def as_html(table_class='code-difftable', line_class='line',

            old_lineno_class='lineno old', new_lineno_class='lineno new',

            no_lineno_class='lineno',

            code_class='code', parsed_lines=None):

    """

    Return given diff as html table with customized css classes

    """

    _html_empty = True

    _html = []

    _html.append('''<table class="%(table_class)s">\n''' % {

        'table_class': table_class

    })

    for file_info in parsed_lines:

        count_no_lineno = 0  # counter to allow comments on lines without new/old line numbers

        for chunk in file_info['chunks']:

            _html_empty = False

            for change in chunk:

                _html.append('''<tr class="%(lc)s %(action)s">\n''' % {

                    'lc': line_class,

                    'action': change['action']

                })

                if change['old_lineno'] or change['new_lineno']:

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

                    # OLD LINE NUMBER

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

                    anchor_old = "%(filename)s_o%(oldline_no)s" % {

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

                        'oldline_no': change['old_lineno']

                    }

                    anchor_old_id = ''

                    if change['old_lineno']:

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

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

                        'a_id': anchor_old_id,

                        'olc': old_lineno_class,

                    })

                    _html.append('''<a href="%(url)s" data-pseudo-content="%(label)s"></a>''' % {

                        'label': change['old_lineno'],

                        'url': '#%s' % anchor_old,

                    })

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

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

                    # NEW LINE NUMBER

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

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

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

                        'newline_no': change['new_lineno']

                    }

                    anchor_new_id = ''

                    if change['new_lineno']:

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

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

                        'a_id': anchor_new_id,

                        'nlc': new_lineno_class

                    })

                    _html.append('''<a href="%(url)s" data-pseudo-content="%(label)s"></a>''' % {

                        'label': change['new_lineno'],

                        'url': '#%s' % anchor_new,

                    })

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

                else:

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

                    # NO LINE NUMBER

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

                    anchor = "%(filename)s_%(count_no_lineno)s" % {

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

                        'count_no_lineno': count_no_lineno,

                    }

                    count_no_lineno += 1

                    _html.append('''\t<td id="%(anchor)s" class="%(olc)s" colspan="2">''' % {

                        'anchor': anchor,

                        'olc': no_lineno_class,

                    })

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

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

                # CODE

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

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

                    'cc': code_class,

                })

                _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

    return '''\

              <table class="code-difftable">

                <tr class="line">

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

                <td class="code"><pre>%s</pre></td>

                </tr>

              </table>''' % html

def wrapped_diff(filenode_old, filenode_new, diff_limit=None,

                ignore_whitespace=True, line_context=3):

    """

    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)

        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(webutils.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:

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

        return b''

NEW_FILENODE = 1

DEL_FILENODE = 2