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import warnings
from dataclasses import dataclass, field
from typing import Any, Optional

from transformers import TrainingArguments


@dataclass
class SFTConfig(TrainingArguments):
    r"""
    Configuration class for the [`SFTTrainer`].

    Only the parameters specific to SFT training are listed here. For details on other parameters, refer to the
    [`~transformers.TrainingArguments`] documentation.

    Using [`~transformers.HfArgumentParser`] we can turn this class into
    [argparse](https://docs.python.org/3/library/argparse#module-argparse) arguments that can be specified on the
    command line.

    Parameters:
        > Parameters that control the model

        model_init_kwargs (`dict[str, Any]` or `None`, *optional*, defaults to `None`):
            Keyword arguments for [`~transformers.AutoModelForCausalLM.from_pretrained`], used when the `model`
            argument of the [`SFTTrainer`] is provided as a string.

        > Parameters that control the data preprocessing

        dataset_text_field (`str`, *optional*, defaults to `"text"`):
            Name of the column that contains text data in the dataset.
        dataset_kwargs (`dict[str, Any]` or `None`, *optional*, defaults to `None`):
            Dictionary of optional keyword arguments for the dataset preparation. The only supported key is
            `skip_prepare_dataset`.
        dataset_num_proc (`int` or `None`, *optional*, defaults to `None`):
            Number of processes to use for processing the dataset.
        eos_token (`str` or `None`, *optional*, defaults to `None`):
            Token used to indicate the end of a turn or sequence. If `None`, it defaults to `processing_class.eos_token`.
        pad_token (`int` or `None`, *optional*, defaults to `None`):
            Token used for padding. If `None`, it defaults to `processing_class.pad_token`, or if that is also `None`,
            it falls back to `processing_class.eos_token`.
        max_length (`int` or `None`, *optional*, defaults to `1024`):
            Maximum length of the tokenized sequence. Sequences longer than `max_length` are truncated from the right.
            If `None`, no truncation is applied. When packing is enabled, this value sets the sequence length.
        packing (`bool`, *optional*, defaults to `False`):
            Whether to pack multiple sequences into a fixed-length format. Uses `max_length` to define sequence length.
        padding_free (`bool`, *optional*, defaults to `False`):
            Whether to perform forward passes without padding by flattening all sequences in the batch into a single
            continuous sequence. This reduces memory usage by eliminating padding overhead. Currently, this is only
            supported with the `flash_attention_2` attention implementation, which can efficiently handle the flattened
            batch structure.
        eval_packing (`bool` or `None`, *optional*, defaults to `None`):
            Whether to pack the eval dataset. If `None`, uses the same value as `packing`.

        > Parameters that control the training

        learning_rate (`float`, *optional*, defaults to `2e-5`):
            Initial learning rate for [`AdamW`] optimizer. The default value replaces that of
            [`~transformers.TrainingArguments`].
        completion_only_loss (`bool` or `None`, *optional*, defaults to `None`):
            Whether to compute loss only on the completion part of the sequence. If set to `True`, loss is computed
            only on the completion, which is supported only for [prompt-completion](#prompt-completion) datasets. If
            `False`, loss is computed on the entire sequence. If `None` (default), the behavior depends on the dataset:
            loss is computed on the completion for [prompt-completion](#prompt-completion) datasets, and on
            the full sequence for [language modeling](#language-modeling) datasets.
    """

    # Parameters that control the model
    model_init_kwargs: Optional[dict[str, Any]] = field(
        default=None,
        metadata={
            "help": "Keyword arguments for `AutoModelForCausalLM.from_pretrained`, used when the `model` argument of "
            "the `SFTTrainer` is provided as a string."
        },
    )

    # Parameters that control the data preprocessing
    dataset_text_field: str = field(
        default="text",
        metadata={"help": "Name of the column that contains text data in the dataset."},
    )
    dataset_kwargs: Optional[dict[str, Any]] = field(
        default=None,
        metadata={
            "help": "Dictionary of optional keyword arguments for the dataset preparation. The only supported key is "
            "`skip_prepare_dataset`."
        },
    )
    dataset_num_proc: Optional[int] = field(
        default=None,
        metadata={"help": "Number of processes to use for processing the dataset."},
    )
    eos_token: Optional[str] = field(
        default=None,
        metadata={
            "help": "Token used to indicate the end of a turn or sequence. If `None`, it defaults to `processing_class.eos_token`."
        },
    )
    pad_token: Optional[str] = field(
        default=None,
        metadata={
            "help": "Token used for padding. If `None`, it defaults to `processing_class.pad_token`, or if that "
            "is also `None`, it falls back to `processing_class.eos_token`."
        },
    )
    max_length: Optional[int] = field(
        default=1024,
        metadata={
            "help": "Maximum length of the tokenized sequence. Sequences longer than `max_length` are truncated from"
            "the right. If `None`, no truncation is applied. When packing is enabled, this value sets the "
            "sequence length."
        },
    )
    packing: bool = field(
        default=False,
        metadata={
            "help": "Whether to pack multiple sequences into a fixed-length format. Uses `max_length` to define "
            "sequence length."
        },
    )
    padding_free: bool = field(
        default=False,
        metadata={
            "help": "Whether to perform forward passes without padding by flattening all sequences in the batch into "
            "a single continuous sequence. This reduces memory usage by eliminating padding overhead. Currently, "
            "this is only supported with the `flash_attention_2` attention implementation, which can efficiently "
            "handle the flattened batch structure."
        },
    )
    eval_packing: Optional[bool] = field(
        default=None,
        metadata={"help": "Whether to pack the eval dataset. If `None`, uses the same value as `packing`."},
    )

    # Parameters that control the training
    learning_rate: float = field(
        default=2.0e-5,
        metadata={
            "help": "Initial learning rate for `AdamW` optimizer. The default value replaces that of "
            "`TrainingArguments`."
        },
    )
    completion_only_loss: Optional[bool] = field(
        default=None,
        metadata={
            "help": (
                "Whether to compute loss only on the completion part of the sequence. If set to `True`, loss is "
                "computed only on the completion, which is supported only for prompt-completion datasets. If `False`, "
                "loss is computed on the entire sequence. If `None` (default), the behavior depends on the dataset: "
                "loss is computed on the completion for prompt-completion datasets, and on the full sequence for "
                "language modeling datasets."
            )
        },
    )

    # Deprecated parameters
    dataset_batch_size: Optional[int] = field(
        default=None,
        metadata={
            "help": "This parameter is deprecated and will be removed in version 0.18.0. You can safely remove this "
            "parameter from your configuration."
        },
    )
    num_of_sequences: Optional[int] = field(
        default=None,
        metadata={
            "help": "This parameter is deprecated and will be removed in version 0.18.0. Use `max_length` instead, "
            "which specifies the maximum length of the tokenized sequence, unlike `num_of_sequences`, which referred "
            "to string sequences."
        },
    )
    chars_per_token: Optional[float] = field(
        default=None,
        metadata={
            "help": "This parameter is deprecated and will be removed in version 0.18.0. If you want to customize the "
            "packing length, use `max_length`."
        },
    )
    max_seq_length: Optional[int] = field(
        default=None,
        metadata={
            "help": "This parameter is deprecated and will be removed in version 0.20.0. Use `max_length` instead."
        },
    )
    use_liger: Optional[bool] = field(
        default=None,
        metadata={
            "help": "This parameter is deprecated and will be removed in version 0.18.0. Use `use_liger_kernel` "
            "instead."
        },
    )

    def __post_init__(self):
        super().__post_init__()

        if self.dataset_batch_size is not None:
            warnings.warn(
                "`dataset_batch_size` is deprecated and will be removed in version 0.18.0. You can safely remove this "
                "parameter from your configuration.",
                DeprecationWarning,
            )

        if self.num_of_sequences is not None:
            warnings.warn(
                "`num_of_sequences` is deprecated and will be removed in version 0.18.0. Use `max_length` instead, "
                "which specifies the maximum length of the tokenized sequence, unlike `num_of_sequences`, which "
                "referred to string sequences.",
                DeprecationWarning,
            )

        if self.chars_per_token is not None:
            warnings.warn(
                "`chars_per_token` is deprecated and will be removed in version 0.18.0. If you want to customize the "
                "packing length, use `max_length`.",
                DeprecationWarning,
            )

        if self.max_seq_length is not None:
            warnings.warn(
                "`max_seq_length` is deprecated and will be removed in version 0.20.0. Use `max_length` instead.",
                DeprecationWarning,
            )
            self.max_length = self.max_seq_length

        if self.use_liger is not None:
            warnings.warn(
                "`use_liger` is deprecated and will be removed in version 0.18.0. Use `use_liger_kernel` instead.",
                DeprecationWarning,
            )
            self.use_liger_kernel = self.use_liger