/* Copyright (C) 2013-2020 TU Dortmund
 * This file is part of LearnLib, http://www.learnlib.de/.
 *
 * 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.
 */
package de.learnlib.mapper;

import de.learnlib.api.SUL;
import de.learnlib.mapper.api.ContextExecutableInput;
import org.checkerframework.checker.nullness.qual.Nullable;

/**
 * Abstract base class for a {@link SUL} that step-wisely executes {@link ContextExecutableInput} symbols.
 * <p>
 * This class does not specify how contexts are created and disposed of, but declares abstract methods for these tasks.
 *
 * @param <I>
 *         input symbol type
 * @param <O>
 *         output symbol type
 * @param <C>
 *         context type
 *
 * @author Malte Isberner
 */
public abstract class AbstractContextExecutableInputSUL<I extends ContextExecutableInput<? extends O, ? super C>, O, C>
        implements SUL<I, O> {

    private @Nullable C currentContext;

    @Override
    public void pre() {
        this.currentContext = createContext();
    }

    protected abstract C createContext();

    @Override
    public void post() {
        disposeContext(currentContext);
        currentContext = null;
    }

    protected abstract void disposeContext(C context);

    @Override
    public O step(I in) {
        return in.execute(currentContext);
    }
}
