/*
 * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
 * or more contributor license agreements. Licensed under the "Elastic License
 * 2.0", the "GNU Affero General Public License v3.0 only", and the "Server Side
 * Public License v 1"; you may not use this file except in compliance with, at
 * your election, the "Elastic License 2.0", the "GNU Affero General Public
 * License v3.0 only", or the "Server Side Public License, v 1".
 */
package org.elasticsearch.search.fetch.subphase.highlight;

import org.apache.lucene.document.Field;
import org.apache.lucene.document.TextField;
import org.apache.lucene.index.IndexReader;
import org.apache.lucene.search.vectorhighlight.BoundaryScanner;
import org.elasticsearch.index.mapper.MappedFieldType;
import org.elasticsearch.index.mapper.ValueFetcher;
import org.elasticsearch.search.fetch.FetchContext;
import org.elasticsearch.search.lookup.Source;

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

public class SourceSimpleFragmentsBuilder extends SimpleFragmentsBuilder {

    private final FetchContext fetchContext;
    private final Source source;
    private final ValueFetcher valueFetcher;

    public SourceSimpleFragmentsBuilder(
        MappedFieldType fieldType,
        FetchContext fetchContext,
        boolean fixBrokenAnalysis,
        Source source,
        String[] preTags,
        String[] postTags,
        BoundaryScanner boundaryScanner
    ) {
        super(fieldType, fixBrokenAnalysis, preTags, postTags, boundaryScanner);
        this.fetchContext = fetchContext;
        this.source = source;
        this.valueFetcher = fieldType.valueFetcher(fetchContext.getSearchExecutionContext(), null);
    }

    public static final Field[] EMPTY_FIELDS = new Field[0];

    @Override
    protected Field[] getFields(IndexReader reader, int docId, String fieldName) throws IOException {
        // we know its low level reader, and matching docId, since that's how we call the highlighter with
        return doGetFields(docId, valueFetcher, source, fetchContext, fieldType);
    }

    static Field[] doGetFields(int docId, ValueFetcher valueFetcher, Source source, FetchContext fetchContext, MappedFieldType fieldType)
        throws IOException {
        List<Object> values = valueFetcher.fetchValues(source, docId, new ArrayList<>());
        if (values.isEmpty()) {
            return EMPTY_FIELDS;
        }
        if (values.size() > 1 && fetchContext.sourceLoader().reordersFieldValues()) {
            throw new IllegalArgumentException(
                "The fast vector highlighter doesn't support loading multi-valued fields from _source in index ["
                    + fetchContext.getIndexName()
                    + "] because _source can reorder field values"
            );
        }
        Field[] fields = new Field[values.size()];
        for (int i = 0; i < values.size(); i++) {
            fields[i] = new Field(fieldType.name(), values.get(i).toString(), TextField.TYPE_NOT_STORED);
        }
        return fields;
    }
}