/*
 * 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.index.fieldvisitor;

import org.apache.lucene.index.FieldInfo;
import org.elasticsearch.common.regex.Regex;

import java.io.IOException;
import java.util.Collections;
import java.util.List;
import java.util.Set;

/**
 * A field visitor that allows to load a selection of the stored fields by exact name or by pattern.
 * Supported pattern styles: "xxx*", "*xxx", "*xxx*" and "xxx*yyy".
 * The Uid field is always loaded.
 * The class is optimized for source loading as it is a common use case.
 */
public class CustomFieldsVisitor extends FieldsVisitor {
    private final Set<String> fields;
    private final List<String> patterns;

    public CustomFieldsVisitor(Set<String> fields, List<String> patterns, boolean loadSource) {
        super(loadSource);
        this.fields = fields;
        this.patterns = patterns;
    }

    public CustomFieldsVisitor(Set<String> fields, boolean loadSource) {
        this(fields, Collections.<String>emptyList(), loadSource);
    }

    @Override
    public Status needsField(FieldInfo fieldInfo) throws IOException {
        if (super.needsField(fieldInfo) == Status.YES) {
            return Status.YES;
        }
        if (fields.contains(fieldInfo.name)) {
            return Status.YES;
        }
        for (String pattern : patterns) {
            if (Regex.simpleMatch(pattern, fieldInfo.name)) {
                return Status.YES;
            }
        }
        return Status.NO;
    }
}
