# Copyright (c) Microsoft Corporation.
# Licensed under the MIT license.

from typing import Dict, List, Optional, Union

import torch
from torch import Tensor

from .base import MetricsCalculator

__all__ = ['NormMetricsCalculator', 'MultiDataNormMetricsCalculator', 'DistMetricsCalculator',
           'APoZRankMetricsCalculator', 'MeanRankMetricsCalculator', 'StraightMetricsCalculator']


class StraightMetricsCalculator(MetricsCalculator):
    """
    This metrics calculator directly returns a copy of data as metrics.
    """
    def calculate_metrics(self, data: Dict[str, Tensor]) -> Dict[str, Tensor]:
        metrics = {}
        for name, tensor in data.items():
            # use inplace detach `detach_` here to avoid creating a new tensor
            metrics[name] = tensor.clone().detach_()
        return metrics


class NormMetricsCalculator(MetricsCalculator):
    """
    Calculate the specify norm for each tensor in data.
    L1, L2, Level, Slim pruner use this to calculate metric.
    """

    def __init__(self, dim: Optional[Union[int, List[int]]] = None, p: Optional[Union[int, float]] = None):
        """
        Parameters
        ----------
        dim
            The dimensions that corresponding to the under pruning weight dimensions in collected data.
            None means one-to-one correspondence between pruned dimensions and data, which equal to set `dim` as all data dimensions.
            Only these `dim` will be kept and other dimensions of the data will be reduced.

            Example:

            If you want to prune the Conv2d weight in filter level, and the weight size is (32, 16, 3, 3) [out-channel, in-channel, kernal-size-1, kernal-size-2].
            Then the under pruning dimensions is [0], which means you want to prune the filter or out-channel.

                Case 1: Directly collect the conv module weight as data to calculate the metric.
                Then the data has size (32, 16, 3, 3).
                Mention that the dimension 0 of the data is corresponding to the under pruning weight dimension 0.
                So in this case, `dim=0` will set in `__init__`.

                Case 2: Use the output of the conv module as data to calculate the metric.
                Then the data has size (batch_num, 32, feature_map_size_1, feature_map_size_2).
                Mention that the dimension 1 of the data is corresponding to the under pruning weight dimension 0.
                So in this case, `dim=1` will set in `__init__`.

            In both of these two case, the metric of this module has size (32,).
        p
            The order of norm. None means Frobenius norm.
        """
        super().__init__(dim=dim)
        self.p = p if p is not None else 'fro'

    def calculate_metrics(self, data: Dict[str, Tensor]) -> Dict[str, Tensor]:
        metrics = {}
        for name, tensor in data.items():
            keeped_dim = list(range(len(tensor.size()))) if self.dim is None else self.dim
            across_dim = list(range(len(tensor.size())))
            [across_dim.pop(i) for i in reversed(keeped_dim)]
            if len(across_dim) == 0:
                metrics[name] = tensor.abs()
            else:
                metrics[name] = tensor.norm(p=self.p, dim=across_dim)
        return metrics


class MultiDataNormMetricsCalculator(NormMetricsCalculator):
    """
    The data value format is a two-element list [batch_number, cumulative_data].
    Directly use the cumulative_data as new_data to calculate norm metric.
    TaylorFO pruner uses this to calculate metric.
    """

    def calculate_metrics(self, data: Dict[str, List[Tensor]]) -> Dict[str, Tensor]:
        new_data = {name: buffer[1] for name, buffer in data.items()}
        return super().calculate_metrics(new_data)


class DistMetricsCalculator(MetricsCalculator):
    """
    Calculate the sum of specify distance for each element with all other elements in specify `dim` in each tensor in data.
    FPGM pruner uses this to calculate metric.
    """

    def __init__(self, p: float, dim: Union[int, List[int]]):
        """
        Parameters
        ----------
        dim
            The dimensions that corresponding to the under pruning weight dimensions in collected data.
            None means one-to-one correspondence between pruned dimensions and data, which equal to set `dim` as all data dimensions.
            Only these `dim` will be kept and other dimensions of the data will be reduced.

            Example:

            If you want to prune the Conv2d weight in filter level, and the weight size is (32, 16, 3, 3) [out-channel, in-channel, kernal-size-1, kernal-size-2].
            Then the under pruning dimensions is [0], which means you want to prune the filter or out-channel.

                Case 1: Directly collect the conv module weight as data to calculate the metric.
                Then the data has size (32, 16, 3, 3).
                Mention that the dimension 0 of the data is corresponding to the under pruning weight dimension 0.
                So in this case, `dim=0` will set in `__init__`.

                Case 2: Use the output of the conv module as data to calculate the metric.
                Then the data has size (batch_num, 32, feature_map_size_1, feature_map_size_2).
                Mention that the dimension 1 of the data is corresponding to the under pruning weight dimension 0.
                So in this case, `dim=1` will set in `__init__`.

            In both of these two case, the metric of this module has size (32,).
        p
            The order of norm.
        """
        super().__init__(dim=dim)
        self.p = p

    def calculate_metrics(self, data: Dict[str, Tensor]) -> Dict[str, Tensor]:
        metrics = {}
        for name, tensor in data.items():
            keeped_dim = list(range(len(tensor.size()))) if self.dim is None else self.dim
            reorder_dim = list(keeped_dim)
            reorder_dim.extend([i for i in range(len(tensor.size())) if i not in keeped_dim])
            reorder_tensor = tensor.permute(*reorder_dim).clone()

            metric = torch.ones(*reorder_tensor.size()[:len(keeped_dim)], device=reorder_tensor.device)
            across_dim = list(range(len(keeped_dim), len(reorder_dim)))
            idxs = metric.nonzero(as_tuple=False)
            for idx in idxs:
                other = reorder_tensor
                for i in idx:
                    other = other[i]
                other = other.clone()
                if len(across_dim) == 0:
                    dist_sum = torch.abs(reorder_tensor - other).sum()
                else:
                    dist_sum = torch.norm((reorder_tensor - other), p=self.p, dim=across_dim).sum()
                # NOTE: this place need refactor when support layer level pruning.
                tmp_metric = metric
                for i in idx[:-1]:
                    tmp_metric = tmp_metric[i]
                tmp_metric[idx[-1]] = dist_sum

            metrics[name] = metric
        return metrics


class APoZRankMetricsCalculator(MetricsCalculator):
    """
    The data value format is a two-element list [batch_number, batch_wise_zeros_count_sum].
    This metric sum the zero number on `dim` then devide the (batch_number * across_dim_size) to calculate the non-zero rate.
    Note that the metric we return is (1 - apoz), because we assume a higher metric value has higher importance.
    APoZRank pruner uses this to calculate metric.
    """
    def calculate_metrics(self, data: Dict[str, List]) -> Dict[str, Tensor]:
        metrics = {}
        for name, (num, zero_counts) in data.items():
            keeped_dim = list(range(len(zero_counts.size()))) if self.dim is None else self.dim
            across_dim = list(range(len(zero_counts.size())))
            [across_dim.pop(i) for i in reversed(keeped_dim)]
            # The element number on each keeped_dim in zero_counts
            total_size = num
            for dim, dim_size in enumerate(zero_counts.size()):
                if dim not in keeped_dim:
                    total_size *= dim_size
            _apoz = torch.sum(zero_counts, dim=across_dim).type_as(zero_counts) / total_size
            # NOTE: the metric is (1 - apoz) because we assume the smaller metric value is more needed to be pruned.
            metrics[name] = torch.ones_like(_apoz) - _apoz
        return metrics


class MeanRankMetricsCalculator(MetricsCalculator):
    """
    The data value format is a two-element list [batch_number, batch_wise_activation_sum].
    This metric simply calculate the average on `self.dim`, then divide by the batch_number.
    MeanRank pruner uses this to calculate metric.
    """
    def calculate_metrics(self, data: Dict[str, List[Tensor]]) -> Dict[str, Tensor]:
        metrics = {}
        for name, (num, activation_sum) in data.items():
            keeped_dim = list(range(len(activation_sum.size()))) if self.dim is None else self.dim
            across_dim = list(range(len(activation_sum.size())))
            [across_dim.pop(i) for i in reversed(keeped_dim)]
            metrics[name] = torch.mean(activation_sum, across_dim) / num
        return metrics
