# Copyright (C) 2015-2018  The Software Heritage developers
# See the AUTHORS file at the top-level directory of this distribution
# License: GNU General Public License version 3, or any later version
# See top-level LICENSE file for more information

import datetime
import dulwich.repo
import os
import shutil

from dulwich.errors import ObjectFormatException, EmptyFileException
from collections import defaultdict

from swh.model import hashutil
from swh.loader.core.loader import SWHStatelessLoader
from . import converters, utils


class GitLoader(SWHStatelessLoader):
    """Load a git repository from a directory.
    """

    CONFIG_BASE_FILENAME = 'loader/git-loader'

    def __init__(self, config=None):
        super().__init__(logging_class='swh.loader.git.Loader', config=config)

    def prepare_origin_visit(self, origin_url, directory, visit_date):
        self.origin_url = origin_url
        self.origin = converters.origin_url_to_origin(self.origin_url)
        self.visit_date = visit_date

    def prepare(self, origin_url, directory, visit_date):
        self.repo = dulwich.repo.Repo(directory)

    def iter_objects(self):
        object_store = self.repo.object_store

        for pack in object_store.packs:
            objs = list(pack.index.iterentries())
            objs.sort(key=lambda x: x[1])
            for sha, offset, crc32 in objs:
                yield hashutil.hash_to_bytehex(sha)

        yield from object_store._iter_loose_objects()
        yield from object_store._iter_alternate_objects()

    def _check(self, obj):
        """Check the object's repository representation.

        If any errors in check exists, an ObjectFormatException is
        raised.

        Args:
            obj (object): Dulwich object read from the repository.

        """
        obj.check()
        from dulwich.objects import Commit, Tag
        try:
            # For additional checks on dulwich objects with date
            # for now, only checks on *time
            if isinstance(obj, Commit):
                commit_time = obj._commit_time
                utils.check_date_time(commit_time)
                author_time = obj._author_time
                utils.check_date_time(author_time)
            elif isinstance(obj, Tag):
                tag_time = obj._tag_time
                utils.check_date_time(tag_time)
        except Exception as e:
            raise ObjectFormatException(e)

    def get_object(self, oid):
        """Given an object id, return the object if it is found and not
           malformed in some way.

        Args:
            oid (bytes): the object's identifier

        Returns:
            The object if found without malformation

        """
        try:
            # some errors are raised when reading the object
            obj = self.repo[oid]
            # some we need to check ourselves
            self._check(obj)
        except KeyError:
            _id = oid.decode('utf-8')
            self.log.warn('object %s not found, skipping' % _id,
                          extra={
                              'swh_type': 'swh_loader_git_missing_object',
                              'swh_object_id': _id,
                              'origin_id': self.origin_id,
                          })
            return None
        except ObjectFormatException:
            _id = oid.decode('utf-8')
            self.log.warn('object %s malformed, skipping' % _id,
                          extra={
                              'swh_type': 'swh_loader_git_missing_object',
                              'swh_object_id': _id,
                              'origin_id': self.origin_id,
                          })
            return None
        except EmptyFileException:
            _id = oid.decode('utf-8')
            self.log.warn('object %s corrupted (empty file), skipping' % _id,
                          extra={
                              'swh_type': 'swh_loader_git_missing_object',
                              'swh_object_id': _id,
                              'origin_id': self.origin_id,
                          })
        else:
            return obj

    def fetch_data(self):
        """Fetch the data from the data source"""
        self.previous_snapshot = self.storage.snapshot_get_latest(
            self.origin_id
        )

        type_to_ids = defaultdict(list)
        for oid in self.iter_objects():
            obj = self.get_object(oid)
            if not obj:
                continue
            type_name = obj.type_name
            type_to_ids[type_name].append(oid)

        self.type_to_ids = type_to_ids

    def has_contents(self):
        """Checks whether we need to load contents"""
        return bool(self.type_to_ids[b'blob'])

    def get_content_ids(self):
        """Get the content identifiers from the git repository"""
        for oid in self.type_to_ids[b'blob']:
            yield converters.dulwich_blob_to_content_id(self.repo[oid])

    def get_contents(self):
        """Get the contents that need to be loaded"""
        max_content_size = self.config['content_size_limit']

        missing_contents = set(self.storage.content_missing(
            self.get_content_ids(), 'sha1_git'))

        for oid in missing_contents:
            yield converters.dulwich_blob_to_content(
                self.repo[hashutil.hash_to_bytehex(oid)], log=self.log,
                max_content_size=max_content_size,
                origin_id=self.origin_id)

    def has_directories(self):
        """Checks whether we need to load directories"""
        return bool(self.type_to_ids[b'tree'])

    def get_directory_ids(self):
        """Get the directory identifiers from the git repository"""
        return (hashutil.hash_to_bytes(id.decode())
                for id in self.type_to_ids[b'tree'])

    def get_directories(self):
        """Get the directories that need to be loaded"""
        missing_dirs = set(self.storage.directory_missing(
            sorted(self.get_directory_ids())))

        for oid in missing_dirs:
            yield converters.dulwich_tree_to_directory(
                self.repo[hashutil.hash_to_bytehex(oid)], log=self.log)

    def has_revisions(self):
        """Checks whether we need to load revisions"""
        return bool(self.type_to_ids[b'commit'])

    def get_revision_ids(self):
        """Get the revision identifiers from the git repository"""
        return (hashutil.hash_to_bytes(id.decode())
                for id in self.type_to_ids[b'commit'])

    def get_revisions(self):
        """Get the revisions that need to be loaded"""
        missing_revs = set(self.storage.revision_missing(
            sorted(self.get_revision_ids())))

        for oid in missing_revs:
            yield converters.dulwich_commit_to_revision(
                self.repo[hashutil.hash_to_bytehex(oid)], log=self.log)

    def has_releases(self):
        """Checks whether we need to load releases"""
        return bool(self.type_to_ids[b'tag'])

    def get_release_ids(self):
        """Get the release identifiers from the git repository"""
        return (hashutil.hash_to_bytes(id.decode())
                for id in self.type_to_ids[b'tag'])

    def get_releases(self):
        """Get the releases that need to be loaded"""
        missing_rels = set(self.storage.release_missing(
            sorted(self.get_release_ids())))

        for oid in missing_rels:
            yield converters.dulwich_tag_to_release(
                self.repo[hashutil.hash_to_bytehex(oid)], log=self.log)

    def get_snapshot(self):
        """Turn the list of branches into a snapshot to load"""
        branches = {}

        for ref, target in self.repo.refs.as_dict().items():
            obj = self.get_object(target)
            if obj:
                branches[ref] = {
                    'target': hashutil.bytehex_to_hash(target),
                    'target_type': converters.DULWICH_TYPES[obj.type_name],
                }
            else:
                branches[ref] = None

        self.snapshot = converters.branches_to_snapshot(branches)
        return self.snapshot

    def get_fetch_history_result(self):
        """Return the data to store in fetch_history for the current loader"""
        return {
            'contents': len(self.type_to_ids[b'blob']),
            'directories': len(self.type_to_ids[b'tree']),
            'revisions': len(self.type_to_ids[b'commit']),
            'releases': len(self.type_to_ids[b'tag']),
        }

    def save_data(self):
        """We already have the data locally, no need to save it"""
        pass

    def load_status(self):
        """The load was eventful if the current occurrences are different to
           the ones we retrieved at the beginning of the run"""
        eventful = False

        if self.previous_snapshot:
            eventful = self.snapshot['id'] != self.previous_snapshot['id']
        else:
            eventful = bool(self.snapshot['branches'])

        return {'status': ('eventful' if eventful else 'uneventful')}


class GitLoaderFromArchive(GitLoader):
    """Load a git repository from an archive.

    """
    def project_name_from_archive(self, archive_path):
        """Compute the project name from the archive's path.

        """
        return os.path.basename(os.path.dirname(archive_path))

    def prepare(self, origin_url, archive_path, visit_date):
        """1. Uncompress the archive in temporary location.
           2. Prepare as the GitLoader does
           3. Load as GitLoader does

        """
        project_name = self.project_name_from_archive(archive_path)
        self.temp_dir, self.repo_path = utils.init_git_repo_from_archive(
            project_name, archive_path)

        self.log.info('Project %s - Uncompressing archive %s at %s' % (
            origin_url, os.path.basename(archive_path), self.repo_path))
        super().prepare(origin_url, self.repo_path, visit_date)

    def cleanup(self):
        """Cleanup the temporary location (if it exists).

        """
        if self.temp_dir and os.path.exists(self.temp_dir):
            shutil.rmtree(self.temp_dir)
        self.log.info('Project %s - Done injecting %s' % (
            self.origin_url, self.repo_path))


if __name__ == '__main__':
    import click
    import logging

    logging.basicConfig(
        level=logging.DEBUG,
        format='%(asctime)s %(process)d %(message)s'
    )

    @click.command()
    @click.option('--origin-url', help='origin url')
    @click.option('--git-directory', help='Path to git repository to load')
    @click.option('--visit-date', default=None, help='Visit date')
    def main(origin_url, git_directory, visit_date):
        if not visit_date:
            visit_date = datetime.datetime.now(tz=datetime.timezone.utc)

        return GitLoader().load(origin_url, git_directory, visit_date)

    main()
