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from collections.abc import Collection

import torch
from torch import Tensor

from torchmetrics.functional.detection._panoptic_quality_common import (
    _get_category_id_to_continuous_id,
    _get_void_color,
    _panoptic_quality_compute,
    _panoptic_quality_update,
    _parse_categories,
    _prepocess_inputs,
    _validate_inputs,
)


def panoptic_quality(
    preds: Tensor,
    target: Tensor,
    things: Collection[int],
    stuffs: Collection[int],
    allow_unknown_preds_category: bool = False,
    return_sq_and_rq: bool = False,
    return_per_class: bool = False,
) -> Tensor:
    r"""Compute `Panoptic Quality`_ for panoptic segmentations.

    .. math::
        PQ = \frac{IOU}{TP + 0.5 FP + 0.5 FN}

    where IOU, TP, FP and FN are respectively the sum of the intersection over union for true positives, the number of
    true positives, false positives and false negatives. This metric is inspired by the PQ implementation of
    panopticapi, a standard implementation for the PQ metric for object detection.

    .. note:
        Points in the target tensor that do not map to a known category ID are automatically ignored in the metric
        computation.

    Args:
        preds:
            torch tensor with panoptic detection of shape [height, width, 2] containing the pair
            (category_id, instance_id) for each pixel of the image. If the category_id refer to a stuff, the
            instance_id is ignored.
        target:
            torch tensor with ground truth of shape [height, width, 2] containing the pair (category_id, instance_id)
            for each pixel of the image. If the category_id refer to a stuff, the instance_id is ignored.
        things:
            Set of ``category_id`` for countable things.
        stuffs:
            Set of ``category_id`` for uncountable stuffs.
        allow_unknown_preds_category:
            Boolean flag to specify if unknown categories in the predictions are to be ignored in the metric
            computation or raise an exception when found.
        return_sq_and_rq:
            Boolean flag to specify if Segmentation Quality and Recognition Quality should be also returned.
        return_per_class:
            Boolean flag to specify if the per-class values should be returned or the class average.

    Raises:
        ValueError:
            If ``things``, ``stuffs`` have at least one common ``category_id``.
        TypeError:
            If ``things``, ``stuffs`` contain non-integer ``category_id``.
        TypeError:
            If ``preds`` or ``target`` is not an ``torch.Tensor``.
        ValueError:
             If ``preds`` or ``target`` has different shape.
        ValueError:
            If ``preds`` has less than 3 dimensions.
        ValueError:
            If the final dimension of ``preds`` has size != 2.

    Example:
        >>> from torch import tensor
        >>> preds = tensor([[[[6, 0], [0, 0], [6, 0], [6, 0]],
        ...                  [[0, 0], [0, 0], [6, 0], [0, 1]],
        ...                  [[0, 0], [0, 0], [6, 0], [0, 1]],
        ...                  [[0, 0], [7, 0], [6, 0], [1, 0]],
        ...                  [[0, 0], [7, 0], [7, 0], [7, 0]]]])
        >>> target = tensor([[[[6, 0], [0, 1], [6, 0], [0, 1]],
        ...                   [[0, 1], [0, 1], [6, 0], [0, 1]],
        ...                   [[0, 1], [0, 1], [6, 0], [1, 0]],
        ...                   [[0, 1], [7, 0], [1, 0], [1, 0]],
        ...                   [[0, 1], [7, 0], [7, 0], [7, 0]]]])
        >>> panoptic_quality(preds, target, things = {0, 1}, stuffs = {6, 7})
        tensor(0.5463, dtype=torch.float64)

    You can also return the segmentation and recognition quality alognside the PQ
        >>> from torch import tensor
        >>> preds = tensor([[[[6, 0], [0, 0], [6, 0], [6, 0]],
        ...                  [[0, 0], [0, 0], [6, 0], [0, 1]],
        ...                  [[0, 0], [0, 0], [6, 0], [0, 1]],
        ...                  [[0, 0], [7, 0], [6, 0], [1, 0]],
        ...                  [[0, 0], [7, 0], [7, 0], [7, 0]]]])
        >>> target = tensor([[[[6, 0], [0, 1], [6, 0], [0, 1]],
        ...                   [[0, 1], [0, 1], [6, 0], [0, 1]],
        ...                   [[0, 1], [0, 1], [6, 0], [1, 0]],
        ...                   [[0, 1], [7, 0], [1, 0], [1, 0]],
        ...                   [[0, 1], [7, 0], [7, 0], [7, 0]]]])
        >>> panoptic_quality(preds, target, things = {0, 1}, stuffs = {6, 7}, return_sq_and_rq=True)
        tensor([0.5463, 0.6111, 0.6667], dtype=torch.float64)

    You can also specify to return the per-class metrics
        >>> from torch import tensor
        >>> preds = tensor([[[[6, 0], [0, 0], [6, 0], [6, 0]],
        ...                  [[0, 0], [0, 0], [6, 0], [0, 1]],
        ...                  [[0, 0], [0, 0], [6, 0], [0, 1]],
        ...                  [[0, 0], [7, 0], [6, 0], [1, 0]],
        ...                  [[0, 0], [7, 0], [7, 0], [7, 0]]]])
        >>> target = tensor([[[[6, 0], [0, 1], [6, 0], [0, 1]],
        ...                   [[0, 1], [0, 1], [6, 0], [0, 1]],
        ...                   [[0, 1], [0, 1], [6, 0], [1, 0]],
        ...                   [[0, 1], [7, 0], [1, 0], [1, 0]],
        ...                   [[0, 1], [7, 0], [7, 0], [7, 0]]]])
        >>> panoptic_quality(preds, target, things = {0, 1}, stuffs = {6, 7}, return_per_class=True)
        tensor([[0.5185, 0.0000, 0.6667, 1.0000]], dtype=torch.float64)

    You can also specify to return the per-class metrics and the segmentation and recognition quality
        >>> from torch import tensor
        >>> preds = tensor([[[[6, 0], [0, 0], [6, 0], [6, 0]],
        ...                  [[0, 0], [0, 0], [6, 0], [0, 1]],
        ...                  [[0, 0], [0, 0], [6, 0], [0, 1]],
        ...                  [[0, 0], [7, 0], [6, 0], [1, 0]],
        ...                  [[0, 0], [7, 0], [7, 0], [7, 0]]]])
        >>> target = tensor([[[[6, 0], [0, 1], [6, 0], [0, 1]],
        ...                   [[0, 1], [0, 1], [6, 0], [0, 1]],
        ...                   [[0, 1], [0, 1], [6, 0], [1, 0]],
        ...                   [[0, 1], [7, 0], [1, 0], [1, 0]],
        ...                   [[0, 1], [7, 0], [7, 0], [7, 0]]]])
        >>> panoptic_quality(preds, target, things = {0, 1}, stuffs = {6, 7},
        ...                  return_per_class=True, return_sq_and_rq=True)
        tensor([[0.5185, 0.7778, 0.6667],
                [0.0000, 0.0000, 0.0000],
                [0.6667, 0.6667, 1.0000],
                [1.0000, 1.0000, 1.0000]], dtype=torch.float64)

    """
    things, stuffs = _parse_categories(things, stuffs)
    _validate_inputs(preds, target)
    void_color = _get_void_color(things, stuffs)
    cat_id_to_continuous_id = _get_category_id_to_continuous_id(things, stuffs)
    flatten_preds = _prepocess_inputs(things, stuffs, preds, void_color, allow_unknown_preds_category)
    flatten_target = _prepocess_inputs(things, stuffs, target, void_color, True)
    iou_sum, true_positives, false_positives, false_negatives = _panoptic_quality_update(
        flatten_preds, flatten_target, cat_id_to_continuous_id, void_color
    )
    pq, sq, rq, pq_avg, sq_avg, rq_avg = _panoptic_quality_compute(
        iou_sum,
        true_positives,
        false_positives,
        false_negatives,
    )
    if return_per_class:
        if return_sq_and_rq:
            return torch.stack((pq, sq, rq), dim=-1)
        return pq.view(1, -1)
    if return_sq_and_rq:
        return torch.stack((pq_avg, sq_avg, rq_avg), dim=0)
    return pq_avg


def modified_panoptic_quality(
    preds: Tensor,
    target: Tensor,
    things: Collection[int],
    stuffs: Collection[int],
    allow_unknown_preds_category: bool = False,
) -> Tensor:
    r"""Compute `Modified Panoptic Quality`_ for panoptic segmentations.

    The metric was introduced in `Seamless Scene Segmentation paper`_, and is an adaptation of the original
    `Panoptic Quality`_ where the metric for a stuff class is computed as

    .. math::
        PQ^{\dagger}_c = \frac{IOU_c}{|S_c|}

    where :math:`IOU_c` is the sum of the intersection over union of all matching segments for a given class, and
    :math:`|S_c|` is the overall number of segments in the ground truth for that class.

    .. note:
        Points in the target tensor that do not map to a known category ID are automatically ignored in the metric
        computation.

    Args:
        preds:
            torch tensor with panoptic detection of shape [height, width, 2] containing the pair
            (category_id, instance_id) for each pixel of the image. If the category_id refer to a stuff, the
            instance_id is ignored.
        target:
            torch tensor with ground truth of shape [height, width, 2] containing the pair (category_id, instance_id)
            for each pixel of the image. If the category_id refer to a stuff, the instance_id is ignored.
        things:
            Set of ``category_id`` for countable things.
        stuffs:
            Set of ``category_id`` for uncountable stuffs.
        allow_unknown_preds_category:
            Boolean flag to specify if unknown categories in the predictions are to be ignored in the metric
            computation or raise an exception when found.

    Raises:
        ValueError:
            If ``things``, ``stuffs`` have at least one common ``category_id``.
        TypeError:
            If ``things``, ``stuffs`` contain non-integer ``category_id``.
        TypeError:
            If ``preds`` or ``target`` is not an ``torch.Tensor``.
        ValueError:
            If ``preds`` or ``target`` has different shape.
        ValueError:
            If ``preds`` has less than 3 dimensions.
        ValueError:
            If the final dimension of ``preds`` has size != 2.

    Example:
        >>> from torch import tensor
        >>> preds = tensor([[[0, 0], [0, 1], [6, 0], [7, 0], [0, 2], [1, 0]]])
        >>> target = tensor([[[0, 1], [0, 0], [6, 0], [7, 0], [6, 0], [255, 0]]])
        >>> modified_panoptic_quality(preds, target, things = {0, 1}, stuffs = {6, 7})
        tensor(0.7667, dtype=torch.float64)

    """
    things, stuffs = _parse_categories(things, stuffs)
    _validate_inputs(preds, target)
    void_color = _get_void_color(things, stuffs)
    cat_id_to_continuous_id = _get_category_id_to_continuous_id(things, stuffs)
    flatten_preds = _prepocess_inputs(things, stuffs, preds, void_color, allow_unknown_preds_category)
    flatten_target = _prepocess_inputs(things, stuffs, target, void_color, True)
    iou_sum, true_positives, false_positives, false_negatives = _panoptic_quality_update(
        flatten_preds,
        flatten_target,
        cat_id_to_continuous_id,
        void_color,
        modified_metric_stuffs=stuffs,
    )
    _, _, _, pq_avg, _, _ = _panoptic_quality_compute(iou_sum, true_positives, false_positives, false_negatives)
    return pq_avg