/*
 * 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.rest.action.admin.indices;

import org.elasticsearch.action.ActionRequestValidationException;
import org.elasticsearch.action.admin.indices.forcemerge.ForceMergeAction;
import org.elasticsearch.action.admin.indices.forcemerge.ForceMergeRequest;
import org.elasticsearch.action.support.IndicesOptions;
import org.elasticsearch.action.support.SubscribableListener;
import org.elasticsearch.action.support.broadcast.BroadcastResponse;
import org.elasticsearch.client.internal.node.NodeClient;
import org.elasticsearch.common.Strings;
import org.elasticsearch.rest.BaseRestHandler;
import org.elasticsearch.rest.RestRequest;
import org.elasticsearch.rest.RestResponse;
import org.elasticsearch.rest.RestStatus;
import org.elasticsearch.rest.Scope;
import org.elasticsearch.rest.ServerlessScope;
import org.elasticsearch.rest.action.RestToXContentListener;
import org.elasticsearch.tasks.LoggingTaskListener;
import org.elasticsearch.tasks.Task;
import org.elasticsearch.xcontent.XContentBuilder;

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

import static org.elasticsearch.rest.RestRequest.Method.POST;

@ServerlessScope(Scope.INTERNAL) // we might block this completely.
public class RestForceMergeAction extends BaseRestHandler {

    @Override
    public List<Route> routes() {
        return List.of(new Route(POST, "/_forcemerge"), new Route(POST, "/{index}/_forcemerge"));
    }

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

    @Override
    public RestChannelConsumer prepareRequest(final RestRequest request, final NodeClient client) throws IOException {
        final ForceMergeRequest mergeRequest = new ForceMergeRequest(Strings.splitStringByCommaToArray(request.param("index")));
        mergeRequest.indicesOptions(IndicesOptions.fromRequest(request, mergeRequest.indicesOptions()));
        mergeRequest.maxNumSegments(request.paramAsInt("max_num_segments", mergeRequest.maxNumSegments()));
        mergeRequest.onlyExpungeDeletes(request.paramAsBoolean("only_expunge_deletes", mergeRequest.onlyExpungeDeletes()));
        mergeRequest.flush(request.paramAsBoolean("flush", mergeRequest.flush()));
        if (request.paramAsBoolean("wait_for_completion", true)) {
            return channel -> client.admin().indices().forceMerge(mergeRequest, new RestToXContentListener<>(channel));
        } else {
            mergeRequest.setShouldStoreResult(true);
            /*
             * Let's try and validate before forking so the user gets some error. The
             * task can't totally validate until it starts but this is better than
             * nothing.
             */
            ActionRequestValidationException validationException = mergeRequest.validate();
            if (validationException != null) {
                throw validationException;
            }
            final var responseListener = new SubscribableListener<BroadcastResponse>();
            final var task = client.executeLocally(ForceMergeAction.INSTANCE, mergeRequest, responseListener);
            responseListener.addListener(new LoggingTaskListener<>(task));
            return sendTask(client.getLocalNodeId(), task);
        }
    }

    private static RestChannelConsumer sendTask(String localNodeId, Task task) {
        return channel -> {
            try (XContentBuilder builder = channel.newBuilder()) {
                builder.startObject();
                builder.field("task", localNodeId + ":" + task.getId());
                builder.endObject();
                channel.sendResponse(new RestResponse(RestStatus.OK, builder));
            }
        };
    }
}