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/**
 * Copyright (C) 2010-2018 Gordon Fraser, Andrea Arcuri and EvoSuite
 * contributors
 *
 * This file is part of EvoSuite.
 *
 * EvoSuite is free software: you can redistribute it and/or modify it
 * under the terms of the GNU Lesser General Public License as published
 * by the Free Software Foundation, either version 3.0 of the License, or
 * (at your option) any later version.
 *
 * EvoSuite is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
 * Lesser Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with EvoSuite. If not, see .
 */
package org.evosuite.symbolic.solver.z3;

import org.evosuite.symbolic.expr.Comparator;
import org.evosuite.symbolic.expr.ConstraintVisitor;
import org.evosuite.symbolic.expr.Expression;
import org.evosuite.symbolic.expr.IntegerConstraint;
import org.evosuite.symbolic.expr.Operator;
import org.evosuite.symbolic.expr.RealConstraint;
import org.evosuite.symbolic.expr.StringConstraint;
import org.evosuite.symbolic.expr.bv.IntegerConstant;
import org.evosuite.symbolic.expr.bv.StringBinaryToIntegerExpression;
import org.evosuite.symbolic.expr.bv.StringComparison;
import org.evosuite.symbolic.solver.SmtExprBuilder;
import org.evosuite.symbolic.solver.smt.ExprToSmtVisitor;
import org.evosuite.symbolic.solver.smt.SmtExpr;

class ConstraintToZ3Visitor implements ConstraintVisitor {

	public ConstraintToZ3Visitor() {
	}

	@Override
	public SmtExpr visit(IntegerConstraint c, Void arg) {
		Expression left = c.getLeftOperand();
		Comparator cmp = c.getComparator();
		Expression right = c.getRightOperand();

		SmtExpr equalsExpr = translateCompareTo(left, cmp, right);
		if (equalsExpr != null) {
			return equalsExpr;
		}

		ExprToSmtVisitor v = new ExprToSmtVisitor();
		SmtExpr leftExpr = left.accept(v, null);
		SmtExpr rightExpr = right.accept(v, null);

		if (leftExpr == null || rightExpr == null) {
			return null;
		}

		return mkComparison(leftExpr, cmp, rightExpr);
	}

	private static SmtExpr translateCompareTo(Expression left, Comparator cmp, Expression right) {

		if (!(left instanceof StringBinaryToIntegerExpression)) {
			return null;
		}
		if (!(right instanceof IntegerConstant)) {
			return null;
		}
		if (cmp != Comparator.NE && cmp != Comparator.EQ) {
			return null;
		}

		StringBinaryToIntegerExpression leftExpr = (StringBinaryToIntegerExpression) left;
		if (leftExpr.getOperator() != Operator.COMPARETO) {
			return null;
		}

		IntegerConstant rightExpr = (IntegerConstant) right;
		if (rightExpr.getConcreteValue() != 0) {
			return null;
		}

		ExprToSmtVisitor v = new ExprToSmtVisitor();
		SmtExpr leftEquals = leftExpr.getLeftOperand().accept(v, null);
		SmtExpr rightEquals = leftExpr.getRightOperand().accept(v, null);

		if (leftEquals == null || rightEquals == null) {
			return null;
		}

		SmtExpr eqExpr = SmtExprBuilder.mkEq(leftEquals, rightEquals);
		if (cmp == Comparator.EQ) {
			return eqExpr;
		} else {
			return SmtExprBuilder.mkNot(eqExpr);
		}
	}

	private static SmtExpr mkComparison(SmtExpr left, Comparator cmp, SmtExpr right) {
		switch (cmp) {
		case LT: {
			SmtExpr lt = SmtExprBuilder.mkLt(left, right);
			return lt;
		}
		case LE: {
			SmtExpr le = SmtExprBuilder.mkLe(left, right);
			return le;
		}
		case GT: {
			SmtExpr gt = SmtExprBuilder.mkGt(left, right);
			return gt;
		}
		case GE: {
			SmtExpr ge = SmtExprBuilder.mkGe(left, right);
			return ge;
		}
		case EQ: {
			SmtExpr ge = SmtExprBuilder.mkEq(left, right);
			return ge;
		}
		case NE: {
			SmtExpr ge = SmtExprBuilder.mkEq(left, right);
			SmtExpr ne = SmtExprBuilder.mkNot(ge);
			return ne;
		}
		default: {
			throw new RuntimeException("Unknown comparator for constraint " + cmp.toString());
		}
		}
	}

	@Override
	public SmtExpr visit(RealConstraint c, Void arg) {
		ExprToSmtVisitor v = new ExprToSmtVisitor();

		SmtExpr left = c.getLeftOperand().accept(v, null);
		SmtExpr right = c.getRightOperand().accept(v, null);

		if (left == null || right == null) {
			return null;
		}

		Comparator cmp = c.getComparator();
		SmtExpr boolExpr = mkComparison(left, cmp, right);
		return boolExpr;
	}

	@Override
	public SmtExpr visit(StringConstraint c, Void arg) {
		ExprToSmtVisitor v = new ExprToSmtVisitor();

		StringComparison stringComparison = (StringComparison) c.getLeftOperand();
		Comparator cmp = c.getComparator();
		IntegerConstant integerConstant = (IntegerConstant) c.getRightOperand();

		SmtExpr left = stringComparison.accept(v, null);
		SmtExpr right = integerConstant.accept(v, null);

		if (left == null || right == null) {
			return null;
		}

		return mkComparison(left, cmp, right);
	}
}