# Protocol Buffers - Google's data interchange format
# Copyright 2008 Google Inc.  All rights reserved.
# https://developers.google.com/protocol-buffers/
#
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"""Provides type checking routines.

This module defines type checking utilities in the forms of dictionaries:

VALUE_CHECKERS: A dictionary of field types and a value validation object.
TYPE_TO_BYTE_SIZE_FN: A dictionary with field types and a size computing
  function.
TYPE_TO_SERIALIZE_METHOD: A dictionary with field types and serialization
  function.
FIELD_TYPE_TO_WIRE_TYPE: A dictionary with field typed and their
  coresponding wire types.
TYPE_TO_DESERIALIZE_METHOD: A dictionary with field types and deserialization
  function.
"""

__author__ = 'robinson@google.com (Will Robinson)'

import six

if six.PY3:
  long = int

from google.protobuf.internal import api_implementation
from google.protobuf.internal import decoder
from google.protobuf.internal import encoder
from google.protobuf.internal import wire_format
from google.protobuf import descriptor

_FieldDescriptor = descriptor.FieldDescriptor

def SupportsOpenEnums(field_descriptor):
  return field_descriptor.containing_type.syntax == "proto3"

def GetTypeChecker(field):
  """Returns a type checker for a message field of the specified types.

  Args:
    field: FieldDescriptor object for this field.

  Returns:
    An instance of TypeChecker which can be used to verify the types
    of values assigned to a field of the specified type.
  """
  if (field.cpp_type == _FieldDescriptor.CPPTYPE_STRING and
      field.type == _FieldDescriptor.TYPE_STRING):
    return UnicodeValueChecker()
  if field.cpp_type == _FieldDescriptor.CPPTYPE_ENUM:
    if SupportsOpenEnums(field):
      # When open enums are supported, any int32 can be assigned.
      return _VALUE_CHECKERS[_FieldDescriptor.CPPTYPE_INT32]
    else:
      return EnumValueChecker(field.enum_type)
  return _VALUE_CHECKERS[field.cpp_type]


# None of the typecheckers below make any attempt to guard against people
# subclassing builtin types and doing weird things.  We're not trying to
# protect against malicious clients here, just people accidentally shooting
# themselves in the foot in obvious ways.

class TypeChecker(object):

  """Type checker used to catch type errors as early as possible
  when the client is setting scalar fields in protocol messages.
  """

  def __init__(self, *acceptable_types):
    self._acceptable_types = acceptable_types

  def CheckValue(self, proposed_value):
    """Type check the provided value and return it.

    The returned value might have been normalized to another type.
    """
    if not isinstance(proposed_value, self._acceptable_types):
      message = ('%.1024r has type %s, but expected one of: %s' %
                 (proposed_value, type(proposed_value), self._acceptable_types))
      raise TypeError(message)
    return proposed_value


class TypeCheckerWithDefault(TypeChecker):

  def __init__(self, default_value, *acceptable_types):
    TypeChecker.__init__(self, acceptable_types)
    self._default_value = default_value

  def DefaultValue(self):
    return self._default_value


# IntValueChecker and its subclasses perform integer type-checks
# and bounds-checks.
class IntValueChecker(object):

  """Checker used for integer fields.  Performs type-check and range check."""

  def CheckValue(self, proposed_value):
    if not isinstance(proposed_value, six.integer_types):
      message = ('%.1024r has type %s, but expected one of: %s' %
                 (proposed_value, type(proposed_value), six.integer_types))
      raise TypeError(message)
    if not self._MIN <= proposed_value <= self._MAX:
      raise ValueError('Value out of range: %d' % proposed_value)
    # We force 32-bit values to int and 64-bit values to long to make
    # alternate implementations where the distinction is more significant
    # (e.g. the C++ implementation) simpler.
    proposed_value = self._TYPE(proposed_value)
    return proposed_value

  def DefaultValue(self):
    return 0


class EnumValueChecker(object):

  """Checker used for enum fields.  Performs type-check and range check."""

  def __init__(self, enum_type):
    self._enum_type = enum_type

  def CheckValue(self, proposed_value):
    if not isinstance(proposed_value, six.integer_types):
      message = ('%.1024r has type %s, but expected one of: %s' %
                 (proposed_value, type(proposed_value), six.integer_types))
      raise TypeError(message)
    if proposed_value not in self._enum_type.values_by_number:
      raise ValueError('Unknown enum value: %d' % proposed_value)
    return proposed_value

  def DefaultValue(self):
    return self._enum_type.values[0].number


class UnicodeValueChecker(object):

  """Checker used for string fields.

  Always returns a unicode value, even if the input is of type str.
  """

  def CheckValue(self, proposed_value):
    if not isinstance(proposed_value, (bytes, six.text_type)):
      message = ('%.1024r has type %s, but expected one of: %s' %
                 (proposed_value, type(proposed_value), (bytes, six.text_type)))
      raise TypeError(message)

    # If the value is of type 'bytes' make sure that it is valid UTF-8 data.
    if isinstance(proposed_value, bytes):
      try:
        proposed_value = proposed_value.decode('utf-8')
      except UnicodeDecodeError:
        raise ValueError('%.1024r has type bytes, but isn\'t valid UTF-8 '
                         'encoding. Non-UTF-8 strings must be converted to '
                         'unicode objects before being added.' %
                         (proposed_value))
    return proposed_value

  def DefaultValue(self):
    return u""