'filename': _safe_id(diff['filename']),

                    'oldline_no': change['old_lineno']

                }

                anchor_new = "%(filename)s_n%(oldline_no)s" % {

                    'filename': _safe_id(diff['filename']),

                    'oldline_no': change['new_lineno']

                }

                cond_old = (change['old_lineno'] != '...' and

                            change['old_lineno'])

                cond_new = (change['new_lineno'] != '...' and

                            change['new_lineno'])

                no_lineno = (change['old_lineno'] == '...' and

                             change['new_lineno'] == '...')

                if cond_old:

                    anchor_old_id = 'id="%s"' % anchor_old

                if cond_new:

                    anchor_new_id = 'id="%s"' % anchor_new

                ###########################################################

                # OLD LINE NUMBER

                ###########################################################

                _html.append('''\t<td %(a_id)s class="%(olc)s" %(colspan)s>''' % {

                    'a_id': anchor_old_id,

                    'olc': no_lineno_class if no_lineno else old_lineno_class,

                    'colspan': 'colspan="2"' if no_lineno else ''

                })

                _html.append('''%(link)s''' % {

                    'link': _link_to_if(not no_lineno, change['old_lineno'],

                                        '#%s' % anchor_old)

                })

                _html.append('''</td>\n''')

                ###########################################################

                # NEW LINE NUMBER

                ###########################################################

                if not no_lineno:

                    _html.append('''\t<td %(a_id)s class="%(nlc)s">''' % {

                        'a_id': anchor_new_id,

                        'nlc': new_lineno_class

                    })

                    _html.append('''%(link)s''' % {

                        'link': _link_to_if(True, change['new_lineno'],

                                            '#%s' % anchor_new)

                    })

                    _html.append('''</td>\n''')

                ###########################################################

                # CODE

                ###########################################################

                comments = '' if enable_comments else 'no-comment'

                _html.append('''\t<td class="%(cc)s %(inc)s">''' % {

                    'cc': code_class,

                    'inc': comments

                })

                _html.append('''\n\t\t<div class="add-bubble"><div>&nbsp;</div></div><pre>%(code)s</pre>\n''' % {

                    'code': change['line']

                })

                _html.append('''\t</td>''')

                _html.append('''\n</tr>\n''')

    _html.append('''</table>''')

    if _html_empty:

        return None

    return ''.join(_html)

def wrap_to_table(html):

    """Given a string with html, return it wrapped in a table, similar to what

    DiffProcessor returns."""

    return '''\

              <table class="code-difftable">

                <tr class="line no-comment">

                <td class="lineno new"></td>

                <td class="code no-comment"><pre>%s</pre></td>

                </tr>

              </table>''' % html

def wrapped_diff(filenode_old, filenode_new, diff_limit=None,

                ignore_whitespace=True, line_context=3,

                enable_comments=False):

    """

    Returns a file diff wrapped into a table.

    Checks for diff_limit and presents a message if the diff is too big.

    """

    if filenode_old is None:

        filenode_old = FileNode(filenode_new.path, '', EmptyChangeset())

    op = None

    a_path = filenode_old.path # default, might be overriden by actual rename in diff

    if filenode_old.is_binary or filenode_new.is_binary:

        html_diff = wrap_to_table(_('Binary file'))

        stats = (0, 0)

    elif diff_limit != -1 and (

            diff_limit is None or

            (filenode_old.size < diff_limit and filenode_new.size < diff_limit)):

        raw_diff = get_gitdiff(filenode_old, filenode_new,

                                ignore_whitespace=ignore_whitespace,

                                context=line_context)

        diff_processor = DiffProcessor(raw_diff)

        if diff_processor.parsed: # there should be exactly one element, for the specified file

            f = diff_processor.parsed[0]

            op = f['operation']

            a_path = f['old_filename']

        html_diff = as_html(parsed_lines=diff_processor.parsed, enable_comments=enable_comments)

        stats = diff_processor.stat()

    else:

        html_diff = wrap_to_table(_('Changeset was too big and was cut off, use '

                               'diff menu to display this diff'))

        stats = (0, 0)

    if not html_diff:

        submodules = [o for o in [filenode_new, filenode_old] if isinstance(o, SubModuleNode)]

        if submodules:

            html_diff = wrap_to_table(h.escape('Submodule %r' % submodules[0]))

        else:

            html_diff = wrap_to_table(_('No changes detected'))

    cs1 = filenode_old.changeset.raw_id

    cs2 = filenode_new.changeset.raw_id

    return cs1, cs2, a_path, html_diff, stats, op

def get_gitdiff(filenode_old, filenode_new, ignore_whitespace=True, context=3):

    """

    Returns git style diff between given ``filenode_old`` and ``filenode_new``.

    """

    # make sure we pass in default context

    context = context or 3

    submodules = [o for o in [filenode_new, filenode_old] if isinstance(o, SubModuleNode)]

    if submodules:

        return b''

    for filenode in (filenode_old, filenode_new):

        if not isinstance(filenode, FileNode):

            raise VCSError("Given object should be FileNode object, not %s"

                % filenode.__class__)

    repo = filenode_new.changeset.repository

    old_raw_id = getattr(filenode_old.changeset, 'raw_id', repo.EMPTY_CHANGESET)

    new_raw_id = getattr(filenode_new.changeset, 'raw_id', repo.EMPTY_CHANGESET)

    vcs_gitdiff = get_diff(repo, old_raw_id, new_raw_id, filenode_new.path,

                           ignore_whitespace, context)

    return vcs_gitdiff

def get_diff(scm_instance, rev1, rev2, path=None, ignore_whitespace=False, context=3):

    """

    A thin wrapper around vcs lib get_diff.

    """

    try:

        return scm_instance.get_diff(rev1, rev2, path=path,

                                     ignore_whitespace=ignore_whitespace, context=context)

    except MemoryError:

        h.flash('MemoryError: Diff is too big', category='error')

        return b''

NEW_FILENODE = 1

DEL_FILENODE = 2

MOD_FILENODE = 3

RENAMED_FILENODE = 4

COPIED_FILENODE = 5

CHMOD_FILENODE = 6

BIN_FILENODE = 7

class DiffProcessor(object):

    """

    Give it a unified or git diff and it returns a list of the files that were

    mentioned in the diff together with a dict of meta information that

    can be used to render it in a HTML template.

    """

    _diff_git_re = re.compile(b'^diff --git', re.MULTILINE)

    def __init__(self, diff, vcs='hg', diff_limit=None, inline_diff=True):

        """

        :param diff:   a text in diff format

        :param vcs: type of version control hg or git

        :param diff_limit: define the size of diff that is considered "big"

            based on that parameter cut off will be triggered, set to None

            to show full diff

        """

        if not isinstance(diff, bytes):

            raise Exception('Diff must be bytes - got %s' % type(diff))

        self.adds = 0

        self.removes = 0

        self.diff_limit = diff_limit

        self.limited_diff = False

        self.vcs = vcs

        self.parsed = self._parse_gitdiff(inline_diff=inline_diff)

    def _parse_gitdiff(self, inline_diff):

        """Parse self._diff and return a list of dicts with meta info and chunks for each file.

        Might set limited_diff.

        Optionally, do an extra pass and to extra markup of one-liner changes.

        """

        _files = [] # list of dicts with meta info and chunks

        starts = [m.start() for m in self._diff_git_re.finditer(self._diff)]

        starts.append(len(self._diff))

        for start, end in zip(starts, starts[1:]):

            if self.diff_limit and end > self.diff_limit:

                self.limited_diff = True

                continue

            op = None

            stats = {

                'added': 0,

                'deleted': 0,

                'binary': False,

                'ops': {},

            }

            if head['deleted_file_mode']:

                op = 'removed'

                stats['binary'] = True

                stats['ops'][DEL_FILENODE] = 'deleted file'

            elif head['new_file_mode']:

                op = 'added'

                stats['binary'] = True

                stats['ops'][NEW_FILENODE] = 'new file %s' % head['new_file_mode']

            else:  # modify operation, can be cp, rename, chmod

                # CHMOD

                if head['new_mode'] and head['old_mode']:

                    op = 'modified'

                    stats['binary'] = True

                    stats['ops'][CHMOD_FILENODE] = ('modified file chmod %s => %s'

                                        % (head['old_mode'], head['new_mode']))

                # RENAME

                if (head['rename_from'] and head['rename_to']

                      and head['rename_from'] != head['rename_to']):

                    op = 'renamed'

                    stats['binary'] = True

                    stats['ops'][RENAMED_FILENODE] = ('file renamed from %s to %s'

                                    % (head['rename_from'], head['rename_to']))

                # COPY

                if head.get('copy_from') and head.get('copy_to'):

                    op = 'modified'

                    stats['binary'] = True

                    stats['ops'][COPIED_FILENODE] = ('file copied from %s to %s'

                                        % (head['copy_from'], head['copy_to']))

                # FALL BACK: detect missed old style add or remove

                if op is None:

                    if not head['a_file'] and head['b_file']:

                        op = 'added'

                        stats['binary'] = True

                        stats['ops'][NEW_FILENODE] = 'new file'

                    elif head['a_file'] and not head['b_file']:

                        op = 'removed'

                        stats['binary'] = True

                        stats['ops'][DEL_FILENODE] = 'deleted file'

                # it's not ADD not DELETE

                if op is None:

                    op = 'modified'

                    stats['binary'] = True

                    stats['ops'][MOD_FILENODE] = 'modified file'

            # a real non-binary diff

            if head['a_file'] or head['b_file']:

                chunks, added, deleted = _parse_lines(diff_lines)

                stats['binary'] = False

                stats['added'] = added

                stats['deleted'] = deleted

                # explicit mark that it's a modified file

                if op == 'modified':

                    stats['ops'][MOD_FILENODE] = 'modified file'

            else:  # Git binary patch (or empty diff)

                # Git binary patch

                if head['bin_patch']:

                    stats['ops'][BIN_FILENODE] = 'binary diff not shown'

                chunks = []

            if op == 'removed' and chunks:

                # a way of seeing deleted content could perhaps be nice - but

                # not with the current UI

                chunks = []

            chunks.insert(0, [{

                'old_lineno': '',

                'new_lineno': '',

                'action':     'context',

                'line':       msg,

                } for _op, msg in stats['ops'].iteritems()

                  if _op not in [MOD_FILENODE]])

            _files.append({

                'old_filename':     head['a_path'],

                'filename':         head['b_path'],

                'old_revision':     head['a_blob_id'],

                'new_revision':     head['b_blob_id'],

                'chunks':           chunks,

                'operation':        op,

                'stats':            stats,

            })

        if not inline_diff:

            return _files

        # highlight inline changes when one del is followed by one add

        for diff_data in _files:

            for chunk in diff_data['chunks']:

                lineiter = iter(chunk)

                try:

                    peekline = next(lineiter)

                    while True:

                        # find a first del line

                        while peekline['action'] != 'del':

                            peekline = next(lineiter)

                        delline = peekline

                        peekline = next(lineiter)

                        # if not followed by add, eat all following del lines

                        if peekline['action'] != 'add':

                            while peekline['action'] == 'del':

                                peekline = next(lineiter)

                            continue

                        # found an add - make sure it is the only one

                        addline = peekline

                        try:

                            peekline = next(lineiter)

                        except StopIteration:

                            # add was last line - ok

                            _highlight_inline_diff(delline, addline)

                            raise

                        if peekline['action'] != 'add':

                            # there was only one add line - ok

                            _highlight_inline_diff(delline, addline)

                except StopIteration:

                    pass

        return _files

    def stat(self):

        """

        Returns tuple of added, and removed lines for this instance

        """

        return self.adds, self.removes

_escape_re = re.compile(r'(&)|(<)|(>)|(\t)|(\r)|(?<=.)( \n| $)')

def _escaper(string):

    """

    Do HTML escaping/markup

    """

    def substitute(m):

        groups = m.groups()

        if groups[0]:

            return '&'

        if groups[1]:

            return '<'

        if groups[2]:

            return '>'

        if groups[3]:

            return '<u>\t</u>'

        if groups[4]:

            return '<u class="cr"></u>'

        if groups[5]:

            return ' <i></i>'

        assert False

    return _escape_re.sub(substitute, safe_unicode(string))

_git_header_re = re.compile(br"""

    ^diff[ ]--git[ ]a/(?P<a_path>.+?)[ ]b/(?P<b_path>.+?)\n

    (?:^old[ ]mode[ ](?P<old_mode>\d+)\n

       ^new[ ]mode[ ](?P<new_mode>\d+)(?:\n|$))?

    (?:^similarity[ ]index[ ](?P<similarity_index>\d+)%\n

       ^rename[ ]from[ ](?P<rename_from>.+)\n

       ^rename[ ]to[ ](?P<rename_to>.+)(?:\n|$))?

    (?:^new[ ]file[ ]mode[ ](?P<new_file_mode>.+)(?:\n|$))?

    (?:^deleted[ ]file[ ]mode[ ](?P<deleted_file_mode>.+)(?:\n|$))?

    (?:^index[ ](?P<a_blob_id>[0-9A-Fa-f]+)

        \.\.(?P<b_blob_id>[0-9A-Fa-f]+)[ ]?(?P<b_mode>.+)?(?:\n|$))?

    (?:^(?P<bin_patch>GIT[ ]binary[ ]patch)(?:\n|$))?

    (?:^---[ ](a/(?P<a_file>.+?)|/dev/null)\t?(?:\n|$))?

    (?:^\+\+\+[ ](b/(?P<b_file>.+?)|/dev/null)\t?(?:\n|$))?

""", re.VERBOSE | re.MULTILINE)

_hg_header_re = re.compile(br"""

    ^diff[ ]--git[ ]a/(?P<a_path>.+?)[ ]b/(?P<b_path>.+?)\n

    (?:^old[ ]mode[ ](?P<old_mode>\d+)\n

       ^new[ ]mode[ ](?P<new_mode>\d+)(?:\n|$))?

    (?:^similarity[ ]index[ ](?P<similarity_index>\d+)%(?:\n|$))?

    (?:^rename[ ]from[ ](?P<rename_from>.+)\n

       ^rename[ ]to[ ](?P<rename_to>.+)(?:\n|$))?

    (?:^copy[ ]from[ ](?P<copy_from>.+)\n

       ^copy[ ]to[ ](?P<copy_to>.+)(?:\n|$))?

    (?:^new[ ]file[ ]mode[ ](?P<new_file_mode>.+)(?:\n|$))?

    (?:^deleted[ ]file[ ]mode[ ](?P<deleted_file_mode>.+)(?:\n|$))?