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

"""

    rhodecode.controllers.summary

    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

    Summary controller for Rhodecode

    :created_on: Apr 18, 2010

    :author: marcink

    :copyright: (C) 2010-2012 Marcin Kuzminski <marcin@python-works.com>

    :license: GPLv3, see COPYING for more details.

"""

# This program is free software: you can redistribute it and/or modify

# it under the terms of the GNU General Public License as published by

# the Free Software Foundation, either version 3 of the License, or

# (at your option) any later version.

#

# This program is distributed in the hope that it will be useful,

# but WITHOUT ANY WARRANTY; without even the implied warranty of

# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

# GNU General Public License for more details.

#

# You should have received a copy of the GNU General Public License

# along with this program.  If not, see <http://www.gnu.org/licenses/>.

import traceback

import calendar

import logging

import urllib

from time import mktime

from datetime import timedelta, date

from urlparse import urlparse

from pylons import tmpl_context as c, request, url, config

from pylons.i18n.translation import _

from webob.exc import HTTPBadRequest

from beaker.cache import cache_region, region_invalidate

from rhodecode.lib.compat import product

from rhodecode.lib.vcs.exceptions import ChangesetError, EmptyRepositoryError, \

    NodeDoesNotExistError

from rhodecode.config.conf import ALL_READMES, ALL_EXTS, LANGUAGES_EXTENSIONS_MAP

from rhodecode.model.db import Statistics, CacheInvalidation

from rhodecode.lib.utils import jsonify

from rhodecode.lib.utils2 import safe_unicode

from rhodecode.lib.auth import LoginRequired, HasRepoPermissionAnyDecorator,\

    NotAnonymous

from rhodecode.lib.base import BaseRepoController, render

from rhodecode.lib.vcs.backends.base import EmptyChangeset

from rhodecode.lib.markup_renderer import MarkupRenderer

from rhodecode.lib.celerylib import run_task

from rhodecode.lib.celerylib.tasks import get_commits_stats

from rhodecode.lib.helpers import RepoPage

from rhodecode.lib.compat import json, OrderedDict

from rhodecode.lib.vcs.nodes import FileNode

log = logging.getLogger(__name__)

README_FILES = [''.join([x[0][0], x[1][0]]) for x in

                    sorted(list(product(ALL_READMES, ALL_EXTS)),

                           key=lambda y:y[0][1] + y[1][1])]

class SummaryController(BaseRepoController):

    @LoginRequired()

    @HasRepoPermissionAnyDecorator('repository.read', 'repository.write',

                                   'repository.admin')

    def __before__(self):

        super(SummaryController, self).__before__()

    def index(self, repo_name):

        c.dbrepo = dbrepo = c.rhodecode_db_repo

        def url_generator(**kw):

            return url('shortlog_home', repo_name=repo_name, size=10, **kw)

        c.repo_changesets = RepoPage(c.rhodecode_repo, page=1,

                                     items_per_page=10, url=url_generator)

        page_revisions = [x.raw_id for x in list(c.repo_changesets)]

        c.statuses = c.rhodecode_db_repo.statuses(page_revisions)

        if self.rhodecode_user.username == 'default':

            # for default(anonymous) user we don't need to pass credentials

            username = ''

            password = ''

        else:

            username = str(self.rhodecode_user.username)

            password = '@'

        parsed_url = urlparse(url.current(qualified=True))

        default_clone_uri = '{scheme}://{user}{pass}{netloc}{path}'

        uri_tmpl = config.get('clone_uri', default_clone_uri)

        uri_tmpl = uri_tmpl.replace('{', '%(').replace('}', ')s')

        decoded_path = safe_unicode(urllib.unquote(parsed_url.path))

        uri_dict = {

           'user': urllib.quote(username),

           'pass': password,

           'scheme': parsed_url.scheme,

           'netloc': parsed_url.netloc,

           'path': decoded_path

        }

        uri = uri_tmpl % uri_dict

        # generate another clone url by id

        uri_dict.update(

         {'path': decoded_path.replace(repo_name, '_%s' % c.dbrepo.repo_id)}

        )

        uri_id = uri_tmpl % uri_dict

        c.clone_repo_url = uri

        c.clone_repo_url_id = uri_id

        c.repo_tags = OrderedDict()

        for name, hash_ in c.rhodecode_repo.tags.items()[:10]:

            try:

                c.repo_tags[name] = c.rhodecode_repo.get_changeset(hash_)

            except ChangesetError:

                c.repo_tags[name] = EmptyChangeset(hash_)

        c.repo_branches = OrderedDict()

        for name, hash_ in c.rhodecode_repo.branches.items()[:10]:

            try:

                c.repo_branches[name] = c.rhodecode_repo.get_changeset(hash_)

            except ChangesetError:

                c.repo_branches[name] = EmptyChangeset(hash_)

        td = date.today() + timedelta(days=1)

        td_1m = td - timedelta(days=calendar.mdays[td.month])

        td_1y = td - timedelta(days=365)

        ts_min_m = mktime(td_1m.timetuple())

        ts_min_y = mktime(td_1y.timetuple())

        ts_max_y = mktime(td.timetuple())

        if dbrepo.enable_statistics:

            c.show_stats = True

            c.no_data_msg = _('No data loaded yet')

            recurse_limit = 500  # don't recurse more than 500 times when parsing

            run_task(get_commits_stats, c.dbrepo.repo_name, ts_min_y,

                     ts_max_y, recurse_limit)

        else:

            c.show_stats = False

            c.no_data_msg = _('Statistics are disabled for this repository')

        c.ts_min = ts_min_m

        c.ts_max = ts_max_y

        stats = self.sa.query(Statistics)\

            .filter(Statistics.repository == dbrepo)\

            .scalar()

        c.stats_percentage = 0

        if stats and stats.languages:

            c.no_data = False is dbrepo.enable_statistics

            lang_stats_d = json.loads(stats.languages)

            c.commit_data = stats.commit_activity

            c.overview_data = stats.commit_activity_combined

            lang_stats = ((x, {"count": y,

                               "desc": LANGUAGES_EXTENSIONS_MAP.get(x)})

                          for x, y in lang_stats_d.items())

            c.trending_languages = json.dumps(

                sorted(lang_stats, reverse=True, key=lambda k: k[1])[:10]

            )

            last_rev = stats.stat_on_revision + 1

            c.repo_last_rev = c.rhodecode_repo.count()\

                    # unlock if we have push from user who locked

                    make_lock = False

                else:

                    # we're not the same user who locked, ban with 423 !

                    locked = True

            if action == 'pull':

                if repo.locked[0] and repo.locked[1]:

                    locked = True

                else:

                    log.debug('Setting lock on repo %s by %s' % (repo, user))

                    make_lock = True

        else:

            log.debug('Repository %s do not have locking enabled' % (repo))

        log.debug('FINAL locking values make_lock:%s,locked:%s,locked_by:%s'

                  % (make_lock, locked, locked_by))

        return make_lock, locked, locked_by

    def __call__(self, environ, start_response):

        start = time.time()

        try:

            return self._handle_request(environ, start_response)

        finally:

            log = logging.getLogger('rhodecode.' + self.__class__.__name__)

            log.debug('Request time: %.3fs' % (time.time() - start))

            meta.Session.remove()

class BaseController(WSGIController):

    def __before__(self):

        """

        __before__ is called before controller methods and after __call__

        """

        c.rhodecode_version = __version__

        c.rhodecode_instanceid = config.get('instance_id')

        c.rhodecode_name = config.get('rhodecode_title')

        c.use_gravatar = str2bool(config.get('use_gravatar'))

        c.ga_code = config.get('rhodecode_ga_code')

        # Visual options

        c.visual = AttributeDict({})

        rc_config = RhodeCodeSetting.get_app_settings()

        c.visual.show_public_icon = str2bool(rc_config.get('rhodecode_show_public_icon'))

        c.visual.show_private_icon = str2bool(rc_config.get('rhodecode_show_private_icon'))

        c.visual.stylify_metatags = str2bool(rc_config.get('rhodecode_stylify_metatags'))

        c.visual.lightweight_dashboard = str2bool(rc_config.get('rhodecode_lightweight_dashboard'))

        c.visual.lightweight_dashboard_items = safe_int(config.get('dashboard_items', 100))

        c.visual.repository_fields = str2bool(rc_config.get('rhodecode_repository_fields'))

        c.repo_name = get_repo_slug(request)

        c.backends = BACKENDS.keys()

        c.unread_notifications = NotificationModel()\

                        .get_unread_cnt_for_user(c.rhodecode_user.user_id)

        self.cut_off_limit = int(config.get('cut_off_limit'))

        self.sa = meta.Session

        self.scm_model = ScmModel(self.sa)

    def __call__(self, environ, start_response):

        """Invoke the Controller"""

        # WSGIController.__call__ dispatches to the Controller method

        # the request is routed to. This routing information is

        # available in environ['pylons.routes_dict']

        try:

            self.ip_addr = _get_ip_addr(environ)

            # make sure that we update permissions each time we call controller

            api_key = request.GET.get('api_key')

            cookie_store = CookieStoreWrapper(session.get('rhodecode_user'))

            user_id = cookie_store.get('user_id', None)

            username = get_container_username(environ, config)

            auth_user = AuthUser(user_id, api_key, username, self.ip_addr)

            request.user = auth_user

            self.rhodecode_user = c.rhodecode_user = auth_user

            if not self.rhodecode_user.is_authenticated and \

                       self.rhodecode_user.user_id is not None:

                self.rhodecode_user.set_authenticated(

                    cookie_store.get('is_authenticated')

                )

            log.info('IP: %s User: %s accessed %s' % (

               self.ip_addr, auth_user, safe_unicode(_get_access_path(environ)))

            )

            return WSGIController.__call__(self, environ, start_response)

        finally:

            meta.Session.remove()

class BaseRepoController(BaseController):

    """

    Base class for controllers responsible for loading all needed data for

    repository loaded items are

    c.rhodecode_repo: instance of scm repository

    c.rhodecode_db_repo: instance of db

    c.repository_followers: number of followers

    c.repository_forks: number of forks

    """

    def __before__(self):

        super(BaseRepoController, self).__before__()

        if c.repo_name:

            dbr = c.rhodecode_db_repo = Repository.get_by_repo_name(c.repo_name)

            c.rhodecode_repo = c.rhodecode_db_repo.scm_instance

            # update last change according to VCS data

            dbr.update_changeset_cache(dbr.get_changeset())

            if c.rhodecode_repo is None:

                log.error('%s this repository is present in database but it '

                          'cannot be created as an scm instance', c.repo_name)

                redirect(url('home'))

            # some globals counter for menu

            c.repository_followers = self.scm_model.get_followers(dbr)

            c.repository_forks = self.scm_model.get_forks(dbr)

            c.repository_pull_requests = self.scm_model.get_pull_requests(dbr)

    :param filenode:

    """

    color_dict = {}

    def gen_color(n=10000):

        """generator for getting n of evenly distributed colors using

        hsv color and golden ratio. It always return same order of colors

        :returns: RGB tuple

        """

        def hsv_to_rgb(h, s, v):

            if s == 0.0:

                return v, v, v

            i = int(h * 6.0)  # XXX assume int() truncates!

            f = (h * 6.0) - i

            p = v * (1.0 - s)

            q = v * (1.0 - s * f)

            t = v * (1.0 - s * (1.0 - f))

            i = i % 6

            if i == 0:

                return v, t, p

            if i == 1:

                return q, v, p

            if i == 2:

                return p, v, t

            if i == 3:

                return p, q, v

            if i == 4:

                return t, p, v

            if i == 5:

                return v, p, q

        golden_ratio = 0.618033988749895

        h = 0.22717784590367374

        for _ in xrange(n):

            h += golden_ratio

            h %= 1

            HSV_tuple = [h, 0.95, 0.95]

            RGB_tuple = hsv_to_rgb(*HSV_tuple)

            yield map(lambda x: str(int(x * 256)), RGB_tuple)

    cgenerator = gen_color()

    def get_color_string(cs):

        if cs in color_dict:

            col = color_dict[cs]

        else:

            col = color_dict[cs] = cgenerator.next()

        return "color: rgb(%s)! important;" % (', '.join(col))

    def url_func(repo_name):

        def _url_func(changeset):

            author = changeset.author

            date = changeset.date

            message = tooltip(changeset.message)

            tooltip_html = ("<div style='font-size:0.8em'><b>Author:</b>"

                            " %s<br/><b>Date:</b> %s</b><br/><b>Message:"

                            "</b> %s<br/></div>")

            tooltip_html = tooltip_html % (author, date, message)

            lnk_format = '%5s:%s' % ('r%s' % changeset.revision,

                                     short_id(changeset.raw_id))

            uri = link_to(

                    lnk_format,

                    url('changeset_home', repo_name=repo_name,

                        revision=changeset.raw_id),

                    style=get_color_string(changeset.raw_id),

                    class_='tooltip',

                    title=tooltip_html

                  )

            uri += '\n'

            return uri

        return _url_func

    return literal(annotate_highlight(filenode, url_func(repo_name), **kwargs))

def is_following_repo(repo_name, user_id):

    from rhodecode.model.scm import ScmModel

    return ScmModel().is_following_repo(repo_name, user_id)

flash = _Flash()

#==============================================================================

# SCM FILTERS available via h.

#==============================================================================

from rhodecode.lib.vcs.utils import author_name, author_email

from rhodecode.lib.utils2 import credentials_filter, age as _age

from rhodecode.model.db import User, ChangesetStatus

capitalize = lambda x: x.capitalize()

email = author_email

short_id = lambda x: x[:12]

hide_credentials = lambda x: ''.join(credentials_filter(x))

def fmt_date(date):

    if date:

        _fmt = _(u"%a, %d %b %Y %H:%M:%S").encode('utf8')

        return date.strftime(_fmt).decode('utf8')

    return ""

def is_git(repository):

    if hasattr(repository, 'alias'):

        _type = repository.alias

    elif hasattr(repository, 'repo_type'):

        _type = repository.repo_type

    else:

        _type = repository

    return _type == 'git'

def is_hg(repository):

    if hasattr(repository, 'alias'):

        _type = repository.alias

    elif hasattr(repository, 'repo_type'):

        _type = repository.repo_type

    else:

        _type = repository

    return _type == 'hg'

def email_or_none(author):

    # extract email from the commit string

    _email = email(author)

    if _email != '':

        # check it against RhodeCode database, and use the MAIN email for this

        # user

        user = User.get_by_email(_email, case_insensitive=True, cache=True)

        if user is not None:

            return user.email

        return _email

    # See if it contains a username we can get an email from

    user = User.get_by_username(author_name(author), case_insensitive=True,

                                cache=True)

    if user is not None:

        return user.email

    # No valid email, not a valid user in the system, none!

    return None

def person(author, show_attr="username_and_name"):

    # attr to return from fetched user

    person_getter = lambda usr: getattr(usr, show_attr)

    # Valid email in the attribute passed, see if they're in the system

    _email = email(author)

    if _email != '':

        user = User.get_by_email(_email, case_insensitive=True, cache=True)

        if user is not None:

            return person_getter(user)

        return _email

    # Maybe it's a username?

    _author = author_name(author)

    user = User.get_by_username(_author, case_insensitive=True,

                                cache=True)

    if user is not None:

        return person_getter(user)

    # Still nothing?  Just pass back the author name then

    return _author

def person_by_id(id_, show_attr="username_and_name"):

    # attr to return from fetched user

    person_getter = lambda usr: getattr(usr, show_attr)

    #maybe it's an ID ?

    if str(id_).isdigit() or isinstance(id_, int):

        id_ = int(id_)

        user = User.get(id_)

        if user is not None:

            return person_getter(user)

    return id_

def desc_stylize(value):

    """

    converts tags from value into html equivalent

    :param value:

            self.page = int(page)  # make it int() if we get it as a string

        except (ValueError, TypeError):

            self.page = 1

        self.items_per_page = items_per_page

        # Unless the user tells us how many items the collections has

        # we calculate that ourselves.

        if item_count is not None:

            self.item_count = item_count

        else:

            self.item_count = len(self.collection)

        # Compute the number of the first and last available page

        if self.item_count > 0:

            self.first_page = 1

            self.page_count = int(math.ceil(float(self.item_count) /

                                            self.items_per_page))

            self.last_page = self.first_page + self.page_count - 1

            # Make sure that the requested page number is the range of

            # valid pages

            if self.page > self.last_page:

                self.page = self.last_page

            elif self.page < self.first_page:

                self.page = self.first_page

            # Note: the number of items on this page can be less than

            #       items_per_page if the last page is not full

            self.first_item = max(0, (self.item_count) - (self.page *

                                                          items_per_page))

            self.last_item = ((self.item_count - 1) - items_per_page *

                              (self.page - 1))

            self.items = list(self.collection[self.first_item:self.last_item + 1])

            # Links to previous and next page

            if self.page > self.first_page:

                self.previous_page = self.page - 1

            else:

                self.previous_page = None

            if self.page < self.last_page:

                self.next_page = self.page + 1

            else:

                self.next_page = None

        # No items available

        else:

            self.first_page = None

            self.page_count = 0

            self.last_page = None

            self.first_item = None

            self.last_item = None

            self.previous_page = None

            self.next_page = None

            self.items = []

        # This is a subclass of the 'list' type. Initialise the list now.

        list.__init__(self, reversed(self.items))

def changed_tooltip(nodes):

    """

    Generates a html string for changed nodes in changeset page.

    It limits the output to 30 entries

    :param nodes: LazyNodesGenerator

    """

    if nodes:

        pref = ': <br/> '

        suf = ''

        if len(nodes) > 30:

            suf = '<br/>' + _(' and %s more') % (len(nodes) - 30)

        return literal(pref + '<br/> '.join([safe_unicode(x.path)

                                             for x in nodes[:30]]) + suf)

    else:

        return ': ' + _('No Files')

def repo_link(groups_and_repos, last_url=None):

    """

    Makes a breadcrumbs link to repo within a group

    joins » on each group to create a fancy link

    ex::

        group >> subgroup >> repo

    :param groups_and_repos:

    :param last_url:

    """

    groups, repo_name = groups_and_repos

    last_link = link_to(repo_name, last_url) if last_url else repo_name

    if not groups:

        if last_url:

    else:

        def make_link(group):

            return link_to(group.name,

                           url('repos_group_home', group_name=group.group_name))

def fancy_file_stats(stats):

    """

    Displays a fancy two colored bar for number of added/deleted

    lines of code on file

    :param stats: two element list of added/deleted lines of code

    """

    def cgen(l_type, a_v, d_v):

        mapping = {'tr': 'top-right-rounded-corner-mid',

                   'tl': 'top-left-rounded-corner-mid',

                   'br': 'bottom-right-rounded-corner-mid',

                   'bl': 'bottom-left-rounded-corner-mid'}

        map_getter = lambda x: mapping[x]

        if l_type == 'a' and d_v:

            #case when added and deleted are present

            return ' '.join(map(map_getter, ['tl', 'bl']))

        if l_type == 'a' and not d_v:

            return ' '.join(map(map_getter, ['tr', 'br', 'tl', 'bl']))

        if l_type == 'd' and a_v:

            return ' '.join(map(map_getter, ['tr', 'br']))

        if l_type == 'd' and not a_v:

            return ' '.join(map(map_getter, ['tr', 'br', 'tl', 'bl']))

    a, d = stats[0], stats[1]

    width = 100

    if a == 'b':

        #binary mode

        b_d = '<div class="bin%s %s" style="width:100%%">%s</div>' % (d, cgen('a', a_v='', d_v=0), 'bin')

        b_a = '<div class="bin1" style="width:0%%">%s</div>' % ('bin')

        return literal('<div style="width:%spx">%s%s</div>' % (width, b_a, b_d))

    t = stats[0] + stats[1]

    unit = float(width) / (t or 1)

    # needs > 9% of width to be visible or 0 to be hidden

    a_p = max(9, unit * a) if a > 0 else 0

    d_p = max(9, unit * d) if d > 0 else 0

    p_sum = a_p + d_p

    if p_sum > width:

        #adjust the percentage to be == 100% since we adjusted to 9

        if a_p > d_p:

            a_p = a_p - (p_sum - width)

        else:

            d_p = d_p - (p_sum - width)

    a_v = a if a > 0 else ''

    d_v = d if d > 0 else ''

    d_a = '<div class="added %s" style="width:%s%%">%s</div>' % (

        cgen('a', a_v, d_v), a_p, a_v

    )

    d_d = '<div class="deleted %s" style="width:%s%%">%s</div>' % (

        cgen('d', a_v, d_v), d_p, d_v

    )

    return literal('<div style="width:%spx">%s%s</div>' % (width, d_a, d_d))

def urlify_text(text_, safe=True):

    """

    Extrac urls from text and make html links out of them

    :param text_:

    """

    url_pat = re.compile(r'''(http[s]?://(?:[a-zA-Z]|[0-9]|[$-_@.&+]'''

                         '''|[!*\(\),]|(?:%[0-9a-fA-F][0-9a-fA-F]))+)''')

    def url_func(match_obj):

        url_full = match_obj.groups()[0]

        return '<a href="%(url)s">%(url)s</a>' % ({'url': url_full})

    _newtext = url_pat.sub(url_func, text_)

    if safe:

        return literal(_newtext)

    return _newtext

def urlify_changesets(text_, repository):

    """

    Extract revision ids from changeset and make link from them

    :param text_:

    :param repository: repo name to build the URL with

    """

    from pylons import url  # doh, we need to re-import url to mock it later

    URL_PAT = re.compile(r'(^|\s)([0-9a-fA-F]{12,40})($|\s)')

    def url_func(match_obj):

        rev = match_obj.groups()[1]

        DEFAULT_ENCODINGS = aslist(rhodecode.CONFIG.get('default_encoding',

                                                        'utf8'), sep=',')

        to_encoding = DEFAULT_ENCODINGS

    if not isinstance(to_encoding, (list, tuple)):

        to_encoding = [to_encoding]

    for enc in to_encoding:

        try:

            return unicode_.encode(enc)

        except UnicodeEncodeError:

            pass

    try:

        import chardet

        encoding = chardet.detect(unicode_)['encoding']

        if encoding is None:

            raise UnicodeEncodeError()

        return unicode_.encode(encoding)

    except (ImportError, UnicodeEncodeError):

        return unicode_.encode(to_encoding[0], 'replace')

    return safe_str

def remove_suffix(s, suffix):

    if s.endswith(suffix):

        s = s[:-1 * len(suffix)]

    return s

def remove_prefix(s, prefix):

    if s.startswith(prefix):

        s = s[len(prefix):]

    return s

def engine_from_config(configuration, prefix='sqlalchemy.', **kwargs):

    """

    Custom engine_from_config functions that makes sure we use NullPool for

    file based sqlite databases. This prevents errors on sqlite. This only

    applies to sqlalchemy versions < 0.7.0

    """

    import sqlalchemy

    from sqlalchemy import engine_from_config as efc

    import logging

    if int(sqlalchemy.__version__.split('.')[1]) < 7:

        # This solution should work for sqlalchemy < 0.7.0, and should use

        # proxy=TimerProxy() for execution time profiling

        from sqlalchemy.pool import NullPool

        url = configuration[prefix + 'url']

        if url.startswith('sqlite'):

            kwargs.update({'poolclass': NullPool})

        return efc(configuration, prefix, **kwargs)

    else:

        import time

        from sqlalchemy import event

        from sqlalchemy.engine import Engine

        log = logging.getLogger('sqlalchemy.engine')

        BLACK, RED, GREEN, YELLOW, BLUE, MAGENTA, CYAN, WHITE = xrange(30, 38)

        engine = efc(configuration, prefix, **kwargs)

        def color_sql(sql):

            COLOR_SEQ = "\033[1;%dm"

            COLOR_SQL = YELLOW

            normal = '\x1b[0m'

            return ''.join([COLOR_SEQ % COLOR_SQL, sql, normal])

        if configuration['debug']:

            #attach events only for debug configuration

            def before_cursor_execute(conn, cursor, statement,

                                    parameters, context, executemany):

                context._query_start_time = time.time()

                log.info(color_sql(">>>>> STARTING QUERY >>>>>"))

            def after_cursor_execute(conn, cursor, statement,

                                    parameters, context, executemany):

                total = time.time() - context._query_start_time

                log.info(color_sql("<<<<< TOTAL TIME: %f <<<<<" % total))

            event.listen(engine, "before_cursor_execute",

                         before_cursor_execute)

            event.listen(engine, "after_cursor_execute",

                         after_cursor_execute)

    return engine

    """

    turns a datetime into an age string.

    :param prevdate: datetime object

    :rtype: unicode

    :returns: unicode words describing age

    """

    now = datetime.datetime.now()

    now = now.replace(microsecond=0)

    order = ['year', 'month', 'day', 'hour', 'minute', 'second']

    deltas = {}

    future = False

    if prevdate > now:

        now, prevdate = prevdate, now

        future = True

    # Get date parts deltas

    for part in order:

        if future:

            from dateutil import relativedelta

            d = relativedelta.relativedelta(now, prevdate)

            deltas[part] = getattr(d, part + 's')

        else:

            deltas[part] = getattr(now, part) - getattr(prevdate, part)

    # Fix negative offsets (there is 1 second between 10:59:59 and 11:00:00,

    # not 1 hour, -59 minutes and -59 seconds)

    for num, length in [(5, 60), (4, 60), (3, 24)]:  # seconds, minutes, hours

        part = order[num]

        carry_part = order[num - 1]

        if deltas[part] < 0:

            deltas[part] += length

            deltas[carry_part] -= 1

    # Same thing for days except that the increment depends on the (variable)

    # number of days in the month

    month_lengths = [31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31]

    if deltas['day'] < 0:

        if prevdate.month == 2 and (prevdate.year % 4 == 0 and

            (prevdate.year % 100 != 0 or prevdate.year % 400 == 0)):

            deltas['day'] += 29

        else:

            deltas['day'] += month_lengths[prevdate.month - 1]

        deltas['month'] -= 1

    if deltas['month'] < 0:

        deltas['month'] += 12

        deltas['year'] -= 1

    # Format the result

    fmt_funcs = {

        'year': lambda d: ungettext(u'%d year', '%d years', d) % d,