diff env/lib/python3.9/site-packages/lxml/html/diff.py @ 0:4f3585e2f14b draft default tip

"planemo upload commit 60cee0fc7c0cda8592644e1aad72851dec82c959"

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/env/lib/python3.9/site-packages/lxml/html/diff.py	Mon Mar 22 18:12:50 2021 +0000
@@ -0,0 +1,884 @@
+# cython: language_level=3
+
+from __future__ import absolute_import
+
+import difflib
+from lxml import etree
+from lxml.html import fragment_fromstring
+import re
+
+__all__ = ['html_annotate', 'htmldiff']
+
+try:
+    from html import escape as html_escape
+except ImportError:
+    from cgi import escape as html_escape
+try:
+    _unicode = unicode
+except NameError:
+    # Python 3
+    _unicode = str
+try:
+    basestring
+except NameError:
+    # Python 3
+    basestring = str
+
+############################################################
+## Annotation
+############################################################
+
+def default_markup(text, version):
+    return '<span title="%s">%s</span>' % (
+        html_escape(_unicode(version), 1), text)
+
+def html_annotate(doclist, markup=default_markup):
+    """
+    doclist should be ordered from oldest to newest, like::
+
+        >>> version1 = 'Hello World'
+        >>> version2 = 'Goodbye World'
+        >>> print(html_annotate([(version1, 'version 1'),
+        ...                      (version2, 'version 2')]))
+        <span title="version 2">Goodbye</span> <span title="version 1">World</span>
+
+    The documents must be *fragments* (str/UTF8 or unicode), not
+    complete documents
+
+    The markup argument is a function to markup the spans of words.
+    This function is called like markup('Hello', 'version 2'), and
+    returns HTML.  The first argument is text and never includes any
+    markup.  The default uses a span with a title:
+
+        >>> print(default_markup('Some Text', 'by Joe'))
+        <span title="by Joe">Some Text</span>
+    """
+    # The basic strategy we have is to split the documents up into
+    # logical tokens (which are words with attached markup).  We then
+    # do diffs of each of the versions to track when a token first
+    # appeared in the document; the annotation attached to the token
+    # is the version where it first appeared.
+    tokenlist = [tokenize_annotated(doc, version)
+                 for doc, version in doclist]
+    cur_tokens = tokenlist[0]
+    for tokens in tokenlist[1:]:
+        html_annotate_merge_annotations(cur_tokens, tokens)
+        cur_tokens = tokens
+
+    # After we've tracked all the tokens, we can combine spans of text
+    # that are adjacent and have the same annotation
+    cur_tokens = compress_tokens(cur_tokens)
+    # And finally add markup
+    result = markup_serialize_tokens(cur_tokens, markup)
+    return ''.join(result).strip()
+
+def tokenize_annotated(doc, annotation): 
+    """Tokenize a document and add an annotation attribute to each token
+    """
+    tokens = tokenize(doc, include_hrefs=False)
+    for tok in tokens: 
+        tok.annotation = annotation
+    return tokens
+
+def html_annotate_merge_annotations(tokens_old, tokens_new): 
+    """Merge the annotations from tokens_old into tokens_new, when the
+    tokens in the new document already existed in the old document.
+    """
+    s = InsensitiveSequenceMatcher(a=tokens_old, b=tokens_new)
+    commands = s.get_opcodes()
+
+    for command, i1, i2, j1, j2 in commands:
+        if command == 'equal': 
+            eq_old = tokens_old[i1:i2]
+            eq_new = tokens_new[j1:j2]
+            copy_annotations(eq_old, eq_new)
+
+def copy_annotations(src, dest): 
+    """
+    Copy annotations from the tokens listed in src to the tokens in dest
+    """
+    assert len(src) == len(dest)
+    for src_tok, dest_tok in zip(src, dest): 
+        dest_tok.annotation = src_tok.annotation
+
+def compress_tokens(tokens):
+    """
+    Combine adjacent tokens when there is no HTML between the tokens, 
+    and they share an annotation
+    """
+    result = [tokens[0]] 
+    for tok in tokens[1:]: 
+        if (not result[-1].post_tags and 
+            not tok.pre_tags and 
+            result[-1].annotation == tok.annotation): 
+            compress_merge_back(result, tok)
+        else: 
+            result.append(tok)
+    return result
+
+def compress_merge_back(tokens, tok): 
+    """ Merge tok into the last element of tokens (modifying the list of
+    tokens in-place).  """
+    last = tokens[-1]
+    if type(last) is not token or type(tok) is not token: 
+        tokens.append(tok)
+    else:
+        text = _unicode(last)
+        if last.trailing_whitespace:
+            text += last.trailing_whitespace
+        text += tok
+        merged = token(text,
+                       pre_tags=last.pre_tags,
+                       post_tags=tok.post_tags,
+                       trailing_whitespace=tok.trailing_whitespace)
+        merged.annotation = last.annotation
+        tokens[-1] = merged
+    
+def markup_serialize_tokens(tokens, markup_func):
+    """
+    Serialize the list of tokens into a list of text chunks, calling
+    markup_func around text to add annotations.
+    """
+    for token in tokens:
+        for pre in token.pre_tags:
+            yield pre
+        html = token.html()
+        html = markup_func(html, token.annotation)
+        if token.trailing_whitespace:
+            html += token.trailing_whitespace
+        yield html
+        for post in token.post_tags:
+            yield post
+
+
+############################################################
+## HTML Diffs
+############################################################
+
+def htmldiff(old_html, new_html):
+    ## FIXME: this should take parsed documents too, and use their body
+    ## or other content.
+    """ Do a diff of the old and new document.  The documents are HTML
+    *fragments* (str/UTF8 or unicode), they are not complete documents
+    (i.e., no <html> tag).
+
+    Returns HTML with <ins> and <del> tags added around the
+    appropriate text.  
+
+    Markup is generally ignored, with the markup from new_html
+    preserved, and possibly some markup from old_html (though it is
+    considered acceptable to lose some of the old markup).  Only the
+    words in the HTML are diffed.  The exception is <img> tags, which
+    are treated like words, and the href attribute of <a> tags, which
+    are noted inside the tag itself when there are changes.
+    """ 
+    old_html_tokens = tokenize(old_html)
+    new_html_tokens = tokenize(new_html)
+    result = htmldiff_tokens(old_html_tokens, new_html_tokens)
+    result = ''.join(result).strip()
+    return fixup_ins_del_tags(result)
+
+def htmldiff_tokens(html1_tokens, html2_tokens):
+    """ Does a diff on the tokens themselves, returning a list of text
+    chunks (not tokens).
+    """
+    # There are several passes as we do the differences.  The tokens
+    # isolate the portion of the content we care to diff; difflib does
+    # all the actual hard work at that point.  
+    #
+    # Then we must create a valid document from pieces of both the old
+    # document and the new document.  We generally prefer to take
+    # markup from the new document, and only do a best effort attempt
+    # to keep markup from the old document; anything that we can't
+    # resolve we throw away.  Also we try to put the deletes as close
+    # to the location where we think they would have been -- because
+    # we are only keeping the markup from the new document, it can be
+    # fuzzy where in the new document the old text would have gone.
+    # Again we just do a best effort attempt.
+    s = InsensitiveSequenceMatcher(a=html1_tokens, b=html2_tokens)
+    commands = s.get_opcodes()
+    result = []
+    for command, i1, i2, j1, j2 in commands:
+        if command == 'equal':
+            result.extend(expand_tokens(html2_tokens[j1:j2], equal=True))
+            continue
+        if command == 'insert' or command == 'replace':
+            ins_tokens = expand_tokens(html2_tokens[j1:j2])
+            merge_insert(ins_tokens, result)
+        if command == 'delete' or command == 'replace':
+            del_tokens = expand_tokens(html1_tokens[i1:i2])
+            merge_delete(del_tokens, result)
+    # If deletes were inserted directly as <del> then we'd have an
+    # invalid document at this point.  Instead we put in special
+    # markers, and when the complete diffed document has been created
+    # we try to move the deletes around and resolve any problems.
+    result = cleanup_delete(result)
+
+    return result
+
+def expand_tokens(tokens, equal=False):
+    """Given a list of tokens, return a generator of the chunks of
+    text for the data in the tokens.
+    """
+    for token in tokens:
+        for pre in token.pre_tags:
+            yield pre
+        if not equal or not token.hide_when_equal:
+            if token.trailing_whitespace:
+                yield token.html() + token.trailing_whitespace
+            else:
+                yield token.html()
+        for post in token.post_tags:
+            yield post
+
+def merge_insert(ins_chunks, doc):
+    """ doc is the already-handled document (as a list of text chunks);
+    here we add <ins>ins_chunks</ins> to the end of that.  """
+    # Though we don't throw away unbalanced_start or unbalanced_end
+    # (we assume there is accompanying markup later or earlier in the
+    # document), we only put <ins> around the balanced portion.
+    unbalanced_start, balanced, unbalanced_end = split_unbalanced(ins_chunks)
+    doc.extend(unbalanced_start)
+    if doc and not doc[-1].endswith(' '):
+        # Fix up the case where the word before the insert didn't end with 
+        # a space
+        doc[-1] += ' '
+    doc.append('<ins>')
+    if balanced and balanced[-1].endswith(' '):
+        # We move space outside of </ins>
+        balanced[-1] = balanced[-1][:-1]
+    doc.extend(balanced)
+    doc.append('</ins> ')
+    doc.extend(unbalanced_end)
+
+# These are sentinals to represent the start and end of a <del>
+# segment, until we do the cleanup phase to turn them into proper
+# markup:
+class DEL_START:
+    pass
+class DEL_END:
+    pass
+
+class NoDeletes(Exception):
+    """ Raised when the document no longer contains any pending deletes
+    (DEL_START/DEL_END) """
+
+def merge_delete(del_chunks, doc):
+    """ Adds the text chunks in del_chunks to the document doc (another
+    list of text chunks) with marker to show it is a delete.
+    cleanup_delete later resolves these markers into <del> tags."""
+    doc.append(DEL_START)
+    doc.extend(del_chunks)
+    doc.append(DEL_END)
+
+def cleanup_delete(chunks):
+    """ Cleans up any DEL_START/DEL_END markers in the document, replacing
+    them with <del></del>.  To do this while keeping the document
+    valid, it may need to drop some tags (either start or end tags).
+
+    It may also move the del into adjacent tags to try to move it to a
+    similar location where it was originally located (e.g., moving a
+    delete into preceding <div> tag, if the del looks like (DEL_START,
+    'Text</div>', DEL_END)"""
+    while 1:
+        # Find a pending DEL_START/DEL_END, splitting the document
+        # into stuff-preceding-DEL_START, stuff-inside, and
+        # stuff-following-DEL_END
+        try:
+            pre_delete, delete, post_delete = split_delete(chunks)
+        except NoDeletes:
+            # Nothing found, we've cleaned up the entire doc
+            break
+        # The stuff-inside-DEL_START/END may not be well balanced
+        # markup.  First we figure out what unbalanced portions there are:
+        unbalanced_start, balanced, unbalanced_end = split_unbalanced(delete)
+        # Then we move the span forward and/or backward based on these
+        # unbalanced portions:
+        locate_unbalanced_start(unbalanced_start, pre_delete, post_delete)
+        locate_unbalanced_end(unbalanced_end, pre_delete, post_delete)
+        doc = pre_delete
+        if doc and not doc[-1].endswith(' '):
+            # Fix up case where the word before us didn't have a trailing space
+            doc[-1] += ' '
+        doc.append('<del>')
+        if balanced and balanced[-1].endswith(' '):
+            # We move space outside of </del>
+            balanced[-1] = balanced[-1][:-1]
+        doc.extend(balanced)
+        doc.append('</del> ')
+        doc.extend(post_delete)
+        chunks = doc
+    return chunks
+
+def split_unbalanced(chunks):
+    """Return (unbalanced_start, balanced, unbalanced_end), where each is
+    a list of text and tag chunks.
+
+    unbalanced_start is a list of all the tags that are opened, but
+    not closed in this span.  Similarly, unbalanced_end is a list of
+    tags that are closed but were not opened.  Extracting these might
+    mean some reordering of the chunks."""
+    start = []
+    end = []
+    tag_stack = []
+    balanced = []
+    for chunk in chunks:
+        if not chunk.startswith('<'):
+            balanced.append(chunk)
+            continue
+        endtag = chunk[1] == '/'
+        name = chunk.split()[0].strip('<>/')
+        if name in empty_tags:
+            balanced.append(chunk)
+            continue
+        if endtag:
+            if tag_stack and tag_stack[-1][0] == name:
+                balanced.append(chunk)
+                name, pos, tag = tag_stack.pop()
+                balanced[pos] = tag
+            elif tag_stack:
+                start.extend([tag for name, pos, tag in tag_stack])
+                tag_stack = []
+                end.append(chunk)
+            else:
+                end.append(chunk)
+        else:
+            tag_stack.append((name, len(balanced), chunk))
+            balanced.append(None)
+    start.extend(
+        [chunk for name, pos, chunk in tag_stack])
+    balanced = [chunk for chunk in balanced if chunk is not None]
+    return start, balanced, end
+
+def split_delete(chunks):
+    """ Returns (stuff_before_DEL_START, stuff_inside_DEL_START_END,
+    stuff_after_DEL_END).  Returns the first case found (there may be
+    more DEL_STARTs in stuff_after_DEL_END).  Raises NoDeletes if
+    there's no DEL_START found. """
+    try:
+        pos = chunks.index(DEL_START)
+    except ValueError:
+        raise NoDeletes
+    pos2 = chunks.index(DEL_END)
+    return chunks[:pos], chunks[pos+1:pos2], chunks[pos2+1:]
+
+def locate_unbalanced_start(unbalanced_start, pre_delete, post_delete):
+    """ pre_delete and post_delete implicitly point to a place in the
+    document (where the two were split).  This moves that point (by
+    popping items from one and pushing them onto the other).  It moves
+    the point to try to find a place where unbalanced_start applies.
+
+    As an example::
+
+        >>> unbalanced_start = ['<div>']
+        >>> doc = ['<p>', 'Text', '</p>', '<div>', 'More Text', '</div>']
+        >>> pre, post = doc[:3], doc[3:]
+        >>> pre, post
+        (['<p>', 'Text', '</p>'], ['<div>', 'More Text', '</div>'])
+        >>> locate_unbalanced_start(unbalanced_start, pre, post)
+        >>> pre, post
+        (['<p>', 'Text', '</p>', '<div>'], ['More Text', '</div>'])
+
+    As you can see, we moved the point so that the dangling <div> that
+    we found will be effectively replaced by the div in the original
+    document.  If this doesn't work out, we just throw away
+    unbalanced_start without doing anything.
+    """
+    while 1:
+        if not unbalanced_start:
+            # We have totally succeeded in finding the position
+            break
+        finding = unbalanced_start[0]
+        finding_name = finding.split()[0].strip('<>')
+        if not post_delete:
+            break
+        next = post_delete[0]
+        if next is DEL_START or not next.startswith('<'):
+            # Reached a word, we can't move the delete text forward
+            break
+        if next[1] == '/':
+            # Reached a closing tag, can we go further?  Maybe not...
+            break
+        name = next.split()[0].strip('<>')
+        if name == 'ins':
+            # Can't move into an insert
+            break
+        assert name != 'del', (
+            "Unexpected delete tag: %r" % next)
+        if name == finding_name:
+            unbalanced_start.pop(0)
+            pre_delete.append(post_delete.pop(0))
+        else:
+            # Found a tag that doesn't match
+            break
+
+def locate_unbalanced_end(unbalanced_end, pre_delete, post_delete):
+    """ like locate_unbalanced_start, except handling end tags and
+    possibly moving the point earlier in the document.  """
+    while 1:
+        if not unbalanced_end:
+            # Success
+            break
+        finding = unbalanced_end[-1]
+        finding_name = finding.split()[0].strip('<>/')
+        if not pre_delete:
+            break
+        next = pre_delete[-1]
+        if next is DEL_END or not next.startswith('</'):
+            # A word or a start tag
+            break
+        name = next.split()[0].strip('<>/')
+        if name == 'ins' or name == 'del':
+            # Can't move into an insert or delete
+            break
+        if name == finding_name:
+            unbalanced_end.pop()
+            post_delete.insert(0, pre_delete.pop())
+        else:
+            # Found a tag that doesn't match
+            break
+
+class token(_unicode):
+    """ Represents a diffable token, generally a word that is displayed to
+    the user.  Opening tags are attached to this token when they are
+    adjacent (pre_tags) and closing tags that follow the word
+    (post_tags).  Some exceptions occur when there are empty tags
+    adjacent to a word, so there may be close tags in pre_tags, or
+    open tags in post_tags.
+
+    We also keep track of whether the word was originally followed by
+    whitespace, even though we do not want to treat the word as
+    equivalent to a similar word that does not have a trailing
+    space."""
+
+    # When this is true, the token will be eliminated from the
+    # displayed diff if no change has occurred:
+    hide_when_equal = False
+
+    def __new__(cls, text, pre_tags=None, post_tags=None, trailing_whitespace=""):
+        obj = _unicode.__new__(cls, text)
+
+        if pre_tags is not None:
+            obj.pre_tags = pre_tags
+        else:
+            obj.pre_tags = []
+
+        if post_tags is not None:
+            obj.post_tags = post_tags
+        else:
+            obj.post_tags = []
+
+        obj.trailing_whitespace = trailing_whitespace
+
+        return obj
+
+    def __repr__(self):
+        return 'token(%s, %r, %r, %r)' % (_unicode.__repr__(self), self.pre_tags,
+                                          self.post_tags, self.trailing_whitespace)
+
+    def html(self):
+        return _unicode(self)
+
+class tag_token(token):
+
+    """ Represents a token that is actually a tag.  Currently this is just
+    the <img> tag, which takes up visible space just like a word but
+    is only represented in a document by a tag.  """
+
+    def __new__(cls, tag, data, html_repr, pre_tags=None, 
+                post_tags=None, trailing_whitespace=""):
+        obj = token.__new__(cls, "%s: %s" % (type, data), 
+                            pre_tags=pre_tags, 
+                            post_tags=post_tags, 
+                            trailing_whitespace=trailing_whitespace)
+        obj.tag = tag
+        obj.data = data
+        obj.html_repr = html_repr
+        return obj
+
+    def __repr__(self):
+        return 'tag_token(%s, %s, html_repr=%s, post_tags=%r, pre_tags=%r, trailing_whitespace=%r)' % (
+            self.tag, 
+            self.data, 
+            self.html_repr, 
+            self.pre_tags, 
+            self.post_tags, 
+            self.trailing_whitespace)
+    def html(self):
+        return self.html_repr
+
+class href_token(token):
+
+    """ Represents the href in an anchor tag.  Unlike other words, we only
+    show the href when it changes.  """
+
+    hide_when_equal = True
+
+    def html(self):
+        return ' Link: %s' % self
+
+def tokenize(html, include_hrefs=True):
+    """
+    Parse the given HTML and returns token objects (words with attached tags).
+
+    This parses only the content of a page; anything in the head is
+    ignored, and the <head> and <body> elements are themselves
+    optional.  The content is then parsed by lxml, which ensures the
+    validity of the resulting parsed document (though lxml may make
+    incorrect guesses when the markup is particular bad).
+
+    <ins> and <del> tags are also eliminated from the document, as
+    that gets confusing.
+
+    If include_hrefs is true, then the href attribute of <a> tags is
+    included as a special kind of diffable token."""
+    if etree.iselement(html):
+        body_el = html
+    else:
+        body_el = parse_html(html, cleanup=True)
+    # Then we split the document into text chunks for each tag, word, and end tag:
+    chunks = flatten_el(body_el, skip_tag=True, include_hrefs=include_hrefs)
+    # Finally re-joining them into token objects:
+    return fixup_chunks(chunks)
+
+def parse_html(html, cleanup=True):
+    """
+    Parses an HTML fragment, returning an lxml element.  Note that the HTML will be
+    wrapped in a <div> tag that was not in the original document.
+
+    If cleanup is true, make sure there's no <head> or <body>, and get
+    rid of any <ins> and <del> tags.
+    """
+    if cleanup:
+        # This removes any extra markup or structure like <head>:
+        html = cleanup_html(html)
+    return fragment_fromstring(html, create_parent=True)
+
+_body_re = re.compile(r'<body.*?>', re.I|re.S)
+_end_body_re = re.compile(r'</body.*?>', re.I|re.S)
+_ins_del_re = re.compile(r'</?(ins|del).*?>', re.I|re.S)
+
+def cleanup_html(html):
+    """ This 'cleans' the HTML, meaning that any page structure is removed
+    (only the contents of <body> are used, if there is any <body).
+    Also <ins> and <del> tags are removed.  """
+    match = _body_re.search(html)
+    if match:
+        html = html[match.end():]
+    match = _end_body_re.search(html)
+    if match:
+        html = html[:match.start()]
+    html = _ins_del_re.sub('', html)
+    return html
+    
+
+end_whitespace_re = re.compile(r'[ \t\n\r]$')
+
+def split_trailing_whitespace(word):
+    """
+    This function takes a word, such as 'test\n\n' and returns ('test','\n\n')
+    """
+    stripped_length = len(word.rstrip())
+    return word[0:stripped_length], word[stripped_length:]
+
+
+def fixup_chunks(chunks):
+    """
+    This function takes a list of chunks and produces a list of tokens.
+    """
+    tag_accum = []
+    cur_word = None
+    result = []
+    for chunk in chunks:
+        if isinstance(chunk, tuple):
+            if chunk[0] == 'img':
+                src = chunk[1]
+                tag, trailing_whitespace = split_trailing_whitespace(chunk[2])
+                cur_word = tag_token('img', src, html_repr=tag,
+                                     pre_tags=tag_accum,
+                                     trailing_whitespace=trailing_whitespace)
+                tag_accum = []
+                result.append(cur_word)
+
+            elif chunk[0] == 'href':
+                href = chunk[1]
+                cur_word = href_token(href, pre_tags=tag_accum, trailing_whitespace=" ")
+                tag_accum = []
+                result.append(cur_word)
+            continue
+
+        if is_word(chunk):
+            chunk, trailing_whitespace = split_trailing_whitespace(chunk)
+            cur_word = token(chunk, pre_tags=tag_accum, trailing_whitespace=trailing_whitespace)
+            tag_accum = []
+            result.append(cur_word)
+
+        elif is_start_tag(chunk):
+            tag_accum.append(chunk)
+
+        elif is_end_tag(chunk):
+            if tag_accum:
+                tag_accum.append(chunk)
+            else:
+                assert cur_word, (
+                    "Weird state, cur_word=%r, result=%r, chunks=%r of %r"
+                    % (cur_word, result, chunk, chunks))
+                cur_word.post_tags.append(chunk)
+        else:
+            assert False
+
+    if not result:
+        return [token('', pre_tags=tag_accum)]
+    else:
+        result[-1].post_tags.extend(tag_accum)
+
+    return result
+
+
+# All the tags in HTML that don't require end tags:
+empty_tags = (
+    'param', 'img', 'area', 'br', 'basefont', 'input',
+    'base', 'meta', 'link', 'col')
+
+block_level_tags = (
+    'address',
+    'blockquote',
+    'center',
+    'dir',
+    'div',
+    'dl',
+    'fieldset',
+    'form',
+    'h1',
+    'h2',
+    'h3',
+    'h4',
+    'h5',
+    'h6',
+    'hr',
+    'isindex',
+    'menu',
+    'noframes',
+    'noscript',
+    'ol',
+    'p',
+    'pre',
+    'table',
+    'ul',
+    )
+
+block_level_container_tags = (
+    'dd',
+    'dt',
+    'frameset',
+    'li',
+    'tbody',
+    'td',
+    'tfoot',
+    'th',
+    'thead',
+    'tr',
+    )
+
+
+def flatten_el(el, include_hrefs, skip_tag=False):
+    """ Takes an lxml element el, and generates all the text chunks for
+    that tag.  Each start tag is a chunk, each word is a chunk, and each
+    end tag is a chunk.
+
+    If skip_tag is true, then the outermost container tag is
+    not returned (just its contents)."""
+    if not skip_tag:
+        if el.tag == 'img':
+            yield ('img', el.get('src'), start_tag(el))
+        else:
+            yield start_tag(el)
+    if el.tag in empty_tags and not el.text and not len(el) and not el.tail:
+        return
+    start_words = split_words(el.text)
+    for word in start_words:
+        yield html_escape(word)
+    for child in el:
+        for item in flatten_el(child, include_hrefs=include_hrefs):
+            yield item
+    if el.tag == 'a' and el.get('href') and include_hrefs:
+        yield ('href', el.get('href'))
+    if not skip_tag:
+        yield end_tag(el)
+        end_words = split_words(el.tail)
+        for word in end_words:
+            yield html_escape(word)
+
+split_words_re = re.compile(r'\S+(?:\s+|$)', re.U)
+
+def split_words(text):
+    """ Splits some text into words. Includes trailing whitespace
+    on each word when appropriate.  """
+    if not text or not text.strip():
+        return []
+
+    words = split_words_re.findall(text)
+    return words
+
+start_whitespace_re = re.compile(r'^[ \t\n\r]')
+
+def start_tag(el):
+    """
+    The text representation of the start tag for a tag.
+    """
+    return '<%s%s>' % (
+        el.tag, ''.join([' %s="%s"' % (name, html_escape(value, True))
+                         for name, value in el.attrib.items()]))
+
+def end_tag(el):
+    """ The text representation of an end tag for a tag.  Includes
+    trailing whitespace when appropriate.  """
+    if el.tail and start_whitespace_re.search(el.tail):
+        extra = ' '
+    else:
+        extra = ''
+    return '</%s>%s' % (el.tag, extra)
+
+def is_word(tok):
+    return not tok.startswith('<')
+
+def is_end_tag(tok):
+    return tok.startswith('</')
+
+def is_start_tag(tok):
+    return tok.startswith('<') and not tok.startswith('</')
+
+def fixup_ins_del_tags(html):
+    """ Given an html string, move any <ins> or <del> tags inside of any
+    block-level elements, e.g. transform <ins><p>word</p></ins> to
+    <p><ins>word</ins></p> """
+    doc = parse_html(html, cleanup=False)
+    _fixup_ins_del_tags(doc)
+    html = serialize_html_fragment(doc, skip_outer=True)
+    return html
+
+def serialize_html_fragment(el, skip_outer=False):
+    """ Serialize a single lxml element as HTML.  The serialized form
+    includes the elements tail.  
+
+    If skip_outer is true, then don't serialize the outermost tag
+    """
+    assert not isinstance(el, basestring), (
+        "You should pass in an element, not a string like %r" % el)
+    html = etree.tostring(el, method="html", encoding=_unicode)
+    if skip_outer:
+        # Get rid of the extra starting tag:
+        html = html[html.find('>')+1:]
+        # Get rid of the extra end tag:
+        html = html[:html.rfind('<')]
+        return html.strip()
+    else:
+        return html
+
+def _fixup_ins_del_tags(doc):
+    """fixup_ins_del_tags that works on an lxml document in-place
+    """
+    for tag in ['ins', 'del']:
+        for el in doc.xpath('descendant-or-self::%s' % tag):
+            if not _contains_block_level_tag(el):
+                continue
+            _move_el_inside_block(el, tag=tag)
+            el.drop_tag()
+            #_merge_element_contents(el)
+
+def _contains_block_level_tag(el):
+    """True if the element contains any block-level elements, like <p>, <td>, etc.
+    """
+    if el.tag in block_level_tags or el.tag in block_level_container_tags:
+        return True
+    for child in el:
+        if _contains_block_level_tag(child):
+            return True
+    return False
+
+def _move_el_inside_block(el, tag):
+    """ helper for _fixup_ins_del_tags; actually takes the <ins> etc tags
+    and moves them inside any block-level tags.  """
+    for child in el:
+        if _contains_block_level_tag(child):
+            break
+    else:
+        # No block-level tags in any child
+        children_tag = etree.Element(tag)
+        children_tag.text = el.text
+        el.text = None
+        children_tag.extend(list(el))
+        el[:] = [children_tag]
+        return
+    for child in list(el):
+        if _contains_block_level_tag(child):
+            _move_el_inside_block(child, tag)
+            if child.tail:
+                tail_tag = etree.Element(tag)
+                tail_tag.text = child.tail
+                child.tail = None
+                el.insert(el.index(child)+1, tail_tag)
+        else:
+            child_tag = etree.Element(tag)
+            el.replace(child, child_tag)
+            child_tag.append(child)
+    if el.text:
+        text_tag = etree.Element(tag)
+        text_tag.text = el.text
+        el.text = None
+        el.insert(0, text_tag)
+            
+def _merge_element_contents(el):
+    """
+    Removes an element, but merges its contents into its place, e.g.,
+    given <p>Hi <i>there!</i></p>, if you remove the <i> element you get
+    <p>Hi there!</p>
+    """
+    parent = el.getparent()
+    text = el.text or ''
+    if el.tail:
+        if not len(el):
+            text += el.tail
+        else:
+            if el[-1].tail:
+                el[-1].tail += el.tail
+            else:
+                el[-1].tail = el.tail
+    index = parent.index(el)
+    if text:
+        if index == 0:
+            previous = None
+        else:
+            previous = parent[index-1]
+        if previous is None:
+            if parent.text:
+                parent.text += text
+            else:
+                parent.text = text
+        else:
+            if previous.tail:
+                previous.tail += text
+            else:
+                previous.tail = text
+    parent[index:index+1] = el.getchildren()
+
+class InsensitiveSequenceMatcher(difflib.SequenceMatcher):
+    """
+    Acts like SequenceMatcher, but tries not to find very small equal
+    blocks amidst large spans of changes
+    """
+
+    threshold = 2
+    
+    def get_matching_blocks(self):
+        size = min(len(self.b), len(self.b))
+        threshold = min(self.threshold, size / 4)
+        actual = difflib.SequenceMatcher.get_matching_blocks(self)
+        return [item for item in actual
+                if item[2] > threshold
+                or not item[2]]
+
+if __name__ == '__main__':
+    from lxml.html import _diffcommand
+    _diffcommand.main()
+