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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.
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 * 
 * http://opensource.org/licenses/BSD-3-Clause
 * 
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 * modification, are permitted provided that the following conditions
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 * 
 * 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.
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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
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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package com.sri.ai.grinder.sgdpllt.theory.linearrealarithmetic;

import static com.sri.ai.grinder.sgdpllt.library.FunctorConstants.LESS_THAN;
import static com.sri.ai.grinder.sgdpllt.library.FunctorConstants.LESS_THAN_OR_EQUAL_TO;
import static com.sri.ai.util.Util.arrayList;
import static com.sri.ai.util.base.Pair.pair;

import com.google.common.annotations.Beta;
import com.sri.ai.expresso.api.Expression;
import com.sri.ai.expresso.type.RealInterval;
import com.sri.ai.grinder.sgdpllt.api.Context;
import com.sri.ai.grinder.sgdpllt.theory.numeric.AbstractSingleVariableNumericConstraintFeasibilityRegionStepSolver;
import com.sri.ai.util.base.Pair;

/**
 * A {@link AbstractSingleVariableNumericConstraintFeasibilityRegionStepSolver}
 * for a {@link SingleVariableLinearRealArithmeticConstraint}.
 * 
 * @author braz
 *
 */
@Beta
public abstract class AbstractSingleVariableLinearRealArithmeticConstraintFeasibilityRegionStepSolver extends AbstractSingleVariableNumericConstraintFeasibilityRegionStepSolver {

	public AbstractSingleVariableLinearRealArithmeticConstraintFeasibilityRegionStepSolver(SingleVariableLinearRealArithmeticConstraint constraint) {
		super(constraint);
	}

	@Override
	public AbstractSingleVariableLinearRealArithmeticConstraintFeasibilityRegionStepSolver clone() {
		return (AbstractSingleVariableLinearRealArithmeticConstraintFeasibilityRegionStepSolver) super.clone();
	}

	@Override
	public SingleVariableLinearRealArithmeticConstraint getConstraint() {
		return (SingleVariableLinearRealArithmeticConstraint) super.getConstraint();
	}

	protected
	AbstractSingleVariableLinearRealArithmeticConstraintFeasibilityRegionStepSolver 
	makeSequelStepSolver(
			AbstractSingleVariableNumericConstraintFeasibilityRegionStepSolver 
			sequelBase) {
		return 
				(AbstractSingleVariableLinearRealArithmeticConstraintFeasibilityRegionStepSolver) 
				super.makeSequelStepSolver(sequelBase);
	}

	@Override
	protected Expression makeLiteralCheckingWhetherThereAreAnyValuesWithinBounds(Expression lowerBound, Expression upperBound, Context context) {
		Expression result;
		boolean lowerBoundIsStrict = getMapFromLowerBoundsToStrictness(context).get(lowerBound);
		boolean upperBoundIsStrict = getMapFromUpperBoundsToStrictness(context).get(upperBound);
		String operator;
		if (lowerBoundIsStrict || upperBoundIsStrict) {
			operator = LESS_THAN;
		}
		else {
			operator = LESS_THAN_OR_EQUAL_TO; // only way it is ok for them to be equal is if both are non-strict
		}
		result = applyAndSimplify(operator, arrayList(lowerBound, upperBound), context);
		return result;
	}
	
	private Pair typeLowerBoundAndStrictness;
	
	protected Pair getTypeLowerBoundAndStrictness(Context context) {
		if (typeLowerBoundAndStrictness == null) {
			RealInterval type = getType(context);
			Expression lowerBound = type.getLowerBound();
			typeLowerBoundAndStrictness = pair(lowerBound, type.lowerBoundIsOpen());
		}
		return typeLowerBoundAndStrictness;
	}

	private Pair typeUpperBoundAndStrictess;
	
	protected Pair getTypeUpperBoundAndStrictness(Context context) {
		if (typeUpperBoundAndStrictess == null) {
			RealInterval type = getType(context);
			Expression upperBound = type.getUpperBound();
			typeUpperBoundAndStrictess = pair(upperBound, type.upperBoundIsOpen());
		}
		return typeUpperBoundAndStrictess;
	}

	protected RealInterval getType(Context context) {
		return getConstraint().getType(context);
	}
}