/*
 * SPDX-License-Identifier: Apache-2.0
 *
 * The OpenSearch Contributors require contributions made to
 * this file be licensed under the Apache-2.0 license or a
 * compatible open source license.
 */

/*
 * 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.
 */

/*
 * Modifications Copyright OpenSearch Contributors. See
 * GitHub history for details.
 */

package org.opensearch.rest.action.document;

import org.opensearch.action.get.MultiGetRequest;
import org.opensearch.client.node.NodeClient;
import org.opensearch.common.settings.Settings;
import org.opensearch.core.common.Strings;
import org.opensearch.core.xcontent.XContentParser;
import org.opensearch.rest.BaseRestHandler;
import org.opensearch.rest.RestRequest;
import org.opensearch.rest.action.RestToXContentListener;
import org.opensearch.search.fetch.subphase.FetchSourceContext;

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

import static java.util.Arrays.asList;
import static java.util.Collections.unmodifiableList;
import static org.opensearch.rest.RestRequest.Method.GET;
import static org.opensearch.rest.RestRequest.Method.POST;

/**
 * Transport action to perform a multi get
 *
 * @opensearch.api
 */
public class RestMultiGetAction extends BaseRestHandler {
    private final boolean allowExplicitIndex;

    public RestMultiGetAction(Settings settings) {
        this.allowExplicitIndex = MULTI_ALLOW_EXPLICIT_INDEX.get(settings);
    }

    @Override
    public List<Route> routes() {
        return unmodifiableList(
            asList(new Route(GET, "/_mget"), new Route(POST, "/_mget"), new Route(GET, "/{index}/_mget"), new Route(POST, "/{index}/_mget"))
        );
    }

    @Override
    public String getName() {
        return "document_mget_action";
    }

    @Override
    public RestChannelConsumer prepareRequest(final RestRequest request, final NodeClient client) throws IOException {
        MultiGetRequest multiGetRequest = new MultiGetRequest();
        multiGetRequest.refresh(request.paramAsBoolean("refresh", multiGetRequest.refresh()));
        multiGetRequest.preference(request.param("preference"));
        multiGetRequest.realtime(request.paramAsBoolean("realtime", multiGetRequest.realtime()));
        if (request.param("fields") != null) {
            throw new IllegalArgumentException(
                "The parameter [fields] is no longer supported, "
                    + "please use [stored_fields] to retrieve stored fields or _source filtering if the field is not stored"
            );
        }
        String[] sFields = null;
        String sField = request.param("stored_fields");
        if (sField != null) {
            sFields = Strings.splitStringByCommaToArray(sField);
        }

        FetchSourceContext defaultFetchSource = FetchSourceContext.parseFromRestRequest(request);
        try (XContentParser parser = request.contentOrSourceParamParser()) {
            multiGetRequest.add(request.param("index"), sFields, defaultFetchSource, request.param("routing"), parser, allowExplicitIndex);
        }

        return channel -> client.multiGet(multiGetRequest, new RestToXContentListener<>(channel));
    }
}