/*
 *  ******************************************************************************
 *  *
 *  *
 *  * 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.deeplearning4j.optimize.stepfunctions;

import org.deeplearning4j.optimize.api.StepFunction;

public class StepFunctions {

    private static final DefaultStepFunction DEFAULT_STEP_FUNCTION_INSTANCE = new DefaultStepFunction();
    private static final GradientStepFunction GRADIENT_STEP_FUNCTION_INSTANCE = new GradientStepFunction();
    private static final NegativeDefaultStepFunction NEGATIVE_DEFAULT_STEP_FUNCTION_INSTANCE =
                    new NegativeDefaultStepFunction();
    private static final NegativeGradientStepFunction NEGATIVE_GRADIENT_STEP_FUNCTION_INSTANCE =
                    new NegativeGradientStepFunction();

    private StepFunctions() {}

    public static StepFunction createStepFunction(org.deeplearning4j.nn.conf.stepfunctions.StepFunction stepFunction) {
        if (stepFunction == null)
            return null;
        if (stepFunction instanceof org.deeplearning4j.nn.conf.stepfunctions.DefaultStepFunction)
            return DEFAULT_STEP_FUNCTION_INSTANCE;
        if (stepFunction instanceof org.deeplearning4j.nn.conf.stepfunctions.GradientStepFunction)
            return GRADIENT_STEP_FUNCTION_INSTANCE;
        if (stepFunction instanceof org.deeplearning4j.nn.conf.stepfunctions.NegativeDefaultStepFunction)
            return NEGATIVE_DEFAULT_STEP_FUNCTION_INSTANCE;
        if (stepFunction instanceof org.deeplearning4j.nn.conf.stepfunctions.NegativeGradientStepFunction)
            return NEGATIVE_GRADIENT_STEP_FUNCTION_INSTANCE;

        throw new RuntimeException("unknown step function: " + stepFunction);
    }
}
