#!/usr/bin/env python2.7
#
# Copyright 2007 Google Inc.
#
# 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.
#




"""A Python blobstore API used by app developers.

Contains methods uses to interface with Blobstore API.  Defines db.Key-like
class representing a blob-key.  Contains API part that forward to apiproxy.
"""








import datetime
import time

from google.appengine.api import apiproxy_stub_map
from google.appengine.api import datastore
from google.appengine.api import datastore_errors
from google.appengine.api import datastore_types
from google.appengine.api import api_base_pb
from google.appengine.api.blobstore import blobstore_service_pb
from google.appengine.runtime import apiproxy_errors


__all__ = ['BLOB_INFO_KIND',
           'BLOB_KEY_HEADER',
           'BLOB_MIGRATION_KIND',
           'BLOB_RANGE_HEADER',
           'MAX_BLOB_FETCH_SIZE',
           'UPLOAD_INFO_CREATION_HEADER',
           'CLOUD_STORAGE_OBJECT_HEADER',
           'GS_PREFIX',
           'BlobFetchSizeTooLargeError',
           'BlobKey',
           'BlobNotFoundError',
           'DataIndexOutOfRangeError',
           'PermissionDeniedError',
           'Error',
           'InternalError',
           'create_rpc',
           'create_upload_url',
           'create_upload_url_async',
           'delete',
           'delete_async',
           'fetch_data',
           'fetch_data_async',
           'create_gs_key',
           'create_gs_key_async',
          ]


BlobKey = datastore_types.BlobKey



BLOB_INFO_KIND = '__BlobInfo__'

BLOB_KEY_HEADER = 'X-AppEngine-BlobKey'

BLOB_MIGRATION_KIND = '__BlobMigration__'

BLOB_RANGE_HEADER = 'X-AppEngine-BlobRange'

MAX_BLOB_FETCH_SIZE = (1 << 20) - (1 << 15)

GS_PREFIX = '/gs/'



UPLOAD_INFO_CREATION_HEADER = 'X-AppEngine-Upload-Creation'
CLOUD_STORAGE_OBJECT_HEADER = 'X-AppEngine-Cloud-Storage-Object'
_BASE_CREATION_HEADER_FORMAT = '%Y-%m-%d %H:%M:%S'

class Error(Exception):
  """Base blobstore error type."""


class InternalError(Error):
  """Raised when an internal error occurs within API."""


class BlobNotFoundError(Error):
  """Raised when attempting to access blob data for non-existant blob."""


class DataIndexOutOfRangeError(Error):
  """Raised when attempting to access indexes out of range in wrong order."""


class BlobFetchSizeTooLargeError(Error):
  """Raised when attempting to fetch too large a block from a blob."""


class _CreationFormatError(Error):
  """Raised when attempting to parse bad creation date format."""


class PermissionDeniedError(Error):
  """Raised when permissions are lacking for a requested operation."""


def _ToBlobstoreError(error):
  """Translate an application error to a datastore Error, if possible.

  Args:
    error: An ApplicationError to translate.
  """
  error_map = {
      blobstore_service_pb.BlobstoreServiceError.INTERNAL_ERROR:
      InternalError,
      blobstore_service_pb.BlobstoreServiceError.BLOB_NOT_FOUND:
      BlobNotFoundError,
      blobstore_service_pb.BlobstoreServiceError.DATA_INDEX_OUT_OF_RANGE:
      DataIndexOutOfRangeError,
      blobstore_service_pb.BlobstoreServiceError.BLOB_FETCH_SIZE_TOO_LARGE:
      BlobFetchSizeTooLargeError,
      blobstore_service_pb.BlobstoreServiceError.PERMISSION_DENIED:
      PermissionDeniedError,
      }
  desired_exc = error_map.get(error.application_error)
  return desired_exc(error.error_detail) if desired_exc else error


def _format_creation(stamp):
  """Format an upload creation timestamp with milliseconds.

  This method is necessary to format a timestamp with microseconds on Python
  versions before 2.6.

  Cannot simply convert datetime objects to str because the microseconds are
  stripped from the format when set to 0.  The upload creation date format will
  always have microseconds padded out to 6 places.

  Args:
    stamp: datetime.datetime object to format.

  Returns:
    Formatted datetime as Python 2.6 format '%Y-%m-%d %H:%M:%S.%f'.
  """
  return '%s.%06d' % (stamp.strftime(_BASE_CREATION_HEADER_FORMAT),
                      stamp.microsecond)


def _parse_creation(creation_string, field_name):
  """Parses upload creation string from header format.

  Parse creation date of the format:

    YYYY-mm-dd HH:MM:SS.ffffff

    Y: Year
    m: Month (01-12)
    d: Day (01-31)
    H: Hour (00-24)
    M: Minute (00-59)
    S: Second (00-59)
    f: Microsecond

  Args:
    creation_string: String creation date format.

  Returns:
    datetime object parsed from creation_string.

  Raises:
    _CreationFormatError when the creation string is formatted incorrectly.
  """


  split_creation_string = creation_string.split('.', 1)
  if len(split_creation_string) != 2:
    raise _CreationFormatError(
        'Could not parse creation %s in field %s.' % (creation_string,
                                                      field_name))
  timestamp_string, microsecond = split_creation_string

  try:
    timestamp = time.strptime(timestamp_string,
                              _BASE_CREATION_HEADER_FORMAT)
    microsecond = int(microsecond)
  except ValueError:
    raise _CreationFormatError('Could not parse creation %s in field %s.'
                               % (creation_string, field_name))

  return datetime.datetime(*timestamp[:6] + tuple([microsecond]))


def create_rpc(deadline=None, callback=None):
  """Creates an RPC object for use with the blobstore API.

  Args:
    deadline: Optional deadline in seconds for the operation; the default
      is a system-specific deadline (typically 5 seconds).
    callback: Optional callable to invoke on completion.

  Returns:
    An apiproxy_stub_map.UserRPC object specialized for this service.
  """
  return apiproxy_stub_map.UserRPC('blobstore', deadline, callback)


def _make_async_call(rpc, method, request, response,
                     get_result_hook, user_data):
  if rpc is None:
    rpc = create_rpc()
  rpc.make_call(method, request, response, get_result_hook, user_data)
  return rpc


def _get_result_hook(rpc):
  try:
    rpc.check_success()
  except apiproxy_errors.ApplicationError, err:
    raise _ToBlobstoreError(err)
  hook = rpc.user_data
  return hook(rpc)


def create_upload_url(success_path,
                      max_bytes_per_blob=None,
                      max_bytes_total=None,
                      rpc=None,
                      gs_bucket_name=None):
  """Create upload URL for POST form.

  Args:
    success_path: Path within application to call when POST is successful
      and upload is complete.
    max_bytes_per_blob: The maximum size in bytes that any one blob in the
      upload can be or None for no maximum size.
    max_bytes_total: The maximum size in bytes that the aggregate sizes of all
      of the blobs in the upload can be or None for no maximum size.
    rpc: Optional UserRPC object.
    gs_bucket_name: The Google Storage bucket name that the blobs should be
      uploaded to. The application's service account must have the correct
      permissions to write to this bucket. The bucket name may be of the foramt
      'bucket/path/', in which case the included path will be prepended to the
      uploaded object name.

  Returns:
    The upload URL.

  Raises:
    TypeError: If max_bytes_per_blob or max_bytes_total are not integral types.
    ValueError: If max_bytes_per_blob or max_bytes_total are not
      positive values.
  """
  rpc = create_upload_url_async(success_path,
                                max_bytes_per_blob=max_bytes_per_blob,
                                max_bytes_total=max_bytes_total,
                                rpc=rpc,
                                gs_bucket_name=gs_bucket_name)
  return rpc.get_result()


def create_upload_url_async(success_path,
                            max_bytes_per_blob=None,
                            max_bytes_total=None,
                            rpc=None,
                            gs_bucket_name=None):
  """Create upload URL for POST form -- async version.

  Args:
    success_path: Path within application to call when POST is successful
      and upload is complete.
    max_bytes_per_blob: The maximum size in bytes that any one blob in the
      upload can be or None for no maximum size.
    max_bytes_total: The maximum size in bytes that the aggregate sizes of all
      of the blobs in the upload can be or None for no maximum size.
    rpc: Optional UserRPC object.
    gs_bucket_name: The Google Storage bucket name that the blobs should be
      uploaded to. The application's service account must have the correct
      permissions to write to this bucket. The bucket name may be of the foramt
      'bucket/path/', in which case the included path will be prepended to the
      uploaded object name.

  Returns:
    A UserRPC whose result will be the upload URL.

  Raises:
    TypeError: If max_bytes_per_blob or max_bytes_total are not integral types.
    ValueError: If max_bytes_per_blob or max_bytes_total are not
      positive values.
  """
  request = blobstore_service_pb.CreateUploadURLRequest()
  response = blobstore_service_pb.CreateUploadURLResponse()
  request.set_success_path(success_path)

  if max_bytes_per_blob is not None:
    if not isinstance(max_bytes_per_blob, (int, long)):
      raise TypeError('max_bytes_per_blob must be integer.')
    if max_bytes_per_blob < 1:
      raise ValueError('max_bytes_per_blob must be positive.')
    request.set_max_upload_size_per_blob_bytes(max_bytes_per_blob)

  if max_bytes_total is not None:
    if not isinstance(max_bytes_total, (int, long)):
      raise TypeError('max_bytes_total must be integer.')
    if max_bytes_total < 1:
      raise ValueError('max_bytes_total must be positive.')
    request.set_max_upload_size_bytes(max_bytes_total)

  if (request.has_max_upload_size_bytes() and
      request.has_max_upload_size_per_blob_bytes()):
    if (request.max_upload_size_bytes() <
        request.max_upload_size_per_blob_bytes()):
      raise ValueError('max_bytes_total can not be less'
                       ' than max_upload_size_per_blob_bytes')

  if gs_bucket_name is not None:
    if not isinstance(gs_bucket_name, basestring):
      raise TypeError('gs_bucket_name must be a string.')
    request.set_gs_bucket_name(gs_bucket_name)

  return _make_async_call(rpc, 'CreateUploadURL', request, response,
                          _get_result_hook, lambda rpc: rpc.response.url())


def delete(blob_keys, rpc=None):
  """Delete a blob from Blobstore.

  Args:
    blob_keys: Single instance or list of blob keys.  A blob-key can be either
      a string or an instance of BlobKey.
    rpc: Optional UserRPC object.

  Returns:
    None.
  """
  rpc = delete_async(blob_keys, rpc)
  return rpc.get_result()


def delete_async(blob_keys, rpc=None):
  """Delete a blob from Blobstore -- async version.

  Args:
    blob_keys: Single instance or list of blob keys.  A blob-key can be either
      a string or an instance of BlobKey.
    rpc: Optional UserRPC object.

  Returns:
    A UserRPC whose result will be None.
  """
  if isinstance(blob_keys, (basestring, BlobKey)):
    blob_keys = [blob_keys]
  request = blobstore_service_pb.DeleteBlobRequest()
  for blob_key in blob_keys:
    request.add_blob_key(str(blob_key))
  response = api_base_pb.VoidProto()

  return _make_async_call(rpc, 'DeleteBlob', request, response,
                          _get_result_hook, lambda rpc: None)


def fetch_data(blob_key, start_index, end_index, rpc=None):
  """Fetch data for blob.

  See docstring for ext.blobstore.fetch_data for more details.

  Args:
    blob: BlobKey, str or unicode representation of BlobKey of
      blob to fetch data from.
    start_index: Start index of blob data to fetch.  May not be negative.
    end_index: End index (exclusive) of blob data to fetch.  Must be
      >= start_index.
    rpc: Optional UserRPC object.

  Returns:
    A str containing partial data of blob.  See docstring for
    ext.blobstore.fetch_data for more details.

  Raises:
    See docstring for ext.blobstore.fetch_data for more details.
  """
  rpc = fetch_data_async(blob_key, start_index, end_index, rpc)
  return rpc.get_result()


def fetch_data_async(blob_key, start_index, end_index, rpc=None):
  """Fetch data for blob -- async version.

  See docstring for ext.blobstore.fetch_data for more details.

  Args:
    blob: BlobKey, str or unicode representation of BlobKey of
      blob to fetch data from.
    start_index: Start index of blob data to fetch.  May not be negative.
    end_index: End index (exclusive) of blob data to fetch.  Must be
      >= start_index.
    rpc: Optional UserRPC object.

  Returns:
    A UserRPC whose result will be a str as returned by fetch_data().

  Raises:
    See docstring for ext.blobstore.fetch_data for more details.
  """
  if not isinstance(start_index, (int, long)):
    raise TypeError('start_index must be integer.')

  if not isinstance(end_index, (int, long)):
    raise TypeError('end_index must be integer.')

  if isinstance(blob_key, BlobKey):
    blob_key = str(blob_key).decode('utf-8')
  elif isinstance(blob_key, str):
    blob_key = blob_key.decode('utf-8')
  elif not isinstance(blob_key, unicode):
    raise TypeError('Blob-key must be str, unicode or BlobKey: %s' % blob_key)


  if start_index < 0:
    raise DataIndexOutOfRangeError(
        'May not fetch blob at negative index.')


  if end_index < start_index:
    raise DataIndexOutOfRangeError(
        'Start index %d > end index %d' % (start_index, end_index))


  fetch_size = end_index - start_index + 1

  if fetch_size > MAX_BLOB_FETCH_SIZE:
    raise BlobFetchSizeTooLargeError(
        'Blob fetch size is too large: %d' % fetch_size)

  request = blobstore_service_pb.FetchDataRequest()
  response = blobstore_service_pb.FetchDataResponse()

  request.set_blob_key(blob_key)
  request.set_start_index(start_index)
  request.set_end_index(end_index)

  return _make_async_call(rpc, 'FetchData', request, response,
                          _get_result_hook, lambda rpc: rpc.response.data())


def create_gs_key(filename, rpc=None):
  """Create an encoded key for a Google Storage file.

  The created blob key will include short lived access token using the
  application's service account for authorization.

  This blob key should not be stored permanently as the access token will
  expire.

  Args:
    filename: The filename of the google storage object to create the key for.
    rpc: Optional UserRPC object.

  Returns:
    An encrypted blob key object that also contains a short term access token
      that represents the application's service account.
  """
  rpc = create_gs_key_async(filename, rpc)
  return rpc.get_result()


def create_gs_key_async(filename, rpc=None):
  """Create an encoded key for a google storage file - async version.

  The created blob key will include short lived access token using the
  application's service account for authorization.

  This blob key should not be stored permanently as the access token will
  expire.

  Args:
    filename: The filename of the google storage object to create the
      key for.
    rpc: Optional UserRPC object.

  Returns:
    A UserRPC whose result will be a str as returned by create_gs_key.

  Raises:
    TypeError: If filename is not a string.
    ValueError: If filename is not in the format '/gs/bucket_name/object_name'
  """

  if not isinstance(filename, basestring):
    raise TypeError('filename must be str: %s' % filename)
  if not filename.startswith(GS_PREFIX):
    raise ValueError('filename must start with "/gs/": %s' % filename)
  if not '/' in filename[4:]:
    raise ValueError('filename must have the format '
                     '"/gs/bucket_name/object_name": %s' % filename)

  request = blobstore_service_pb.CreateEncodedGoogleStorageKeyRequest()
  response = blobstore_service_pb.CreateEncodedGoogleStorageKeyResponse()

  request.set_filename(filename)

  return _make_async_call(rpc,
                          'CreateEncodedGoogleStorageKey',
                          request,
                          response,
                          _get_result_hook,
                          lambda rpc: rpc.response.blob_key())
