# Copyright 2019 Google LLC
#
# 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.

import os
import pathlib
import tempfile

class GCSHelper(object):
  """ GCSHelper manages the connection with the GCS storage """

  @staticmethod
  def get_blob_from_gcs_uri(gcs_path):
    """
    Args:
      gcs_path (str) : gcs blob path
    Returns:
      gcs_blob: gcs blob object(https://github.com/googleapis/google-cloud-python/blob/5c9bb42cb3c9250131cfeef6e0bafe8f4b7c139f/storage/google/cloud/storage/blob.py#L105)
    """
    from google.cloud import storage
    pure_path = pathlib.PurePath(gcs_path)
    gcs_bucket = pure_path.parts[1]
    gcs_blob = '/'.join(pure_path.parts[2:])
    client = storage.Client()
    bucket = client.get_bucket(gcs_bucket)
    blob = bucket.blob(gcs_blob)
    return blob

  @staticmethod
  def upload_gcs_file(local_path, gcs_path):
    """
    Args:
      local_path (str): local file path
      gcs_path (str) : gcs blob path
    """
    blob = GCSHelper.get_blob_from_gcs_uri(gcs_path)
    blob.upload_from_filename(local_path)

  @staticmethod
  def write_to_gcs_path(path: str, content: str) -> None:
    """Writes serialized content to a GCS location.

    Args:
      path: GCS path to write to.
      content: The content to be written.
    """
    fd, temp_path = tempfile.mkstemp()
    try:
      with os.fdopen(fd, 'w') as tmp:
        tmp.write(content)

      if not GCSHelper.get_blob_from_gcs_uri(path):
        pure_path = pathlib.PurePath(path)
        gcs_bucket = pure_path.parts[1]
        GCSHelper.create_gcs_bucket_if_not_exist(gcs_bucket)

      GCSHelper.upload_gcs_file(temp_path, path)
    finally:
      os.remove(temp_path)

  @staticmethod
  def remove_gcs_blob(gcs_path):
    """
    Args:
      gcs_path (str) : gcs blob path
    """
    blob = GCSHelper.get_blob_from_gcs_uri(gcs_path)
    blob.delete()

  @staticmethod
  def download_gcs_blob(local_path, gcs_path):
    """
    Args:
      local_path (str): local file path
      gcs_path (str) : gcs blob path
    """
    blob = GCSHelper.get_blob_from_gcs_uri(gcs_path)
    blob.download_to_filename(local_path)

  @staticmethod
  def read_from_gcs_path(gcs_path: str) -> str:
    """Reads the content of a file hosted on GCS."""
    fd, temp_path = tempfile.mkstemp()
    try:
      GCSHelper.download_gcs_blob(temp_path, gcs_path)
      with os.fdopen(fd, 'r') as tmp:
        result = tmp.read()
    finally:
      os.remove(temp_path)
    return result

  @staticmethod
  def create_gcs_bucket_if_not_exist(gcs_bucket):
    """
    Args:
      gcs_bucket (str) : gcs bucket name
    """
    from google.cloud import storage
    from google.cloud.exceptions import NotFound
    client = storage.Client()
    try:
      client.get_bucket(gcs_bucket)
    except NotFound:
      client.create_bucket(gcs_bucket)