# Copyright The PyTorch Lightning team.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
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#     http://www.apache.org/licenses/LICENSE-2.0
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from typing import Any, Optional

import torch
from torch import Tensor
from typing_extensions import Literal

from torchmetrics.functional.classification.exact_match import (
    _exact_match_reduce,
    _multiclass_exact_match_update,
    _multilabel_exact_match_update,
)
from torchmetrics.functional.classification.stat_scores import (
    _multiclass_stat_scores_arg_validation,
    _multiclass_stat_scores_format,
    _multiclass_stat_scores_tensor_validation,
    _multilabel_stat_scores_arg_validation,
    _multilabel_stat_scores_format,
    _multilabel_stat_scores_tensor_validation,
)
from torchmetrics.metric import Metric
from torchmetrics.utilities.data import dim_zero_cat


class MulticlassExactMatch(Metric):
    r"""Computes Exact match (also known as subset accuracy) for multiclass tasks. Exact Match is a stricter version
    of accuracy where all labels have to match exactly for the sample to be correctly classified.

    As input to ``forward`` and ``update`` the metric accepts the following input:

    - ``preds`` (:class:`~torch.Tensor`): An int tensor of shape ``(N, ...)`` or float tensor of shape ``(N, C, ..)``.
      If preds is a floating point we apply ``torch.argmax`` along the ``C`` dimension to automatically convert
      probabilities/logits into an int tensor.
    - ``target`` (:class:`~torch.Tensor`): An int tensor of shape ``(N, ...)``.


    As output to ``forward`` and ``compute`` the metric returns the following output:

    - ``mcem`` (:class:`~torch.Tensor`): A tensor whose returned shape depends on the ``multidim_average`` argument:

        - If ``multidim_average`` is set to ``global`` the output will be a scalar tensor
        - If ``multidim_average`` is set to ``samplewise`` the output will be a tensor of shape ``(N,)``

    Args:
        num_classes: Integer specifing the number of labels
        multidim_average:
            Defines how additionally dimensions ``...`` should be handled. Should be one of the following:

            - ``global``: Additional dimensions are flatted along the batch dimension
            - ``samplewise``: Statistic will be calculated independently for each sample on the ``N`` axis.
              The statistics in this case are calculated over the additional dimensions.

        ignore_index:
            Specifies a target value that is ignored and does not contribute to the metric calculation
        validate_args: bool indicating if input arguments and tensors should be validated for correctness.
            Set to ``False`` for faster computations.

    Example (multidim tensors):
        >>> from torchmetrics.classification import MulticlassExactMatch
        >>> target = torch.tensor([[[0, 1], [2, 1], [0, 2]], [[1, 1], [2, 0], [1, 2]]])
        >>> preds = torch.tensor([[[0, 1], [2, 1], [0, 2]], [[2, 2], [2, 1], [1, 0]]])
        >>> metric = MulticlassExactMatch(num_classes=3, multidim_average='global')
        >>> metric(preds, target)
        tensor(0.5000)

    Example (multidim tensors):
        >>> from torchmetrics.classification import MulticlassExactMatch
        >>> target = torch.tensor([[[0, 1], [2, 1], [0, 2]], [[1, 1], [2, 0], [1, 2]]])
        >>> preds = torch.tensor([[[0, 1], [2, 1], [0, 2]], [[2, 2], [2, 1], [1, 0]]])
        >>> metric = MulticlassExactMatch(num_classes=3, multidim_average='samplewise')
        >>> metric(preds, target)
        tensor([1., 0.])
    """
    is_differentiable = False
    higher_is_better = True
    full_state_update: bool = False

    def __init__(
        self,
        num_classes: int,
        multidim_average: Literal["global", "samplewise"] = "global",
        ignore_index: Optional[int] = None,
        validate_args: bool = True,
        **kwargs: Any,
    ) -> None:
        super().__init__(**kwargs)
        top_k, average = 1, None
        if validate_args:
            _multiclass_stat_scores_arg_validation(num_classes, top_k, average, multidim_average, ignore_index)
        self.num_classes = num_classes
        self.multidim_average = multidim_average
        self.ignore_index = ignore_index
        self.validate_args = validate_args

        self.add_state(
            "correct",
            torch.zeros(1, dtype=torch.long) if self.multidim_average == "global" else [],
            dist_reduce_fx="sum" if self.multidim_average == "global" else "cat",
        )
        self.add_state(
            "total",
            torch.zeros(1, dtype=torch.long),
            dist_reduce_fx="sum" if self.multidim_average == "global" else "mean",
        )

    def update(self, preds, target) -> None:
        if self.validate_args:
            _multiclass_stat_scores_tensor_validation(
                preds, target, self.num_classes, self.multidim_average, self.ignore_index
            )
        preds, target = _multiclass_stat_scores_format(preds, target, 1)
        correct, total = _multiclass_exact_match_update(preds, target, self.multidim_average)
        if self.multidim_average == "samplewise":
            self.correct.append(correct)
            self.total = total
        else:
            self.correct += correct
            self.total += total

    def compute(self) -> Tensor:
        correct = dim_zero_cat(self.correct) if isinstance(self.correct, list) else self.correct
        return _exact_match_reduce(correct, self.total)


class MultilabelExactMatch(Metric):
    r"""Computes Exact match (also known as subset accuracy) for multilabel tasks. Exact Match is a stricter version
    of accuracy where all labels have to match exactly for the sample to be correctly classified.

    As input to ``forward`` and ``update`` the metric accepts the following input:

    - ``preds`` (:class:`~torch.Tensor`): An int tensor or float tensor of shape ``(N, C, ..)``. If preds is a
      floating point tensor with values outside [0,1] range we consider the input to be logits and will auto apply
      sigmoid per element. Addtionally, we convert to int tensor with thresholding using the value in ``threshold``.
    - ``target`` (:class:`~torch.Tensor`): An int tensor of shape ``(N, C, ...)``.


    As output to ``forward`` and ``compute`` the metric returns the following output:

    - ``mlem`` (:class:`~torch.Tensor`): A tensor whose returned shape depends on the ``multidim_average`` argument:

        - If ``multidim_average`` is set to ``global`` the output will be a scalar tensor
        - If ``multidim_average`` is set to ``samplewise`` the output will be a tensor of shape ``(N,)``

    Args:
        num_labels: Integer specifing the number of labels
        threshold: Threshold for transforming probability to binary (0,1) predictions
        multidim_average:
            Defines how additionally dimensions ``...`` should be handled. Should be one of the following:

            - ``global``: Additional dimensions are flatted along the batch dimension
            - ``samplewise``: Statistic will be calculated independently for each sample on the ``N`` axis.
              The statistics in this case are calculated over the additional dimensions.

        ignore_index:
            Specifies a target value that is ignored and does not contribute to the metric calculation
        validate_args: bool indicating if input arguments and tensors should be validated for correctness.
            Set to ``False`` for faster computations.

    Example (preds is int tensor):
        >>> from torchmetrics.classification import MultilabelExactMatch
        >>> target = torch.tensor([[0, 1, 0], [1, 0, 1]])
        >>> preds = torch.tensor([[0, 0, 1], [1, 0, 1]])
        >>> metric = MultilabelExactMatch(num_labels=3)
        >>> metric(preds, target)
        tensor(0.5000)

    Example (preds is float tensor):
        >>> from torchmetrics.classification import MultilabelExactMatch
        >>> target = torch.tensor([[0, 1, 0], [1, 0, 1]])
        >>> preds = torch.tensor([[0.11, 0.22, 0.84], [0.73, 0.33, 0.92]])
        >>> metric = MultilabelExactMatch(num_labels=3)
        >>> metric(preds, target)
        tensor(0.5000)

    Example (multidim tensors):
        >>> from torchmetrics.classification import MultilabelExactMatch
        >>> target = torch.tensor([[[0, 1], [1, 0], [0, 1]], [[1, 1], [0, 0], [1, 0]]])
        >>> preds = torch.tensor(
        ...     [
        ...         [[0.59, 0.91], [0.91, 0.99], [0.63, 0.04]],
        ...         [[0.38, 0.04], [0.86, 0.780], [0.45, 0.37]],
        ...     ]
        ... )
        >>> metric = MultilabelExactMatch(num_labels=3, multidim_average='samplewise')
        >>> metric(preds, target)
        tensor([0., 0.])
    """

    is_differentiable = False
    higher_is_better = True
    full_state_update: bool = False

    def __init__(
        self,
        num_labels: int,
        threshold: float = 0.5,
        multidim_average: Literal["global", "samplewise"] = "global",
        ignore_index: Optional[int] = None,
        validate_args: bool = True,
        **kwargs: Any,
    ) -> None:
        super().__init__(**kwargs)
        if validate_args:
            _multilabel_stat_scores_arg_validation(
                num_labels, threshold, average=None, multidim_average=multidim_average, ignore_index=ignore_index
            )
        self.num_labels = num_labels
        self.threshold = threshold
        self.multidim_average = multidim_average
        self.ignore_index = ignore_index
        self.validate_args = validate_args

        self.add_state(
            "correct",
            torch.zeros(1, dtype=torch.long) if self.multidim_average == "global" else [],
            dist_reduce_fx="sum" if self.multidim_average == "global" else "cat",
        )
        self.add_state(
            "total",
            torch.zeros(1, dtype=torch.long),
            dist_reduce_fx="sum" if self.multidim_average == "global" else "mean",
        )

    def update(self, preds: Tensor, target: Tensor) -> None:  # type: ignore
        """Update state with predictions and targets."""
        if self.validate_args:
            _multilabel_stat_scores_tensor_validation(
                preds, target, self.num_labels, self.multidim_average, self.ignore_index
            )
        preds, target = _multilabel_stat_scores_format(
            preds, target, self.num_labels, self.threshold, self.ignore_index
        )
        correct, total = _multilabel_exact_match_update(preds, target, self.num_labels, self.multidim_average)
        if self.multidim_average == "samplewise":
            self.correct.append(correct)
            self.total = total
        else:
            self.correct += correct
            self.total += total

    def compute(self) -> Tensor:
        correct = dim_zero_cat(self.correct) if isinstance(self.correct, list) else self.correct
        return _exact_match_reduce(correct, self.total)


class ExactMatch:
    r"""Computes Exact match (also known as subset accuracy). Exact Match is a stricter version of accuracy where
    all labels have to match exactly for the sample to be correctly classified.

    This module is a simple wrapper to get the task specific versions of this metric, which is done by setting the
    ``task`` argument to either ``'multiclass'`` or ``multilabel``. See the documentation of
    :mod:`MulticlassExactMatch` and :mod:`MultilabelExactMatch` for the specific details of
    each argument influence and examples.

        Legacy Example:
        >>> target = torch.tensor([[[0, 1], [2, 1], [0, 2]], [[1, 1], [2, 0], [1, 2]]])
        >>> preds = torch.tensor([[[0, 1], [2, 1], [0, 2]], [[2, 2], [2, 1], [1, 0]]])
        >>> metric = ExactMatch(task="multiclass", num_classes=3, multidim_average='global')
        >>> metric(preds, target)
        tensor(0.5000)

        >>> target = torch.tensor([[[0, 1], [2, 1], [0, 2]], [[1, 1], [2, 0], [1, 2]]])
        >>> preds = torch.tensor([[[0, 1], [2, 1], [0, 2]], [[2, 2], [2, 1], [1, 0]]])
        >>> metric = ExactMatch(task="multiclass", num_classes=3, multidim_average='samplewise')
        >>> metric(preds, target)
        tensor([1., 0.])
    """

    def __new__(
        cls,
        task: Literal["binary", "multiclass", "multilabel"],
        threshold: float = 0.5,
        num_classes: Optional[int] = None,
        num_labels: Optional[int] = None,
        multidim_average: Literal["global", "samplewise"] = "global",
        ignore_index: Optional[int] = None,
        validate_args: bool = True,
        **kwargs: Any,
    ) -> Metric:
        kwargs.update(dict(multidim_average=multidim_average, ignore_index=ignore_index, validate_args=validate_args))
        if task == "multiclass":
            assert isinstance(num_classes, int)
            return MulticlassExactMatch(num_classes, **kwargs)
        if task == "multilabel":
            assert isinstance(num_labels, int)
            return MultilabelExactMatch(num_labels, threshold, **kwargs)
        raise ValueError(f"Expected argument `task` to either be `'multiclass'` or `'multilabel'` but got {task}")