# Copyright 2025-present the HuggingFace Inc. team.
#
# 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.

from __future__ import annotations

import warnings

import torch
from transformers.pytorch_utils import Conv1D

from peft.tuners.tuners_utils import BaseTuner, BaseTunerLayer
from peft.utils import TRANSFORMERS_MODELS_TO_GRALORA_TARGET_MODULES_MAPPING

from .layer import GraloraLayer, Linear


class GraloraModel(BaseTuner):
    """
    Creates Vector-based Random Matrix Adaptation (Gralora) model from a pretrained transformers model.

    Args:
        model ([`~transformers.PreTrainedModel`]): The model to be adapted.
        config ([`GraloraConfig`]): The configuration of the Gralora model.
        adapter_name (`str`): The name of the adapter, defaults to `"default"`.

    Returns:
        `torch.nn.Module`: The Gralora model.

    Example:

        ```py
        >>> from transformers import AutoModelForCausalLM
        >>> from peft import GraloraConfig, get_peft_model

        >>> base_model = AutoModelForCausalLM.from_pretrained("facebook/opt-125m")
        >>> config = GraloraConfig(r=128)
        >>> model = get_peft_model(base_model, config)
        ```

    **Attributes**:
        - **model** ([`~transformers.PreTrainedModel`]) -- The model to be adapted.
        - **peft_config** ([`GraloraConfig`]): The configuration of the Gralora model.
    """

    # The unique prefix for GraLoRA method
    prefix: str = "gralora_"
    # The class of tuner layer for GraLoRA method
    tuner_layer_cls = GraloraLayer

    target_module_mapping = TRANSFORMERS_MODELS_TO_GRALORA_TARGET_MODULES_MAPPING

    def _create_and_replace(
        self,
        gralora_config,
        adapter_name,
        target,
        target_name,
        parent,
        current_key,
        **optional_kwargs,
    ):
        if current_key is None:
            raise ValueError("Current Key shouldn't be `None`")

        r = gralora_config.r
        bias = hasattr(target, "bias") and target.bias is not None
        kwargs = {
            "r": r,
            "alpha": gralora_config.alpha,
            "gralora_dropout": gralora_config.gralora_dropout,
            "gralora_k": gralora_config.gralora_k,
            "fan_in_fan_out": gralora_config.fan_in_fan_out,
            "hybrid_r": gralora_config.hybrid_r,
            "init_weights": gralora_config.init_weights,
        }
        kwargs["bias"] = bias

        if isinstance(target, Linear):
            target.update_layer(
                adapter_name,
                current_key,
                r,
                gralora_config.alpha,
                gralora_config.gralora_dropout,
                gralora_config.gralora_k,
                gralora_config.hybrid_r,
                gralora_config.init_weights,
            )
        else:
            new_module = self._create_new_module(gralora_config, adapter_name, target, current_key, **kwargs)
            if adapter_name not in self.active_adapters:
                # adding an additional adapter: it is not automatically trainable
                new_module.requires_grad_(False)
            self._replace_module(parent, target_name, new_module, target)

    @staticmethod
    def _create_new_module(gralora_config, adapter_name, target, module_name, **kwargs):
        if isinstance(target, BaseTunerLayer):
            target_base_layer = target.get_base_layer()
        else:
            target_base_layer = target

        if isinstance(target_base_layer, torch.nn.Linear):
            if kwargs["fan_in_fan_out"]:
                warnings.warn(
                    "fan_in_fan_out is set to True but the target module is `torch.nn.Linear`. "
                    "Setting fan_in_fan_out to False."
                )
                kwargs["fan_in_fan_out"] = gralora_config.fan_in_fan_out = False
        elif isinstance(target_base_layer, Conv1D):
            kwargs["is_target_conv_1d_layer"] = True
            if not kwargs["fan_in_fan_out"]:
                warnings.warn(
                    "fan_in_fan_out is set to False but the target module is `Conv1D`. Setting fan_in_fan_out to True."
                )
                kwargs["fan_in_fan_out"] = gralora_config.fan_in_fan_out = True
        else:
            raise ValueError(
                f"Target module {target} is not supported. Currently, only the following modules are supported: "
                "`torch.nn.Linear`, `transformers.pytorch_utils.Conv1D`."
            )
        new_module = Linear(
            target,
            adapter_name,
            module_name,
            **kwargs,
        )

        return new_module
