/**
 * 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.hadoop.metadata.discovery.graph;

import com.thinkaurelius.titan.core.TitanVertex;
import org.apache.hadoop.metadata.MetadataException;
import org.apache.hadoop.metadata.query.Expressions;
import org.apache.hadoop.metadata.query.GraphPersistenceStrategies;
import org.apache.hadoop.metadata.query.TypeUtils;
import org.apache.hadoop.metadata.repository.MetadataRepository;
import org.apache.hadoop.metadata.repository.graph.Constants;
import org.apache.hadoop.metadata.repository.graph.GraphBackedMetadataRepository;
import org.apache.hadoop.metadata.typesystem.ITypedReferenceableInstance;
import org.apache.hadoop.metadata.typesystem.ITypedStruct;
import org.apache.hadoop.metadata.typesystem.persistence.Id;
import org.apache.hadoop.metadata.typesystem.types.AttributeInfo;
import org.apache.hadoop.metadata.typesystem.types.IDataType;
import org.apache.hadoop.metadata.typesystem.types.Multiplicity;
import org.apache.hadoop.metadata.typesystem.types.StructType;
import org.apache.hadoop.metadata.typesystem.types.TraitType;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.util.List;

/**
 * Default implementation of GraphPersistenceStrategy.
 */
public class DefaultGraphPersistenceStrategy implements GraphPersistenceStrategies {

    private static final Logger LOG = LoggerFactory
            .getLogger(DefaultGraphPersistenceStrategy.class);

    private final GraphBackedMetadataRepository metadataRepository;

    public DefaultGraphPersistenceStrategy(MetadataRepository metadataRepository) {
        this.metadataRepository = (GraphBackedMetadataRepository) metadataRepository;
    }

    @Override
    public String typeAttributeName() {
        return metadataRepository.getTypeAttributeName();
    }

    @Override
    public String edgeLabel(IDataType<?> dataType, AttributeInfo aInfo) {
        return metadataRepository.getEdgeLabel(dataType, aInfo);
    }

    @Override
    public String traitLabel(IDataType<?> dataType, String traitName) {
        return metadataRepository.getTraitLabel(dataType, traitName);
    }

    @Override
    public String fieldNameInVertex(IDataType<?> dataType, AttributeInfo aInfo) {
        return metadataRepository.getFieldNameInVertex(dataType, aInfo);
    }

    @Override
    public List<String> traitNames(TitanVertex vertex) {
        return metadataRepository.getTraitNames(vertex);
    }

    @Override
    public String fieldPrefixInSelect() {
        return "it";
    }

    @Override
    public Id getIdFromVertex(String dataTypeName, TitanVertex vertex) {
        return metadataRepository.getIdFromVertex(dataTypeName, vertex);
    }

    @Override
    public <U> U constructInstance(IDataType<U> dataType, Object value) {
        try {
            switch (dataType.getTypeCategory()) {
                case PRIMITIVE:
                case ENUM:
                    return dataType.convert(value, Multiplicity.OPTIONAL);

                case ARRAY:
                    // todo
                    break;

                case MAP:
                    // todo
                    break;

                case STRUCT:
                    TitanVertex structVertex = (TitanVertex) value;
                    StructType structType = (StructType) dataType;
                    ITypedStruct structInstance = structType.createInstance();
                    metadataRepository.getGraphToInstanceMapper().mapVertexToInstance(
                            structVertex, structInstance, structType.fieldMapping().fields);
                    return dataType.convert(structInstance, Multiplicity.OPTIONAL);

                case TRAIT:
                    TitanVertex traitVertex = (TitanVertex) value;
                    TraitType traitType = (TraitType) dataType;
                    ITypedStruct traitInstance = traitType.createInstance();
                    // todo - this is not right, we should load the Instance associated with this
                    // trait. for now just loading the trait struct.
                    // metadataRepository.getGraphToInstanceMapper().mapVertexToTraitInstance(
                    //        traitVertex, dataType.getName(), , traitType, traitInstance);
                    metadataRepository.getGraphToInstanceMapper().mapVertexToInstance(
                            traitVertex, traitInstance, traitType.fieldMapping().fields);
                    break;

                case CLASS:
                    TitanVertex classVertex = (TitanVertex) value;
                    ITypedReferenceableInstance classInstance =
                            metadataRepository.getGraphToInstanceMapper().mapGraphToTypedInstance(
                                    classVertex.<String>getProperty(Constants.GUID_PROPERTY_KEY),
                                    classVertex);
                    return dataType.convert(classInstance, Multiplicity.OPTIONAL);

                default:
                    throw new UnsupportedOperationException(
                            "Load for type " + dataType + "is not supported");
            }
        } catch (MetadataException e) {
            LOG.error("error while constructing an instance", e);
        }

        return null;
    }

    @Override
    public String edgeLabel(TypeUtils.FieldInfo fInfo) {
        return fInfo.reverseDataType() == null
                ? edgeLabel(fInfo.dataType(), fInfo.attrInfo())
                : edgeLabel(fInfo.reverseDataType(), fInfo.attrInfo());
    }

    @Override
    public String gremlinCompOp(Expressions.ComparisonExpression op) {
        switch (op.symbol()) {
            case "=":
                return "T.eq";

            case "!=":
                return "T.neq";

            case ">":
                return "T.gt";

            case ">=":
                return "T.gte";

            case "<":
                return "T.lt";

            case "<=":
                return "T.lte";

            default:
                throw new RuntimeException(("Comparison operator not supported in Gremlin: " + op));
        }
    }

    @Override
    public String loopObjectExpression(IDataType<?> dataType) {
        return "{it.object." + typeAttributeName() + " == '" + dataType.getName() + "'}";
    }
}
