"""

    Git repository backend.

    """

    DEFAULT_BRANCH_NAME = 'master'

    scm = 'git'

    def __init__(self, repo_path, create=False, src_url=None,

                 update_after_clone=False, bare=False):

        self.path = abspath(repo_path)

        repo = self._get_repo(create, src_url, update_after_clone, bare)

        self.bare = repo.bare

    @property

    def _config_files(self):

        return [

            self.bare and abspath(self.path, 'config')

                      or abspath(self.path, '.git', 'config'),

             abspath(get_user_home(), '.gitconfig'),

         ]

    @property

    def _repo(self):

        return Repo(self.path)

    @property

    def head(self):

        try:

            return self._repo.head()

        except KeyError:

            return None

    @property

    def _empty(self):

        """

        Checks if repository is empty ie. without any changesets

        """

        try:

            self.revisions[0]

        except (KeyError, IndexError):

            return True

        return False

    @LazyProperty

    def revisions(self):

        """

        Returns list of revisions' ids, in ascending order.  Being lazy

        attribute allows external tools to inject shas from cache.

        """

        return self._get_all_revisions()

    @classmethod

    def _run_git_command(cls, cmd, **opts):

        """

        Runs given ``cmd`` as git command and returns tuple

        (stdout, stderr).

        :param cmd: git command to be executed

        :param opts: env options to pass into Subprocess command

        """

        if '_bare' in opts:

            _copts = []

            del opts['_bare']

        else:

            _copts = ['-c', 'core.quotepath=false', ]

        safe_call = False

        if '_safe' in opts:

            #no exc on failure

            del opts['_safe']

            safe_call = True

        _str_cmd = False

        if isinstance(cmd, basestring):

            cmd = [cmd]

            _str_cmd = True

        gitenv = os.environ

        # need to clean fix GIT_DIR !

        if 'GIT_DIR' in gitenv:

            del gitenv['GIT_DIR']

        gitenv['GIT_CONFIG_NOGLOBAL'] = '1'

        _git_path = settings.GIT_EXECUTABLE_PATH

        cmd = [_git_path] + _copts + cmd

        if _str_cmd:

            cmd = ' '.join(cmd)

        try:

            _opts = dict(

                env=gitenv,

                shell=True,

            )

            _opts.update(opts)

            p = subprocessio.SubprocessIOChunker(cmd, **_opts)

        except (EnvironmentError, OSError), err:

            tb_err = ("Couldn't run git command (%s).\n"

                      "Original error was:%s\n" % (cmd, err))

            log.error(tb_err)

            if safe_call:

                return '', err

            else:

                raise RepositoryError(tb_err)

        return ''.join(p.output), ''.join(p.error)

    def run_git_command(self, cmd):

        opts = {}

        if os.path.isdir(self.path):

            opts['cwd'] = self.path

        return self._run_git_command(cmd, **opts)

    @classmethod

    def _check_url(cls, url):

        """

        Functon will check given url and try to verify if it's a valid

        link. Sometimes it may happened that mercurial will issue basic

        auth request that can cause whole API to hang when used from python

        or other external calls.

        On failures it'll raise urllib2.HTTPError

        """

        # check first if it's not an local url

        if os.path.isdir(url) or url.startswith('file:'):

            return True

        if('+' in url[:url.find('://')]):

            url = url[url.find('+') + 1:]

        handlers = []

        test_uri, authinfo = hg_url(url).authinfo()

        if not test_uri.endswith('info/refs'):

            test_uri = test_uri.rstrip('/') + '/info/refs'

        if authinfo:

            #create a password manager

            passmgr = urllib2.HTTPPasswordMgrWithDefaultRealm()

            passmgr.add_password(*authinfo)

            handlers.extend((httpbasicauthhandler(passmgr),

                             httpdigestauthhandler(passmgr)))

        o = urllib2.build_opener(*handlers)

        o.addheaders = [('User-Agent', 'git/1.7.8.0')]  # fake some git

        q = {"service": 'git-upload-pack'}

        qs = '?%s' % urllib.urlencode(q)

        cu = "%s%s" % (test_uri, qs)

        req = urllib2.Request(cu, None, {})

        try:

            resp = o.open(req)

            return resp.code == 200

        except Exception, e:

            # means it cannot be cloned

            raise urllib2.URLError("[%s] %s" % (url, e))

    def _get_repo(self, create, src_url=None, update_after_clone=False,

                  bare=False):

        if create and os.path.exists(self.path):

            raise RepositoryError("Location already exist")

        if src_url and not create:

            raise RepositoryError("Create should be set to True if src_url is "

                                  "given (clone operation creates repository)")

        try:

            if create and src_url:

                GitRepository._check_url(src_url)

                self.clone(src_url, update_after_clone, bare)

                return Repo(self.path)

            elif create:

                os.mkdir(self.path)

                if bare:

                    return Repo.init_bare(self.path)

                else:

                    return Repo.init(self.path)

            else:

                return self._repo

        except (NotGitRepository, OSError), err:

            raise RepositoryError(err)

    def _get_all_revisions(self):

        # we must check if this repo is not empty, since later command

        # fails if it is. And it's cheaper to ask than throw the subprocess

        # errors

        try:

            self._repo.head()

        except KeyError:

            return []

        rev_filter = _git_path = settings.GIT_REV_FILTER

        cmd = 'rev-list %s --reverse --date-order' % (rev_filter)

        try:

            so, se = self.run_git_command(cmd)

        except RepositoryError:

            # Can be raised for empty repositories

            return []

        return so.splitlines()

    def _get_all_revisions2(self):

        #alternate implementation using dulwich

        includes = [x[1][0] for x in self._parsed_refs.iteritems()

                    if x[1][1] != 'T']

        return [c.commit.id for c in self._repo.get_walker(include=includes)]

    def _get_revision(self, revision):

        """

        For git backend we always return integer here. This way we ensure

        that changset's revision attribute would become integer.

        """

        is_null = lambda o: len(o) == revision.count('0')

        if self._empty:

            raise EmptyRepositoryError("There are no changesets yet")

        if revision in (None, '', 'tip', 'HEAD', 'head', -1):

            return self.revisions[-1]

        is_bstr = isinstance(revision, (str, unicode))

        if ((is_bstr and revision.isdigit() and len(revision) < 12)

            or isinstance(revision, int) or is_null(revision)):

            try:

                revision = self.revisions[int(revision)]

            except Exception:

                raise ChangesetDoesNotExistError("Revision %s does not exist "

                    "for this repository" % (revision))

        elif is_bstr:

            # get by branch/tag name

            _ref_revision = self._parsed_refs.get(revision)

            if _ref_revision:  # and _ref_revision[1] in ['H', 'RH', 'T']:

                return _ref_revision[0]

            _tags_shas = self.tags.values()

            # maybe it's a tag ? we don't have them in self.revisions

            if revision in _tags_shas:

                return _tags_shas[_tags_shas.index(revision)]

            elif not SHA_PATTERN.match(revision) or revision not in self.revisions:

                raise ChangesetDoesNotExistError("Revision %s does not exist "

                    "for this repository" % (revision))

        # Ensure we return full id

        if not SHA_PATTERN.match(str(revision)):

            raise ChangesetDoesNotExistError("Given revision %s not recognized"

                % revision)

        return revision

    def _get_archives(self, archive_name='tip'):

        for i in [('zip', '.zip'), ('gz', '.tar.gz'), ('bz2', '.tar.bz2')]:

                yield {"type": i[0], "extension": i[1], "node": archive_name}

    def _get_url(self, url):

        """

        Returns normalized url. If schema is not given, would fall to

        filesystem (``file:///``) schema.

        """

        url = str(url)

        if url != 'default' and not '://' in url:

            url = ':///'.join(('file', url))

        return url

    def get_hook_location(self):

        """

        returns absolute path to location where hooks are stored

        """

        loc = os.path.join(self.path, 'hooks')

        if not self.bare:

            loc = os.path.join(self.path, '.git', 'hooks')

        return loc

    @LazyProperty

    def name(self):

        return os.path.basename(self.path)

    @LazyProperty

    def last_change(self):

        """

        Returns last change made on this repository as datetime object

        """

        return date_fromtimestamp(self._get_mtime(), makedate()[1])

    def _get_mtime(self):

        try:

            return time.mktime(self.get_changeset().date.timetuple())

        except RepositoryError:

            idx_loc = '' if self.bare else '.git'

            # fallback to filesystem

            in_path = os.path.join(self.path, idx_loc, "index")

            he_path = os.path.join(self.path, idx_loc, "HEAD")

            if os.path.exists(in_path):

                return os.stat(in_path).st_mtime

            else:

                return os.stat(he_path).st_mtime

    @LazyProperty

    def description(self):

        idx_loc = '' if self.bare else '.git'

        undefined_description = u'unknown'

        description_path = os.path.join(self.path, idx_loc, 'description')

        if os.path.isfile(description_path):

            return safe_unicode(open(description_path).read())

        else:

            return undefined_description

    @LazyProperty

    def contact(self):

        undefined_contact = u'Unknown'

        return undefined_contact

    @property

    def branches(self):

        if not self.revisions:

            return {}

        sortkey = lambda ctx: ctx[0]

        _branches = [(x[0], x[1][0])

                     for x in self._parsed_refs.iteritems() if x[1][1] == 'H']

        return OrderedDict(sorted(_branches, key=sortkey, reverse=False))

    @LazyProperty

    def closed_branches(self):

        return {}

    @LazyProperty

    def tags(self):

        return self._get_tags()

    def _get_tags(self):

        if not self.revisions:

            return {}

        sortkey = lambda ctx: ctx[0]

        _tags = [(x[0], x[1][0])

                 for x in self._parsed_refs.iteritems() if x[1][1] == 'T']

        return OrderedDict(sorted(_tags, key=sortkey, reverse=True))

    def tag(self, name, user, revision=None, message=None, date=None,

            **kwargs):

        """

        Creates and returns a tag for the given ``revision``.

        :param name: name for new tag

        :param user: full username, i.e.: "Joe Doe <joe.doe@example.com>"

        :param revision: changeset id for which new tag would be created

        :param message: message of the tag's commit

        :param date: date of tag's commit

        :raises TagAlreadyExistError: if tag with same name already exists

        """

        if name in self.tags:

            raise TagAlreadyExistError("Tag %s already exists" % name)

        changeset = self.get_changeset(revision)

        message = message or "Added tag %s for commit %s" % (name,

            changeset.raw_id)

        self._repo.refs["refs/tags/%s" % name] = changeset._commit.id

        self._parsed_refs = self._get_parsed_refs()

        self.tags = self._get_tags()

        return changeset

    def remove_tag(self, name, user, message=None, date=None):

        """

        Removes tag with the given ``name``.

        :param name: name of the tag to be removed

        :param user: full username, i.e.: "Joe Doe <joe.doe@example.com>"

        :param message: message of the tag's removal commit

        :param date: date of tag's removal commit

        :raises TagDoesNotExistError: if tag with given name does not exists

        """

        if name not in self.tags:

            raise TagDoesNotExistError("Tag %s does not exist" % name)

        tagpath = posixpath.join(self._repo.refs.path, 'refs', 'tags', name)

        try:

            os.remove(tagpath)

            self._parsed_refs = self._get_parsed_refs()

            self.tags = self._get_tags()

        except OSError, e:

            raise RepositoryError(e.strerror)

    @LazyProperty

    def _parsed_refs(self):

        return self._get_parsed_refs()

    def _get_parsed_refs(self):

        # cache the property

        _repo = self._repo

        refs = _repo.get_refs()

        keys = [('refs/heads/', 'H'),

                ('refs/remotes/origin/', 'RH'),

                ('refs/tags/', 'T')]

        _refs = {}

        for ref, sha in refs.iteritems():

            for k, type_ in keys:

                if ref.startswith(k):

                    _key = ref[len(k):]

                    if type_ == 'T':

                        obj = _repo.get_object(sha)

                        if isinstance(obj, Tag):

                            sha = _repo.get_object(sha).object[1]

                    _refs[_key] = [sha, type_]

                    break

        return _refs

    def _heads(self, reverse=False):

        refs = self._repo.get_refs()

        heads = {}

        for key, val in refs.items():

            for ref_key in ['refs/heads/', 'refs/remotes/origin/']:

                if key.startswith(ref_key):

                    n = key[len(ref_key):]

                    if n not in ['HEAD']:

                        heads[n] = val

        return heads if reverse else dict((y, x) for x, y in heads.iteritems())

    def get_changeset(self, revision=None):

        """

        Returns ``GitChangeset`` object representing commit from git repository

        at the given revision or head (most recent commit) if None given.

        """

        if isinstance(revision, GitChangeset):

            return revision

        revision = self._get_revision(revision)

        changeset = GitChangeset(repository=self, revision=revision)

        return changeset

    def get_changesets(self, start=None, end=None, start_date=None,

           end_date=None, branch_name=None, reverse=False):

        """

        Returns iterator of ``GitChangeset`` objects from start to end (both

        are inclusive), in ascending date order (unless ``reverse`` is set).

        :param start: changeset ID, as str; first returned changeset

        :param end: changeset ID, as str; last returned changeset

        :param start_date: if specified, changesets with commit date less than

          ``start_date`` would be filtered out from returned set

        :param end_date: if specified, changesets with commit date greater than

          ``end_date`` would be filtered out from returned set

        :param branch_name: if specified, changesets not reachable from given

          branch would be filtered out from returned set

        :param reverse: if ``True``, returned generator would be reversed

          (meaning that returned changesets would have descending date order)

        :raise BranchDoesNotExistError: If given ``branch_name`` does not

            exist.

        :raise ChangesetDoesNotExistError: If changeset for given ``start`` or

          ``end`` could not be found.

        """

        if branch_name and branch_name not in self.branches:

            raise BranchDoesNotExistError("Branch '%s' not found" \

                                          % branch_name)

        # actually we should check now if it's not an empty repo to not spaw

        # subprocess commands

        if self._empty:

            raise EmptyRepositoryError("There are no changesets yet")

        # %H at format means (full) commit hash, initial hashes are retrieved

        # in ascending date order

        cmd_template = 'log --date-order --reverse --pretty=format:"%H"'

        cmd_params = {}

        if start_date:

            cmd_template += ' --since "$since"'

            cmd_params['since'] = start_date.strftime('%m/%d/%y %H:%M:%S')

        if end_date:

            cmd_template += ' --until "$until"'

            cmd_params['until'] = end_date.strftime('%m/%d/%y %H:%M:%S')

        if branch_name:

            cmd_template += ' $branch_name'

            cmd_params['branch_name'] = branch_name

        else:

            rev_filter = _git_path = settings.GIT_REV_FILTER

            cmd_template += ' %s' % (rev_filter)

        cmd = string.Template(cmd_template).safe_substitute(**cmd_params)

        revs = self.run_git_command(cmd)[0].splitlines()

        start_pos = 0

        end_pos = len(revs)

        if start:

            _start = self._get_revision(start)

            try:

                start_pos = revs.index(_start)

            except ValueError:

                pass

        if end is not None:

            _end = self._get_revision(end)

            try:

                end_pos = revs.index(_end)

            except ValueError:

                pass

        if None not in [start, end] and start_pos > end_pos:

            raise RepositoryError('start cannot be after end')

        if end_pos is not None:

            end_pos += 1

        revs = revs[start_pos:end_pos]

        if reverse:

            revs = reversed(revs)

        return CollectionGenerator(self, revs)

    def get_diff(self, rev1, rev2, path=None, ignore_whitespace=False,

                 context=3):

        """

        Returns (git like) *diff*, as plain text. Shows changes introduced by

        ``rev2`` since ``rev1``.

        :param rev1: Entry point from which diff is shown. Can be

          ``self.EMPTY_CHANGESET`` - in this case, patch showing all

          the changes since empty state of the repository until ``rev2``

        :param rev2: Until which revision changes should be shown.

        :param ignore_whitespace: If set to ``True``, would not show whitespace

          changes. Defaults to ``False``.

        :param context: How many lines before/after changed lines should be

          shown. Defaults to ``3``.

        """

        flags = ['-U%s' % context, '--full-index', '--binary', '-p', '-M', '--abbrev=40']

        if ignore_whitespace:

            flags.append('-w')

        if hasattr(rev1, 'raw_id'):

            rev1 = getattr(rev1, 'raw_id')

        if hasattr(rev2, 'raw_id'):

            rev2 = getattr(rev2, 'raw_id')

        if rev1 == self.EMPTY_CHANGESET:

            rev2 = self.get_changeset(rev2).raw_id

            cmd = ' '.join(['show'] + flags + [rev2])

        else:

            rev1 = self.get_changeset(rev1).raw_id

            rev2 = self.get_changeset(rev2).raw_id

            cmd = ' '.join(['diff'] + flags + [rev1, rev2])

        if path:

            cmd += ' -- "%s"' % path

        stdout, stderr = self.run_git_command(cmd)

        # If we used 'show' command, strip first few lines (until actual diff

        # starts)

        if rev1 == self.EMPTY_CHANGESET:

            lines = stdout.splitlines()

            x = 0

            for line in lines:

                if line.startswith('diff'):

                    break

                x += 1

            # Append new line just like 'diff' command do

            stdout = '\n'.join(lines[x:]) + '\n'

        return stdout

    @LazyProperty

    def in_memory_changeset(self):

        """

        Returns ``GitInMemoryChangeset`` object for this repository.

        """

        return GitInMemoryChangeset(self)

    def clone(self, url, update_after_clone=True, bare=False):

        """

        Tries to clone changes from external location.

        :param update_after_clone: If set to ``False``, git won't checkout

          working directory

        :param bare: If set to ``True``, repository would be cloned into

          *bare* git repository (no working directory at all).

        """

        url = self._get_url(url)

        cmd = ['clone']

        if bare:

            cmd.append('--bare')

        elif not update_after_clone:

            cmd.append('--no-checkout')

        cmd += ['--', '"%s"' % url, '"%s"' % self.path]

        cmd = ' '.join(cmd)

        # If error occurs run_git_command raises RepositoryError already

        self.run_git_command(cmd)

    def pull(self, url):

        """

        Tries to pull changes from external location.

        """

        url = self._get_url(url)

        cmd = ['pull', "--ff-only", url]

        cmd = ' '.join(cmd)

        # If error occurs run_git_command raises RepositoryError already

        self.run_git_command(cmd)

    def fetch(self, url):

        """

        Tries to pull changes from external location.

        """

        url = self._get_url(url)

        so, se = self.run_git_command('ls-remote -h %s' % url)

        refs = []

        for line in (x for x in so.splitlines()):

            sha, ref = line.split('\t')

            refs.append(ref)

        refs = ' '.join(('+%s:%s' % (r, r) for r in refs))

        cmd = '''fetch %s -- %s''' % (url, refs)

        self.run_git_command(cmd)

    @LazyProperty

    def workdir(self):

        """

        Returns ``Workdir`` instance for this repository.

        """

        return GitWorkdir(self)

    def get_config_value(self, section, name, config_file=None):

        """

        Returns configuration value for a given [``section``] and ``name``.

        :param section: Section we want to retrieve value from

        :param name: Name of configuration we want to retrieve

        :param config_file: A path to file which should be used to retrieve

          configuration from (might also be a list of file paths)

        """

        if config_file is None:

            config_file = []

        elif isinstance(config_file, basestring):

            config_file = [config_file]

        def gen_configs():

            for path in config_file + self._config_files:

                try:

                    yield ConfigFile.from_path(path)

                except (IOError, OSError, ValueError):

                    continue

        for config in gen_configs():

            try:

                return config.get(section, name)

            except KeyError:

                continue

        return None

    def get_user_name(self, config_file=None):

        """

        Returns user's name from global configuration file.

        :param config_file: A path to file which should be used to retrieve

          configuration from (might also be a list of file paths)

        """

        return self.get_config_value('user', 'name', config_file)

    def get_user_email(self, config_file=None):

        """

        Returns user's email from global configuration file.

        :param config_file: A path to file which should be used to retrieve

          configuration from (might also be a list of file paths)

        """

        return self.get_config_value('user', 'email', config_file)