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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
 * notice, this list of conditions and the following disclaimer in the
 * documentation and/or other materials provided with the distribution.
 * 
 * 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
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
 * COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, 
 * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES 
 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
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 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, 
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 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
 * OF THE POSSIBILITY OF SUCH DAMAGE.
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package com.sri.ai.grinder.sgdpllt.theory.linearrealarithmetic;

import static com.sri.ai.expresso.helper.Expressions.apply;
import static com.sri.ai.grinder.sgdpllt.library.set.Sets.EMPTY_SET;
import static com.sri.ai.util.Util.getFirst;

import com.google.common.annotations.Beta;
import com.sri.ai.expresso.api.Expression;
import com.sri.ai.expresso.core.DefaultExtensionalUniSet;
import com.sri.ai.grinder.sgdpllt.api.Context;
import com.sri.ai.grinder.sgdpllt.library.FunctorConstants;
import com.sri.ai.grinder.sgdpllt.theory.numeric.AbstractSingleVariableNumericConstraintFeasibilityRegionStepSolver;

/**
 * A step solver computing an interval of values for the variable of
 * a single-variable linear arithmetic constraint
 * that has the same measure as its set of solutions,
 * which is an interval minus the distinct disequals (which have measure zero).
 * 
 * In other words, given the set of solutions [a;b] \ {d_1,...,d_n},
 * this step solver returns [a;b] (and analogously for open bounds),
 * which has the same measure.
 * @author braz
 *
 */
@Beta
public class IntervalWithMeasureEquivalentToSingleVariableLinearRealArithmeticConstraintStepSolver extends AbstractSingleVariableLinearRealArithmeticConstraintFeasibilityRegionStepSolver {

	public IntervalWithMeasureEquivalentToSingleVariableLinearRealArithmeticConstraintStepSolver(SingleVariableLinearRealArithmeticConstraint constraint) {
		super(constraint);
	}
	
	@Override
	public IntervalWithMeasureEquivalentToSingleVariableLinearRealArithmeticConstraintStepSolver clone() {
		return (IntervalWithMeasureEquivalentToSingleVariableLinearRealArithmeticConstraintStepSolver) super.clone();
	}

	@Override
	protected Step getSolutionStepAfterBoundsAreCheckedForFeasibility(Expression lowerBound, Expression upperBound, AbstractSingleVariableNumericConstraintFeasibilityRegionStepSolver sequelBase, Context context) {

		boolean lowerBoundIsStrict = getMapFromLowerBoundsToStrictness(context).get(lowerBound);

		boolean upperBoundIsStrict = getMapFromUpperBoundsToStrictness(context).get(upperBound);

		Expression solutionExpression;
		
		if (lowerBoundIsStrict && upperBoundIsStrict) {
			solutionExpression = apply(FunctorConstants.REAL_INTERVAL_OPEN_OPEN, lowerBound, upperBound);
		}
		else if (!lowerBoundIsStrict && upperBoundIsStrict) {
			solutionExpression = apply(FunctorConstants.REAL_INTERVAL_CLOSED_OPEN, lowerBound, upperBound);
		}
		else if (lowerBoundIsStrict && !upperBoundIsStrict) {
			solutionExpression = apply(FunctorConstants.REAL_INTERVAL_OPEN_CLOSED, lowerBound, upperBound);
		}
		else {
			solutionExpression = apply(FunctorConstants.REAL_INTERVAL_CLOSED_CLOSED, lowerBound, upperBound);
		}
		
		return new Solution(solutionExpression);
	}

	@Override
	public boolean unboundedVariableProducesShortCircuitSolution() {
		return false;
	}

	@Override
	public Expression getSolutionExpressionForUnboundedVariables() {
		throw new Error("getSolutionExpressionForUnboundedVariables should not be used because just knowing that the variable is unbounded is not enough to determine value set");
	}

	@Override
	public Expression getSolutionExpressionForBoundVariable() {
		Expression oneOfTheVariableValues = getFirst(getEquals());
		DefaultExtensionalUniSet result = new DefaultExtensionalUniSet(oneOfTheVariableValues);
		return result;
	}

	@Override
	protected Expression getSolutionExpressionGivenContradiction() {
		return EMPTY_SET;
	}
}