# Copyright 2019 Red Hat, Inc.
#
# This module 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 software 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 software.  If not, see <http://www.gnu.org/licenses/>.

import logging
import os
import tempfile

from . import storageutils


DISK_CHUNK_SIZE = 64 * 1024


class FilesystemDriver(storageutils.StorageDriver):
    log = logging.getLogger('registry.filesystem')

    def __init__(self, conf):
        self.root = conf['root']

    def list_objects(self, path):
        self.log.debug("List objects %s", path)
        path = os.path.join(self.root, path)
        if not os.path.isdir(path):
            return []
        ret = []
        for f in os.listdir(path):
            obj_path = os.path.join(path, f)
            ret.append(storageutils.ObjectInfo(
                obj_path, f, os.stat(obj_path).st_ctime,
                os.path.isdir(obj_path)))
        return ret

    def get_object_size(self, path):
        path = os.path.join(self.root, path)
        if not os.path.exists(path):
            return None
        return os.stat(path).st_size

    def put_object(self, path, data, uuid=None):
        path = os.path.join(self.root, path)
        os.makedirs(os.path.dirname(path), exist_ok=True)
        with open(path, 'wb') as f:
            size = 0
            if isinstance(data, bytes):
                f.write(data)
                size += len(data)
            else:
                for chunk in data:
                    f.write(chunk)
                    size += len(chunk)
            f.flush()
            os.fsync(f.fileno())
        self.log.debug("[u: %s] Upload object %s size: %s",
                       uuid, path, size)

    def get_object(self, path):
        path = os.path.join(self.root, path)
        if not os.path.exists(path):
            return None
        with open(path, 'rb') as f:
            return f.read()

    def stream_object(self, path):
        path = os.path.join(self.root, path)
        if not os.path.exists(path):
            return None, None
        f = open(path, 'rb', buffering=DISK_CHUNK_SIZE)
        try:
            size = os.fstat(f.fileno()).st_size
        except OSError:
            f.close()
            raise

        def data_iter(f=f):
            with f:
                yield b''  # will get discarded; see note below
                yield from iter(lambda: f.read(DISK_CHUNK_SIZE), b'')

        ret = data_iter()
        # This looks a little funny, because it is. We're going to discard the
        # empty bytes added at the start, but that's not the important part.
        # We want to ensure that
        #
        #   1. the generator has started executing and
        #   2. it left off *inside the with block*
        #
        # This ensures that when the generator gets cleaned up (either because
        # everything went according to plan and the generator exited cleanly
        # *or* there was an error which eventually raised a GeneratorExit),
        # the file we opened will get closed.
        next(ret)
        return size, ret

    def delete_object(self, path):
        path = os.path.join(self.root, path)
        if os.path.exists(path):
            if os.path.isdir(path):
                os.rmdir(path)
            else:
                os.unlink(path)

    def move_object(self, src_path, dst_path, uuid=None):
        src_path = os.path.join(self.root, src_path)
        dst_path = os.path.join(self.root, dst_path)
        self.log.debug("[u: %s] Move object %s %s",
                       uuid, src_path, dst_path)
        os.makedirs(os.path.dirname(dst_path), exist_ok=True)
        os.rename(src_path, dst_path)
        self.log.debug("[u: %s] Moved object %s %s",
                       uuid, src_path, dst_path)

    def cat_objects(self, path, chunks, uuid=None):
        path = os.path.join(self.root, path)
        os.makedirs(os.path.dirname(path), exist_ok=True)
        # We write to a temporary file in the same directory as the destiation
        # file to ensure that we can rename it atomically once fully written.
        # This is important because there may be multiple concurrent writes to
        # the same object and due to client behavior we cannot return until
        # at least one write is completed. To facilitate this we ensure each
        # write happens completely then make that safe with atomic renames.
        with tempfile.NamedTemporaryFile(dir=os.path.dirname(path),
                                         delete=False) as outf:
            for chunk in chunks:
                chunk_path = os.path.join(self.root, chunk['path'])
                with open(chunk_path, 'rb') as inf:
                    while True:
                        d = inf.read(4096)
                        if not d:
                            break
                        outf.write(d)
            outf.flush()
            os.fsync(outf.fileno())
            os.rename(outf.name, path)
        for chunk in chunks:
            chunk_path = os.path.join(self.root, chunk['path'])
            os.unlink(chunk_path)


Driver = FilesystemDriver