/*
 * 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.ResourceNotFoundException;
import org.opensearch.action.ActionRequestValidationException;
import org.opensearch.action.get.GetRequest;
import org.opensearch.action.get.GetResponse;
import org.opensearch.client.node.NodeClient;
import org.opensearch.core.common.bytes.BytesReference;
import org.opensearch.core.xcontent.MediaTypeRegistry;
import org.opensearch.core.xcontent.XContentBuilder;
import org.opensearch.rest.BaseRestHandler;
import org.opensearch.rest.BytesRestResponse;
import org.opensearch.rest.RestChannel;
import org.opensearch.rest.RestRequest;
import org.opensearch.rest.RestResponse;
import org.opensearch.rest.action.RestResponseListener;
import org.opensearch.search.fetch.subphase.FetchSourceContext;

import java.io.IOException;
import java.io.InputStream;
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.HEAD;
import static org.opensearch.core.rest.RestStatus.OK;

/**
 * The REST handler for get source and head source APIs.
 *
 * @opensearch.api
 */
public class RestGetSourceAction extends BaseRestHandler {

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

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

    @Override
    public RestChannelConsumer prepareRequest(final RestRequest request, final NodeClient client) throws IOException {
        final GetRequest getRequest = new GetRequest(request.param("index"), request.param("id"));
        getRequest.refresh(request.paramAsBoolean("refresh", getRequest.refresh()));
        getRequest.routing(request.param("routing"));
        getRequest.preference(request.param("preference"));
        getRequest.realtime(request.paramAsBoolean("realtime", getRequest.realtime()));

        getRequest.fetchSourceContext(FetchSourceContext.parseFromRestRequest(request));

        return channel -> {
            if (getRequest.fetchSourceContext() != null && !getRequest.fetchSourceContext().fetchSource()) {
                final ActionRequestValidationException validationError = new ActionRequestValidationException();
                validationError.addValidationError("fetching source can not be disabled");
                channel.sendResponse(new BytesRestResponse(channel, validationError));
            } else {
                client.get(getRequest, new RestGetSourceResponseListener(channel, request));
            }
        };
    }

    static class RestGetSourceResponseListener extends RestResponseListener<GetResponse> {
        private final RestRequest request;

        RestGetSourceResponseListener(RestChannel channel, RestRequest request) {
            super(channel);
            this.request = request;
        }

        @Override
        public RestResponse buildResponse(final GetResponse response) throws Exception {
            checkResource(response);

            final XContentBuilder builder = channel.newBuilder(request.getMediaType(), false);
            final BytesReference source = response.getSourceInternal();
            try (InputStream stream = source.streamInput()) {
                builder.rawValue(stream, MediaTypeRegistry.xContentType(source));
            }
            return new BytesRestResponse(OK, builder);
        }

        /**
         * Checks if the requested document or source is missing.
         *
         * @param response a response
         * @throws ResourceNotFoundException if the document or source is missing
         */
        private void checkResource(final GetResponse response) {
            final String index = response.getIndex();
            final String id = response.getId();

            if (response.isExists() == false) {
                throw new ResourceNotFoundException("Document not found [" + index + "]/[" + id + "]");
            } else if (response.isSourceEmpty()) {
                throw new ResourceNotFoundException("Source not found [" + index + "]/[" + id + "]");
            }
        }
    }
}