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Fili web service library provides core capabilities for RESTful aggregation navigation, query planning and metadata
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// Copyright 2020 Oath Inc.
// Licensed under the terms of the Apache license. Please see LICENSE.md file distributed with this work for terms.

package com.yahoo.bard.webservice.web;

import com.yahoo.bard.webservice.data.Result;
import com.yahoo.bard.webservice.data.ResultSet;
import com.yahoo.bard.webservice.data.ResultSetSchema;

import com.yahoo.bard.webservice.data.metric.LogicalMetricInfo;
import com.yahoo.bard.webservice.data.metric.mappers.NoOpResultSetMapper;
import com.yahoo.bard.webservice.data.metric.mappers.RenamableResultSetMapper;
import com.yahoo.bard.webservice.data.metric.mappers.ResultSetMapper;

import java.util.ArrayList;
import java.util.List;
import java.util.Objects;
import java.util.stream.Collectors;

/**
 * This Mapper provides ability to chain additional ResultSetMappers along with the mappers from dependent metric.
 *
 */
public class ChainingResultSetMapper  extends ResultSetMapper implements RenamableResultSetMapper {

    private final List chainedResultSetMappers;

    /**
     * Constructor that accepts list of chained ResultSetMappers and filter out any NoOp Mappers.
     *
     * @param chainedResultSetMappers  The Combined list of ResultSetMappers from dependent metric and
     *                                 additional Mappers to be chained.
     */
    public ChainingResultSetMapper(List chainedResultSetMappers) {
        this.chainedResultSetMappers = chainedResultSetMappers.stream()
                                        .filter(m -> !(m instanceof NoOpResultSetMapper))
                                        .collect(Collectors.toCollection(ArrayList::new));
    }

    /**
     * Utility method to Create and Rename the ResultSetMappers in the chained List.
     *
     * @param info  LogicalMetricInfo used to rename the mapper with final metric name.
     * @param mappers  The List of mappers from dependent metrics and additional mappers to be chained in list.
     *
     * @return  The The Chained ResultSetMapper
     */
    public static ResultSetMapper createAndRenameResultSetMapperChain(LogicalMetricInfo info,
                                                                      ResultSetMapper... mappers) {
        List chainedResultSetMappers = new ArrayList<>();

        for (ResultSetMapper mapper : mappers) {
            if (mapper instanceof ChainingResultSetMapper) {
                chainedResultSetMappers.addAll(((ChainingResultSetMapper) mapper).getMappersList());
            }
            else {
                chainedResultSetMappers.add(mapper);
            }
        }

        return getRenamedMappers(chainedResultSetMappers, info.getName());
    }

    @Override
    public ResultSetMapper withColumnName(String newColumnName) {
        return getRenamedMappers(chainedResultSetMappers, newColumnName);
    }

    /**
     * This method loop through all ResultSetMappers and Rename them if necessary.
     *
     * @param chainedResultSetMappers  The List of ResultSetMappers in Chain.
     * @param newColumnName  The new name of the mapper
     *
     * @return  The  Chained Renamed List of mappers.
     */
    public static ResultSetMapper getRenamedMappers(List chainedResultSetMappers,
                                                    String newColumnName) {
        ResultSetMapper renamedMapper;
        List renamedMapperList = new ArrayList<>();

        for (ResultSetMapper m : chainedResultSetMappers) {
            if (m instanceof RenamableResultSetMapper) {
                renamedMapper = ((RenamableResultSetMapper) m).withColumnName(newColumnName);
                renamedMapperList.add(renamedMapper);
            } else {
                renamedMapperList.add(m);
            }
        }

        return new ChainingResultSetMapper(renamedMapperList);
    }

    /**
     * Getter to return list of chained mappers.
     *
     * @return  The List of ResultSetMappers in chain.
     */
    public List getMappersList() {
        return new ArrayList<>(chainedResultSetMappers);
    }

    @Override
    protected Result map(Result result, ResultSetSchema schema) {
        //NOOP
        return null;
    }

    @Override
    protected ResultSetSchema map(ResultSetSchema schema) {
        //NOOP
        return null;
    }

    /**
     * Take a complete result set and replace it with one altered according to the rules of the concrete
     *  mappers in the Chain. It delegates to the map method of corresponding mapper.
     *
     * @param resultSet  The unmapped result set
     *
     * @return The mapped result set.
     */
    @Override
    public ResultSet map(ResultSet resultSet) {
        ResultSet finalResultSet = resultSet ;

        for (ResultSetMapper m : chainedResultSetMappers) {
            finalResultSet = m.map(finalResultSet);
        }

        return finalResultSet;
    }

    @Override
    public boolean equals(Object o) {
        if (this == o) { return true; }
        if (o == null || getClass() != o.getClass()) { return false; }
        ChainingResultSetMapper that = (ChainingResultSetMapper) o;
        return super.equals(o) &&
                Objects.equals(chainedResultSetMappers, that.chainedResultSetMappers);
    }

    @Override
    public int hashCode() {
        return Objects.hash(super.hashCode(), chainedResultSetMappers);
    }
}