/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You 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 at
 *
 *     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 org.apache.vxquery.runtime.functions.qname;

import java.io.DataOutput;

import org.apache.hyracks.algebricks.runtime.base.IScalarEvaluator;
import org.apache.hyracks.algebricks.runtime.base.IScalarEvaluatorFactory;
import org.apache.hyracks.api.context.IHyracksTaskContext;
import org.apache.hyracks.api.exceptions.HyracksDataException;
import org.apache.hyracks.data.std.api.IPointable;
import org.apache.hyracks.data.std.primitive.UTF8StringPointable;
import org.apache.hyracks.data.std.util.ArrayBackedValueStorage;
import org.apache.vxquery.datamodel.accessors.SequencePointable;
import org.apache.vxquery.datamodel.accessors.TaggedValuePointable;
import org.apache.vxquery.datamodel.accessors.atomic.XSQNamePointable;
import org.apache.vxquery.datamodel.values.ValueTag;
import org.apache.vxquery.datamodel.values.XDMConstants;
import org.apache.vxquery.exceptions.ErrorCode;
import org.apache.vxquery.exceptions.SystemException;
import org.apache.vxquery.runtime.functions.base.AbstractTaggedValueArgumentScalarEvaluator;
import org.apache.vxquery.runtime.functions.base.AbstractTaggedValueArgumentScalarEvaluatorFactory;

public class FnPrefixFromQNameScalarEvaluatorFactory extends AbstractTaggedValueArgumentScalarEvaluatorFactory {
    private static final long serialVersionUID = 1L;

    public FnPrefixFromQNameScalarEvaluatorFactory(IScalarEvaluatorFactory[] args) {
        super(args);
    }

    @Override
    protected IScalarEvaluator createEvaluator(IHyracksTaskContext ctx, IScalarEvaluator[] args)
            throws HyracksDataException {
        final XSQNamePointable qnamep = (XSQNamePointable) XSQNamePointable.FACTORY.createPointable();
        final SequencePointable seqp = (SequencePointable) SequencePointable.FACTORY.createPointable();
        final UTF8StringPointable stringp = (UTF8StringPointable) UTF8StringPointable.FACTORY.createPointable();
        final ArrayBackedValueStorage abvs = new ArrayBackedValueStorage();
        final DataOutput dOut = abvs.getDataOutput();

        return new AbstractTaggedValueArgumentScalarEvaluator(args) {
            @Override
            protected void evaluate(TaggedValuePointable[] args, IPointable result) throws SystemException {
                TaggedValuePointable tvp1 = args[0];

                // Only accept a QNames or empty sequence.
                if (tvp1.getTag() == ValueTag.SEQUENCE_TAG) {
                    tvp1.getValue(seqp);
                    if (seqp.getEntryCount() == 0) {
                        XDMConstants.setEmptySequence(result);
                        return;
                    }
                    // Pass through.
                }
                if (tvp1.getTag() != ValueTag.XS_QNAME_TAG) {
                    throw new SystemException(ErrorCode.FORG0006);
                }
                tvp1.getValue(qnamep);
                qnamep.getPrefix(stringp);

                try {
                    // Return empty sequence if no prefix.
                    if (qnamep.getPrefixLength() == 0) {
                        XDMConstants.setEmptySequence(result);
                    } else {
                        abvs.reset();
                        dOut.write(ValueTag.XS_NCNAME_TAG);
                        dOut.write(stringp.getByteArray(), stringp.getStartOffset(), stringp.getLength());
                        result.set(abvs);
                    }
                } catch (Exception e) {
                    throw new SystemException(ErrorCode.SYSE0001, e);
                }
            }
        };
    }
}