algebricks/algebricks-core/src/main/java/edu/uci/ics/hyracks/algebricks/core/algebra/expressions/ConstantExpression.java

/*
 * Copyright 2009-2013 by The Regents of the University of California
 * 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 from
 * 
 *     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 edu.uci.ics.hyracks.algebricks.core.algebra.expressions;

import java.util.Collection;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

import org.apache.commons.lang3.mutable.Mutable;

import edu.uci.ics.hyracks.algebricks.common.exceptions.AlgebricksException;
import edu.uci.ics.hyracks.algebricks.core.algebra.base.ILogicalExpression;
import edu.uci.ics.hyracks.algebricks.core.algebra.base.LogicalExpressionTag;
import edu.uci.ics.hyracks.algebricks.core.algebra.base.LogicalVariable;
import edu.uci.ics.hyracks.algebricks.core.algebra.visitors.ILogicalExpressionVisitor;

public final class ConstantExpression extends AbstractLogicalExpression {
    private IAlgebricksConstantValue value;

    public final static ConstantExpression TRUE = new ConstantExpression(new IAlgebricksConstantValue() {

        @Override
        public boolean isTrue() {
            return true;
        }

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

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

        @Override
        public String toString() {
            return "TRUE";
        }
    });
    public final static ConstantExpression FALSE = new ConstantExpression(new IAlgebricksConstantValue() {

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

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

        @Override
        public boolean isFalse() {
            return true;
        }

        @Override
        public String toString() {
            return "FALSE";
        }
    });
    public final static ConstantExpression NULL = new ConstantExpression(new IAlgebricksConstantValue() {

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

        @Override
        public boolean isNull() {
            return true;
        }

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

        @Override
        public String toString() {
            return "NULL";
        }
    });

    private Map<Object, IExpressionAnnotation> annotationMap = new HashMap<Object, IExpressionAnnotation>();

    public ConstantExpression(IAlgebricksConstantValue value) {
        this.value = value;
    }

    public IAlgebricksConstantValue getValue() {
        return value;
    }

    public void setValue(IAlgebricksConstantValue value) {
        this.value = value;
    }

    @Override
    public LogicalExpressionTag getExpressionTag() {
        return LogicalExpressionTag.CONSTANT;
    }

    @Override
    public String toString() {
        return value.toString();
    }

    @Override
    public void getUsedVariables(Collection<LogicalVariable> vars) {
        // do nothing
    }

    @Override
    public void substituteVar(LogicalVariable v1, LogicalVariable v2) {
        // do nothing
    }

    @Override
    public boolean equals(Object obj) {
        if (!(obj instanceof ConstantExpression)) {
            return false;
        } else {
            return value.equals(((ConstantExpression) obj).getValue());
        }
    }

    @Override
    public int hashCode() {
        return value.hashCode();
    }

    @Override
    public <R, T> R accept(ILogicalExpressionVisitor<R, T> visitor, T arg) throws AlgebricksException {
        return visitor.visitConstantExpression(this, arg);
    }

    @Override
    public AbstractLogicalExpression cloneExpression() {
        Map<Object, IExpressionAnnotation> m = new HashMap<Object, IExpressionAnnotation>();
        for (Object k : annotationMap.keySet()) {
            IExpressionAnnotation annot2 = annotationMap.get(k).copy();
            m.put(k, annot2);
        }
        ConstantExpression c = new ConstantExpression(value);
        c.annotationMap = m;
        return c;
    }

    public Map<Object, IExpressionAnnotation> getAnnotations() {
        return annotationMap;
    }

    @Override
    public boolean splitIntoConjuncts(List<Mutable<ILogicalExpression>> conjs) {
        return false;
    }
}