package edu.uci.ics.asterix.runtime.aggregates.std;

import java.io.DataOutput;
import java.io.DataOutputStream;
import java.io.IOException;
import java.util.ArrayList;
import java.util.List;

import edu.uci.ics.asterix.common.config.GlobalConfig;
import edu.uci.ics.asterix.dataflow.data.nontagged.serde.ADoubleSerializerDeserializer;
import edu.uci.ics.asterix.dataflow.data.nontagged.serde.AFloatSerializerDeserializer;
import edu.uci.ics.asterix.dataflow.data.nontagged.serde.AInt16SerializerDeserializer;
import edu.uci.ics.asterix.dataflow.data.nontagged.serde.AInt32SerializerDeserializer;
import edu.uci.ics.asterix.dataflow.data.nontagged.serde.AInt64SerializerDeserializer;
import edu.uci.ics.asterix.dataflow.data.nontagged.serde.AInt8SerializerDeserializer;
import edu.uci.ics.asterix.formats.nontagged.AqlSerializerDeserializerProvider;
import edu.uci.ics.asterix.om.base.ADouble;
import edu.uci.ics.asterix.om.base.AInt32;
import edu.uci.ics.asterix.om.base.AMutableDouble;
import edu.uci.ics.asterix.om.base.AMutableInt32;
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.ARecordType;
import edu.uci.ics.asterix.om.types.ATypeTag;
import edu.uci.ics.asterix.om.types.AUnionType;
import edu.uci.ics.asterix.om.types.BuiltinType;
import edu.uci.ics.asterix.om.types.EnumDeserializer;
import edu.uci.ics.asterix.om.types.IAType;
import edu.uci.ics.asterix.runtime.aggregates.base.AbstractAggregateFunctionDynamicDescriptor;
import edu.uci.ics.asterix.runtime.evaluators.common.AccessibleByteArrayEval;
import edu.uci.ics.asterix.runtime.evaluators.common.ClosedRecordConstructorEvalFactory.ClosedRecordConstructorEval;
import edu.uci.ics.hyracks.algebricks.common.exceptions.AlgebricksException;
import edu.uci.ics.hyracks.algebricks.common.exceptions.NotImplementedException;
import edu.uci.ics.hyracks.algebricks.core.algebra.functions.FunctionIdentifier;
import edu.uci.ics.hyracks.algebricks.runtime.base.ICopyAggregateFunction;
import edu.uci.ics.hyracks.algebricks.runtime.base.ICopyAggregateFunctionFactory;
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.util.ArrayBackedValueStorage;
import edu.uci.ics.hyracks.data.std.util.ByteArrayAccessibleOutputStream;
import edu.uci.ics.hyracks.dataflow.common.data.accessors.IFrameTupleReference;

public class AvgAggregateDescriptor extends AbstractAggregateFunctionDynamicDescriptor {

    private static final long serialVersionUID = 1L;
    public static final IFunctionDescriptorFactory FACTORY = new IFunctionDescriptorFactory() {
        public IFunctionDescriptor createFunctionDescriptor() {
            return new AvgAggregateDescriptor();
        }
    };

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

    @Override
    public ICopyAggregateFunctionFactory createAggregateFunctionFactory(final ICopyEvaluatorFactory[] args)
            throws AlgebricksException {
        List<IAType> unionList = new ArrayList<IAType>();
        unionList.add(BuiltinType.ANULL);
        unionList.add(BuiltinType.ADOUBLE);
        final ARecordType recType = new ARecordType(null, new String[] { "sum", "count" }, new IAType[] {
                new AUnionType(unionList, "OptionalDouble"), BuiltinType.AINT32 }, true);

        return new ICopyAggregateFunctionFactory() {
            private static final long serialVersionUID = 1L;

            @Override
            public ICopyAggregateFunction createAggregateFunction(final IDataOutputProvider provider)
                    throws AlgebricksException {

                return new ICopyAggregateFunction() {

                    private DataOutput out = provider.getDataOutput();
                    private ArrayBackedValueStorage inputVal = new ArrayBackedValueStorage();
                    private ICopyEvaluator eval = args[0].createEvaluator(inputVal);                    
                    private double sum;
                    private int count;
                    private ATypeTag aggType;
                    private AMutableDouble aDouble = new AMutableDouble(0);
                    private AMutableInt32 aInt32 = new AMutableInt32(0);

                    private ArrayBackedValueStorage avgBytes = new ArrayBackedValueStorage();
                    private ByteArrayAccessibleOutputStream sumBytes = new ByteArrayAccessibleOutputStream();
                    private DataOutput sumBytesOutput = new DataOutputStream(sumBytes);
                    private ByteArrayAccessibleOutputStream countBytes = new ByteArrayAccessibleOutputStream();
                    private DataOutput countBytesOutput = new DataOutputStream(countBytes);
                    private ICopyEvaluator evalSum = new AccessibleByteArrayEval(avgBytes.getDataOutput(), sumBytes);
                    private ICopyEvaluator evalCount = new AccessibleByteArrayEval(avgBytes.getDataOutput(), countBytes);
                    private ClosedRecordConstructorEval recordEval = new ClosedRecordConstructorEval(recType,
                            new ICopyEvaluator[] { evalSum, evalCount }, avgBytes, out);

                    @SuppressWarnings("unchecked")
                    private ISerializerDeserializer<ADouble> doubleSerde = AqlSerializerDeserializerProvider.INSTANCE
                            .getSerializerDeserializer(BuiltinType.ADOUBLE);
                    @SuppressWarnings("unchecked")
                    private ISerializerDeserializer<AInt32> intSerde = AqlSerializerDeserializerProvider.INSTANCE
                            .getSerializerDeserializer(BuiltinType.AINT32);
                    @SuppressWarnings("unchecked")
                    private ISerializerDeserializer<ANull> nullSerde = AqlSerializerDeserializerProvider.INSTANCE
                            .getSerializerDeserializer(BuiltinType.ANULL);

                    @Override
                    public void init() throws AlgebricksException {
                        aggType = ATypeTag.SYSTEM_NULL;
                        sum = 0.0;
                        count = 0;
                    }

                    @Override
                    public void step(IFrameTupleReference tuple) throws AlgebricksException {
                        inputVal.reset();
                        eval.evaluate(tuple);                        
                        ATypeTag typeTag = EnumDeserializer.ATYPETAGDESERIALIZER
                                .deserialize(inputVal.getByteArray()[0]);
                        if (typeTag == ATypeTag.NULL || aggType == ATypeTag.NULL) {
                            aggType = ATypeTag.NULL;
                            return;
                        } else if (aggType == ATypeTag.SYSTEM_NULL) {                           
                            aggType = typeTag;
                        } else if (typeTag != ATypeTag.SYSTEM_NULL && typeTag != aggType) {
                            throw new AlgebricksException("Unexpected type " + typeTag
                                    + " in aggregation input stream. Expected type " + aggType + ".");
                        }
                        if (typeTag != ATypeTag.SYSTEM_NULL) {
                            ++count;
                        }                        
                        switch (typeTag) {
                            case INT8: {
                                byte val = AInt8SerializerDeserializer.getByte(inputVal.getByteArray(), 1);
                                sum += val;
                                break;
                            }
                            case INT16: {
                                short val = AInt16SerializerDeserializer.getShort(inputVal.getByteArray(), 1);
                                sum += val;
                                break;
                            }
                            case INT32: {
                                int val = AInt32SerializerDeserializer.getInt(inputVal.getByteArray(), 1);
                                sum += val;
                                break;
                            }
                            case INT64: {
                                long val = AInt64SerializerDeserializer.getLong(inputVal.getByteArray(), 1);
                                sum += val;
                                break;
                            }
                            case FLOAT: {
                                float val = AFloatSerializerDeserializer.getFloat(inputVal.getByteArray(), 1);
                                sum += val;
                                break;
                            }
                            case DOUBLE: {
                                double val = ADoubleSerializerDeserializer.getDouble(inputVal.getByteArray(), 1);
                                sum += val;
                                break;
                            }
                            case NULL: {
                                break;
                            }
                            default: {
                                throw new NotImplementedException("Cannot compute AVG for values of type " + typeTag);
                            }
                        }
                    }

                    @Override
                    public void finish() throws AlgebricksException {
                        try {
                            if (count == 0 || aggType == ATypeTag.NULL) {
                                nullSerde.serialize(ANull.NULL, out);
                            } else {
                                aDouble.setValue(sum / count);
                                doubleSerde.serialize(aDouble, out);
                            }
                        } catch (IOException e) {
                            throw new AlgebricksException(e);
                        }
                    }

                    @Override
                    public void finishPartial() throws AlgebricksException {
                        if (count == 0) {
                            if (GlobalConfig.DEBUG) {
                                GlobalConfig.ASTERIX_LOGGER.finest("AVG aggregate ran over empty input.");
                            }
                        } else {
                            try {
                                if (aggType == ATypeTag.NULL) {
                                    sumBytes.reset();
                                    nullSerde.serialize(ANull.NULL, sumBytesOutput);
                                } else {
                                    sumBytes.reset();
                                    aDouble.setValue(sum);
                                    doubleSerde.serialize(aDouble, sumBytesOutput);
                                }
                                countBytes.reset();
                                aInt32.setValue(count);
                                intSerde.serialize(aInt32, countBytesOutput);
                                recordEval.evaluate(null);
                            } catch (IOException e) {
                                throw new AlgebricksException(e);
                            }
                        }
                    }
                };
            }
        };
    }

}