/*
 * 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.asterix.runtime.evaluators.functions;

import java.io.DataOutput;

import org.apache.asterix.builders.RecordBuilder;
import org.apache.asterix.om.functions.BuiltinFunctions;
import org.apache.asterix.om.functions.IFunctionDescriptor;
import org.apache.asterix.om.functions.IFunctionDescriptorFactory;
import org.apache.asterix.om.types.ATypeTag;
import org.apache.asterix.runtime.evaluators.base.AbstractScalarFunctionDynamicDescriptor;
import org.apache.hyracks.algebricks.core.algebra.functions.FunctionIdentifier;
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.VoidPointable;
import org.apache.hyracks.data.std.util.ArrayBackedValueStorage;
import org.apache.hyracks.dataflow.common.data.accessors.IFrameTupleReference;

public class ToObjectDescriptor extends AbstractScalarFunctionDynamicDescriptor {
    private static final long serialVersionUID = -4146417699529927812L;

    public static final IFunctionDescriptorFactory FACTORY = new IFunctionDescriptorFactory() {
        @Override
        public IFunctionDescriptor createFunctionDescriptor() {
            return new ToObjectDescriptor();
        }
    };

    @Override
    public IScalarEvaluatorFactory createEvaluatorFactory(final IScalarEvaluatorFactory[] args) {
        return new IScalarEvaluatorFactory() {
            private static final long serialVersionUID = 1L;

            @Override
            public IScalarEvaluator createScalarEvaluator(final IHyracksTaskContext ctx) throws HyracksDataException {

                return new IScalarEvaluator() {

                    private final IScalarEvaluator eval0 = args[0].createScalarEvaluator(ctx);
                    private final IPointable arg0 = new VoidPointable();
                    private final RecordBuilder recordBuilder = new RecordBuilder();
                    private final ArrayBackedValueStorage resultStorage = new ArrayBackedValueStorage();
                    private final DataOutput out = resultStorage.getDataOutput();
                    private boolean wroteEmpty;

                    @Override
                    public void evaluate(IFrameTupleReference tuple, IPointable resultPointable)
                            throws HyracksDataException {
                        eval0.evaluate(tuple, arg0);
                        byte[] data = arg0.getByteArray();
                        int offset = arg0.getStartOffset();
                        if (data[offset] == ATypeTag.SERIALIZED_RECORD_TYPE_TAG) {
                            resultPointable.set(arg0);
                        } else {
                            writeEmpty();
                            resultPointable.set(resultStorage);
                        }
                    }

                    private void writeEmpty() throws HyracksDataException {
                        if (!wroteEmpty) {
                            resultStorage.reset();
                            recordBuilder.reset(null);
                            recordBuilder.init();
                            recordBuilder.write(out, true);
                            wroteEmpty = true;
                        }
                    }
                };
            }
        };
    }

    @Override
    public FunctionIdentifier getIdentifier() {
        return BuiltinFunctions.TO_OBJECT;
    }
}
