#!/usr/bin/env python
"""
Python-Markdown
===============

Converts Markdown to HTML.  Basic usage as a module:

    import markdown
    md = Markdown()
    html = md.convert(your_text_string)

See <http://www.freewisdom.org/projects/python-markdown/> for more
information and instructions on how to extend the functionality of the
script.  (You might want to read that before you try modifying this
file.)

Started by [Manfred Stienstra](http://www.dwerg.net/).  Continued and
maintained  by [Yuri Takhteyev](http://www.freewisdom.org) and [Waylan
Limberg](http://achinghead.com/).

Contact: 

* <yuri@freewisdom.org>
* <waylan@gmail.com>

License: [GPL 2](http://www.gnu.org/copyleft/gpl.html) or BSD

"""

version = "1.7"
version_info = (1,7,0,"rc-2")
__revision__ = "$Rev$"



import re, sys, codecs

from logging import getLogger, StreamHandler, Formatter, \
                    DEBUG, INFO, WARN, ERROR, CRITICAL


MESSAGE_THRESHOLD = CRITICAL


# Configure debug message logger (the hard way - to support python 2.3)
logger = getLogger('MARKDOWN')
logger.setLevel(DEBUG) # This is restricted by handlers later
console_hndlr = StreamHandler()
formatter = Formatter('%(name)s-%(levelname)s: "%(message)s"')
console_hndlr.setFormatter(formatter)
console_hndlr.setLevel(MESSAGE_THRESHOLD)
logger.addHandler(console_hndlr)


def message(level, text):
    ''' A wrapper method for logging debug messages. '''
    logger.log(level, text)


# --------------- CONSTANTS YOU MIGHT WANT TO MODIFY -----------------

TAB_LENGTH = 4            # expand tabs to this many spaces
ENABLE_ATTRIBUTES = True  # @id = xyz -> <... id="xyz">
SMART_EMPHASIS = 1        # this_or_that does not become this<i>or</i>that
HTML_REMOVED_TEXT = "[HTML_REMOVED]" # text used instead of HTML in safe mode

RTL_BIDI_RANGES = ( (u'\u0590', u'\u07FF'),
                    # from Hebrew to Nko (includes Arabic, Syriac and Thaana)
                    (u'\u2D30', u'\u2D7F'),
                    # Tifinagh
                    )

# Unicode Reference Table:
# 0590-05FF - Hebrew
# 0600-06FF - Arabic
# 0700-074F - Syriac
# 0750-077F - Arabic Supplement
# 0780-07BF - Thaana
# 07C0-07FF - Nko

BOMS = { 'utf-8': (codecs.BOM_UTF8, ),
         'utf-16': (codecs.BOM_UTF16_LE, codecs.BOM_UTF16_BE),
         #'utf-32': (codecs.BOM_UTF32_LE, codecs.BOM_UTF32_BE)
         }

def removeBOM(text, encoding):
    """
    Used by `markdownFromFile` to remove a "byte order mark" from the begining
    of an utf-8, utf-16 or utf-32 encoded file.
    """
    
    convert = isinstance(text, unicode)
    for bom in BOMS[encoding]:
        bom = convert and bom.decode(encoding) or bom
        if text.startswith(bom):
            return text.lstrip(bom)
    return text

# The following constant specifies the name used in the usage
# statement displayed for python versions lower than 2.3.  (With
# python2.3 and higher the usage statement is generated by optparse
# and uses the actual name of the executable called.)

EXECUTABLE_NAME_FOR_USAGE = "python markdown.py"
                    

# --------------- CONSTANTS YOU _SHOULD NOT_ HAVE TO CHANGE ----------

# a template for html placeholders
HTML_PLACEHOLDER_PREFIX = "qaodmasdkwaspemas"
HTML_PLACEHOLDER = HTML_PLACEHOLDER_PREFIX + "%dajkqlsmdqpakldnzsdfls"

BLOCK_LEVEL_ELEMENTS = ['p', 'div', 'blockquote', 'pre', 'table',
                        'dl', 'ol', 'ul', 'script', 'noscript',
                        'form', 'fieldset', 'iframe', 'math', 'ins',
                        'del', 'hr', 'hr/', 'style']

def isBlockLevel (tag):
    """
    Used by HTMLBlockPreprocessor to check if a given tag is a block level 
    element.
    """
    return ( (tag in BLOCK_LEVEL_ELEMENTS) or
             (tag[0] == 'h' and tag[1] in "0123456789") )

"""
======================================================================
========================== NANODOM ===================================
======================================================================

The three classes below implement some of the most basic DOM
methods.  I use this instead of minidom because I need a simpler
functionality and do not want to require additional libraries.

Importantly, NanoDom does not do normalization, which is what we
want. It also adds extra white space when converting DOM to string
"""

ENTITY_NORMALIZATION_EXPRESSIONS = [ (re.compile("&"), "&amp;"),
                                     (re.compile("<"), "&lt;"),
                                     (re.compile(">"), "&gt;")]

ENTITY_NORMALIZATION_EXPRESSIONS_SOFT = [ (re.compile("&(?!\#)"), "&amp;"),
                                     (re.compile("<"), "&lt;"),
                                     (re.compile(">"), "&gt;"),
                                     (re.compile("\""), "&quot;")]


def getBidiType(text):
    """
    Get Bi-directional text type. Used by TextNode to determine text direction.
    """

    if not text: return None

    ch = text[0]

    if not isinstance(ch, unicode) or not ch.isalpha():
        return None

    else:

        for min, max in RTL_BIDI_RANGES:
            if ( ch >= min and ch <= max ):
                return "rtl"
        else:
            return "ltr"


class Document:
    """
    Document root of the NanoDom. An instance stores DOM elements as children.

    """

    def __init__ (self):
        """ Create a NanoDom document. """
        self.bidi = "ltr"

    def appendChild(self, child):
        """ Add a dom element as a child of the document root. """
        self.documentElement = child
        child.isDocumentElement = True
        child.parent = self
        self.entities = {}

    def setBidi(self, bidi):
        """ Set text direction (right-left or left-right)."""
        if bidi:
            self.bidi = bidi

    def createElement(self, tag, textNode=None):
        """ Given a tag or textNode, return a dom element. """
        el = Element(tag)
        el.doc = self
        if textNode:
            el.appendChild(self.createTextNode(textNode))
        return el

    def createTextNode(self, text):
        """ Return given text as a TextNode. """
        node = TextNode(text)
        node.doc = self
        return node

    def createEntityReference(self, entity):
        """ Return an html entitry reference (i.e.: `&amp;`). """
        if entity not in self.entities:
            self.entities[entity] = EntityReference(entity)
        return self.entities[entity]

    def createCDATA(self, text):
        """ Return the given text as a CDATA node. """
        node = CDATA(text)
        node.doc = self
        return node

    def toxml (self):
        """ Convert document to xml and return a string. """
        return self.documentElement.toxml()

    def normalizeEntities(self, text, avoidDoubleNormalizing=False):
        """ Return the given text as an html entity (i.e.: `<` => `&gt;`). """
        if avoidDoubleNormalizing:
            regexps = ENTITY_NORMALIZATION_EXPRESSIONS_SOFT
        else:
            regexps = ENTITY_NORMALIZATION_EXPRESSIONS

        for regexp, substitution in regexps:
            text = regexp.sub(substitution, text)
        return text

    def find(self, test):
        """ Return a list of descendants that pass the test function """
        return self.documentElement.find(test)

    def unlink(self):
        """ Cleanup: Remove all children from the document. """
        self.documentElement.unlink()
        self.documentElement = None


class CDATA:
    """ CDATA node type of NanoDom. """
    type = "cdata"

    def __init__ (self, text):
        """ Create a CDATA node with given text. """
        self.text = text

    def handleAttributes(self):
        """ Not implemented for CDATA node type. """
        pass

    def toxml (self):
        """ Return CDATA node as a string. """
        return "<![CDATA[" + self.text + "]]>"

class Element:
    """ 
    Element node type of Nanodom. 
    
    All html tags would most likely be represented as Elements.

    """
    type = "element"

    def __init__ (self, tag):
        """ Create an Element node instance. """
        self.nodeName = tag
        self.attributes = []
        self.attribute_values = {}
        self.childNodes = []
        self.bidi = None
        self.isDocumentElement = False

    def setBidi(self, bidi):
        """ Set text direction (i.e.: right-left or left-right). """
        if bidi:

            orig_bidi = self.bidi

            if not self.bidi or self.isDocumentElement:
                # Once the bidi is set don't change it (except for doc element)
                self.bidi = bidi
                self.parent.setBidi(bidi)


    def unlink(self):
        """ Cleanup: Remove all children of the Element. """
        for child in self.childNodes:
            if child.type == "element":
                child.unlink()
        self.childNodes = None

    def setAttribute(self, attr, value):
        """ 
        Assign an html/xml attribute to the Element (i.e.: id, class, href). 
        """
        if not attr in self.attributes:
            self.attributes.append(attr)

        self.attribute_values[attr] = value

    def insertChild(self, position, child):
        """ Insert a child Element at the given position. """
        self.childNodes.insert(position, child)
        child.parent = self

    def removeChild(self, child):
        """ Remove the given child from the Element. """
        self.childNodes.remove(child)

    def replaceChild(self, oldChild, newChild):
        """ Replace an old child Element with a new child Element. """
        position = self.childNodes.index(oldChild)
        self.removeChild(oldChild)
        self.insertChild(position, newChild)

    def appendChild(self, child):
        """ Append a new child Element to the end of the child Elements. """
        self.childNodes.append(child)
        child.parent = self

    def handleAttributes(self):
        """ Not implemented for Element node type. """
        pass

    def find(self, test, depth=0):
        """ Returns a list of descendants that pass the test function """
        matched_nodes = []
        for child in self.childNodes:
            if test(child):
                matched_nodes.append(child)
            if child.type == "element":
                matched_nodes += child.find(test, depth+1)
        return matched_nodes

    def toxml(self):
        """ Return the Element and all children as a string. """
        if ENABLE_ATTRIBUTES:
            for child in self.childNodes:
                child.handleAttributes()

        buffer = ""
        if self.nodeName in ['h1', 'h2', 'h3', 'h4']:
            buffer += "\n"
        elif self.nodeName in ['li']:
            buffer += "\n "

        # Process children FIRST, then do the attributes

        childBuffer = ""

        if self.childNodes or self.nodeName in ['blockquote']:
            childBuffer += ">"
            for child in self.childNodes:
                childBuffer += child.toxml()
            if self.nodeName == 'p':
                childBuffer += "\n"
            elif self.nodeName == 'li':
                childBuffer += "\n "
            childBuffer += "</%s>" % self.nodeName
        else:
            childBuffer += "/>"


            
        buffer += "<" + self.nodeName

        if self.nodeName in ['p', 'li', 'ul', 'ol',
                             'h1', 'h2', 'h3', 'h4', 'h5', 'h6']:

            if not self.attribute_values.has_key("dir"):
                if self.bidi:
                    bidi = self.bidi
                else:
                    bidi = self.doc.bidi
                    
                if bidi=="rtl":
                    self.setAttribute("dir", "rtl")
        
        for attr in self.attributes:
            value = self.attribute_values[attr]
            value = self.doc.normalizeEntities(value,
                                               avoidDoubleNormalizing=True)
            buffer += ' %s="%s"' % (attr, value)


        # Now let's actually append the children

        buffer += childBuffer

        if self.nodeName in ['p', 'br ', 'li', 'ul', 'ol',
                             'h1', 'h2', 'h3', 'h4'] :
            buffer += "\n"

        return buffer


class TextNode:
    """ A Text node type of the NanoDom. """
    type = "text"
    attrRegExp = re.compile(r'\{@([^\}]*)=([^\}]*)}') # {@id=123}

    def __init__ (self, text):
        """ Create a TextNode with the given text. """
        self.value = text        

    def attributeCallback(self, match):
        """ Regex callback method to set attribute on parent. """
        self.parent.setAttribute(match.group(1), match.group(2))

    def handleAttributes(self):
        """ Parse and assign attributes to the parent Element. """
        self.value = self.attrRegExp.sub(self.attributeCallback, self.value)

    def toxml(self):
        """ Return the TextNode as a string. """
        text = self.value

        self.parent.setBidi(getBidiType(text))
        
        if not text.startswith(HTML_PLACEHOLDER_PREFIX):
            if self.parent.nodeName == "p":
                text = text.replace("\n", "\n   ")
            elif (self.parent.nodeName == "li"
                  and self.parent.childNodes[0]==self):
                text = "\n     " + text.replace("\n", "\n     ")
        text = self.doc.normalizeEntities(text)
        return text


class EntityReference:
    """ EntityReference node type of NanoDom. """
    type = "entity_ref"

    def __init__(self, entity):
        """ Create an EntityReference of the given entity. """
        self.entity = entity

    def handleAttributes(self):
        """ Not implemented for EntityReference. """
        pass

    def toxml(self):
        """ Return the EntityReference as a string. """
        return "&" + self.entity + ";"


"""
======================================================================
========================== PRE-PROCESSORS ============================
======================================================================

Preprocessors munge source text before we start doing anything too
complicated.

There are two types of preprocessors: TextPreprocessor and Preprocessor.

"""


class TextPreprocessor:
    """
    TextPreprocessors are run before the text is broken into lines.
    
    Each TextPreprocessor implements a "run" method that takes a pointer to a
    text string of the document, modifies it as necessary and returns
    either the same pointer or a pointer to a new string.  
    
    TextPreprocessors must extend markdown.TextPreprocessor.

    """

    def run(self, text):
        """ 
        Each subclass of TextPreprocessor should override the `run` method, 
        which takes the document text as a single string and returns the 
        (possibly modified) document as a single string.
        
        """
        pass


class Preprocessor:
    """
    Preprocessors are run after the text is broken into lines.

    Each preprocessor implements a "run" method that takes a pointer to a
    list of lines of the document, modifies it as necessary and returns
    either the same pointer or a pointer to a new list.  
    
    Preprocessors must extend markdown.Preprocessor.
    
    """

    def run(self, lines):
        """
        Each subclass of Preprocessor should override the `run` method, which
        takes the document as a list of strings split by newlines and returns
        the (possibly modified) list of lines.

        """
        pass
 

class HtmlBlockPreprocessor(TextPreprocessor):
    """
    Remove html blocks from the source text and store them for later retrieval.
    """
    
    def _get_left_tag(self, block):
        return block[1:].replace(">", " ", 1).split()[0].lower()


    def _get_right_tag(self, left_tag, block):
        return block.rstrip()[-len(left_tag)-2:-1].lower()

    def _equal_tags(self, left_tag, right_tag):
        
        if left_tag == 'div' or left_tag[0] in ['?', '@', '%']: # handle PHP, etc.
            return True
        if ("/" + left_tag) == right_tag:
            return True
        if (right_tag == "--" and left_tag == "--"):
            return True
        elif left_tag == right_tag[1:] \
            and right_tag[0] != "<":
            return True
        else:
            return False

    def _is_oneliner(self, tag):
        return (tag in ['hr', 'hr/'])

    
    def run(self, text):
        """ Find and remove raw html from text. """

        new_blocks = []
        text = text.split("\n\n")
        
        items = []
        left_tag = ''
        right_tag = ''
        in_tag = False # flag
        
        for block in text:
            if block.startswith("\n"):
                block = block[1:]

            if not in_tag:

                if block.startswith("<"):
                    
                    left_tag = self._get_left_tag(block)
                    right_tag = self._get_right_tag(left_tag, block)

                    if not (isBlockLevel(left_tag) \
                        or block[1] in ["!", "?", "@", "%"]):
                        new_blocks.append(block)
                        continue

                    if self._is_oneliner(left_tag):
                        new_blocks.append(block.strip())
                        continue
                        
                    if block[1] == "!":
                        # is a comment block
                        left_tag = "--"
                        right_tag = self._get_right_tag(left_tag, block)
                        # keep checking conditions below and maybe just append
                        
                    if block.rstrip().endswith(">") \
                        and self._equal_tags(left_tag, right_tag):
                        new_blocks.append(
                            self.stash.store(block.strip()))
                        continue
                    else: #if not block[1] == "!":
                        # if is block level tag and is not complete
                        items.append(block.strip())
                        in_tag = True
                        continue

                new_blocks.append(block)

            else:
                items.append(block.strip())
                
                right_tag = self._get_right_tag(left_tag, block)
                
                if self._equal_tags(left_tag, right_tag):
                    # if find closing tag
                    in_tag = False
                    new_blocks.append(
                        self.stash.store('\n\n'.join(items)))
                    items = []

        if items:
            new_blocks.append(self.stash.store('\n\n'.join(items)))
            new_blocks.append('\n')
            
        return "\n\n".join(new_blocks)

HTML_BLOCK_PREPROCESSOR = HtmlBlockPreprocessor()


class HeaderPreprocessor(Preprocessor):

    """
    Replace underlined headers with hashed headers to avoid
    the nead for lookahead later.
    """

    def run (self, lines):
        """ Find and replace underlined headers. """

        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

HEADER_PREPROCESSOR = HeaderPreprocessor()


class LinePreprocessor(Preprocessor):
    """ 
    Convert HR lines to raw html and store (needs to be done before 
    processing lists).
    
    """

    blockquote_re = re.compile(r'^(> )+')

    def run (self, lines):
        """ Find a store HR 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 + self.stash.store("<hr />", safe=True)
        return lines

    def _isLine(self, block):
        """Determine if a block should be replaced with an <HR>"""

        if block.startswith("    "): return 0  # a code block
        text = "".join([x for x in block if not x.isspace()])
        if len(text) <= 2:
            return 0
        for pattern in ['isline1', 'isline2', 'isline3']:
            m = RE.regExp[pattern].match(text)
            if (m and m.group(1)):
                return 1
        else:
            return 0

LINE_PREPROCESSOR = LinePreprocessor()


class ReferencePreprocessor(Preprocessor):
    """
    Remove reference definitions from the text and store them for later use.
    
    """

    def run (self, lines):
        """ Remove and store reference defs. """
        new_text = [];
        for line in lines:
            m = RE.regExp['reference-def'].match(line)
            if m:
                id = m.group(2).strip().lower()
                t = m.group(4).strip()  # potential title
                if not t:
                    self.references[id] = (m.group(3), t)
                elif (len(t) >= 2
                      and (t[0] == t[-1] == "\""
                           or t[0] == t[-1] == "\'"
                           or (t[0] == "(" and t[-1] == ")") ) ):
                    self.references[id] = (m.group(3), t[1:-1])
                else:
                    new_text.append(line)
            else:
                new_text.append(line)

        return new_text #+ "\n"

REFERENCE_PREPROCESSOR = ReferencePreprocessor()

"""
======================================================================
========================== INLINE PATTERNS ===========================
======================================================================

Inline patterns such as *emphasis* are handled by means of auxiliary
objects, one per pattern.  Pattern objects must be instances of classes
that extend markdown.Pattern.  Each pattern object uses a single regular
expression and needs support the following methods:

  pattern.getCompiledRegExp() - returns a regular expression

  pattern.handleMatch(m, doc) - takes a match object and returns
                                a NanoDom node (as a part of the provided
                                doc) or None

All of python markdown's built-in patterns subclass from Patter,
but you can add additional patterns that don't.

Also note that all the regular expressions used by inline must
capture the whole block.  For this reason, they all start with
'^(.*)' and end with '(.*)!'.  In case with built-in expression
Pattern takes care of adding the "^(.*)" and "(.*)!".

Finally, the order in which regular expressions are applied is very
important - e.g. if we first replace http://.../ links with <a> tags
and _then_ try to replace inline html, we would end up with a mess.
So, we apply the expressions in the following order:

       * escape and backticks have to go before everything else, so
         that we can preempt any markdown patterns by escaping them.

       * then we handle auto-links (must be done before inline html)

       * then we handle inline HTML.  At this point we will simply
         replace all inline HTML strings with a placeholder and add
         the actual HTML to a hash.

       * then inline images (must be done before links)

       * then bracketed links, first regular then reference-style

       * finally we apply strong and emphasis
"""

NOBRACKET = r'[^\]\[]*'
BRK = ( r'\[('
        + (NOBRACKET + r'(\[')*6
        + (NOBRACKET+ r'\])*')*6
        + NOBRACKET + r')\]' )
NOIMG = r'(?<!\!)'

BACKTICK_RE = r'\`([^\`]*)\`'                    # `e= m*c^2`
DOUBLE_BACKTICK_RE =  r'\`\`(.*?)\`\`'            # ``e=f("`")``
ESCAPE_RE = r'\\(.)'                             # \<
EMPHASIS_RE = r'\*([^\*]*)\*'                    # *emphasis*
STRONG_RE = r'\*\*(.*?)\*\*'                      # **strong**
STRONG_EM_RE = r'\*\*\*(.*?)\*\*\*'            # ***strong***

if SMART_EMPHASIS:
    EMPHASIS_2_RE = r'(?<!\S)_(\S[^_]*)_'        # _emphasis_
else:
    EMPHASIS_2_RE = r'_([^_]*)_'                 # _emphasis_

STRONG_2_RE = r'__(.*?)__'                     # __strong__
STRONG_EM_2_RE = r'___(.*?)___'                # ___strong___

LINK_RE = NOIMG + BRK + r'\s*\(([^\)]*)\)'               # [text](url)
LINK_ANGLED_RE = NOIMG + BRK + r'\s*\(<([^\)]*)>\)'      # [text](<url>)
IMAGE_LINK_RE = r'\!' + BRK + r'\s*\(([^\)]*)\)' # ![alttxt](http://x.com/)
REFERENCE_RE = NOIMG + BRK+ r'\s*\[([^\]]*)\]'           # [Google][3]
IMAGE_REFERENCE_RE = r'\!' + BRK + '\s*\[([^\]]*)\]' # ![alt text][2]
NOT_STRONG_RE = r'( \* )'                        # stand-alone * or _
AUTOLINK_RE = r'<((?:f|ht)tps?://[^>]*)>'        # <http://www.123.com>
AUTOMAIL_RE = r'<([^> \!]*@[^> ]*)>'               # <me@example.com>
#HTML_RE = r'(\<[^\>]*\>)'                        # <...>
HTML_RE = r'(\<[a-zA-Z/][^\>]*\>)'               # <...>
ENTITY_RE = r'(&[\#a-zA-Z0-9]*;)'                # &amp;
LINE_BREAK_RE = r'  \n'                     # two spaces at end of line
LINE_BREAK_2_RE = r'  $'                    # two spaces at end of text

class Pattern:

    def __init__ (self, pattern):
        self.pattern = pattern
        self.compiled_re = re.compile("^(.*?)%s(.*?)$" % pattern, re.DOTALL)

    def getCompiledRegExp (self):
        return self.compiled_re

BasePattern = Pattern # for backward compatibility

class SimpleTextPattern (Pattern):

    def handleMatch(self, m, doc):
        return doc.createTextNode(m.group(2))

class SimpleTagPattern (Pattern):

    def __init__ (self, pattern, tag):
        Pattern.__init__(self, pattern)
        self.tag = tag

    def handleMatch(self, m, doc):
        el = doc.createElement(self.tag)
        el.appendChild(doc.createTextNode(m.group(2)))
        return el

class SubstituteTagPattern (SimpleTagPattern):

    def handleMatch (self, m, doc):
        return doc.createElement(self.tag)

class BacktickPattern (Pattern):

    def __init__ (self, pattern):
        Pattern.__init__(self, pattern)
        self.tag = "code"

    def handleMatch(self, m, doc):
        el = doc.createElement(self.tag)
        text = m.group(2).strip()
        #text = text.replace("&", "&amp;")
        el.appendChild(doc.createTextNode(text))
        return el


class DoubleTagPattern (SimpleTagPattern): 

    def handleMatch(self, m, doc):
        tag1, tag2 = self.tag.split(",")
        el1 = doc.createElement(tag1)
        el2 = doc.createElement(tag2)
        el1.appendChild(el2)
        el2.appendChild(doc.createTextNode(m.group(2)))
        return el1


class HtmlPattern (Pattern):

    def handleMatch (self, m, doc):
        rawhtml = m.group(2)
        inline = True
        place_holder = self.stash.store(rawhtml)
        return doc.createTextNode(place_holder)


class LinkPattern (Pattern):

    def handleMatch(self, m, doc):
        el = doc.createElement('a')
        el.appendChild(doc.createTextNode(m.group(2)))
        parts = m.group(9).split('"')
        # We should now have [], [href], or [href, title]
        if parts:
            el.setAttribute('href', parts[0].strip())
        else:
            el.setAttribute('href', "")
        if len(parts) > 1:
            # we also got a title
            title = '"' + '"'.join(parts[1:]).strip()
            title = dequote(title) #.replace('"', "&quot;")
            el.setAttribute('title', title)
        return el


class ImagePattern (Pattern):

    def handleMatch(self, m, doc):
        el = doc.createElement('img')
        src_parts = m.group(9).split()
        if src_parts:
            el.setAttribute('src', src_parts[0])
        else:
            el.setAttribute('src', "")
        if len(src_parts) > 1:
            el.setAttribute('title', dequote(" ".join(src_parts[1:])))
        if ENABLE_ATTRIBUTES:
            text = doc.createTextNode(m.group(2))
            el.appendChild(text)
            text.handleAttributes()
            truealt = text.value
            el.childNodes.remove(text)
        else:
            truealt = m.group(2)
        el.setAttribute('alt', truealt)
        return el

class ReferencePattern (Pattern):

    def handleMatch(self, m, doc):

        if m.group(9):
            id = m.group(9).lower()
        else:
            # if we got something like "[Google][]"
            # we'll use "google" as the id
            id = m.group(2).lower()

        if not self.references.has_key(id): # ignore undefined refs
            return None
        href, title = self.references[id]
        text = m.group(2)
        return self.makeTag(href, title, text, doc)

    def makeTag(self, href, title, text, doc):
        el = doc.createElement('a')
        el.setAttribute('href', href)
        if title:
            el.setAttribute('title', title)
        el.appendChild(doc.createTextNode(text))
        return el


class ImageReferencePattern (ReferencePattern):

    def makeTag(self, href, title, text, doc):
        el = doc.createElement('img')
        el.setAttribute('src', href)
        if title:
            el.setAttribute('title', title)
        el.setAttribute('alt', text)
        return el


class AutolinkPattern (Pattern):

    def handleMatch(self, m, doc):
        el = doc.createElement('a')
        el.setAttribute('href', m.group(2))
        el.appendChild(doc.createTextNode(m.group(2)))
        return el

class AutomailPattern (Pattern):

    def handleMatch(self, m, doc):
        el = doc.createElement('a')
        email = m.group(2)
        if email.startswith("mailto:"):
            email = email[len("mailto:"):]
        for letter in email:
            entity = doc.createEntityReference("#%d" % ord(letter))
            el.appendChild(entity)
        mailto = "mailto:" + email
        mailto = "".join(['&#%d;' % ord(letter) for letter in mailto])
        el.setAttribute('href', mailto)
        return el

ESCAPE_PATTERN          = SimpleTextPattern(ESCAPE_RE)
NOT_STRONG_PATTERN      = SimpleTextPattern(NOT_STRONG_RE)

BACKTICK_PATTERN        = BacktickPattern(BACKTICK_RE)
DOUBLE_BACKTICK_PATTERN = BacktickPattern(DOUBLE_BACKTICK_RE)
STRONG_PATTERN          = SimpleTagPattern(STRONG_RE, 'strong')
STRONG_PATTERN_2        = SimpleTagPattern(STRONG_2_RE, 'strong')
EMPHASIS_PATTERN        = SimpleTagPattern(EMPHASIS_RE, 'em')
EMPHASIS_PATTERN_2      = SimpleTagPattern(EMPHASIS_2_RE, 'em')

STRONG_EM_PATTERN       = DoubleTagPattern(STRONG_EM_RE, 'strong,em')
STRONG_EM_PATTERN_2     = DoubleTagPattern(STRONG_EM_2_RE, 'strong,em')

LINE_BREAK_PATTERN      = SubstituteTagPattern(LINE_BREAK_RE, 'br ')
LINE_BREAK_PATTERN_2    = SubstituteTagPattern(LINE_BREAK_2_RE, 'br ')

LINK_PATTERN            = LinkPattern(LINK_RE)
LINK_ANGLED_PATTERN     = LinkPattern(LINK_ANGLED_RE)
IMAGE_LINK_PATTERN      = ImagePattern(IMAGE_LINK_RE)
IMAGE_REFERENCE_PATTERN = ImageReferencePattern(IMAGE_REFERENCE_RE)
REFERENCE_PATTERN       = ReferencePattern(REFERENCE_RE)

HTML_PATTERN            = HtmlPattern(HTML_RE)
ENTITY_PATTERN          = HtmlPattern(ENTITY_RE)

AUTOLINK_PATTERN        = AutolinkPattern(AUTOLINK_RE)
AUTOMAIL_PATTERN        = AutomailPattern(AUTOMAIL_RE)


"""
======================================================================
========================== POST-PROCESSORS ===========================
======================================================================

Markdown also allows post-processors, which are similar to
preprocessors in that they need to implement a "run" method. However,
they are run after core processing.

There are two types of post-processors: Postprocessor and TextPostprocessor
"""


class Postprocessor:
    """
    Postprocessors are run before the dom it converted back into text.
    
    Each Postprocessor implements a "run" method that takes a pointer to a
    NanoDom document, modifies it as necessary and returns a NanoDom 
    document.
    
    Postprocessors must extend markdown.Postprocessor.

    There are currently no standard post-processors, but the footnote
    extension uses one.
    
    """

    def run(self, dom):
        """
        Subclasses of Postprocessor should implement a `run` method, which
        takes a NanoDOm document and returns a (possably modified) NanoDom
        document.

        """
        pass



class TextPostprocessor:
    """
    TextPostprocessors are run after the dom it converted back into text.
    
    Each TextPostprocessor implements a "run" method that takes a pointer to a
    text string, modifies it as necessary and returns a text string.
    
    TextPostprocessors must extend markdown.TextPostprocessor.
    
    """

    def run(self, text):
        """
        Subclasses of TextPostprocessor should implement a `run` method, which
        takes the html document as a single text string and returns a 
        (possably modified) string.

        """
        pass


class RawHtmlTextPostprocessor(TextPostprocessor):
    """ Restore raw html to the document. """
    def __init__(self):
        pass

    def run(self, text):
        """ Iterate over html stash and restore "safe" html. """

        for i in range(self.stash.html_counter):
            html, safe  = self.stash.rawHtmlBlocks[i]
            if self.safeMode and not safe:
                if str(self.safeMode).lower() == 'escape':
                    html = self.escape(html)
                elif str(self.safeMode).lower() == 'remove':
                    html = ''
                else:
                    html = HTML_REMOVED_TEXT
                                   
            text = text.replace("<p>%s\n</p>" % (HTML_PLACEHOLDER % i),
                              html + "\n")
            text =  text.replace(HTML_PLACEHOLDER % i, html)
        return text

    def escape(self, html):
        """ Basic html escaping """
        html = html.replace('&', '&amp;')
        html = html.replace('<', '&lt;')
        html = html.replace('>', '&gt;')
        return html.replace('"', '&quot;')

RAWHTMLTEXTPOSTPROCESSOR = RawHtmlTextPostprocessor()

"""
======================================================================
========================== MISC AUXILIARY CLASSES ====================
======================================================================
"""

class HtmlStash:
    """
    This class is used for stashing HTML objects that we extract
    in the beginning and replace with place-holders.
    """

    def __init__ (self):
        """ Create a HtmlStash. """
        self.html_counter = 0 # for counting inline html segments
        self.rawHtmlBlocks=[]

    def store(self, html, safe=False):
        """
        Saves an HTML segment for later reinsertion.  Returns a
        placeholder string that needs to be inserted into the
        document.

        Keyword arguments:
        
        * html: an html segment
        * safe: label an html segment as safe for safemode
        
        Returns : a placeholder string 
        
        """
        self.rawHtmlBlocks.append((html, safe))
        placeholder = HTML_PLACEHOLDER % self.html_counter
        self.html_counter += 1
        return placeholder


class BlockGuru:
    """ Parse document for block level constructs (paragraphs, lists, etc.)."""

    def _findHead(self, lines, fn, allowBlank=0):

        """
        Functional magic to help determine boundaries of indented
        blocks.

        Keyword arguments:
        
        * lines: an array of strings
        * fn: a function that returns a substring of a string
           if the string matches the necessary criteria
        * allowBlank: specifies whether it's ok to have blank
           lines between matching functions
        
        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

        for line in lines:

            if not line.strip() and not allowBlank:
                return items, lines[i:]

            if not line.strip() and allowBlank:
                # If we see a blank line, this _might_ be the end
                i += 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 => this is the end
                    break

                # Check if the next non-blank line is still a part of the list

                part = fn(next)

                if part:
                    items.append("")
                    continue
                else:
                    break # found end of the list

            part = fn(line)

            if part:
                items.append(part)
                i += 1
                continue
            else:
                return items, lines[i:]
        else:
            i += 1

        return items, lines[i:]


    def detabbed_fn(self, line):
        """ An auxiliary method to be passed to _findHead """
        m = RE.regExp['tabbed'].match(line)
        if m:
            return m.group(4)
        else:
            return None


    def detectTabbed(self, lines):
        """ Find indented text and remove indent before further proccesing. """
        return self._findHead(lines, self.detabbed_fn,
                              allowBlank = 1)


def dequote(string):
    """ Removes quotes from around a string """
    if ( ( string.startswith('"') and string.endswith('"'))
         or (string.startswith("'") and string.endswith("'")) ):
        return string[1:-1]
    else:
        return string

"""
======================================================================
========================== CORE MARKDOWN =============================
======================================================================

This stuff is ugly, so if you are thinking of extending the syntax,
see first if you can do it via pre-processors, post-processors,
inline patterns or a combination of the three.
"""

class CorePatterns:
    """
    This class is scheduled for removal as part of a refactoring effort.
    """

    patterns = {
        'header':          r'(#*)([^#]*)(#*)', # # A title
        'reference-def':   r'(\ ?\ ?\ ?)\[([^\]]*)\]:\s*([^ ]*)(.*)',
                           # [Google]: http://www.google.com/
        'containsline':    r'([-]*)$|^([=]*)', # -----, =====, etc.
        'ol':              r'[ ]{0,3}[\d]*\.\s+(.*)', # 1. text
        'ul':              r'[ ]{0,3}[*+-]\s+(.*)', # "* text"
        'isline1':         r'(\**)', # ***
        'isline2':         r'(\-*)', # ---
        'isline3':         r'(\_*)', # ___
        'tabbed':          r'((\t)|(    ))(.*)', # an indented line
        'quoted':          r'[ ]{0,2}> ?(.*)', # a quoted block ("> ...")
    }

    def __init__ (self):

        self.regExp = {}
        for key in self.patterns.keys():
            self.regExp[key] = re.compile("^%s$" % self.patterns[key],
                                          re.DOTALL)

        self.regExp['containsline'] = re.compile(r'^([-]*)$|^([=]*)$', re.M)

RE = CorePatterns()


class Markdown:
    """ 
    Markdown formatter class for creating an html document from Markdown text.
    """


    def __init__(self, source=None,  # depreciated
                 extensions=[],
                 extension_configs={},
                 safe_mode = False):
        """
        Creates a new Markdown instance.

        Keyword arguments:
        
        * source: The text in Markdown format. Depreciated!
        * extensions: A list of extensions.  
           If they are of type string, the module mdx_name.py will be loaded.  
           If they are a subclass of markdown.Extension, they will be used 
           as-is.
        * extension-configs: Configuration setting for extensions.
        * safe_mode: Disallow raw html. 
        
        """

        self.source = source
        if source is not None:
            message(WARN, "The `source` arg of Markdown.__init__() is depreciated and will be removed in the future. Use `instance.convert(source)` instead.")
        self.safeMode = safe_mode
        self.blockGuru = BlockGuru()
        self.registeredExtensions = []
        self.stripTopLevelTags = 1
        self.docType = ""

        self.textPreprocessors = [HTML_BLOCK_PREPROCESSOR]

        self.preprocessors = [HEADER_PREPROCESSOR,
                              LINE_PREPROCESSOR,
                              # A footnote preprocessor will
                              # get inserted here
                              REFERENCE_PREPROCESSOR]


        self.postprocessors = [] # a footnote postprocessor will get
                                 # inserted later

        self.textPostprocessors = [# a footnote postprocessor will get
                                   # inserted here
                                   RAWHTMLTEXTPOSTPROCESSOR]

        self.prePatterns = []
        

        self.inlinePatterns = [DOUBLE_BACKTICK_PATTERN,
                               BACKTICK_PATTERN,
                               ESCAPE_PATTERN,
                               REFERENCE_PATTERN,
                               LINK_ANGLED_PATTERN,
                               LINK_PATTERN,
                               IMAGE_LINK_PATTERN,
			                   IMAGE_REFERENCE_PATTERN,
			                   AUTOLINK_PATTERN,
                               AUTOMAIL_PATTERN,
                               LINE_BREAK_PATTERN_2,
                               LINE_BREAK_PATTERN,
                               HTML_PATTERN,
                               ENTITY_PATTERN,
                               NOT_STRONG_PATTERN,
                               STRONG_EM_PATTERN,
                               STRONG_EM_PATTERN_2,
                               STRONG_PATTERN,
                               STRONG_PATTERN_2,
                               EMPHASIS_PATTERN,
                               EMPHASIS_PATTERN_2
                               # The order of the handlers matters!!!
                               ]

        self.registerExtensions(extensions = extensions,
                                configs = extension_configs)

        self.reset()


    def registerExtensions(self, extensions, configs):
        """ 
        Register extensions with this instance of Markdown.

        Keyword aurguments:
        
        * extensions: A list of extensions, which can either
           be strings or objects.  See the docstring on Markdown.
        * configs: A dictionary mapping module names to config options. 
        
        """

        for ext in extensions:
            if isinstance(ext, basestring):
                ext = load_extension(ext, configs.get(ext, []))
            elif hasattr(ext, 'extendMarkdown'):
                # Looks like an Extension.
                # Nothing to do here.
                pass
            else:
                message(ERROR, "Incorrect type! Extension '%s' is "
                               "neither a string or an Extension." %(repr(ext)))
                continue
            ext.extendMarkdown(self, globals())

    def registerExtension(self, extension):
        """ This gets called by the extension """
        self.registeredExtensions.append(extension)

    def reset(self):
        """
        Resets all state variables so that we can start with a new text.
        """
        self.references={}
        self.htmlStash = HtmlStash()

        HTML_BLOCK_PREPROCESSOR.stash = self.htmlStash
        LINE_PREPROCESSOR.stash = self.htmlStash
        REFERENCE_PREPROCESSOR.references = self.references
        HTML_PATTERN.stash = self.htmlStash
        ENTITY_PATTERN.stash = self.htmlStash
        REFERENCE_PATTERN.references = self.references
        IMAGE_REFERENCE_PATTERN.references = self.references
        RAWHTMLTEXTPOSTPROCESSOR.stash = self.htmlStash
        RAWHTMLTEXTPOSTPROCESSOR.safeMode = self.safeMode

        for extension in self.registeredExtensions:
            extension.reset()


    def _transform(self):
        """Transforms the Markdown text into a XHTML body document

        Returns: A NanoDom Document 
        
        """

        # Setup the document

        self.doc = Document()
        self.top_element = self.doc.createElement("span")
        self.top_element.appendChild(self.doc.createTextNode('\n'))
        self.top_element.setAttribute('class', 'markdown')
        self.doc.appendChild(self.top_element)

        # Split into lines and run the preprocessors that will work with
        # self.lines

        self.lines = self.source.split("\n")

        # Run the pre-processors on the lines
        for prep in self.preprocessors :
            self.lines = prep.run(self.lines)

        # Create a NanoDom tree from the lines and attach it to Document


        buffer = []
        for line in self.lines:
            if line.startswith("#"):
                self._processSection(self.top_element, buffer)
                buffer = [line]
            else:
                buffer.append(line)
        self._processSection(self.top_element, buffer)
        
        #self._processSection(self.top_element, self.lines)

        # Not sure why I put this in but let's leave it for now.
        self.top_element.appendChild(self.doc.createTextNode('\n'))

        # Run the post-processors
        for postprocessor in self.postprocessors:
            postprocessor.run(self.doc)

        return self.doc


    def _processSection(self, parent_elem, lines,
                        inList = 0, looseList = 0):
        """
        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: A NanoDom 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:

            # Check if this section starts with a list, a blockquote or
            # a code block

            processFn = { 'ul':     self._processUList,
                          'ol':     self._processOList,
                          'quoted': self._processQuote,
                          'tabbed': self._processCodeBlock}

            for regexp in ['ul', 'ol', 'quoted', 'tabbed']:
                m = RE.regExp[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:
                                 RE.regExp['ul'].match(line)
                                 or RE.regExp['ol'].match(line)
                                                  or not line.strip()))

                self._processSection(parent_elem, start,
                                     inList - 1, looseList = looseList)
                inList = inList-1

            else: # Ok, so it's just a simple block

                paragraph, lines = self._linesUntil(lines, lambda line:
                                                     not line.strip())

                if len(paragraph) and paragraph[0].startswith('#'):
                    self._processHeader(parent_elem, paragraph)

                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 _processHeader(self, parent_elem, paragraph):
        m = RE.regExp['header'].match(paragraph[0])
        if m:
            level = len(m.group(1))
            h = self.doc.createElement("h%d" % level)
            parent_elem.appendChild(h)
            for item in self._handleInline(m.group(2).strip()):
                h.appendChild(item)
        else:
            message(CRITICAL, "We've got a problem header!")


    def _processParagraph(self, parent_elem, paragraph, inList, looseList):
        list = self._handleInline("\n".join(paragraph))

        if ( parent_elem.nodeName == 'li'
                and not (looseList or parent_elem.childNodes)):

            # If this is the first paragraph inside "li", don't
            # put <p> around it - append the paragraph bits directly
            # onto parent_elem
            el = parent_elem
        else:
            # Otherwise make a "p" element
            el = self.doc.createElement("p")
            parent_elem.appendChild(el)

        for item in list:
            el.appendChild(item)
 

    def _processUList(self, parent_elem, lines, inList):
        self._processList(parent_elem, lines, inList,
                         listexpr='ul', tag = 'ul')

    def _processOList(self, parent_elem, lines, inList):
        self._processList(parent_elem, lines, inList,
                         listexpr='ol', tag = 'ol')


    def _processList(self, parent_elem, 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:
        
        * parent_elem: A dom element to which the content will be added
        * lines: a list of lines
        * inList: a level
        
        Returns: None
        
        """

        ul = self.doc.createElement(tag)  # ul might actually be '<ol>'
        parent_elem.appendChild(ul)

        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 ( RE.regExp['ul'].match(next) or
                     RE.regExp['ol'].match(next) or 
                     RE.regExp['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 = RE.regExp[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 dom elements
        for item in items:
            li = self.doc.createElement("li")
            ul.appendChild(li)

            self._processSection(li, item, inList + 1, looseList = looseList)

        # Process the remaining part of the section

        self._processSection(parent_elem, 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, parent_elem, 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:
        
        * parent_elem: DOM 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 = RE.regExp['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 = self.doc.createElement('blockquote')
        parent_elem.appendChild(blockquote)

        self._processSection(blockquote, dequoted, inList)
        self._processSection(parent_elem, lines[i:], inList)




    def _processCodeBlock(self, parent_elem, lines, inList):
        """
        Given a list of document lines starting with a code block
        finds the end of the block, puts it into the dom verbatim
        wrapped in ("<pre><code>") and recursively processes the
        the remainder of the text file.

        Keyword arguments:
        
        * parent_elem: DOM element to which the content will be added
        * lines: a list of lines
        * inList: a level
        
        Returns: None
        
        """

        detabbed, theRest = self.blockGuru.detectTabbed(lines)

        pre = self.doc.createElement('pre')
        code = self.doc.createElement('code')
        parent_elem.appendChild(pre)
        pre.appendChild(code)
        text = "\n".join(detabbed).rstrip()+"\n"
        #text = text.replace("&", "&amp;")
        code.appendChild(self.doc.createTextNode(text))
        self._processSection(parent_elem, theRest, inList)



    def _handleInline (self, line, patternIndex=0):
        """
        Transform a Markdown line with inline elements to an XHTML
        fragment.

        This function uses auxiliary objects called inline patterns.
        See notes on inline patterns above.

        Keyword arguments:
        
        * line: A line of Markdown text
        * patternIndex: The index of the inlinePattern to start with
        
        Return: A list of NanoDom nodes 
        
        """


        parts = [line]

        while patternIndex < len(self.inlinePatterns):

            i = 0

            while i < len(parts):
                
                x = parts[i]

                if isinstance(x, (str, unicode)):
                    result = self._applyPattern(x, \
                                self.inlinePatterns[patternIndex], \
                                patternIndex)

                    if result:
                        i -= 1
                        parts.remove(x)
                        for y in result:
                            parts.insert(i+1,y)

                i += 1
            patternIndex += 1

        for i in range(len(parts)):
            x = parts[i]
            if isinstance(x, (str, unicode)):
                parts[i] = self.doc.createTextNode(x)

        return parts
        

    def _applyPattern(self, line, pattern, patternIndex):

        """ 
        Given a pattern name, this function checks if the line
        fits the pattern, creates the necessary elements, and returns
        back a list consisting of NanoDom elements and/or strings.
        
        Keyword arguments:
        
        * line: the text to be processed
        * pattern: the pattern to be checked

        Returns: The appropriate newly created NanoDom element if the
           pattern matches, None otherwise.
        """

        # match the line to pattern's pre-compiled reg exp.
        # if no match, move on.



        m = pattern.getCompiledRegExp().match(line)
        if not m:
            return None

        # if we got a match let the pattern make us a NanoDom node
        # if it doesn't, move on
        node = pattern.handleMatch(m, self.doc)

        # check if any of this nodes have children that need processing

        if isinstance(node, Element):

            if not node.nodeName in ["code", "pre"]:
                for child in node.childNodes:
                    if isinstance(child, TextNode):
                        
                        result = self._handleInline(child.value, patternIndex+1)
                        
                        if result:

                            if result == [child]:
                                continue
                                
                            result.reverse()
                            #to make insertion easier

                            position = node.childNodes.index(child)
                            
                            node.removeChild(child)

                            for item in result:

                                if isinstance(item, (str, unicode)):
                                    if len(item) > 0:
                                        node.insertChild(position,
                                             self.doc.createTextNode(item))
                                else:
                                    node.insertChild(position, item)
                



        if node:
            # Those are in the reverse order!
            return ( m.groups()[-1], # the string to the left
                     node,           # the new node
                     m.group(1))     # the string to the right of the match

        else:
            return None

    def convert (self, source=None):
        """
        Return the document in XHTML format.

        Keyword arguments:
        
        * source: An ascii or unicode string of Markdown formated text.

        Returns: A serialized XHTML body.

        """

        if source is not None: #Allow blank string
            self.source = source

        if not self.source:
            return u""

        try:
            self.source = unicode(self.source)
        except UnicodeDecodeError:
            message(CRITICAL, 'UnicodeDecodeError: Markdown only accepts unicode or ascii  input.')
            return u""

        # Fixup the source text
        self.source = self.source.replace("\r\n", "\n").replace("\r", "\n")
        self.source += "\n\n"
        self.source = self.source.expandtabs(TAB_LENGTH)

        for pp in self.textPreprocessors:
            self.source = pp.run(self.source)

        doc = self._transform()
        xml = doc.toxml()


        # Return everything but the top level tag

        if self.stripTopLevelTags:
            xml = xml.strip()[23:-7] + "\n"

        for pp in self.textPostprocessors:
            xml = pp.run(xml)

        return (self.docType + xml).strip()


    def __str__(self):
        ''' Report info about instance. Markdown always returns unicode. '''

        if self.source is None:
            status = 'in which no source text has been assinged.'
        else:
            status = 'which contains %d chars and %d line(s) of source.'%\
                     (len(self.source), self.source.count('\n')+1)
        return 'An instance of "%s" %s'% (self.__class__, status)

    __unicode__ = convert # markdown should always return a unicode string





# ====================================================================

def markdownFromFile(input = None,
                     output = None,
                     extensions = [],
                     encoding = None,
                     message_threshold = CRITICAL,
                     safe = False):
    """
    Convenience wrapper function that takes a filename as input.

    Used from the command-line, although may be useful in other situations. 
    Decodes the file using the provided encoding (defaults to utf-8), passes 
    the file content to markdown, and outputs the html to either the provided
    filename or stdout in the same encoding as the source file.

    **Note:** This is the only place that decoding and encoding takes place
    in Python-Markdown.

    Keyword arguments:

    * input: Name of source text file.
    * output: Name of output file. Writes to stdout if `None`.
    * extensions: A list of extension names (may contain config args).  
    * encoding: Encoding of input and output files. Defaults to utf-8.
    * message_threshold: Error reporting level.
    * safe_mode: Disallow raw html. One of "remove", "replace" or "escape".

    Returns: An HTML document as a string.

    """

    global console_hndlr
    console_hndlr.setLevel(message_threshold)

    message(DEBUG, "input file: %s" % input)

    if not encoding:
        encoding = "utf-8"

    input_file = codecs.open(input, mode="r", encoding=encoding)
    text = input_file.read()
    input_file.close()

    text = removeBOM(text, encoding)

    new_text = markdown(text, extensions, safe_mode = safe)

    if output:
        output_file = codecs.open(output, "w", encoding=encoding)
        output_file.write(new_text)
        output_file.close()

    else:
        sys.stdout.write(new_text.encode(encoding))

def markdown(text,
             extensions = [],
             safe_mode = False):
    """
    Convenience wrapper function for `Markdown` class.

    Useful in a typical use case. Initializes an instance of the `Markdown` 
    class, loads any extensions and runs the parser on the given text. 

    Keyword arguments:

    * text: An ascii or Unicode string of Markdown formatted text.
    * extensions: A list of extension names (may contain config args).  
    * safe_mode: Disallow raw html. One of "remove", "replace" or "escape".

    Returns: An HTML document as a string.

    """
    message(DEBUG, "in markdown.markdown(), received text:\n%s" % text)

    extensions = [load_extension(e) for e in extensions]

    md = Markdown(extensions=extensions,
                  safe_mode = safe_mode)

    return md.convert(text)
        

class Extension:

    def __init__(self, configs = {}):
        self.config = configs

    def getConfig(self, key):
        if self.config.has_key(key):
            return self.config[key][0]
        else:
            return ""

    def getConfigInfo(self):
        return [(key, self.config[key][1]) for key in self.config.keys()]

    def setConfig(self, key, value):
        self.config[key][0] = value


def load_extension(ext_name, configs = []):
    """ 
    Load extension by name, then return the module.
    
    The extension name may contain arguments as part of the string in the 
    following format:

        "extname(key1=value1,key2=value2)"
    
    Print an error message and exit on failure. 
    
    """

    # I am making the assumption that the order of config options
    # does not matter.
    configs = dict(configs)
    pos = ext_name.find("(") 
    if pos > 0:
        ext_args = ext_name[pos+1:-1]
        ext_name = ext_name[:pos]
        pairs = [x.split("=") for x in ext_args.split(",")]
        configs.update([(x.strip(), y.strip()) for (x, y) in pairs])

    extension_module_name = "mdx_" + ext_name

    try:
        module = __import__(extension_module_name)

    except:
        message(CRITICAL,
                "couldn't load extension %s (looking for %s module)"
                % (ext_name, extension_module_name) )
        sys.exit(1)

    return module.makeExtension(configs.items())    


OPTPARSE_WARNING = """
Python 2.3 or higher required for advanced command line options.
For lower versions of Python use:

      %s INPUT_FILE > OUTPUT_FILE
    
""" % EXECUTABLE_NAME_FOR_USAGE

def parse_options():
    """
    Define and parse `optparse` options for command-line usage.
    """

    try:
        optparse = __import__("optparse")
    except:
        if len(sys.argv) == 2:
            return {'input': sys.argv[1],
                    'output': None,
                    'message_threshold': CRITICAL,
                    'safe': False,
                    'extensions': [],
                    'encoding': None }

        else:
            print OPTPARSE_WARNING
            return None

    parser = optparse.OptionParser(usage="%prog INPUTFILE [options]")

    parser.add_option("-f", "--file", dest="filename",
                      help="write output to OUTPUT_FILE",
                      metavar="OUTPUT_FILE")
    parser.add_option("-e", "--encoding", dest="encoding",
                      help="encoding for input and output files",)
    parser.add_option("-q", "--quiet", default = CRITICAL,
                      action="store_const", const=60, dest="verbose",
                      help="suppress all messages")
    parser.add_option("-v", "--verbose",
                      action="store_const", const=INFO, dest="verbose",
                      help="print info messages")
    parser.add_option("-s", "--safe", dest="safe", default=False,
                      metavar="SAFE_MODE",
                      help="safe mode ('replace', 'remove' or 'escape'  user's HTML tag)")
    
    parser.add_option("--noisy",
                      action="store_const", const=DEBUG, dest="verbose",
                      help="print debug messages")
    parser.add_option("-x", "--extension", action="append", dest="extensions",
                      help = "load extension EXTENSION", metavar="EXTENSION")

    (options, args) = parser.parse_args()

    if not len(args) == 1:
        parser.print_help()
        return None
    else:
        input_file = args[0]

    if not options.extensions:
        options.extensions = []

    return {'input': input_file,
            'output': options.filename,
            'message_threshold': options.verbose,
            'safe': options.safe,
            'extensions': options.extensions,
            'encoding': options.encoding }

if __name__ == '__main__':
    """ Run Markdown from the command line. """

    options = parse_options()

    #if os.access(inFile, os.R_OK):

    if not options:
        sys.exit(0)
    
    markdownFromFile(**options)