# Copyright 2024 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.

import math
from functools import lru_cache
from typing import Optional, Union

import numpy as np
import torch

from ...image_processing_backends import TorchvisionBackend
from ...image_processing_utils import BatchFeature
from ...image_transforms import group_images_by_shape, reorder_images, split_to_tiles
from ...image_utils import (
    IMAGENET_STANDARD_MEAN,
    IMAGENET_STANDARD_STD,
    ImageInput,
    PILImageResampling,
    SizeDict,
    make_nested_list_of_images,
)
from ...processing_utils import ImagesKwargs, Unpack
from ...utils import TensorType, auto_docstring, is_vision_available


if is_vision_available():
    from PIL import Image

from torchvision.transforms.v2 import functional as tvF


class MllamaImageProcessorKwargs(ImagesKwargs, total=False):
    """
    max_image_tiles (`int`, *optional*):
        The maximum number of tiles allowed.
    """

    max_image_tiles: int


@lru_cache(maxsize=10)
def get_all_supported_aspect_ratios(max_image_tiles: int) -> list[tuple[int, int]]:
    """
    Computes all allowed aspect ratios for a given maximum number of input tiles.

    This function calculates all possible arrangements of tiles that can be formed
    within the constraint of the maximum number of tiles. Each arrangement is
    represented by its aspect ratio (width/height) and the corresponding tile configuration.

    Args:
        max_image_tiles (`int`):
            The maximum number of tiles allowed.

    Returns:
        `list[tuple[int, int]]`: A list of tuples, each tuple representing a valid (width, height)
        configuration in terms of number of tiles.

    Example:
        >>> get_all_supported_aspect_ratios(4)
        [(1, 1), (1, 2), (1, 3), (1, 4), (2, 1), (2, 2), (3, 1), (4, 1)]

    """
    aspect_ratios = []
    for width in range(1, max_image_tiles + 1):
        for height in range(1, max_image_tiles + 1):
            if width * height <= max_image_tiles:
                aspect_ratios.append((width, height))
    return aspect_ratios


def get_image_size_fit_to_canvas(
    image_height: int,
    image_width: int,
    canvas_height: int,
    canvas_width: int,
    tile_size: int,
) -> tuple[int, int]:
    """
    Calculates the new size of an image to fit within a canvas while maintaining aspect ratio.

    This function calculates the optimal size for an image to fit within a canvas defined by
    canvas_height and canvas_width, while ensuring that the image dimensions are not smaller than
    tile_size. If the image is larger than the canvas, the returned size will fit within the canvas.
    If the image already fits within the canvas, the size remains unchanged.
    The aspect ratio of the original image is preserved as much as possible.

    Args:
        image_height (`int`):
            The height of the original image.
        image_width (`int`):
            The width of the original image.
        canvas_height (`int`):
            The height of the canvas.
        canvas_width (`int`):
            The width of the canvas.
        tile_size (`int`):
            The tile size.

    Returns:
        `tuple[int, int]`: A tuple containing the new height and width of the image.

    """
    # Set target image size in between `tile_size` and canvas_size
    target_width = np.clip(image_width, tile_size, canvas_width)
    target_height = np.clip(image_height, tile_size, canvas_height)

    scale_h = target_height / image_height
    scale_w = target_width / image_width

    if scale_w < scale_h:
        new_width = target_width
        # minimum height is 1 to avoid invalid height of 0
        new_height = min(math.floor(image_height * scale_w) or 1, target_height)
    else:
        new_height = target_height
        # minimum width is 1 to avoid invalid width of 0
        new_width = min(math.floor(image_width * scale_h) or 1, target_width)

    return new_height, new_width


@lru_cache(maxsize=100)
def get_optimal_tiled_canvas(
    image_height: int,
    image_width: int,
    max_image_tiles: int,
    tile_size: int,
) -> tuple[int, int]:
    r"""
    Determines the best canvas based on image and tile size and maximum number of tiles.

    First, calculates possible resolutions based on the maximum number of tiles and tile size.
    For each possible resolution, calculates the scaling factors for width and height, and selects
    the smallest one. If upscaling is possible, picks the smallest upscaling factor > 1.
    If upscaling is not possible, picks the largest scaling factor <= 1.
    If there are multiple resolutions with the same max scale, picks the one with the lowest area.

    Args:
        image_height (`int`):
            The height of the image.
        image_width (`int`):
            The width of the image.
        max_image_tiles (`int`):
            The maximum number of tiles any image can be split into.
        tile_size (`int`):
            The tile size.

    Returns:
        `tuple[int, int]`: The best canvas resolution [height, width] for the given image.
    """
    possible_tile_arrangements = get_all_supported_aspect_ratios(max_image_tiles)
    possible_canvas_sizes = np.array(possible_tile_arrangements) * tile_size

    target_heights, target_widths = np.array(possible_canvas_sizes).T

    scale_h = target_heights / image_height
    scale_w = target_widths / image_width

    scales = np.where(scale_w > scale_h, scale_h, scale_w)

    upscaling_options = scales[scales >= 1]
    if len(upscaling_options) > 0:
        selected_scale = np.min(upscaling_options)
    else:
        downscaling_options = scales[scales < 1]
        selected_scale = np.max(downscaling_options)

    chosen_canvas = possible_canvas_sizes[scales == selected_scale]

    if len(chosen_canvas) > 1:
        areas = chosen_canvas[:, 0] * chosen_canvas[:, 1]
        optimal_idx = np.argmin(areas)
        optimal_canvas = chosen_canvas[optimal_idx]
    else:
        optimal_canvas = chosen_canvas[0]

    return tuple(optimal_canvas)


def _validate_size(size: SizeDict) -> None:
    if not (size.height and size.width):
        raise ValueError(f"Argument `size` must be a dictionary with keys 'height' and 'width'. Got: {size}")
    if size.height != size.width:
        raise ValueError(f"Argument `size` must have the same height and width, got {size}")


def _validate_mllama_preprocess_arguments(do_resize, size, do_pad, max_image_tiles):
    if not do_pad:
        raise ValueError("MllamaImageProcessor doesn't support `do_pad=False` mode.")
    if not do_resize:
        raise ValueError("MllamaImageProcessor doesn't support `do_resize=False` mode.")
    if max_image_tiles is None or max_image_tiles <= 0:
        raise ValueError(f"MllamaImageProcessor `max_image_tiles` must be a positive integer, got {max_image_tiles}.")
    _validate_size(size)


def build_aspect_ratio_mask(
    aspect_ratios: list[list[tuple[int, int]]],
    max_image_tiles: int,
    device: Optional["torch.device"] = None,
) -> "torch.Tensor":
    """
    Builds a mask for the aspect ratios of the images.

    Args:
        aspect_ratios (`List[List[Tuple[int, int]]]`):
            A list of lists containing aspect ratios for each image in the batch.
            Each aspect ratio is represented as a tuple of (width, height) in terms of number of tiles.
        max_image_tiles (`int`):
            The maximum number of tiles any image can be split into.
        device (`torch.device`, *optional*):
            The device to create the tensor on. Defaults to CPU.

    Returns:
        `torch.Tensor`: A 3D torch.Tensor of shape (batch_size, max_num_images, max_image_tiles).
            The mask contains 1s for valid tiles and 0s for padding.
    """
    batch_size = len(aspect_ratios)
    max_num_images = max(len(row) for row in aspect_ratios)

    aspect_ratio_mask = torch.zeros((batch_size, max_num_images, max_image_tiles), dtype=torch.long, device=device)

    # Set the first tile to 1 for all aspect ratios
    # because in original implementation aspect ratios are padded with (1, 1),
    # but original code examples are not built to handle batches, so we might remove it later
    aspect_ratio_mask[:, :, 0] = 1

    # Set the aspect ratio mask for the rest of the tiles
    for i, sample_aspect_ratios in enumerate(aspect_ratios):
        for j, (num_tiles_w, num_tiles_h) in enumerate(sample_aspect_ratios):
            aspect_ratio_mask[i, j, : num_tiles_w * num_tiles_h] = 1

    return aspect_ratio_mask


def pad_batches_and_tiles(
    batch_images: list[list["torch.Tensor"]],
    max_image_tiles: int,
) -> tuple["torch.Tensor", list[list[int]]]:
    """
    Stack a list of lists of images with variable lengths into a torch.Tensor, applying zero padding as needed.
    Each list in the input represents a batch sample, and each image within a list is expected to be
    pre-split into tiles. The resulting array will have a shape of
    (batch_size, max_num_images, max_image_tiles, channels, tile_height, tile_width).

    Args:
        batch_images (`List[List[torch.Tensor]]`):
            A list of lists of image tiles. Each inner list represents
            a batch sample containing multiple images, where each image is pre-split into tiles.
            The shape of each tile array is (num_tiles, channels, tile_height, tile_width).
        max_image_tiles (int):
            The maximum number of tiles any image was potantially split.

    Returns:
        `Tuple[torch.Tensor, List[List[int]]]`: A tuple containing:
            - stacked_images (`torch.Tensor`):
                A numpy array of stacked images with shape
                (batch_size, max_num_images, max_image_tiles, channels, tile_height, tile_width).
            - all_num_tiles (`List[List[int]]`):
                A list of lists containing the number of tiles
                for each image in each batch sample.
    """
    # Determine output shape
    batch_size = len(batch_images)
    max_num_images = max(len(images) for images in batch_images)
    shapes = [image.shape for images in batch_images for image in images]
    _, channels, tile_height, tile_width = shapes[0]

    # Initialize the stacked images array with zeros
    stacked_images = torch.zeros(
        (batch_size, max_num_images, max_image_tiles, channels, tile_height, tile_width),
        dtype=torch.float32,
        device=batch_images[0][0].device,
    )

    # Fill the stacked images array with the tiled images from the batch
    all_num_tiles = []
    for i, images in enumerate(batch_images):
        num_sample_tiles = []
        for j, image in enumerate(images):
            num_tiles = image.shape[0]
            stacked_images[i, j, :num_tiles] = image
            num_sample_tiles.append(num_tiles)
        all_num_tiles.append(num_sample_tiles)

    return stacked_images, all_num_tiles


def convert_aspect_ratios_to_ids(
    aspect_ratios: list[list[tuple[int, int]]],
    max_image_tiles: int,
    device: Optional["torch.device"] = None,
) -> "torch.Tensor":
    """
    Convert aspect ratio tuples to unique ids.

    For batch padding we use 0, because there might be different number of images in each batch.
    The aspect ratio ids start from 1, with 1 corresponding to the first supported aspect ratio.

    Args:
        aspect_ratios (`List[List[Tuple[int, int]]]`):
            A list of aspect ratios for each image in the batch.
        max_image_tiles (`int`):
            The maximum number of tiles any image can be split into.
        device (`torch.device`, *optional*):
            The device to create the tensor on. Defaults to CPU.

    Returns:
        `torch.Tensor`:
            The aspect ratios ids as a numpy array with shape (batch_size, max_num_images).
            Each id corresponds to the index of the aspect ratio in the list of supported aspect ratios,
            offset by 1 (so 0 can be used for padding).
    """
    batch_size = len(aspect_ratios)
    max_num_images = max(len(row) for row in aspect_ratios)
    supported_aspect_ratios = get_all_supported_aspect_ratios(max_image_tiles)

    aspect_ratios_ids = torch.zeros((batch_size, max_num_images), dtype=torch.long, device=device)
    for i, sample_aspect_ratios in enumerate(aspect_ratios):
        for j, (num_tiles_h, num_tiles_w) in enumerate(sample_aspect_ratios):
            aspect_ratios_ids[i, j] = supported_aspect_ratios.index((num_tiles_h, num_tiles_w)) + 1
    return aspect_ratios_ids


# Copied from transformers.models.idefics2.image_processing_idefics2.convert_to_rgb
def convert_to_rgb(image: ImageInput) -> ImageInput:
    """
    Converts an image to RGB format. Only converts if the image is of type PIL.Image.Image, otherwise returns the image
    as is.
    """
    if not is_vision_available() or not isinstance(image, Image.Image):
        return image

    if image.mode == "RGB":
        return image

    image_rgba = image.convert("RGBA")
    background = Image.new("RGBA", image_rgba.size, (255, 255, 255))
    alpha_composite = Image.alpha_composite(background, image_rgba)
    alpha_composite = alpha_composite.convert("RGB")
    return alpha_composite


@auto_docstring
class MllamaImageProcessor(TorchvisionBackend):
    resample = PILImageResampling.BILINEAR
    image_mean = IMAGENET_STANDARD_MEAN
    image_std = IMAGENET_STANDARD_STD
    size = {"height": 224, "width": 224}
    do_resize = True  # trf-ignore: TRF016 (enforced by validator)
    do_rescale = True
    do_normalize = True
    do_convert_rgb = True
    do_pad = True  # trf-ignore: TRF016 (enforced by validator)
    max_image_tiles = 4
    valid_kwargs = MllamaImageProcessorKwargs
    model_input_names = ["pixel_values", "num_tiles", "aspect_ratio_ids", "aspect_ratio_mask"]

    def __init__(self, **kwargs: Unpack[MllamaImageProcessorKwargs]):
        super().__init__(**kwargs)
        _validate_mllama_preprocess_arguments(self.do_resize, self.size, self.do_pad, self.max_image_tiles)

    def _validate_preprocess_kwargs(self, **kwargs):
        super()._validate_preprocess_kwargs(**kwargs)
        _validate_mllama_preprocess_arguments(self.do_resize, self.size, self.do_pad, self.max_image_tiles)

    @auto_docstring
    def preprocess(self, images: ImageInput, **kwargs: Unpack[MllamaImageProcessorKwargs]) -> BatchFeature:
        return super().preprocess(images, **kwargs)

    def _prepare_images_structure(self, images: ImageInput, expected_ndims: int = 3) -> ImageInput:
        """Prepare a nested images structure for processing."""
        images = self.fetch_images(images)
        return make_nested_list_of_images(images, expected_ndims=expected_ndims)

    def convert_to_rgb(self, image: ImageInput) -> ImageInput:
        """Converts an image to RGB format."""
        return convert_to_rgb(image)

    def pad(
        self,
        image: "torch.Tensor",
        size: SizeDict,
        aspect_ratio: tuple[int, int],
    ) -> "torch.Tensor":
        """
        Pad an image to the `size` x `aspect_ratio`. For example, if size is {height: 224, width: 224} and aspect ratio is
        (1, 2), the image will be padded to 224x448.

        Args:
            image (`torch.Tensor`):
                Image to pad.
            size (`Dict[str, int]`):
                Size of the output image.
            aspect_ratio (`Tuple[int, int]`):
                The aspect ratio of the image.

        Returns:
            `torch.Tensor`: The padded image.
        """
        image_height, image_width = image.shape[-2:]
        num_tiles_height, num_tiles_width = aspect_ratio
        padded_height = num_tiles_height * size.height
        padded_width = num_tiles_width * size.width
        pad_size = (0, 0, padded_width - image_width, padded_height - image_height)

        image = tvF.pad(image, pad_size, fill=0)
        return image

    def resize(
        self,
        image: "torch.Tensor",
        size: SizeDict,
        max_image_tiles: int,
        resample: Optional["tvF.InterpolationMode"] = None,
        antialias: bool = True,
    ) -> Union["torch.Tensor", tuple[int, int]]:
        """
        Resizes an image to fit within a tiled canvas while maintaining its aspect ratio.
        The optimal canvas size is calculated based on the maximum number of tiles and the tile size.

        The function first determines the best tile arrangement for the image, then resizes the image
        to fit within this canvas. The resized image and the number of tiles along the height and width
        dimensions are returned.

        Args:
            image (`torch.Tensor`):
                Image to resize.
            size (`Dict[str, int]`):
                Size of the output image.
            max_image_tiles (`int`):
                The maximum number of tiles to split the image into.
            resample (`PILImageResampling`, *optional*, defaults to `PILImageResampling.BILINEAR`):
                Resampling filter to use when resizing the image.

        Returns:
            `Union[torch.Tensor, Tuple[int, int]]`: The resized image and a tuple containing the number of tiles
            along the height and width dimensions.
        """
        image_height, image_width = image.shape[-2:]
        tile_size = size.height

        canvas_height, canvas_width = get_optimal_tiled_canvas(
            image_height=image_height,
            image_width=image_width,
            max_image_tiles=max_image_tiles,
            tile_size=tile_size,
        )
        num_tiles_height = canvas_height // tile_size
        num_tiles_width = canvas_width // tile_size

        new_height, new_width = get_image_size_fit_to_canvas(
            image_height=image_height,
            image_width=image_width,
            canvas_height=canvas_height,
            canvas_width=canvas_width,
            tile_size=tile_size,
        )

        image = super().resize(
            image, SizeDict(height=new_height, width=new_width), resample=resample, antialias=antialias
        )

        return image, (num_tiles_height, num_tiles_width)

    def _preprocess(
        self,
        images: list[list["torch.Tensor"]],
        size: SizeDict,
        resample: "PILImageResampling | tvF.InterpolationMode | int | None",
        do_rescale: bool,
        rescale_factor: float,
        do_normalize: bool,
        image_mean: float | list[float] | None,
        image_std: float | list[float] | None,
        max_image_tiles: int | None,
        return_tensors: str | TensorType | None,
        disable_grouping: bool | None,
        **kwargs,
    ) -> BatchFeature:
        # Group images by size for batched resizing (nested structure)
        grouped_images, grouped_images_index = group_images_by_shape(
            images, is_nested=True, disable_grouping=disable_grouping
        )
        split_images_grouped = {}
        aspect_ratio_grouped = {}
        for shape, stacked_images in grouped_images.items():
            stacked_images, aspect_ratio = self.resize(
                image=stacked_images, size=size, resample=resample, max_image_tiles=max_image_tiles
            )
            stacked_images = self.pad(
                image=stacked_images,
                size=size,
                aspect_ratio=aspect_ratio,
            )
            num_tiles_height, num_tiles_width = aspect_ratio
            aspect_ratio_grouped[shape] = [aspect_ratio] * len(stacked_images)
            # same aspect ratio for all images in the batch
            split_images = split_to_tiles(stacked_images, num_tiles_height, num_tiles_width)

            # Rescale and normalize
            split_images = self.rescale_and_normalize(
                split_images, do_rescale, rescale_factor, do_normalize, image_mean, image_std
            )
            split_images_grouped[shape] = split_images

        split_images = reorder_images(split_images_grouped, grouped_images_index, is_nested=True)
        aspect_ratios = reorder_images(aspect_ratio_grouped, grouped_images_index, is_nested=True)

        split_images, num_tiles = pad_batches_and_tiles(split_images, max_image_tiles)

        # Use the same device as the processed image tiles so that all output tensors are consistent.
        pixel_values_device = split_images.device
        aspect_ratio_ids = convert_aspect_ratios_to_ids(
            aspect_ratios, max_image_tiles=max_image_tiles, device=pixel_values_device
        )
        aspect_ratio_mask = build_aspect_ratio_mask(
            aspect_ratios, max_image_tiles=max_image_tiles, device=pixel_values_device
        )

        encoded_inputs = BatchFeature(
            data={
                "pixel_values": split_images,
                "aspect_ratio_ids": aspect_ratio_ids,
                "aspect_ratio_mask": aspect_ratio_mask,
            },
            tensor_type=return_tensors,
        )
        encoded_inputs["num_tiles"] = num_tiles

        return encoded_inputs


__all__ = ["MllamaImageProcessor"]
