"""

Table of Contents Extension for Python-Markdown

* * *

(c) 2008 [Jack Miller](http://codezen.org)

Dependencies:

* [Markdown 2.0+](http://www.freewisdom.org/projects/python-markdown/)

"""

import markdown

from markdown import etree

import re

class TocTreeprocessor(markdown.treeprocessors.Treeprocessor):

    # Iterator wrapper to get parent and child all at once

    def iterparent(self, root):

        for parent in root.getiterator():

            for child in parent:

                yield parent, child

    def run(self, doc):

        div = etree.Element("div")

        div.attrib["class"] = "toc"

        last_li = None

        # Add title to the div

        if self.config["title"][0]:

            header = etree.SubElement(div, "span")

            header.attrib["class"] = "toctitle"

            header.text = self.config["title"][0]

        level = 0

        list_stack=[div]

        header_rgx = re.compile("[Hh][123456]")

        # Get a list of id attributes

        used_ids = []

        for c in doc.getiterator():

            if "id" in c.attrib:

                used_ids.append(c.attrib["id"])

        for (p, c) in self.iterparent(doc):

            if not c.text:

                continue

            # To keep the output from screwing up the

            # validation by putting a <div> inside of a <p>

            # we actually replace the <p> in its entirety.

            # We do not allow the marker inside a header as that

            # would causes an enless loop of placing a new TOC 

            # inside previously generated TOC.

            if c.text.find(self.config["marker"][0]) > -1 and not header_rgx.match(c.tag):

                for i in range(len(p)):

                    if p[i] == c:

                        p[i] = div

                        break

            if header_rgx.match(c.tag):

                tag_level = int(c.tag[-1])

                while tag_level < level:

                    list_stack.pop()

                    level -= 1

                if tag_level > level:

                    newlist = etree.Element("ul")

                    if last_li:

                        last_li.append(newlist)

                    else:

                        list_stack[-1].append(newlist)

                    list_stack.append(newlist)

                    if level == 0:

                        level = tag_level

                    else:

                        level += 1

                # Do not override pre-existing ids 

                if not "id" in c.attrib:

                    id = self.config["slugify"][0](c.text)

                    if id in used_ids:

                        ctr = 1

                        while "%s_%d" % (id, ctr) in used_ids:

                            ctr += 1

                        id = "%s_%d" % (id, ctr)

                    used_ids.append(id)

                    c.attrib["id"] = id

                else:

                    id = c.attrib["id"]

                # List item link, to be inserted into the toc div

                last_li = etree.Element("li")

                link = etree.SubElement(last_li, "a")

                link.text = c.text

                link.attrib["href"] = '#' + id

                if int(self.config["anchorlink"][0]):

                    anchor = etree.SubElement(c, "a")

                    anchor.text = c.text

                    anchor.attrib["href"] = "#" + id

                    anchor.attrib["class"] = "toclink"

                    c.text = ""

                list_stack[-1].append(last_li)

class TocExtension(markdown.Extension):

    def __init__(self, configs):

        self.config = { "marker" : ["[TOC]", 

                            "Text to find and replace with Table of Contents -"

                            "Defaults to \"[TOC]\""],

                        "slugify" : [self.slugify,

                            "Function to generate anchors based on header text-"

                            "Defaults to a built in slugify function."],

                        "title" : [None,

                            "Title to insert into TOC <div> - "

                            "Defaults to None"],

                        "anchorlink" : [0,

                            "1 if header should be a self link"

                            "Defaults to 0"]}

        for key, value in configs:

            self.setConfig(key, value)

    # This is exactly the same as Django's slugify

    def slugify(self, value):

        """ Slugify a string, to make it URL friendly. """

        import unicodedata

        value = unicodedata.normalize('NFKD', value).encode('ascii', 'ignore')

        value = unicode(re.sub('[^\w\s-]', '', value).strip().lower())

        return re.sub('[-\s]+','-',value)

    def extendMarkdown(self, md, md_globals):

        tocext = TocTreeprocessor(md)

        tocext.config = self.config

        md.treeprocessors.add("toc", tocext, "_begin")

def makeExtension(configs={}):

    return TocExtension(configs=configs)