# Copyright 2019 Yan Yan
#
# 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 torch
from torch.autograd import Function
from torch.cuda.amp import custom_bwd, custom_fwd

from . import ops as ops


class SparseConvFunction(Function):
    @staticmethod
    @custom_fwd(cast_inputs=torch.half)
    def forward(
        ctx, features, filters, indice_pairs, indice_pair_num, num_activate_out
    ):
        ctx.save_for_backward(indice_pairs, indice_pair_num, features, filters)
        return ops.indice_conv(
            features, filters, indice_pairs, indice_pair_num, num_activate_out, False
        )

    @staticmethod
    @custom_bwd
    def backward(ctx, grad_output):
        indice_pairs, indice_pair_num, features, filters = ctx.saved_tensors
        input_bp, filters_bp = ops.indice_conv_backward(
            features, filters, grad_output, indice_pairs, indice_pair_num, False
        )

        return input_bp, filters_bp, None, None, None


class SparseInverseConvFunction(Function):
    @staticmethod
    @custom_fwd(cast_inputs=torch.half)
    def forward(
        ctx, features, filters, indice_pairs, indice_pair_num, num_activate_out
    ):
        ctx.save_for_backward(indice_pairs, indice_pair_num, features, filters)
        return ops.indice_conv(
            features,
            filters,
            indice_pairs,
            indice_pair_num,
            num_activate_out,
            True,
            False,
        )

    @staticmethod
    @custom_bwd
    def backward(ctx, grad_output):
        indice_pairs, indice_pair_num, features, filters = ctx.saved_tensors
        input_bp, filters_bp = ops.indice_conv_backward(
            features, filters, grad_output, indice_pairs, indice_pair_num, True, False
        )

        return input_bp, filters_bp, None, None, None


class SubMConvFunction(Function):
    @staticmethod
    @custom_fwd(cast_inputs=torch.half)
    def forward(
        ctx, features, filters, indice_pairs, indice_pair_num, num_activate_out
    ):
        ctx.save_for_backward(indice_pairs, indice_pair_num, features, filters)
        return ops.indice_conv(
            features,
            filters,
            indice_pairs,
            indice_pair_num,
            num_activate_out,
            False,
            True,
        )

    @staticmethod
    @custom_bwd
    def backward(ctx, grad_output):
        indice_pairs, indice_pair_num, features, filters = ctx.saved_tensors
        input_bp, filters_bp = ops.indice_conv_backward(
            features, filters, grad_output, indice_pairs, indice_pair_num, False, True
        )

        return input_bp, filters_bp, None, None, None


class SparseMaxPoolFunction(Function):
    @staticmethod
    @custom_fwd(cast_inputs=torch.half)
    def forward(ctx, features, indice_pairs, indice_pair_num, num_activate_out):
        out = ops.indice_maxpool(
            features, indice_pairs, indice_pair_num, num_activate_out
        )
        ctx.save_for_backward(indice_pairs, indice_pair_num, features, out)
        return out

    @staticmethod
    @custom_bwd
    def backward(ctx, grad_output):
        indice_pairs, indice_pair_num, features, out = ctx.saved_tensors
        input_bp = ops.indice_maxpool_backward(
            features, out, grad_output, indice_pairs, indice_pair_num
        )
        return input_bp, None, None, None


indice_conv = SparseConvFunction.apply
indice_inverse_conv = SparseInverseConvFunction.apply
indice_subm_conv = SubMConvFunction.apply
indice_maxpool = SparseMaxPoolFunction.apply