# coding=utf-8
# Copyright 2020 The HuggingFace Inc. team.
# Copyright (c) 2018, NVIDIA CORPORATION.  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.

import copy
import logging

from .configuration_utils import PretrainedConfig


logger = logging.getLogger(__name__)


class EncoderDecoderConfig(PretrainedConfig):
    r"""
        :class:`~transformers.EncoderDecoderConfig` is the configuration class to store the configuration of a `EncoderDecoderModel`.

        It is used to instantiate an Encoder Decoder model according to the specified arguments, defining the encoder and decoder configs.
        Configuration objects inherit from  :class:`~transformers.PretrainedConfig`
        and can be used to control the model outputs.
        See the documentation for :class:`~transformers.PretrainedConfig` for more information.

        Args:
            kwargs (`optional`):
                Remaining dictionary of keyword arguments. Notably:
                    encoder (:class:`PretrainedConfig`, optional, defaults to `None`):
                        An instance of a configuration object that defines the encoder config.
                    encoder (:class:`PretrainedConfig`, optional, defaults to `None`):
                        An instance of a configuration object that defines the decoder config.

        Example::

            from transformers import BertConfig, EncoderDecoderConfig, EncoderDecoderModel

            # Initializing a BERT bert-base-uncased style configuration
            config_encoder = BertConfig()
            config_decoder = BertConfig()

            config = EncoderDecoderConfig.from_encoder_decoder_configs(config_encoder, config_decoder)

            # Initializing a Bert2Bert model from the bert-base-uncased style configurations
            model = EncoderDecoderModel(config=config)

            # Accessing the model configuration
            config_encoder = model.config.encoder
            config_decoder  = model.config.decoder
    """
    model_type = "encoder_decoder"

    def __init__(self, **kwargs):
        super().__init__(**kwargs)
        assert (
            "encoder" in kwargs and "decoder" in kwargs
        ), "Config has to be initialized with encoder and decoder config"
        encoder_config = kwargs.pop("encoder")
        encoder_model_type = encoder_config.pop("model_type")
        decoder_config = kwargs.pop("decoder")
        decoder_model_type = decoder_config.pop("model_type")

        from transformers import AutoConfig

        self.encoder = AutoConfig.for_model(encoder_model_type, **encoder_config)
        self.decoder = AutoConfig.for_model(decoder_model_type, **decoder_config)
        self.is_encoder_decoder = True

    @classmethod
    def from_encoder_decoder_configs(
        cls, encoder_config: PretrainedConfig, decoder_config: PretrainedConfig
    ) -> PretrainedConfig:
        r"""
        Instantiate a :class:`~transformers.EncoderDecoderConfig` (or a derived class) from a pre-trained encoder model configuration and decoder model configuration.

        Returns:
            :class:`EncoderDecoderConfig`: An instance of a configuration object
        """
        logger.info("Set `config.is_decoder=True` for decoder_config")
        decoder_config.is_decoder = True

        return cls(encoder=encoder_config.to_dict(), decoder=decoder_config.to_dict())

    def to_dict(self):
        """
        Serializes this instance to a Python dictionary. Override the default `to_dict()` from `PretrainedConfig`.

        Returns:
            :obj:`Dict[str, any]`: Dictionary of all the attributes that make up this configuration instance,
        """
        output = copy.deepcopy(self.__dict__)
        output["encoder"] = self.encoder.to_dict()
        output["decoder"] = self.decoder.to_dict()
        output["model_type"] = self.__class__.model_type
        return output
