/*
 *  ******************************************************************************
 *  *
 *  *
 *  * This program and the accompanying materials are made available under the
 *  * terms of the Apache License, Version 2.0 which is available at
 *  * https://www.apache.org/licenses/LICENSE-2.0.
 *  *
 *  *  See the NOTICE file distributed with this work for additional
 *  *  information regarding copyright ownership.
 *  * 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.
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 *  * SPDX-License-Identifier: Apache-2.0
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package org.nd4j.linalg.api.ops.impl.transforms.custom;

import lombok.NoArgsConstructor;
import org.nd4j.autodiff.samediff.SDVariable;
import org.nd4j.autodiff.samediff.SameDiff;
import org.nd4j.common.base.Preconditions;
import org.nd4j.common.util.ArrayUtil;
import org.nd4j.imports.NoOpNameFoundException;
import org.nd4j.linalg.api.buffer.DataType;
import org.nd4j.linalg.api.ndarray.INDArray;
import org.nd4j.linalg.api.ops.impl.transforms.BaseDynamicTransformOp;
import org.nd4j.linalg.factory.Nd4j;

import java.util.Collections;
import java.util.List;

/**
 * Inverse of index permutation.
 *
 * @author Max Pumperla
 */
@NoArgsConstructor
public class InvertPermutation extends BaseDynamicTransformOp {

    public InvertPermutation(SameDiff sameDiff, SDVariable input) {
        this(sameDiff, input, false);
    }

    public InvertPermutation(SameDiff sameDiff, SDVariable input, boolean inPlace) {
        super( sameDiff, new SDVariable[] {input}, inPlace);
    }

    public InvertPermutation(INDArray input) {
        addInputArgument(input);
    }

    @Override
    public String opName() {
        return "invert_permutation";
    }

    @Override
    public String onnxName() {
        throw new NoOpNameFoundException("No onnx name found for shape " + opName());
    }

    @Override
    public String tensorflowName() {
        return "InvertPermutation";
    }

    @Override
    public INDArray generateFake(long... shape) {
        return Nd4j.arange(0, ArrayUtil.prod(shape),1.0).reshape(shape).castTo(Nd4j.defaultFloatingPointType());
    }

    @Override
    public INDArray generateFake(DataType dataType, long... shape) {
        return Nd4j.arange(0, ArrayUtil.prod(shape),1.0).reshape(shape).castTo(dataType);
    }

    public InvertPermutation(SameDiff sameDiff, SDVariable[] args, boolean inPlace) {
        super(sameDiff, args, inPlace);
    }

    @Override
    public List<SDVariable> doDiff(List<SDVariable> grad) {
        SDVariable gradient = grad.get(0);
        SDVariable invertedGradient = sameDiff.invertPermutation(gradient);
        return Collections.singletonList(invertedGradient);
    }

    @Override
    public List<DataType> calculateOutputDataTypes(List<DataType> dataTypes){
        Preconditions.checkState(dataTypes != null && dataTypes.size() == 1, "Expected exactly 1 input datatype for %s, got %s", getClass(), dataTypes);
        return dataTypes;
    }

}
