# Copyright (c) Facebook, Inc. and its affiliates.
#
# This source code is licensed under the MIT license found in the
# LICENSE file in the root directory of this source tree.
"""isort:skip_file"""

import argparse
import importlib
import os
from argparse import Namespace
from typing import Union

import fairseq
from fairseq.dataclass import FairseqDataclass
from omegaconf import DictConfig, OmegaConf

from .composite_encoder import CompositeEncoder
from .distributed_fairseq_model import DistributedFairseqModel
from .fairseq_decoder import FairseqDecoder
from .fairseq_encoder import FairseqEncoder
from .fairseq_incremental_decoder import FairseqIncrementalDecoder
from .fairseq_model import (
    BaseFairseqModel,
    FairseqEncoderDecoderModel,
    FairseqEncoderModel,
    FairseqLanguageModel,
    FairseqModel,
    FairseqMultiModel,
)


MODEL_REGISTRY = {}
MODEL_DATACLASS_REGISTRY = {}
ARCH_MODEL_REGISTRY = {}
ARCH_MODEL_NAME_REGISTRY = {}
ARCH_MODEL_INV_REGISTRY = {}
ARCH_CONFIG_REGISTRY = {}


__all__ = [
    "BaseFairseqModel",
    "CompositeEncoder",
    "DistributedFairseqModel",
    "FairseqDecoder",
    "FairseqEncoder",
    "FairseqEncoderDecoderModel",
    "FairseqEncoderModel",
    "FairseqIncrementalDecoder",
    "FairseqLanguageModel",
    "FairseqModel",
    "FairseqMultiModel",
]


def build_model(model_cfg: Union[DictConfig, Namespace], task):
    if isinstance(model_cfg, DictConfig):
        return ARCH_MODEL_REGISTRY[model_cfg._name].build_model(model_cfg, task)
    return ARCH_MODEL_REGISTRY[model_cfg.arch].build_model(model_cfg, task)


def register_model(name, dataclass=None):
    """
    New model types can be added to fairseq with the :func:`register_model`
    function decorator.

    For example::

        @register_model('lstm')
        class LSTM(FairseqEncoderDecoderModel):
            (...)

    .. note:: All models must implement the :class:`BaseFairseqModel` interface.
        Typically you will extend :class:`FairseqEncoderDecoderModel` for
        sequence-to-sequence tasks or :class:`FairseqLanguageModel` for
        language modeling tasks.

    Args:
        name (str): the name of the model
    """

    def register_model_cls(cls):
        if name in MODEL_REGISTRY:
            raise ValueError("Cannot register duplicate model ({})".format(name))
        if not issubclass(cls, BaseFairseqModel):
            raise ValueError(
                "Model ({}: {}) must extend BaseFairseqModel".format(name, cls.__name__)
            )
        MODEL_REGISTRY[name] = cls
        if dataclass is not None and not issubclass(dataclass, FairseqDataclass):
            raise ValueError(
                "Dataclass {} must extend FairseqDataclass".format(dataclass)
            )

        cls.__dataclass = dataclass
        MODEL_DATACLASS_REGISTRY[name] = dataclass
        return cls

    return register_model_cls


def register_model_architecture(model_name, arch_name):
    """
    New model architectures can be added to fairseq with the
    :func:`register_model_architecture` function decorator. After registration,
    model architectures can be selected with the ``--arch`` command-line
    argument.

    For example::

        @register_model_architecture('lstm', 'lstm_luong_wmt_en_de')
        def lstm_luong_wmt_en_de(args):
            args.encoder_embed_dim = getattr(args, 'encoder_embed_dim', 1000)
            (...)

    The decorated function should take a single argument *args*, which is a
    :class:`argparse.Namespace` of arguments parsed from the command-line. The
    decorated function should modify these arguments in-place to match the
    desired architecture.

    Args:
        model_name (str): the name of the Model (Model must already be
            registered)
        arch_name (str): the name of the model architecture (``--arch``)
    """

    def arch_override_from_yaml(args, arch):
        root_dir = os.path.dirname(os.path.dirname(fairseq.__file__))
        yaml_path = os.path.join(root_dir, "config/model/{}.yaml".format(arch))
        if not os.path.exists(yaml_path):
            raise RuntimeError(f"yaml file {yaml_path} does not exist!")
        arch_cfg = OmegaConf.load(yaml_path)
        for k, v in arch_cfg.items():
            setattr(args, k, getattr(args, k, v))

    def register_model_arch_fn(fn):
        if model_name not in MODEL_REGISTRY:
            raise ValueError(
                "Cannot register model architecture for unknown model type ({})".format(
                    model_name
                )
            )
        if arch_name in ARCH_MODEL_REGISTRY:
            raise ValueError(
                "Cannot register duplicate model architecture ({})".format(arch_name)
            )
        if not callable(fn):
            raise ValueError(
                "Model architecture must be callable ({})".format(arch_name)
            )
        ARCH_MODEL_REGISTRY[arch_name] = MODEL_REGISTRY[model_name]
        ARCH_MODEL_NAME_REGISTRY[arch_name] = model_name
        ARCH_MODEL_INV_REGISTRY.setdefault(model_name, []).append(arch_name)
        if type(fn) is type and issubclass(fn, BaseFairseqModel):
            # for model classes migrated with hydra
            # in this case, we are using this decorator directly on model class since
            # we do not need arch overriding functions.
            ARCH_CONFIG_REGISTRY[arch_name] = lambda args: arch_override_from_yaml(
                args, arch=arch_name
            )
        else:
            ARCH_CONFIG_REGISTRY[arch_name] = fn
        return fn

    return register_model_arch_fn


# automatically import any Python files in the models/ directory
models_dir = os.path.dirname(__file__)
for file in os.listdir(models_dir):
    path = os.path.join(models_dir, file)
    if (
        not file.startswith("_")
        and not file.startswith(".")
        and (file.endswith(".py") or os.path.isdir(path))
    ):
        model_name = file[: file.find(".py")] if file.endswith(".py") else file
        module = importlib.import_module("fairseq.models." + model_name)

        # extra `model_parser` for sphinx
        if model_name in MODEL_REGISTRY:
            parser = argparse.ArgumentParser(add_help=False)
            group_archs = parser.add_argument_group("Named architectures")
            group_archs.add_argument(
                "--arch", choices=ARCH_MODEL_INV_REGISTRY[model_name]
            )
            group_args = parser.add_argument_group("Additional command-line arguments")
            MODEL_REGISTRY[model_name].add_args(group_args)
            globals()[model_name + "_parser"] = parser
