package edu.uci.ics.asterix.runtime.evaluators.functions;

import java.io.DataOutput;
import java.io.IOException;

import edu.uci.ics.asterix.common.functions.FunctionConstants;
import edu.uci.ics.asterix.formats.nontagged.AqlSerializerDeserializerProvider;
import edu.uci.ics.asterix.om.base.ANull;
import edu.uci.ics.asterix.om.functions.AsterixBuiltinFunctions;
import edu.uci.ics.asterix.om.functions.IFunctionDescriptor;
import edu.uci.ics.asterix.om.functions.IFunctionDescriptorFactory;
import edu.uci.ics.asterix.om.types.ATypeTag;
import edu.uci.ics.asterix.om.types.BuiltinType;
import edu.uci.ics.asterix.runtime.evaluators.base.AbstractScalarFunctionDynamicDescriptor;
import edu.uci.ics.hyracks.algebricks.common.exceptions.AlgebricksException;
import edu.uci.ics.hyracks.algebricks.core.algebra.functions.FunctionIdentifier;
import edu.uci.ics.hyracks.algebricks.runtime.base.ICopyEvaluator;
import edu.uci.ics.hyracks.algebricks.runtime.base.ICopyEvaluatorFactory;
import edu.uci.ics.hyracks.api.dataflow.value.ISerializerDeserializer;
import edu.uci.ics.hyracks.data.std.api.IDataOutputProvider;
import edu.uci.ics.hyracks.data.std.primitive.UTF8StringPointable;
import edu.uci.ics.hyracks.data.std.util.ArrayBackedValueStorage;
import edu.uci.ics.hyracks.dataflow.common.data.accessors.IFrameTupleReference;
import edu.uci.ics.hyracks.dataflow.common.data.util.StringUtils;

/**
 * @author Xiaoyu Ma
 */
public class StringLowerCaseDescriptor extends AbstractScalarFunctionDynamicDescriptor {
    private static final long serialVersionUID = 1L;

    public static final IFunctionDescriptorFactory FACTORY = new IFunctionDescriptorFactory() {
        public IFunctionDescriptor createFunctionDescriptor() {
            return new StringLowerCaseDescriptor();
        }
    };
    private final static byte SER_STRING_TYPE_TAG = ATypeTag.STRING.serialize();
    private final static byte SER_NULL_TYPE_TAG = ATypeTag.NULL.serialize();

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

            @Override
            public ICopyEvaluator createEvaluator(final IDataOutputProvider output) throws AlgebricksException {
                return new ICopyEvaluator() {

                    private DataOutput out = output.getDataOutput();
                    private ArrayBackedValueStorage outInput = new ArrayBackedValueStorage();
                    private ICopyEvaluator eval = args[0].createEvaluator(outInput);
                    private String errorMessage = "This is not an instance of string";
                    private final byte stt = ATypeTag.STRING.serialize();

                    @SuppressWarnings("unchecked")
                    private ISerializerDeserializer<ANull> nullSerde = AqlSerializerDeserializerProvider.INSTANCE
                            .getSerializerDeserializer(BuiltinType.ANULL);

                    @Override
                    public void evaluate(IFrameTupleReference tuple) throws AlgebricksException {

                        try {
                            outInput.reset();
                            eval.evaluate(tuple);
                            byte[] serString = outInput.getByteArray();

                            if (serString[0] == SER_STRING_TYPE_TAG) {
                                byte[] bytes = outInput.getByteArray();
                                int len = UTF8StringPointable.getUTFLength(bytes, 1);

                                out.writeByte(stt);
                                StringUtils.writeUTF8Len(len, out);

                                int pos = 3;
                                while (pos < len + 3) {
                                    char c1 = UTF8StringPointable.charAt(bytes, pos);
                                    c1 = Character.toLowerCase(c1);
                                    pos += UTF8StringPointable.charSize(bytes, pos);
                                    StringUtils.writeCharAsModifiedUTF8(c1, out);
                                }
                            } else if (serString[0] == SER_NULL_TYPE_TAG)
                                nullSerde.serialize(ANull.NULL, out);
                            else
                                throw new AlgebricksException(errorMessage);
                        } catch (IOException e1) {
                            throw new AlgebricksException(errorMessage);
                        }
                    }
                };
            }
        };
    }

    @Override
    public FunctionIdentifier getIdentifier() {
        return AsterixBuiltinFunctions.STRING_LOWERCASE;
    }

}