/*
 * 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.script.mustache;

import org.elasticsearch.action.support.IndicesOptions;
import org.elasticsearch.client.internal.node.NodeClient;
import org.elasticsearch.common.settings.Settings;
import org.elasticsearch.rest.BaseRestHandler;
import org.elasticsearch.rest.RestRequest;
import org.elasticsearch.rest.Scope;
import org.elasticsearch.rest.ServerlessScope;
import org.elasticsearch.rest.action.RestToXContentListener;
import org.elasticsearch.rest.action.search.RestMultiSearchAction;
import org.elasticsearch.rest.action.search.RestSearchAction;
import org.elasticsearch.search.crossproject.CrossProjectModeDecider;
import org.elasticsearch.xcontent.XContentType;

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

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

@ServerlessScope(Scope.PUBLIC)
public class RestMultiSearchTemplateAction extends BaseRestHandler {
    static final String TYPES_DEPRECATION_MESSAGE = "[types removal]"
        + " Specifying types in multi search template requests is deprecated.";

    private static final Set<String> RESPONSE_PARAMS = Set.of(RestSearchAction.TYPED_KEYS_PARAM, RestSearchAction.TOTAL_HITS_AS_INT_PARAM);

    private final boolean allowExplicitIndex;
    private final CrossProjectModeDecider crossProjectModeDecider;

    public RestMultiSearchTemplateAction(Settings settings) {
        this.allowExplicitIndex = MULTI_ALLOW_EXPLICIT_INDEX.get(settings);
        this.crossProjectModeDecider = new CrossProjectModeDecider(settings);
    }

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

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

    @Override
    public RestChannelConsumer prepareRequest(RestRequest request, NodeClient client) throws IOException {
        MultiSearchTemplateRequest multiRequest = parseRequest(request, allowExplicitIndex);
        return channel -> client.execute(MustachePlugin.MULTI_SEARCH_TEMPLATE_ACTION, multiRequest, new RestToXContentListener<>(channel));
    }

    /**
     * Parses a {@link RestRequest} body and returns a {@link MultiSearchTemplateRequest}
     */
    public MultiSearchTemplateRequest parseRequest(RestRequest restRequest, boolean allowExplicitIndex) throws IOException {
        boolean crossProjectEnabled = crossProjectModeDecider.crossProjectEnabled();
        MultiSearchTemplateRequest multiRequest = new MultiSearchTemplateRequest();

        if (crossProjectEnabled && multiRequest.allowsCrossProject()) {
            multiRequest.setProjectRouting(restRequest.param("project_routing"));
            multiRequest.indicesOptions(
                IndicesOptions.builder(multiRequest.indicesOptions())
                    .crossProjectModeOptions(new IndicesOptions.CrossProjectModeOptions(true))
                    .build()
            );
        }

        if (restRequest.hasParam("max_concurrent_searches")) {
            multiRequest.maxConcurrentSearchRequests(restRequest.paramAsInt("max_concurrent_searches", 0));
        }

        RestMultiSearchAction.parseMultiLineRequest(
            restRequest,
            multiRequest.indicesOptions(),
            allowExplicitIndex,
            (searchRequest, bytes) -> {
                SearchTemplateRequest searchTemplateRequest = SearchTemplateRequest.fromXContent(bytes);
                /*
                 * For multisearch requests, project_routing could appear within the request body as:
                 * {"project_routing": ...}
                 * {"id": ...}
                 *
                 * In such cases, it is picked up by MultiSearchRequest#readMultiLineFormat() and is associated with the
                 * SearchRequest object that represents the corresponding msearch request. However, it could also erroneously
                 * appear as:
                 * {...}
                 * {"project_routing": ..., "id": ...}
                 *
                 * This is because, the same parser is shared between _msearch/template and _search/template and the above
                 * format is valid only for the latter. For this reason, we need to explicitly check if project_routing got
                 * associated with the SearchTemplateRequest instead of SearchRequest and error out if needed.
                 */
                if (searchTemplateRequest.getProjectRouting() != null) {
                    throw new IllegalArgumentException("Unknown key for a VALUE_STRING in [project_routing]");
                }
                if (searchTemplateRequest.getScript() != null) {
                    searchTemplateRequest.setRequest(searchRequest);
                    multiRequest.add(searchTemplateRequest);
                } else {
                    throw new IllegalArgumentException("Malformed search template");
                }
                RestSearchAction.validateSearchRequest(restRequest, searchRequest);
            },
            (k, v, r) -> false,
            Optional.of(crossProjectEnabled),
            multiRequest.getProjectRouting()
        );
        return multiRequest;
    }

    @Override
    public boolean mediaTypesValid(RestRequest request) {
        return super.mediaTypesValid(request) && XContentType.supportsDelimitedBulkRequests(request.getXContentType());
    }

    @Override
    protected Set<String> responseParams() {
        return RESPONSE_PARAMS;
    }
}