# object_store.py -- Object store for git objects
# Copyright (C) 2008-2013 Jelmer Vernooij <jelmer@jelmer.uk>
#                         and others
#
# Dulwich is dual-licensed under the Apache License, Version 2.0 and the GNU
# General Public License as public by the Free Software Foundation; version 2.0
# or (at your option) any later version. You can redistribute it and/or
# modify it under the terms of either of these two licenses.
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
#
# You should have received a copy of the licenses; if not, see
# <http://www.gnu.org/licenses/> for a copy of the GNU General Public License
# and <http://www.apache.org/licenses/LICENSE-2.0> for a copy of the Apache
# License, Version 2.0.
#


"""Git object store interfaces and implementation."""

from io import BytesIO
import errno
import os
import stat
import sys
import tempfile

from dulwich.diff_tree import (
    tree_changes,
    walk_trees,
    )
from dulwich.errors import (
    NotTreeError,
    )
from dulwich.file import GitFile
from dulwich.objects import (
    Commit,
    ShaFile,
    Tag,
    Tree,
    ZERO_SHA,
    hex_to_sha,
    sha_to_hex,
    hex_to_filename,
    S_ISGITLINK,
    object_class,
    )
from dulwich.pack import (
    Pack,
    PackData,
    PackInflater,
    PackFileDisappeared,
    iter_sha1,
    pack_objects_to_data,
    write_pack_header,
    write_pack_index_v2,
    write_pack_data,
    write_pack_object,
    compute_file_sha,
    PackIndexer,
    PackStreamCopier,
    )
from dulwich.refs import ANNOTATED_TAG_SUFFIX

INFODIR = 'info'
PACKDIR = 'pack'


class BaseObjectStore(object):
    """Object store interface."""

    def determine_wants_all(self, refs):
        return [sha for (ref, sha) in refs.items()
                if sha not in self and
                not ref.endswith(ANNOTATED_TAG_SUFFIX) and
                not sha == ZERO_SHA]

    def iter_shas(self, shas):
        """Iterate over the objects for the specified shas.

        :param shas: Iterable object with SHAs
        :return: Object iterator
        """
        return ObjectStoreIterator(self, shas)

    def contains_loose(self, sha):
        """Check if a particular object is present by SHA1 and is loose."""
        raise NotImplementedError(self.contains_loose)

    def contains_packed(self, sha):
        """Check if a particular object is present by SHA1 and is packed."""
        raise NotImplementedError(self.contains_packed)

    def __contains__(self, sha):
        """Check if a particular object is present by SHA1.

        This method makes no distinction between loose and packed objects.
        """
        return self.contains_packed(sha) or self.contains_loose(sha)

    @property
    def packs(self):
        """Iterable of pack objects."""
        raise NotImplementedError

    def get_raw(self, name):
        """Obtain the raw text for an object.

        :param name: sha for the object.
        :return: tuple with numeric type and object contents.
        """
        raise NotImplementedError(self.get_raw)

    def __getitem__(self, sha):
        """Obtain an object by SHA1."""
        type_num, uncomp = self.get_raw(sha)
        return ShaFile.from_raw_string(type_num, uncomp, sha=sha)

    def __iter__(self):
        """Iterate over the SHAs that are present in this store."""
        raise NotImplementedError(self.__iter__)

    def add_object(self, obj):
        """Add a single object to this object store.

        """
        raise NotImplementedError(self.add_object)

    def add_objects(self, objects, progress=None):
        """Add a set of objects to this object store.

        :param objects: Iterable over a list of (object, path) tuples
        """
        raise NotImplementedError(self.add_objects)

    def add_pack_data(self, count, pack_data, progress=None):
        """Add pack data to this object store.

        :param num_items: Number of items to add
        :param pack_data: Iterator over pack data tuples
        """
        if count == 0:
            # Don't bother writing an empty pack file
            return
        f, commit, abort = self.add_pack()
        try:
            write_pack_data(f, count, pack_data, progress)
        except BaseException:
            abort()
            raise
        else:
            return commit()

    def tree_changes(self, source, target, want_unchanged=False,
                     include_trees=False, change_type_same=False):
        """Find the differences between the contents of two trees

        :param source: SHA1 of the source tree
        :param target: SHA1 of the target tree
        :param want_unchanged: Whether unchanged files should be reported
        :param include_trees: Whether to include trees
        :param change_type_same: Whether to report files changing
            type in the same entry.
        :return: Iterator over tuples with
            (oldpath, newpath), (oldmode, newmode), (oldsha, newsha)
        """
        for change in tree_changes(self, source, target,
                                   want_unchanged=want_unchanged,
                                   include_trees=include_trees,
                                   change_type_same=change_type_same):
            yield ((change.old.path, change.new.path),
                   (change.old.mode, change.new.mode),
                   (change.old.sha, change.new.sha))

    def iter_tree_contents(self, tree_id, include_trees=False):
        """Iterate the contents of a tree and all subtrees.

        Iteration is depth-first pre-order, as in e.g. os.walk.

        :param tree_id: SHA1 of the tree.
        :param include_trees: If True, include tree objects in the iteration.
        :return: Iterator over TreeEntry namedtuples for all the objects in a
            tree.
        """
        for entry, _ in walk_trees(self, tree_id, None):
            if ((entry.mode is not None and
                 not stat.S_ISDIR(entry.mode)) or include_trees):
                yield entry

    def find_missing_objects(self, haves, wants, progress=None,
                             get_tagged=None,
                             get_parents=lambda commit: commit.parents,
                             depth=None):
        """Find the missing objects required for a set of revisions.

        :param haves: Iterable over SHAs already in common.
        :param wants: Iterable over SHAs of objects to fetch.
        :param progress: Simple progress function that will be called with
            updated progress strings.
        :param get_tagged: Function that returns a dict of pointed-to sha ->
            tag sha for including tags.
        :param get_parents: Optional function for getting the parents of a
            commit.
        :return: Iterator over (sha, path) pairs.
        """
        finder = MissingObjectFinder(self, haves, wants, progress, get_tagged,
                                     get_parents=get_parents)
        return iter(finder.next, None)

    def find_common_revisions(self, graphwalker):
        """Find which revisions this store has in common using graphwalker.

        :param graphwalker: A graphwalker object.
        :return: List of SHAs that are in common
        """
        haves = []
        sha = next(graphwalker)
        while sha:
            if sha in self:
                haves.append(sha)
                graphwalker.ack(sha)
            sha = next(graphwalker)
        return haves

    def generate_pack_contents(self, have, want, progress=None):
        """Iterate over the contents of a pack file.

        :param have: List of SHA1s of objects that should not be sent
        :param want: List of SHA1s of objects that should be sent
        :param progress: Optional progress reporting method
        """
        return self.iter_shas(self.find_missing_objects(have, want, progress))

    def generate_pack_data(self, have, want, progress=None, ofs_delta=True):
        """Generate pack data objects for a set of wants/haves.

        :param have: List of SHA1s of objects that should not be sent
        :param want: List of SHA1s of objects that should be sent
        :param ofs_delta: Whether OFS deltas can be included
        :param progress: Optional progress reporting method
        """
        # TODO(jelmer): More efficient implementation
        return pack_objects_to_data(
            self.generate_pack_contents(have, want, progress))

    def peel_sha(self, sha):
        """Peel all tags from a SHA.

        :param sha: The object SHA to peel.
        :return: The fully-peeled SHA1 of a tag object, after peeling all
            intermediate tags; if the original ref does not point to a tag,
            this will equal the original SHA1.
        """
        obj = self[sha]
        obj_class = object_class(obj.type_name)
        while obj_class is Tag:
            obj_class, sha = obj.object
            obj = self[sha]
        return obj

    def _collect_ancestors(self, heads, common=set(),
                           get_parents=lambda commit: commit.parents):
        """Collect all ancestors of heads up to (excluding) those in common.

        :param heads: commits to start from
        :param common: commits to end at, or empty set to walk repository
            completely
        :param get_parents: Optional function for getting the parents of a
            commit.
        :return: a tuple (A, B) where A - all commits reachable
            from heads but not present in common, B - common (shared) elements
            that are directly reachable from heads
        """
        bases = set()
        commits = set()
        queue = []
        queue.extend(heads)
        while queue:
            e = queue.pop(0)
            if e in common:
                bases.add(e)
            elif e not in commits:
                commits.add(e)
                cmt = self[e]
                queue.extend(get_parents(cmt))
        return (commits, bases)

    def close(self):
        """Close any files opened by this object store."""
        # Default implementation is a NO-OP


class PackBasedObjectStore(BaseObjectStore):

    def __init__(self):
        self._pack_cache = {}

    @property
    def alternates(self):
        return []

    def contains_packed(self, sha):
        """Check if a particular object is present by SHA1 and is packed.

        This does not check alternates.
        """
        for pack in self.packs:
            try:
                if sha in pack:
                    return True
            except PackFileDisappeared:
                pass
        return False

    def __contains__(self, sha):
        """Check if a particular object is present by SHA1.

        This method makes no distinction between loose and packed objects.
        """
        if self.contains_packed(sha) or self.contains_loose(sha):
            return True
        for alternate in self.alternates:
            if sha in alternate:
                return True
        return False

    def _add_cached_pack(self, base_name, pack):
        """Add a newly appeared pack to the cache by path.

        """
        prev_pack = self._pack_cache.get(base_name)
        if prev_pack is not pack:
            self._pack_cache[base_name] = pack
            if prev_pack:
                prev_pack.close()

    def _clear_cached_packs(self):
        pack_cache = self._pack_cache
        self._pack_cache = {}
        while pack_cache:
            (name, pack) = pack_cache.popitem()