/*
 * Licensed to Elasticsearch under one or more contributor
 * license agreements. See the NOTICE file distributed with
 * this work for additional information regarding copyright
 * ownership. Elasticsearch 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.elasticsearch.search;

import org.elasticsearch.common.io.stream.StreamInput;
import org.elasticsearch.common.io.stream.StreamOutput;
import org.elasticsearch.common.io.stream.Streamable;
import org.elasticsearch.index.mapper.MapperService;

import java.io.IOException;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;
import java.util.Objects;

/**
 * A single field name and values part of a {@link SearchHit}.
 *
 * @see SearchHit
 */
public final class SearchHitField implements Streamable, Iterable<Object> {

    private String name;
    private List<Object> values;

    private SearchHitField() {
    }

    public SearchHitField(String name, List<Object> values) {
        this.name = name;
        this.values = values;
    }

    /**
     * The name of the field.
     */
    public String getName() {
        return name;
    }

    /**
     * The first value of the hit.
     */
    public <V> V getValue() {
        if (values == null || values.isEmpty()) {
            return null;
        }
        return (V)values.get(0);
    }

    /**
     * The field values.
     */
    public List<Object> getValues() {
        return values;
    }

    /**
     * @return The field is a metadata field
     */
    public boolean isMetadataField() {
        return MapperService.isMetadataField(name);
    }

    @Override
    public Iterator<Object> iterator() {
        return values.iterator();
    }

    public static SearchHitField readSearchHitField(StreamInput in) throws IOException {
        SearchHitField result = new SearchHitField();
        result.readFrom(in);
        return result;
    }

    @Override
    public void readFrom(StreamInput in) throws IOException {
        name = in.readString();
        int size = in.readVInt();
        values = new ArrayList<>(size);
        for (int i = 0; i < size; i++) {
            values.add(in.readGenericValue());
        }
    }

    @Override
    public void writeTo(StreamOutput out) throws IOException {
        out.writeString(name);
        out.writeVInt(values.size());
        for (Object value : values) {
            out.writeGenericValue(value);
        }
    }

    @Override
    public boolean equals(Object obj) {
        if (obj == null || getClass() != obj.getClass()) {
            return false;
        }
        SearchHitField other = (SearchHitField) obj;
        return Objects.equals(name, other.name)
                && Objects.equals(values, other.values);
    }

    @Override
    public int hashCode() {
        return Objects.hash(name, values);
    }
}
