# Copyright 2024 The HuggingFace Inc. team. 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
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# 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.
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import itertools
from contextlib import contextmanager
from dataclasses import dataclass
from typing import TYPE_CHECKING, Literal, Optional, Tuple, Union

from accelerate.utils import is_deepspeed_available
from transformers import PreTrainedModel, PreTrainedTokenizer

from .modeling_value_head import AutoModelForCausalLMWithValueHead, AutoModelForSeq2SeqLMWithValueHead


SUPPORTED_ARCHITECTURES = (
    AutoModelForCausalLMWithValueHead,
    AutoModelForSeq2SeqLMWithValueHead,
)

if is_deepspeed_available():
    import deepspeed

if TYPE_CHECKING:
    from accelerate import Accelerator
    from deepspeed.runtime.engine import DeepSpeedEngine
    from torch.nn.parallel.distributed import DistributedDataParallel

    from .modeling_base import PreTrainedModelWrapper


# TODO: Add Abstract Base Class if more formats are added
@dataclass
class ChatMlSpecialTokens:
    """Dataclass for special tokens used in ChatML, including system, user, assistant, bos, eos, and pad tokens."""

    bos_token: str = "<|im_start|>"
    eos_token: str = "<|im_end|>"
    pad_token: str = "<|im_end|>"

    @property
    def system(self):
        return f"{self.bos_token}system"

    @property
    def user(self):
        return f"{self.bos_token}user"

    @property
    def assistant(self):
        return f"{self.bos_token}assistant"

    @property
    def chat_template(self):
        return (
            "{% for message in messages %}"
            f"{{{{'{self.bos_token}' + message['role'] + '\n' + message['content'] + '{self.eos_token}' + '\n'}}}}"
            "{% endfor %}"
            "{% if add_generation_prompt %}"
            f"{{{{ '{self.assistant}\n' }}}}"
            "{% endif %}"
        )


FORMAT_MAPPING = {"chatml": ChatMlSpecialTokens}


def setup_chat_format(
    model: PreTrainedModel,
    tokenizer: PreTrainedTokenizer,
    format: Optional[Literal["chatml"]] = "chatml",
    resize_to_multiple_of: Optional[int] = None,
) -> Tuple[PreTrainedModel, PreTrainedTokenizer]:
    """
    Setup chat format by adding special tokens to the tokenizer, setting the correct format, and extending the embedding layer of the model based on the new special tokens.

    If the model already has a chat template, this will throw an error. If you want to overwrite it, please set `tokenizer.chat_template` to `None`.

    Args:
        model (`~transformers.PreTrainedModel`): The model to be modified.
        tokenizer (`~transformers.PreTrainedTokenizer`): The tokenizer to be modified.
        format (`Optional[Literal["chatml"]]`): The format to be set. Defaults to "chatml".
        resize_to_multiple_of (`Optional[int]`): Number to resize the embedding layer to. Defaults to None.

    Returns:
        model (`~transformers.PreTrainedModel`): The modified model.
        tokenizer (`~transformers.PreTrainedTokenizer`): The modified tokenizer.
    """
    # check if model already had a chat template
    if tokenizer.chat_template is not None:
        raise ValueError(
            "Chat template is already added to the tokenizer. If you want to overwrite it, please set it to None"
        )

    # check if format available and retrieve
    if format not in FORMAT_MAPPING:
        raise ValueError(f"Format {format} not available. Please use one of {FORMAT_MAPPING.keys()}")

    chat_format = FORMAT_MAPPING[format]()

    # set special tokens and them
    tokenizer.eos_token = chat_format.eos_token
    tokenizer.pad_token = chat_format.pad_token
    tokenizer.bos_token = chat_format.bos_token
    tokenizer.add_special_tokens({"additional_special_tokens": [chat_format.bos_token, chat_format.eos_token]})
    # set chat format for tokenizer
    tokenizer.chat_template = chat_format.chat_template

    # resize embedding layer to a multiple of 64, https://x.com/karpathy/status/1621578354024677377
    model.resize_token_embeddings(
        len(tokenizer), pad_to_multiple_of=resize_to_multiple_of if resize_to_multiple_of is not None else None
    )
    # Update the model config to use the new eos & bos tokens
    if getattr(model, "config", None) is not None:
        model.config.pad_token_id = tokenizer.pad_token_id
        model.config.bos_token_id = tokenizer.bos_token_id
        model.config.eos_token_id = tokenizer.eos_token_id
    # Update the generation config to use the new eos & bos token
    if getattr(model, "generation_config", None) is not None:
        model.generation_config.bos_token_id = tokenizer.bos_token_id
        model.generation_config.eos_token_id = tokenizer.eos_token_id
        model.generation_config.pad_token_id = tokenizer.pad_token_id

    return model, tokenizer


def remove_hooks(model: "DeepSpeedEngine") -> None:
    """Removes the optimizer hooks from a DeepSpeed ZeRO-3 model."""
    if model.optimizer is not None and hasattr(model.optimizer, "parameter_offload"):
        optimizer_offload = model.optimizer.parameter_offload
    elif model.optimizer is not None:
        optimizer_offload = model.optimizer

    for param in iter_params(optimizer_offload.module, recurse=True):
        param.ds_active_sub_modules.clear()

    for hook in optimizer_offload.forward_hooks:
        hook.remove()
    for hook in optimizer_offload.backward_hooks:
        hook.remove()

    optimizer_offload.forward_hooks = []
    optimizer_offload.backward_hooks = []


def get_all_parameters(sub_module, recurse=False):
    return itertools.chain(sub_module.named_parameters(recurse=recurse), sub_module.ds_external_parameters())


def iter_params(module, recurse=False):
    return [param for _, param in get_all_parameters(module, recurse)]


def add_hooks(model: "DeepSpeedEngine") -> None:
    """Adds the optimizer hooks from a DeepSpeed ZeRO-3 model."""
    if model.optimizer is not None and hasattr(model.optimizer, "parameter_offload"):
        optimizer_offload = model.optimizer.parameter_offload
    elif model.optimizer is not None:
        optimizer_offload = model.optimizer
    optimizer_offload._register_hooks_recursively(optimizer_offload.module)


@contextmanager
def unwrap_model_for_generation(
    model: Union["DistributedDataParallel", "DeepSpeedEngine"], accelerator: "Accelerator", is_peft_model: bool = False
) -> Union["PreTrainedModelWrapper", "DeepSpeedEngine"]:
    """Context manager to unwrap a model for generation.
    For ZeRO-3 models, we gather the weights once to speed up generation.
    """
    unwrapped_model = accelerator.unwrap_model(model)
    if is_peft_model:
        unwrapped_model.pretrained_model.disable_adapter()
    if accelerator.state.deepspeed_plugin is not None and accelerator.state.deepspeed_plugin.zero_stage == 3:
        with deepspeed.zero.GatheredParameters(model.parameters()):
            remove_hooks(model)
            yield accelerator.unwrap_model(model)
            add_hooks(model)
    else:
        yield unwrapped_model