# -*- coding: utf-8 -*-

#

# Copyright (C) 2004-2009 Edgewall Software

# Copyright (C) 2004-2006 Christopher Lenz <cmlenz@gmx.de>

# All rights reserved.

#

# This software is licensed as described in the file COPYING, which

# you should have received as part of this distribution. The terms

# are also available at http://trac.edgewall.org/wiki/TracLicense.

#

# This software consists of voluntary contributions made by many

# individuals. For the exact contribution history, see the revision

# history and logs, available at http://trac.edgewall.org/log/.

#

# Author: Christopher Lenz <cmlenz@gmx.de>

from trac.util.html import escape, Markup

from trac.util.text import expandtabs

from difflib import SequenceMatcher

import re

__all__ = ['get_diff_options', 'hdf_diff', 'diff_blocks', 'unified_diff']

def _get_change_extent(str1, str2):

    """

    Determines the extent of differences between two strings. Returns a tuple

    containing the offset at which the changes start, and the negative offset

    at which the changes end. If the two strings have neither a common prefix

    nor a common suffix, (0, 0) is returned.

    """

    start = 0

    limit = min(len(str1), len(str2))

    while start < limit and str1[start] == str2[start]:

        start += 1

    end = -1

    limit = limit - start

    while -end <= limit and str1[end] == str2[end]:

        end -= 1

    return (start, end + 1)

def _get_opcodes(fromlines, tolines, ignore_blank_lines=False,

                 ignore_case=False, ignore_space_changes=False):

    """

    Generator built on top of SequenceMatcher.get_opcodes().

    This function detects line changes that should be ignored and emits them

    as tagged as 'equal', possibly joined with the preceding and/or following

    'equal' block.

    """

    def is_ignorable(tag, fromlines, tolines):

        if tag == 'delete' and ignore_blank_lines:

            if ''.join(fromlines) == '':

                return True

        elif tag == 'insert' and ignore_blank_lines:

            if ''.join(tolines) == '':

                return True

        elif tag == 'replace' and (ignore_case or ignore_space_changes):

            if len(fromlines) != len(tolines):

                return False

            def f(str):

                if ignore_case:

                    str = str.lower()

                if ignore_space_changes:

                    str = ' '.join(str.split())

                return str

            for i in range(len(fromlines)):

                if f(fromlines[i]) != f(tolines[i]):

                    return False

            return True

    matcher = SequenceMatcher(None, fromlines, tolines)

    previous = None

    for tag, i1, i2, j1, j2 in matcher.get_opcodes():

        if tag == 'equal':

            if previous:

                previous = (tag, previous[1], i2, previous[3], j2)

            else:

                previous = (tag, i1, i2, j1, j2)

        else:

            if is_ignorable(tag, fromlines[i1:i2], tolines[j1:j2]):

                if previous:

                    previous = 'equal', previous[1], i2, previous[3], j2

                else:

                    previous = 'equal', i1, i2, j1, j2

                continue

            if previous:

                yield previous

            yield tag, i1, i2, j1, j2

            previous = None

    if previous:

        yield previous

def _group_opcodes(opcodes, n=3):

    """

    Python 2.2 doesn't have SequenceMatcher.get_grouped_opcodes(), so let's

    provide equivalent here. The opcodes parameter can be any iterable or

    sequence.

    This function can also be used to generate full-context diffs by passing 

    None for the parameter n.

    """

    # Full context produces all the opcodes

    if n is None:

        yield list(opcodes)

        return

    # Otherwise we leave at most n lines with the tag 'equal' before and after

    # every change

    nn = n + n

    group = []

    for idx, (tag, i1, i2, j1, j2) in enumerate(opcodes):

        if idx == 0 and tag == 'equal': # Fixup leading unchanged block

            i1, j1 = max(i1, i2 - n), max(j1, j2 - n)

        elif tag == 'equal' and i2 - i1 > nn:

            group.append((tag, i1, min(i2, i1 + n), j1, min(j2, j1 + n)))

            yield group

            group = []

            i1, j1 = max(i1, i2 - n), max(j1, j2 - n)

        group.append((tag, i1, i2, j1 ,j2))

    if group and not (len(group) == 1 and group[0][0] == 'equal'):

        if group[-1][0] == 'equal': # Fixup trailing unchanged block

            tag, i1, i2, j1, j2 = group[-1]

            group[-1] = tag, i1, min(i2, i1 + n), j1, min(j2, j1 + n)

        yield group

def hdf_diff(*args, **kwargs):

    return diff_blocks(*args, **kwargs)

def diff_blocks(fromlines, tolines, context=None, tabwidth=8,

                ignore_blank_lines=0, ignore_case=0, ignore_space_changes=0):

    """Return an array that is adequate for adding to the data dictionary

    See the diff_div.html template.

    """

    type_map = {'replace': 'mod', 'delete': 'rem', 'insert': 'add',

                'equal': 'unmod'}

    space_re = re.compile(' ( +)|^ ')

    def htmlify(match):

        div, mod = divmod(len(match.group(0)), 2)

        return div * '  ' + mod * ' '

    def markup_intraline_changes(opcodes):

        for tag, i1, i2, j1, j2 in opcodes:

            if tag == 'replace' and i2 - i1 == j2 - j1:

                for i in range(i2 - i1):

                    fromline, toline = fromlines[i1 + i], tolines[j1 + i]

                    (start, end) = _get_change_extent(fromline, toline)

                    if start != 0 or end != 0:

                        last = end+len(fromline)

                        fromlines[i1+i] = fromline[:start] + '\0' + fromline[start:last] + \

                                       '\1' + fromline[last:]

                        last = end+len(toline)

                        tolines[j1+i] = toline[:start] + '\0' + toline[start:last] + \

                                     '\1' + toline[last:]

            yield tag, i1, i2, j1, j2

    changes = []

    opcodes = _get_opcodes(fromlines, tolines, ignore_blank_lines, ignore_case,

                           ignore_space_changes)

    for group in _group_opcodes(opcodes, context):

        blocks = []

        last_tag = None

        for tag, i1, i2, j1, j2 in markup_intraline_changes(group):

            if tag != last_tag:

                blocks.append({'type': type_map[tag],

                               'base': {'offset': i1, 'lines': []},

                               'changed': {'offset': j1, 'lines': []}})

            if tag == 'equal':

                for line in fromlines[i1:i2]:

                    line = line.expandtabs(tabwidth)

                    line = space_re.sub(htmlify, escape(line, quotes=False))

                    blocks[-1]['base']['lines'].append(Markup(unicode(line)))

                for line in tolines[j1:j2]:

                    line = line.expandtabs(tabwidth)

                    line = space_re.sub(htmlify, escape(line, quotes=False))

                    blocks[-1]['changed']['lines'].append(Markup(unicode(line)))

            else:

                if tag in ('replace', 'delete'):

                    for line in fromlines[i1:i2]:

                        line = expandtabs(line, tabwidth, '\0\1')

                        line = escape(line, quotes=False)

                        line = '<del>'.join([space_re.sub(htmlify, seg)

                                             for seg in line.split('\0')])

                        line = line.replace('\1', '</del>')

                        blocks[-1]['base']['lines'].append(

                            Markup(unicode(line)))

                if tag in ('replace', 'insert'):

                    for line in tolines[j1:j2]:

                        line = expandtabs(line, tabwidth, '\0\1')

                        line = escape(line, quotes=False)

                        line = '<ins>'.join([space_re.sub(htmlify, seg)

                                             for seg in line.split('\0')])

                        line = line.replace('\1', '</ins>')

                        blocks[-1]['changed']['lines'].append(

                            Markup(unicode(line)))

        changes.append(blocks)

    return changes

def unified_diff(fromlines, tolines, context=None, ignore_blank_lines=0,

                 ignore_case=0, ignore_space_changes=0):

    opcodes = _get_opcodes(fromlines, tolines, ignore_blank_lines, ignore_case,

                           ignore_space_changes)

    for group in _group_opcodes(opcodes, context):

        i1, i2, j1, j2 = group[0][1], group[-1][2], group[0][3], group[-1][4]

        if i1 == 0 and i2 == 0:

            i1, i2 = -1, -1 # support for 'A'dd changes

        yield '@@ -%d,%d +%d,%d @@' % (i1 + 1, i2 - i1, j1 + 1, j2 - j1)

        for tag, i1, i2, j1, j2 in group:

            if tag == 'equal':

                for line in fromlines[i1:i2]:

                    yield ' ' + line

            else:

                if tag in ('replace', 'delete'):

                    for line in fromlines[i1:i2]:

                        yield '-' + line

                if tag in ('replace', 'insert'):

                    for line in tolines[j1:j2]:

                        yield '+' + line

def get_diff_options(req):

    options_data = {}

    data = {'options': options_data}

    def get_bool_option(name, default=0):

        pref = int(req.session.get('diff_' + name, default))

        arg = int(req.args.has_key(name))

        if req.args.has_key('update') and arg != pref:

            req.session['diff_' + name] = arg

        else:

            arg = pref

        return arg

    pref = req.session.get('diff_style', 'inline')

    style = req.args.get('style', pref)

    if req.args.has_key('update') and style != pref:

        req.session['diff_style'] = style

    data['style'] = style

    pref = int(req.session.get('diff_contextlines', 2))

    try:

        arg = int(req.args.get('contextlines', pref))

    except ValueError:

        arg = -1

    if req.args.has_key('update') and arg != pref:

        req.session['diff_contextlines'] = arg

    options = ['-U%d' % arg]

    options_data['contextlines'] = arg

    arg = get_bool_option('ignoreblanklines')

    if arg:

        options.append('-B')

    options_data['ignoreblanklines'] = arg

    arg = get_bool_option('ignorecase')

    if arg:

        options.append('-i')

    options_data['ignorecase'] = arg

    arg = get_bool_option('ignorewhitespace')

    if arg:

        options.append('-b')

    options_data['ignorewhitespace'] = arg

    return (style, options, data)