# -*- coding: utf-8 -*- #
# Copyright 2021 Google LLC. All Rights Reserved.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#    http://www.apache.org/licenses/LICENSE-2.0
#
# 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.
"""Task for streaming downloads.

Typically executed in a task iterator:
googlecloudsdk.command_lib.storage.tasks.task_executor.
"""


import os
import sys
import threading
from typing import Any

from googlecloudsdk.api_lib.storage import api_factory
from googlecloudsdk.api_lib.storage import cloud_api
from googlecloudsdk.api_lib.storage import request_config_factory
from googlecloudsdk.command_lib.storage import bucket_detection_util
from googlecloudsdk.command_lib.storage import hash_util
from googlecloudsdk.command_lib.storage import progress_callbacks
from googlecloudsdk.command_lib.storage.resources import resource_reference
from googlecloudsdk.command_lib.storage.tasks import task_status
from googlecloudsdk.command_lib.storage.tasks.cp import copy_util
from googlecloudsdk.command_lib.storage.tasks.cp import download_util
from googlecloudsdk.command_lib.util import crc32c
from googlecloudsdk.core import properties


def _validate_streaming_download(
    source_resource: resource_reference.ObjectResource,
    destination_resource: resource_reference.Resource,
    digesters: dict[hash_util.HashAlgorithm, Any] | None,
) -> None:
  """Validates the streaming download."""
  if not digesters:
    return
  # Validate the download.
  if hash_util.HashAlgorithm.MD5 in digesters:
    calculated_digest = hash_util.get_base64_hash_digest_string(
        digesters[hash_util.HashAlgorithm.MD5]
    )
    download_util.validate_download_hash_and_delete_corrupt_files(
        destination_resource.storage_url.resource_name,
        source_resource.md5_hash,
        calculated_digest,
    )
    return
  if hash_util.HashAlgorithm.CRC32C in digesters:
    calculated_digest = crc32c.get_hash(
        digesters[hash_util.HashAlgorithm.CRC32C]
    )
    crc32c_hash = download_util.get_crc32c_hash_for_resource(source_resource)
    download_util.validate_download_hash_and_delete_corrupt_files(
        destination_resource.storage_url.resource_name,
        crc32c_hash,
        calculated_digest,
    )


class StreamingDownloadTask(copy_util.ObjectCopyTask):
  """Represents a command operation triggering a streaming download."""

  def __init__(
      self,
      source_resource,
      destination_resource,
      download_stream,
      print_created_message=False,
      print_source_version=False,
      show_url=False,
      start_byte=0,
      end_byte=None,
      user_request_args=None,
      verbose=False,
  ):
    """Initializes task.

    Args:
      source_resource (ObjectResource): Must contain the full path of object to
        download, including bucket. Directories will not be accepted. Does not
        need to contain metadata.
      destination_resource (resource_reference.Resource): Target resource to
        copy to. In this case, it contains the path of the destination stream or
        '-' for stdout.
      download_stream (stream): Reusable stream to write download to.
      print_created_message (bool): See parent class.
      print_source_version (bool): See parent class.
      show_url (bool): Says whether or not to print the header before each
        object's content
      start_byte (int): The byte index to start streaming from.
      end_byte (int|None): The byte index to stop streaming from.
      user_request_args (UserRequestArgs|None): See parent class.
      verbose (bool): See parent class.
    """
    super(StreamingDownloadTask, self).__init__(
        source_resource,
        destination_resource,
        print_created_message=print_created_message,
        print_source_version=print_source_version,
        user_request_args=user_request_args,
        verbose=verbose,
    )
    self._download_stream = download_stream
    self._show_url = show_url
    self._start_byte = start_byte
    self._end_byte = end_byte

  @property
  def is_bidi_download(self):
    return bucket_detection_util.is_gcs_zonal_bucket(
        provider=self._source_resource.storage_url.scheme,
        bucket_name=self._source_resource.storage_url.bucket_name,
    )

  def execute(self, task_status_queue=None):
    if self._show_url:
      sys.stderr.write('==> {} <==\n'.format(self._source_resource))
    if task_status_queue:
      progress_callback = progress_callbacks.FilesAndBytesProgressCallback(
          status_queue=task_status_queue,
          offset=0,
          length=self._source_resource.size,
          source_url=self._source_resource.storage_url,
          destination_url=self._download_stream.name,
          operation_name=task_status.OperationName.DOWNLOADING,
          process_id=os.getpid(),
          thread_id=threading.get_ident(),
      )
    else:
      progress_callback = None

    if (self._source_resource.size and
        self._start_byte >= self._source_resource.size):
      if progress_callback:
        progress_callback(self._source_resource.size)
      return

    request_config = request_config_factory.get_request_config(
        self._source_resource.storage_url,
        decryption_key_hash_sha256=(
            self._source_resource.decryption_key_hash_sha256),
        user_request_args=self._user_request_args,
    )

    args = [self._source_resource.storage_url.scheme]
    if properties.VALUES.storage.enable_zonal_buckets_bidi_streaming.GetBool():
      args.append(self._source_resource.storage_url.bucket_name)
    api = api_factory.get_api(*args)
    is_full_download = self._start_byte == 0 and (
        self._end_byte is None
        or self._end_byte >= self._source_resource.size - 1
    )
    # Populate digesters only if the API supports on-the-fly checksums or if
    # the download is a full download.
    if (
        is_full_download
        or cloud_api.Capability.ON_THE_FLY_CHECKSUM in api.capabilities
    ):
      digesters = download_util.get_digesters(
          None, self._source_resource, is_streaming=True
      )
    else:
      digesters = None

    api.download_object(
        self._source_resource,
        self._download_stream,
        request_config,
        digesters=digesters,
        download_strategy=cloud_api.DownloadStrategy.ONE_SHOT,
        progress_callback=progress_callback,
        start_byte=self._start_byte,
        end_byte=self._end_byte,
    )
    self._download_stream.flush()

    if is_full_download:
      _validate_streaming_download(
          self._source_resource, self._destination_resource, digesters,
      )

    self._print_created_message_if_requested(self._destination_resource)

  def __eq__(self, other):
    if not isinstance(other, self.__class__):
      return NotImplemented
    return (
        self._source_resource == other._source_resource
        and self._destination_resource == other._destination_resource
        and self._download_stream == other._download_stream
        and self._print_created_message == other._print_created_message
        and self._user_request_args == other._user_request_args
        and self._show_url == other._show_url
        and self._start_byte == other._start_byte
        and self._end_byte == other._end_byte
    )
