# Copyright 2025 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
#
# 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.
"""Fast Image processor class for ImageGPT."""

from typing import Optional

import numpy as np
import torch
from torchvision.transforms.v2 import functional as F

from ...image_processing_utils import BatchFeature
from ...image_processing_utils_fast import (
    BaseImageProcessorFast,
)
from ...image_transforms import group_images_by_shape, reorder_images
from ...image_utils import PILImageResampling
from ...processing_utils import Unpack
from ...utils import (
    TensorType,
    auto_docstring,
)
from .image_processing_imagegpt import ImageGPTImageProcessorKwargs


def squared_euclidean_distance_torch(a: torch.Tensor, b: torch.Tensor) -> torch.Tensor:
    """
    Compute squared Euclidean distances between all pixels and clusters.

    Args:
        a: (N, 3) tensor of pixel RGB values
        b: (M, 3) tensor of cluster RGB values

    Returns:
        (N, M) tensor of squared distances
    """
    b = b.t()  # (3, M)
    a2 = torch.sum(a**2, dim=1)  # (N,)
    b2 = torch.sum(b**2, dim=0)  # (M,)
    ab = torch.matmul(a, b)  # (N, M)
    d = a2[:, None] - 2 * ab + b2[None, :]  # Squared Euclidean Distance: a^2 - 2ab + b^2
    return d  # (N, M) tensor of squared distances


def color_quantize_torch(x: torch.Tensor, clusters: torch.Tensor) -> torch.Tensor:
    """
    Assign each pixel to its nearest color cluster.

    Args:
        x: (H*W, 3) tensor of flattened pixel RGB values
        clusters: (n_clusters, 3) tensor of cluster RGB values

    Returns:
        (H*W,) tensor of cluster indices
    """
    d = squared_euclidean_distance_torch(x, clusters)
    return torch.argmin(d, dim=1)


@auto_docstring
class ImageGPTImageProcessorFast(BaseImageProcessorFast):
    model_input_names = ["input_ids"]
    resample = PILImageResampling.BILINEAR
    do_color_quantize = True
    clusters = None
    image_mean = [0.5, 0.5, 0.5]
    image_std = [0.5, 0.5, 0.5]
    do_rescale = True
    do_normalize = True
    valid_kwargs = ImageGPTImageProcessorKwargs

    def __init__(
        self,
        clusters: list | np.ndarray | torch.Tensor | None = None,  # keep as arg for backwards compatibility
        **kwargs: Unpack[ImageGPTImageProcessorKwargs],
    ):
        r"""
        clusters (`np.ndarray` or `list[list[int]]` or `torch.Tensor`, *optional*):
            The color clusters to use, of shape `(n_clusters, 3)` when color quantizing. Can be overridden by `clusters`
            in `preprocess`.
        """
        clusters = torch.as_tensor(clusters, dtype=torch.float32) if clusters is not None else None
        super().__init__(clusters=clusters, **kwargs)

    def _preprocess(
        self,
        images: list["torch.Tensor"],
        do_resize: bool,
        size: dict[str, int],
        interpolation: Optional["F.InterpolationMode"],
        do_center_crop: bool,
        crop_size: dict[str, int],
        do_rescale: bool,
        rescale_factor: float,
        do_normalize: bool,
        image_mean: float | list[float] | None,
        image_std: float | list[float] | None,
        do_color_quantize: bool | None = None,
        clusters: list | np.ndarray | torch.Tensor | None = None,
        disable_grouping: bool | None = None,
        return_tensors: str | TensorType | None = None,
        **kwargs,
    ):
        # Group images by size for batched resizing
        grouped_images, grouped_images_index = group_images_by_shape(images, disable_grouping=disable_grouping)
        resized_images_grouped = {}
        for shape, stacked_images in grouped_images.items():
            if do_resize:
                stacked_images = self.resize(image=stacked_images, size=size, interpolation=interpolation)
            resized_images_grouped[shape] = stacked_images
        resized_images = reorder_images(resized_images_grouped, grouped_images_index)

        # Group images by size for further processing
        # Needed in case do_resize is False, or resize returns images with different sizes
        grouped_images, grouped_images_index = group_images_by_shape(resized_images, disable_grouping=disable_grouping)
        processed_images_grouped = {}
        for shape, stacked_images in grouped_images.items():
            if do_center_crop:
                stacked_images = self.center_crop(stacked_images, crop_size)
            # Fused rescale and normalize
            stacked_images = self.rescale_and_normalize(
                stacked_images, do_rescale, rescale_factor, do_normalize, image_mean, image_std
            )
            processed_images_grouped[shape] = stacked_images

        pixel_values = reorder_images(processed_images_grouped, grouped_images_index)

        # If color quantization is requested, perform it; otherwise return pixel values
        if do_color_quantize:
            # Prepare clusters
            if clusters is None:
                raise ValueError("Clusters must be provided for color quantization.")
            # Convert to torch tensor if needed (clusters might be passed as list/numpy)
            clusters_torch = (
                torch.as_tensor(clusters, dtype=torch.float32) if not isinstance(clusters, torch.Tensor) else clusters
            ).to(pixel_values[0].device, dtype=pixel_values[0].dtype)

            # Group images by shape for batch processing
            # We need to check if the pixel values are a tensor or a list of tensors
            grouped_images, grouped_images_index = group_images_by_shape(
                pixel_values, disable_grouping=disable_grouping
            )
            # Process each group
            input_ids_grouped = {}

            for shape, stacked_images in grouped_images.items():
                input_ids = color_quantize_torch(
                    stacked_images.permute(0, 2, 3, 1).reshape(-1, 3), clusters_torch
                )  # (B*H*W, C)
                input_ids_grouped[shape] = input_ids.reshape(stacked_images.shape[0], -1).reshape(
                    stacked_images.shape[0], -1
                )  # (B, H, W)

            input_ids = reorder_images(input_ids_grouped, grouped_images_index)

            return BatchFeature(data={"input_ids": input_ids}, tensor_type=return_tensors)

        return BatchFeature(data={"pixel_values": pixel_values}, tensor_type=return_tensors)

    def to_dict(self):
        # Convert torch tensors to lists for JSON serialization
        output = super().to_dict()
        if output.get("clusters") is not None and isinstance(output["clusters"], torch.Tensor):
            output["clusters"] = output["clusters"].tolist()

        return output


__all__ = ["ImageGPTImageProcessorFast"]
