# Copyright (C) 2007-2011 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, Fifth Floor, Boston, MA 02110-1301 USA

"""Tag strategies.

These are contained within a branch and normally constructed
when the branch is opened.  Clients should typically do

  Branch.tags.add('name', 'value')
"""

from collections import defaultdict
import contextlib
import itertools
import re
import sys

# NOTE: I was going to call this tags.py, but vim seems to think all files
# called tags* are ctags files... mbp 20070220.

from .inter import InterObject
from .registry import Registry

from . import (
    errors,
    )


def _reconcile_tags(source_dict, dest_dict, overwrite, selector):
    """Do a two-way merge of two tag dictionaries.

    * only in source => source value
    * only in destination => destination value
    * same definitions => that
    * different definitions => if overwrite is False, keep destination
      value and add to conflict list, otherwise use the source value

    :returns: (result_dict, updates,
        [(conflicting_tag, source_target, dest_target)])
    """
    conflicts = []
    updates = {}
    result = dict(dest_dict)  # copy
    for name, target in source_dict.items():
        if selector and not selector(name):
            continue
        if result.get(name) == target:
            pass
        elif name not in result or overwrite:
            updates[name] = target
            result[name] = target
        else:
            conflicts.append((name, target, result[name]))
    return result, updates, conflicts


class Tags(object):

    def __init__(self, branch):
        self.branch = branch

    def get_tag_dict(self):
        """Return a dictionary mapping tags to revision ids.
        """
        raise NotImplementedError(self.get_tag_dict)

    def get_reverse_tag_dict(self):
        """Returns a dict with revisions as keys
           and a list of tags for that revision as value"""
        d = self.get_tag_dict()
        rev = defaultdict(set)
        for key in d:
            rev[d[key]].add(key)
        return rev

    def merge_to(self, to_tags, overwrite=False, ignore_master=False, selector=None):
        """Copy tags between repositories if necessary and possible.

        This method has common command-line behaviour about handling
        error cases.

        All new definitions are copied across, except that tags that already
        exist keep their existing definitions.

        :param to_tags: Branch to receive these tags
        :param overwrite: Overwrite conflicting tags in the target branch
        :param ignore_master: Do not modify the tags in the target's master
            branch (if any).  Default is false (so the master will be updated).

        :returns: Tuple with tag_updates and tag_conflicts.
            tag_updates is a dictionary with new tags, None is used for
            removed tags
            tag_conflicts is a set of tags that conflicted, each of which is
            (tagname, source_target, dest_target), or None if no copying was
            done.
        """
        intertags = InterTags.get(self, to_tags)
        return intertags.merge(
            overwrite=overwrite, ignore_master=ignore_master,
            selector=selector)

    def set_tag(self, tag_name, revision):
        """Set a tag.

        :param tag_name: Tag name
        :param revision: Revision id
        :raise GhostTagsNotSupported: if revision is not present in
            the branch repository
        """
        raise NotImplementedError(self.set_tag)

    def lookup_tag(self, tag_name):
        """Look up a tag.

        :param tag_name: Tag to look up
        :raise NoSuchTag: Raised when tag does not exist
        :return: Matching revision id
        """
        raise NotImplementedError(self.lookup_tag)

    def delete_tag(self, tag_name):
        """Delete a tag.

        :param tag_name: Tag to delete
        :raise NoSuchTag: Raised when tag does not exist
        """
        raise NotImplementedError(self.delete_tag)

    def rename_revisions(self, rename_map):
        """Rename revisions in this tags dictionary.

        :param rename_map: Dictionary mapping old revids to new revids
        """
        reverse_tags = self.get_reverse_tag_dict()
        for revid, names in reverse_tags.items():
            if revid in rename_map:
                for name in names:
                    self.set_tag(name, rename_map[revid])

    def has_tag(self, tag_name):
        return tag_name in self.get_tag_dict()


class DisabledTags(Tags):
    """Tag storage that refuses to store anything.

    This is used by older formats that can't store tags.
    """

    def _not_supported(self, *a, **k):
        raise errors.TagsNotSupported(self.branch)

    set_tag = _not_supported
    get_tag_dict = _not_supported
    _set_tag_dict = _not_supported
    lookup_tag = _not_supported
    delete_tag = _not_supported

    def merge_to(self, to_tags, overwrite=False, ignore_master=False, selector=None):
        # we never have anything to copy
        return {}, []

    def rename_revisions(self, rename_map):
        # No tags, so nothing to rename
        pass

    def get_reverse_tag_dict(self):
        # There aren't any tags, so the reverse mapping is empty.
        return {}


class InterTags(InterObject):
    """Operations between sets of tags.
    """

    _optimisers = []
    """The available optimised InterTags types."""

    @classmethod
    def is_compatible(klass, source, target):
        # This is the default implementation
        return True

    def merge(self, overwrite=False, ignore_master=False, selector=None):
        """Copy tags between repositories if necessary and possible.

        This method has common command-line behaviour about handling
        error cases.

        All new definitions are copied across, except that tags that already
        exist keep their existing definitions.

        :param to_tags: Branch to receive these tags
        :param overwrite: Overwrite conflicting tags in the target branch
        :param ignore_master: Do not modify the tags in the target's master
            branch (if any).  Default is false (so the master will be updated).
        :param selector: Callback that determines whether a tag should be
            copied. It should take a tag name and as argument and return a
            boolean.

        :returns: Tuple with tag_updates and tag_conflicts.
            tag_updates is a dictionary with new tags, None is used for
            removed tags
            tag_conflicts is a set of tags that conflicted, each of which is
            (tagname, source_target, dest_target), or None if no copying was
            done.
        """
        with contextlib.ExitStack() as stack:
            if self.source.branch == self.target.branch:
                return {}, []
            if not self.source.branch.supports_tags():
                # obviously nothing to copy
                return {}, []
            source_dict = self.source.get_tag_dict()
            if not source_dict:
                # no tags in the source, and we don't want to clobber anything
                # that's in the destination
                return {}, []
            # We merge_to both master and child individually.
            #
            # It's possible for master and child to have differing sets of
            # tags, in which case it's possible to have different sets of
            # conflicts.  We report the union of both conflict sets.  In
            # that case it's likely the child and master have accepted
            # different tags from the source, which may be a surprising result, but
            # the best we can do in the circumstances.
            #
            # Ideally we'd improve this API to report the different conflicts
            # more clearly to the caller, but we don't want to break plugins
            # such as bzr-builddeb that use this API.
            stack.enter_context(self.target.branch.lock_write())
            if ignore_master:
                master = None
            else:
                master = self.target.branch.get_master_branch()
            if master is not None:
                stack.enter_context(master.lock_write())
            updates, conflicts = self._merge_to(
                self.target, source_dict, overwrite, selector=selector)
            if master is not None:
                extra_updates, extra_conflicts = self._merge_to(
                    master.tags, source_dict, overwrite, selector=selector)
                updates.update(extra_updates)
                conflicts += extra_conflicts
            # We use set() to remove any duplicate conflicts from the master
            # branch.
            return updates, set(conflicts)

    @classmethod
    def _merge_to(cls, to_tags, source_dict, overwrite, selector):
        dest_dict = to_tags.get_tag_dict()
        result, updates, conflicts = _reconcile_tags(
            source_dict, dest_dict, overwrite, selector)
        if result != dest_dict:
            to_tags._set_tag_dict(result)
        return updates, conflicts


class MemoryTags(Tags):

    def __init__(self, tag_dict):
        self._tag_dict = tag_dict

    def get_tag_dict(self):
        return self._tag_dict

    def lookup_tag(self, tag_name):
        """Return the referent string of a tag"""
        td = self.get_tag_dict()
        try:
            return td[tag_name]
        except KeyError:
            raise errors.NoSuchTag(tag_name)

    def set_tag(self, name, revid):
        self._tag_dict[name] = revid

    def delete_tag(self, name):
        try:
            del self._tag_dict[name]
        except KeyError:
            raise errors.NoSuchTag(name)

    def rename_revisions(self, revid_map):
        self._tag_dict = {
            name: revid_map.get(revid, revid)
            for name, revid in self._tag_dict.items()}

    def _set_tag_dict(self, result):
        self._tag_dict = dict(result.items())

    def merge_to(self, to_tags, overwrite=False, ignore_master=False, selector=None):
        source_dict = self.get_tag_dict()
        dest_dict = to_tags.get_tag_dict()
        result, updates, conflicts = _reconcile_tags(
            source_dict, dest_dict, overwrite, selector)
        if result != dest_dict:
            to_tags._set_tag_dict(result)
        return updates, conflicts


def sort_natural(branch, tags):
    """Sort tags, with numeric substrings as numbers.

    :param branch: Branch
    :param tags: List of tuples with tag name and revision id.
    """
    def natural_sort_key(tag):
        return [f(s) for f, s in
                zip(itertools.cycle((str.lower, int)),
                    re.split('([0-9]+)', tag[0]))]
    tags.sort(key=natural_sort_key)


def sort_alpha(branch, tags):
    """Sort tags lexicographically, in place.

    :param branch: Branch
    :param tags: List of tuples with tag name and revision id.
    """
    tags.sort()


def sort_time(branch, tags):
    """Sort tags by time inline.

    :param branch: Branch
    :param tags: List of tuples with tag name and revision id.
    """
    timestamps = {}
    for tag, revid in tags:
        try:
            revobj = branch.repository.get_revision(revid)
        except errors.NoSuchRevision:
            timestamp = sys.maxsize  # place them at the end
        else:
            timestamp = revobj.timestamp
        timestamps[revid] = timestamp
    tags.sort(key=lambda x: timestamps[x[1]])


tag_sort_methods = Registry()
tag_sort_methods.register("natural", sort_natural,
                          'Sort numeric substrings as numbers. (default)')
tag_sort_methods.register("alpha", sort_alpha, 'Sort tags lexicographically.')
tag_sort_methods.register("time", sort_time, 'Sort tags chronologically.')
tag_sort_methods.default_key = "natural"


InterTags.register_optimiser(InterTags)