"""
========================= FOOTNOTES =================================
This section adds footnote handling to markdown. It can be used as
an example for extending python-markdown with relatively complex
functionality. While in this case the extension is included inside
the module itself, it could just as easily be added from outside the
module. Not that all markdown classes above are ignorant about
footnotes. All footnote functionality is provided separately and
then added to the markdown instance at the run time.
Footnote functionality is attached by calling extendMarkdown()
method of FootnoteExtension. The method also registers the
extension to allow it's state to be reset by a call to reset()
method.
Example:
Footnotes[^1] have a label[^label] and a definition[^!DEF].
[^1]: This is a footnote
[^label]: A footnote on "label"
[^!DEF]: The footnote for definition
"""
import re, markdown
from markdown import etree
FN_BACKLINK_TEXT = "zz1337820767766393qq"
NBSP_PLACEHOLDER = "qq3936677670287331zz"
DEF_RE = re.compile(r'(\ ?\ ?\ ?)\[\^([^\]]*)\]:\s*(.*)')
TABBED_RE = re.compile(r'((\t)|( ))(.*)')
class FootnoteExtension(markdown.Extension):
""" Footnote Extension. """
def __init__ (self, configs):
""" Setup configs. """
self.config = {'PLACE_MARKER':
["///Footnotes Go Here///",
"The text string that marks where the footnotes go"],
'UNIQUE_IDS':
[False,
"Avoid name collisions across "
"multiple calls to reset()."]}
for key, value in configs:
self.config[key][0] = value
# In multiple invocations, emit links that don't get tangled.
self.unique_prefix = 0
self.reset()
def extendMarkdown(self, md, md_globals):
""" Add pieces to Markdown. """
md.registerExtension(self)
self.parser = md.parser
# Insert a preprocessor before ReferencePreprocessor
md.preprocessors.add("footnote", FootnotePreprocessor(self),
"<reference")
# Insert an inline pattern before ImageReferencePattern
FOOTNOTE_RE = r'\[\^([^\]]*)\]' # blah blah [^1] blah
md.inlinePatterns.add("footnote", FootnotePattern(FOOTNOTE_RE, self),
"<reference")
# Insert a tree-processor that would actually add the footnote div
# This must be before the inline treeprocessor so inline patterns
# run on the contents of the div.
md.treeprocessors.add("footnote", FootnoteTreeprocessor(self),
"<inline")
# Insert a postprocessor after amp_substitute oricessor
md.postprocessors.add("footnote", FootnotePostprocessor(self),
">amp_substitute")
def reset(self):
""" Clear the footnotes on reset, and prepare for a distinct document. """
self.footnotes = markdown.odict.OrderedDict()
self.unique_prefix += 1
def findFootnotesPlaceholder(self, root):
""" Return ElementTree Element that contains Footnote placeholder. """
def finder(element):
for child in element:
if child.text:
if child.text.find(self.getConfig("PLACE_MARKER")) > -1:
return child, True
if child.tail:
if child.tail.find(self.getConfig("PLACE_MARKER")) > -1:
return (child, element), False
finder(child)
return None
res = finder(root)
return res
def setFootnote(self, id, text):
""" Store a footnote for later retrieval. """
self.footnotes[id] = text
def makeFootnoteId(self, id):
""" Return footnote link id. """
if self.getConfig("UNIQUE_IDS"):
return 'fn:%d-%s' % (self.unique_prefix, id)
else:
return 'fn:%s' % id
def makeFootnoteRefId(self, id):
""" Return footnote back-link id. """
if self.getConfig("UNIQUE_IDS"):
return 'fnref:%d-%s' % (self.unique_prefix, id)
else:
return 'fnref:%s' % id
def makeFootnotesDiv(self, root):
""" Return div of footnotes as et Element. """
if not self.footnotes.keys():
return None
div = etree.Element("div")
div.set('class', 'footnote')
hr = etree.SubElement(div, "hr")
ol = etree.SubElement(div, "ol")
for id in self.footnotes.keys():
li = etree.SubElement(ol, "li")
li.set("id", self.makeFootnoteId(id))
self.parser.parseChunk(li, self.footnotes[id])
backlink = etree.Element("a")
backlink.set("href", "#" + self.makeFootnoteRefId(id))
backlink.set("rev", "footnote")
backlink.set("title", "Jump back to footnote %d in the text" % \
(self.footnotes.index(id)+1))
backlink.text = FN_BACKLINK_TEXT
if li.getchildren():
node = li[-1]
if node.tag == "p":
node.text = node.text + NBSP_PLACEHOLDER
node.append(backlink)
else:
p = etree.SubElement(li, "p")
p.append(backlink)
return div
class FootnotePreprocessor(markdown.preprocessors.Preprocessor):
""" Find all footnote references and store for later use. """
def __init__ (self, footnotes):
self.footnotes = footnotes
def run(self, lines):
lines = self._handleFootnoteDefinitions(lines)
text = "\n".join(lines)
return text.split("\n")
def _handleFootnoteDefinitions(self, lines):
"""
Recursively find all footnote definitions in lines.
Keywords:
* lines: A list of lines of text
Return: A list of lines with footnote definitions removed.
"""
i, id, footnote = self._findFootnoteDefinition(lines)
if id :
plain = lines[:i]
detabbed, theRest = self.detectTabbed(lines[i+1:])
self.footnotes.setFootnote(id,
footnote + "\n"
+ "\n".join(detabbed))
more_plain = self._handleFootnoteDefinitions(theRest)
return plain + [""] + more_plain
else :
return lines
def _findFootnoteDefinition(self, lines):
"""
Find the parts of a footnote definition.
Keywords:
* lines: A list of lines of text.
Return: A three item tuple containing the index of the first line of a
footnote definition, the id of the definition and the body of the
definition.
"""
counter = 0
for line in lines:
m = DEF_RE.match(line)
if m:
return counter, m.group(2), m.group(3)
counter += 1
return counter, None, None
def detectTabbed(self, lines):
""" Find indented text and remove indent before further proccesing.
Keyword arguments:
* lines: an array of strings
Returns: a list of post processed 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 = TABBED_RE.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 FootnotePattern(markdown.inlinepatterns.Pattern):
""" InlinePattern for footnote markers in a document's body text. """
def __init__(self, pattern, footnotes):
markdown.inlinepatterns.Pattern.__init__(self, pattern)
self.footnotes = footnotes
def handleMatch(self, m):
sup = etree.Element("sup")
a = etree.SubElement(sup, "a")
id = m.group(2)
sup.set('id', self.footnotes.makeFootnoteRefId(id))
a.set('href', '#' + self.footnotes.makeFootnoteId(id))
a.set('rel', 'footnote')
a.text = str(self.footnotes.footnotes.index(id) + 1)
return sup
class FootnoteTreeprocessor(markdown.treeprocessors.Treeprocessor):
""" Build and append footnote div to end of document. """
def __init__ (self, footnotes):
self.footnotes = footnotes
def run(self, root):
footnotesDiv = self.footnotes.makeFootnotesDiv(root)
if footnotesDiv:
result = self.footnotes.findFootnotesPlaceholder(root)
if result:
node, isText = result
if isText:
node.text = None
node.getchildren().insert(0, footnotesDiv)
else:
child, element = node
ind = element.getchildren().find(child)
element.getchildren().insert(ind + 1, footnotesDiv)
child.tail = None
fnPlaceholder.parent.replaceChild(fnPlaceholder, footnotesDiv)
else:
root.append(footnotesDiv)
class FootnotePostprocessor(markdown.postprocessors.Postprocessor):
""" Replace placeholders with html entities. """
def run(self, text):
text = text.replace(FN_BACKLINK_TEXT, "↩")
return text.replace(NBSP_PLACEHOLDER, " ")
def makeExtension(configs=[]):
""" Return an instance of the FootnoteExtension """
return FootnoteExtension(configs=configs)
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