue
+                else:
+                    break # found end of the list
+
+            # Now we need to detect list items (at the current level)
+            # while also detabing child elements if necessary
+
+            for expr in ['ul', 'ol', 'tabbed']:
+                m = CORE_RE[expr].match(line)
+                if m:
+                    if expr in ['ul', 'ol']:  # We are looking at a new item
+                        #if m.group(1) :
+                        # Removed the check to allow for a blank line
+                        # at the beginning of the list item
+                        items.append([m.group(1)])
+                        item += 1
+                    elif expr == 'tabbed':  # This line needs to be detabbed
+                        items[item].append(m.group(4)) #after the 'tab'
+                    i += 1
+                    break
+            else:
+                items[item].append(line)  # Just regular continuation
+                i += 1 # added on 2006.02.25
+        else:
+            i += 1
+
+        # Add the ElementTree elements
+        for item in items:
+            li = etree.SubElement(ul, "li")
+            self.parseChunk(li, item, inList + 1, looseList = looseList)
+
+        # Process the remaining part of the section
+        self.parseChunk(parentElem, lines[i:], inList)
+
+    def __linesUntil(self, lines, condition):
+        """
+        A utility function to break a list of lines upon the
+        first line that satisfied a condition.  The condition
+        argument should be a predicate function.
+
+        """
+        i = -1
+        for line in lines:
+            i += 1
+            if condition(line):
+                break
+        else:
+            i += 1
+        return lines[:i], lines[i:]
+
+    def __processQuote(self, parentElem, lines, inList):
+        """
+        Given a list of document lines starting with a quote finds
+        the end of the quote, unindents it and recursively
+        processes the body of the quote and the remainder of the
+        text file.
+
+        Keyword arguments:
+
+        * parentElem: ElementTree element to which the content will be added
+        * lines: a list of lines
+        * inList: a level
+
+        Returns: None
+
+        """
+        dequoted = []
+        i = 0
+        blank_line = False # allow one blank line between paragraphs
+        for line in lines:
+            m = CORE_RE['quoted'].match(line)
+            if m:
+                dequoted.append(m.group(1))
+                i += 1
+                blank_line = False
+            elif not blank_line and line.strip() != '':
+                dequoted.append(line)
+                i += 1
+            elif not blank_line and line.strip() == '':
+                dequoted.append(line)
+                i += 1
+                blank_line = True
+            else:
+                break
+
+        blockquote = etree.SubElement(parentElem, "blockquote")
+
+        self.parseChunk(blockquote, dequoted, inList)
+        self.parseChunk(parentElem, lines[i:], inList)
+
+    def __processCodeBlock(self, parentElem, lines, inList):
+        """
+        Given a list of document lines starting with a code block
+        finds the end of the block, puts it into the ElementTree verbatim
+        wrapped in ("
      ") and recursively processes the
+        the remainder of the text file.
+
+        Keyword arguments:
+
+        * parentElem: ElementTree element to which the content will be added
+        * lines: a list of lines
+        * inList: a level
+
+        Returns: None
+
+        """
+        detabbed, theRest = self.detectTabbed(lines)
+        pre = etree.SubElement(parentElem, "pre")
+        code = etree.SubElement(pre, "code")
+        text = "\n".join(detabbed).rstrip()+"\n"
+        code.text = AtomicString(text)
+        self.parseChunk(parentElem, theRest, inList)
+
+    def detectTabbed(self, lines):
+        """ Find indented text and remove indent before further proccesing.
+
+        Keyword arguments:
+
+        * lines: an array of strings
+        * fn: a function that returns a substring of a string
+           if the string matches the necessary criteria
+
+        Returns: a list of post processes items and the unused
+        remainder of the original list
+
+        """
+        items = []
+        item = -1
+        i = 0 # to keep track of where we are
+
+        def detab(line):
+            match = CORE_RE['tabbed'].match(line)
+            if match:
+               return match.group(4)
+
+        for line in lines:
+            if line.strip(): # Non-blank line
+                line = detab(line)
+                if line:
+                    items.append(line)
+                    i += 1
+                    continue
+                else:
+                    return items, lines[i:]
+
+            else: # Blank line: _maybe_ we are done.
+                i += 1 # advance
+
+                # Find the next non-blank line
+                for j in range(i, len(lines)):
+                    if lines[j].strip():
+                        next_line = lines[j]; break
+                else:
+                    break # There is no more text; we are done.
+
+                # Check if the next non-blank line is tabbed
+                if detab(next_line): # Yes, more work to do.
+                    items.append("")
+                    continue
+                else:
+                    break # No, we are done.
+        else:
+            i += 1
+
+        return items, lines[i:]
+
+class HeaderPreprocessor(Preprocessor):
+
+    """Replace underlined headers with hashed headers.
+
+    (To avoid the need for lookahead later.)
+
+    """
+
+    def run (self, lines):
+        i = -1
+        while i+1 < len(lines):
+            i = i+1
+            if not lines[i].strip():
+                continue
+
+            if lines[i].startswith("#"):
+                lines.insert(i+1, "\n")
+
+            if (i+1 <= len(lines)
+                  and lines[i+1]
+                  and lines[i+1][0] in ['-', '=']):
+
+                underline = lines[i+1].strip()
+
+                if underline == "="*len(underline):
+                    lines[i] = "# " + lines[i].strip()
+                    lines[i+1] = ""
+                elif underline == "-"*len(underline):
+                    lines[i] = "## " + lines[i].strip()
+                    lines[i+1] = ""
+
+        return lines
+
+
+class LinePreprocessor(Preprocessor):
+    """Convert HR lines to "___" format."""
+    blockquote_re = re.compile(r'^(> )+')
+
+    def run (self, lines):
+        for i in range(len(lines)):
+            prefix = ''
+            m = self.blockquote_re.search(lines[i])
+            if m:
+                prefix = m.group(0)
+            if self._isLine(lines[i][len(prefix):]):
+                lines[i] = prefix + "___"
+        return lines
+
+    def _isLine(self, block):
+        """Determine if a block should be replaced with an 
      """
+        if block.startswith("    "):
+            return False  # a code block
+        text = "".join([x for x in block if not x.isspace()])
+        if len(text) <= 2:
+            return False
+        for pattern in ['isline1', 'isline2', 'isline3']:
+            m = CORE_RE[pattern].match(text)
+            if (m and m.group(1)):
+                return True
+        else:
+            return False
+
+
+class LegacyExtension(markdown.Extension):
+    """ Replace Markdown's core parser. """
+
+    def extendMarkdown(self, md, md_globals):
+        """ Set the core parser to an instance of MarkdownParser. """
+        md.parser = MarkdownParser()
+        md.preprocessors.add ("header", HeaderPreprocessor(self), "