asterix-om/src/main/java/edu/uci/ics/asterix/om/typecomputer/impl/FieldAccessByIndexResultType.java

package edu.uci.ics.asterix.om.typecomputer.impl;

import edu.uci.ics.asterix.om.base.AInt32;
import edu.uci.ics.asterix.om.base.IAObject;
import edu.uci.ics.asterix.om.constants.AsterixConstantValue;
import edu.uci.ics.asterix.om.typecomputer.base.IResultTypeComputer;
import edu.uci.ics.asterix.om.types.ARecordType;
import edu.uci.ics.asterix.om.types.ATypeTag;
import edu.uci.ics.asterix.om.types.BuiltinType;
import edu.uci.ics.asterix.om.types.IAType;
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.expressions.AbstractFunctionCallExpression;
import edu.uci.ics.hyracks.algebricks.core.algebra.expressions.ConstantExpression;
import edu.uci.ics.hyracks.algebricks.core.algebra.expressions.IVariableTypeEnvironment;
import edu.uci.ics.hyracks.algebricks.core.algebra.metadata.IMetadataProvider;

public class FieldAccessByIndexResultType implements IResultTypeComputer {

    public static final FieldAccessByIndexResultType INSTANCE = new FieldAccessByIndexResultType();

    private FieldAccessByIndexResultType() {
    }

    @Override
    public IAType computeType(ILogicalExpression expression, IVariableTypeEnvironment env,
            IMetadataProvider<?, ?> metadataProvider) throws AlgebricksException {
        AbstractFunctionCallExpression f = (AbstractFunctionCallExpression) expression;
        Object obj;
        try {
            obj = env.getType(f.getArguments().get(0).getValue());
        } catch (AlgebricksException e) {
            throw new AlgebricksException(e);
        }
        if (obj == null) {
            return null;
        }
        IAType type0 = (IAType) obj;
        ARecordType t0 = NonTaggedFieldAccessByNameResultType.getRecordTypeFromType(type0, expression);
        ILogicalExpression arg1 = f.getArguments().get(1).getValue();
        if (arg1.getExpressionTag() != LogicalExpressionTag.CONSTANT) {
            return BuiltinType.ANY;
        }
        ConstantExpression ce = (ConstantExpression) arg1;
        if (!(ce.getValue() instanceof AsterixConstantValue)) {
            throw new AlgebricksException("Typing error: expecting an integer, found " + ce + " instead.");
        }
        IAObject v = ((AsterixConstantValue) ce.getValue()).getObject();
        if (v.getType().getTypeTag() != ATypeTag.INT32) {
            throw new AlgebricksException("Typing error: expecting an INT32, found " + ce + " instead.");
        }
        int pos = ((AInt32) v).getIntegerValue();
        return t0.getFieldTypes()[pos];
    }

}