#!/usr/bin/env python

#

# 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.

#

"""Makes API calls to various Google-provided services.

Provides methods for making calls into Google Apphosting services and APIs

from your application code. This code will only work properly from within

the Google Apphosting environment.

"""

import sys

from google.net.proto import ProtocolBuffer

from google.appengine import runtime

from google.appengine.runtime import apiproxy_errors

from google3.apphosting.runtime import _apphosting_runtime___python__apiproxy

OK                =  0

RPC_FAILED        =  1

CALL_NOT_FOUND    =  2

ARGUMENT_ERROR    =  3

DEADLINE_EXCEEDED =  4

CANCELLED         =  5

APPLICATION_ERROR =  6

OTHER_ERROR       =  7

OVER_QUOTA        =  8

REQUEST_TOO_LARGE =  9

CAPABILITY_DISABLED = 10

_ExceptionsMap = {

  RPC_FAILED:

  (apiproxy_errors.RPCFailedError,

   "The remote RPC to the application server failed for the call %s.%s()."),

  CALL_NOT_FOUND:

  (apiproxy_errors.CallNotFoundError,

   "The API package '%s' or call '%s()' was not found."),

  ARGUMENT_ERROR:

  (apiproxy_errors.ArgumentError,

   "An error occurred parsing (locally or remotely) the arguments to %s.%s()."),

  DEADLINE_EXCEEDED:

  (apiproxy_errors.DeadlineExceededError,

   "The API call %s.%s() took too long to respond and was cancelled."),

  CANCELLED:

  (apiproxy_errors.CancelledError,

   "The API call %s.%s() was explicitly cancelled."),

  OTHER_ERROR:

  (apiproxy_errors.Error,

   "An error occurred for the API request %s.%s()."),

  OVER_QUOTA:

  (apiproxy_errors.OverQuotaError,

  "The API call %s.%s() required more quota than is available."),

  REQUEST_TOO_LARGE:

  (apiproxy_errors.RequestTooLargeError,

  "The request to API call %s.%s() was too large."),

}

class RPC(object):

  """A RPC object, suitable for talking to remote services.

  Each instance of this object can be used only once, and should not be reused.

  Stores the data members and methods for making RPC calls via the APIProxy.

  """

  IDLE = 0

  RUNNING = 1

  FINISHING = 2

  def __init__(self, package=None, call=None, request=None, response=None,

               callback=None):

    """Constructor for the RPC object. All arguments are optional, and

    simply set members on the class. These data members will be

    overriden by values passed to MakeCall.

    Args:

      package: string, the package for the call

      call: string, the call within the package

      request: ProtocolMessage instance, appropriate for the arguments

      response: ProtocolMessage instance, appropriate for the response

      callback: callable, called when call is complete

    """

    self.__exception = None

    self.__traceback = None

    self.__result_dict = {}

    self.__state = RPC.IDLE

    self.package = package

    self.call = call

    self.request = request

    self.response = response

    self.callback = callback

  def MakeCall(self, package=None, call=None, request=None, response=None,

               callback=None):

    """Makes an asynchronous (i.e. non-blocking) API call within the

    specified package for the specified call method. request and response must

    be the appropriately typed ProtocolBuffers for the API call.

    callback, if provided, will be called when the request completes

    successfully or when an error occurs.  If an error has ocurred, the

    exception() method on this class will return the error, which can be

    accessed from the callback.

    Args:

      Same as constructor; see __init__.

    Raises:

      TypeError or AssertionError if an argument is of an invalid type.

      AssertionError or RuntimeError is an RPC is already in use.

    """

    self.callback = callback or self.callback

    self.package = package or self.package

    self.call = call or self.call

    self.request = request or self.request

    self.response = response or self.response

    assert self.__state is RPC.IDLE, ("RPC for %s.%s has already been started" %

                                      (self.package, self.call))

    assert self.callback is None or callable(self.callback)

    assert isinstance(self.request, ProtocolBuffer.ProtocolMessage)

    assert isinstance(self.response, ProtocolBuffer.ProtocolMessage)

    e = ProtocolBuffer.Encoder()

    self.request.Output(e)

    self.__state = RPC.RUNNING

    _apphosting_runtime___python__apiproxy.MakeCall(

        self.package, self.call, e.buffer(), self.__result_dict,

        self.__MakeCallDone, self)

  def Wait(self):

    """Waits on the API call associated with this RPC. The callback,

    if provided, will be executed before Wait() returns. If this RPC

    is already complete, or if the RPC was never started, this

    function will return immediately.

    Raises:

      InterruptedError if a callback throws an uncaught exception.

    """

    try:

      rpc_completed = _apphosting_runtime___python__apiproxy.Wait(self)

    except runtime.DeadlineExceededError:

      raise

    except apiproxy_errors.InterruptedError:

      raise

    except:

      exc_class, exc, tb = sys.exc_info()

      if (isinstance(exc, SystemError) and

          exc.args == ('uncaught RPC exception',)):

        raise

      rpc = None

      if hasattr(exc, "_appengine_apiproxy_rpc"):

        rpc = exc._appengine_apiproxy_rpc

      new_exc = apiproxy_errors.InterruptedError(exc, rpc)

      raise new_exc.__class__, new_exc, tb

    assert rpc_completed, ("RPC for %s.%s was not completed, and no other " +

                           "exception was raised " % (self.package, self.call))

  def CheckSuccess(self):

    """If there was an exception, raise it now.

    Raises:

      Exception of the API call or the callback, if any.

    """

    if self.exception and self.__traceback:

      raise self.exception.__class__, self.exception, self.__traceback

    if self.exception:

      raise self.exception

  @property

  def exception(self):

    return self.__exception

  @property

  def state(self):

    return self.__state

  def __MakeCallDone(self):

    self.__state = RPC.FINISHING

    if self.__result_dict['error'] == APPLICATION_ERROR:

      self.__exception = apiproxy_errors.ApplicationError(

          self.__result_dict['application_error'],

          self.__result_dict['error_detail'])

    elif self.__result_dict['error'] == CAPABILITY_DISABLED:

      if self.__result_dict['error_detail']:

        self.__exception = apiproxy_errors.CapabilityDisabledError(

            self.__result_dict['error_detail'])

      else:

        self.__exception = apiproxy_errors.CapabilityDisabledError(

            "The API call %s.%s() is temporarily unavailable." % (

            self.package, self.call))

    elif _ExceptionsMap.has_key(self.__result_dict['error']):

      exception_entry = _ExceptionsMap[self.__result_dict['error']]

      self.__exception = exception_entry[0](

          exception_entry[1] % (self.package, self.call))

    else:

      try:

        self.response.ParseFromString(self.__result_dict['result_string'])

      except Exception, e:

        self.__exception = e

    if self.callback:

      try:

        self.callback()

      except:

        exc_class, self.__exception, self.__traceback = sys.exc_info()

        self.__exception._appengine_apiproxy_rpc = self

        raise

def MakeSyncCall(package, call, request, response):

  """Makes a synchronous (i.e. blocking) API call within the specified

  package for the specified call method. request and response must be the

  appropriately typed ProtocolBuffers for the API call. An exception is

  thrown if an error occurs when communicating with the system.

  Args:

    See MakeCall above.

  Raises:

    See CheckSuccess() above.

  """

  rpc = RPC()

  rpc.MakeCall(package, call, request, response)

  rpc.Wait()

  rpc.CheckSuccess()