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/*
 * Copyright (c) 2013, SRI International
 * All rights reserved.
 * Licensed under the The BSD 3-Clause License;
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at:
 * 
 * http://opensource.org/licenses/BSD-3-Clause
 * 
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 
 * Redistributions of source code must retain the above copyright
 * notice, this list of conditions and the following disclaimer.
 * 
 * Redistributions in binary form must reproduce the above copyright
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 * Neither the name of the aic-expresso nor the names of its
 * contributors may be used to endorse or promote products derived from
 * this software without specific prior written permission.
 * 
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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package com.sri.ai.grinder.sgdpllt.theory.base;

import java.util.LinkedList;
import java.util.List;

import com.google.common.annotations.Beta;
import com.sri.ai.expresso.api.Expression;
import com.sri.ai.util.collect.ImmutableStackedLinkedList;

/**
 * A context-dependent problem step solver taking a list of expressions e1,...,e_n
 * and computing the sub-list e_{j_1},...,e_{j_m}
 * such that all e_i is in the sub-list if and only if
 * the result of invoking {@link #makeLiteralBasedOn(Expression)} on e_i is true in the context.
 *
 * @author braz
 *
 */
@Beta
public abstract class AbstractSelectionStepSolver extends AbstractExpressionsSequenceStepSolver> {

	private List selection;

	/**
	 * Makes step solver
	 * @param expressions the expressions being examined
	 */
	public AbstractSelectionStepSolver(List expressions) {
		this(expressions, 0, new LinkedList());
	}

	/**
	 * Makes step solver
	 * @param expressions the expressions being examined
	 * @param current the index of the current expression
	 * @param selection the expressions that have already been selected
	 */
	private AbstractSelectionStepSolver(List expressions, int current, List selection) {
		super(expressions, current);
		this.selection = selection;
	}
	
	@Override
	protected AbstractSelectionStepSolver makeSubStepSolverWhenLiteralIsTrue() {
		AbstractSelectionStepSolver result = (AbstractSelectionStepSolver) clone();
		result.current = getCurrent() + 1;
		result.selection = new ImmutableStackedLinkedList(getCurrentExpression(), selection);
		return result;
	}

	@Override
	protected AbstractSelectionStepSolver makeSubStepSolverWhenLiteralIsFalse() {
		AbstractSelectionStepSolver result = (AbstractSelectionStepSolver) clone();
		result.current = getCurrent() + 1;
		// selection remains the same
		return result;
	}

	@Override
	protected Step> makeSolutionWhenAllElementsHaveBeenChecked() {
		Solution> result = new Solution>(selection);
		return result;
	}
}