#
# Copyright (C) 2008, 2009 Canonical Ltd.
#
# 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 2 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, write to the Free Software
# Foundation, Inc., 51 Franklin Street, Suite 500, Boston, MA 02110-1335  USA
#
"""Cache the whole history data needed by loggerhead about a branch."""

import logging
import time

from breezy.revision import NULL_REVISION, is_null
from breezy.tsort import merge_sort


def _strip_NULL_ghosts(revision_graph):
    """
    Copied over from breezy meant as a temporary workaround for
    deprecated methods.
    """
    # Filter ghosts, and null:
    if NULL_REVISION in revision_graph:
        del revision_graph[NULL_REVISION]
    for key, parents in revision_graph.items():
        revision_graph[key] = tuple(parent for parent in parents if parent
            in revision_graph)
    return revision_graph


def compute_whole_history_data(branch):
    """Compute _rev_info and _rev_indices for a branch.

    See History.__doc__ for what these data structures mean.
    """
    z = time.time()

    last_revid = branch.last_revision()

    log = logging.getLogger('loggerhead.%s' %
                            (branch.get_config().get_nickname(),))

    graph = branch.repository.get_graph()
    parent_map = dict((key, value) for key, value in
        graph.iter_ancestry([last_revid]) if value is not None)

    _revision_graph = _strip_NULL_ghosts(parent_map)

    _rev_info = []
    _rev_indices = {}

    if is_null(last_revid):
        _merge_sort = []
    else:
        _merge_sort = merge_sort(
            _revision_graph, last_revid, generate_revno=True)

    for info in _merge_sort:
        seq, revid, merge_depth, revno, end_of_merge = info
        revno_str = '.'.join(str(n) for n in revno)
        parents = _revision_graph[revid]
        _rev_indices[revid] = len(_rev_info)
        _rev_info.append([(seq, revid, merge_depth, revno_str, end_of_merge), (), parents])

    for revid in _revision_graph.keys():
        if _rev_info[_rev_indices[revid]][0][2] == 0:
            continue
        for parent in _revision_graph[revid]:
            c = _rev_info[_rev_indices[parent]]
            if revid not in c[1]:
                c[1] = c[1] + (revid,)

    log.info('built revision graph cache: %.3f secs' % (time.time() - z,))

    return (_rev_info, _rev_indices)