/*
 * 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 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 or the Server
 * Side Public License, v 1.
 */

package org.elasticsearch.rest.action.admin.indices;

import org.apache.logging.log4j.LogManager;
import org.apache.logging.log4j.Logger;
import org.elasticsearch.action.admin.indices.mapping.get.GetFieldMappingsRequest;
import org.elasticsearch.action.admin.indices.mapping.get.GetFieldMappingsResponse;
import org.elasticsearch.action.admin.indices.mapping.get.GetFieldMappingsResponse.FieldMappingMetadata;
import org.elasticsearch.action.support.IndicesOptions;
import org.elasticsearch.client.node.NodeClient;
import org.elasticsearch.common.Strings;
import org.elasticsearch.common.logging.DeprecationCategory;
import org.elasticsearch.common.logging.DeprecationLogger;
import org.elasticsearch.common.xcontent.XContentBuilder;
import org.elasticsearch.rest.BaseRestHandler;
import org.elasticsearch.rest.BytesRestResponse;
import org.elasticsearch.rest.RestRequest;
import org.elasticsearch.rest.RestResponse;
import org.elasticsearch.rest.RestStatus;
import org.elasticsearch.rest.action.RestBuilderListener;

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

import static java.util.Arrays.asList;
import static java.util.Collections.unmodifiableList;
import static org.elasticsearch.rest.RestRequest.Method.GET;
import static org.elasticsearch.rest.RestStatus.NOT_FOUND;
import static org.elasticsearch.rest.RestStatus.OK;

public class RestGetFieldMappingAction extends BaseRestHandler {

    private static final Logger logger = LogManager.getLogger(RestGetFieldMappingAction.class);
    private static final DeprecationLogger deprecationLogger = DeprecationLogger.getLogger(logger.getName());
    public static final String TYPES_DEPRECATION_MESSAGE = "[types removal] Using include_type_name in get " +
        "field mapping requests is deprecated. The parameter will be removed in the next major version.";

    @Override
    public List<Route> routes() {
        return unmodifiableList(asList(
            new Route(GET, "/_mapping/field/{fields}"),
            new Route(GET, "/_mapping/{type}/field/{fields}"),
            new Route(GET, "/{index}/_mapping/field/{fields}"),
            new Route(GET, "/{index}/{type}/_mapping/field/{fields}"),
            new Route(GET, "/{index}/_mapping/{type}/field/{fields}")));
    }

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

    @Override
    public RestChannelConsumer prepareRequest(final RestRequest request, final NodeClient client) throws IOException {
        final String[] indices = Strings.splitStringByCommaToArray(request.param("index"));
        final String[] types = request.paramAsStringArrayOrEmptyIfAll("type");
        final String[] fields = Strings.splitStringByCommaToArray(request.param("fields"));

        boolean includeTypeName = request.paramAsBoolean(INCLUDE_TYPE_NAME_PARAMETER, DEFAULT_INCLUDE_TYPE_NAME_POLICY);
        if (includeTypeName == false && types.length > 0) {
            throw new IllegalArgumentException("Types cannot be specified unless include_type_name" +
                " is set to true.");
        }
        if (request.hasParam(INCLUDE_TYPE_NAME_PARAMETER)) {
            deprecationLogger.deprecate(DeprecationCategory.TYPES, "get_field_mapping_with_types", TYPES_DEPRECATION_MESSAGE);
        }

        GetFieldMappingsRequest getMappingsRequest = new GetFieldMappingsRequest();
        getMappingsRequest.indices(indices).types(types).fields(fields).includeDefaults(request.paramAsBoolean("include_defaults", false));
        getMappingsRequest.indicesOptions(IndicesOptions.fromRequest(request, getMappingsRequest.indicesOptions()));

        if (request.hasParam("local")) {
            deprecationLogger.deprecate(DeprecationCategory.API, "get_field_mapping_local",
                "Use [local] in get field mapping requests is deprecated. "
                    + "The parameter will be removed in the next major version");
        }
        getMappingsRequest.local(request.paramAsBoolean("local", getMappingsRequest.local()));
        return channel ->
                client.admin().indices().getFieldMappings(getMappingsRequest, new RestBuilderListener<GetFieldMappingsResponse>(channel) {
                    @Override
                    public RestResponse buildResponse(GetFieldMappingsResponse response, XContentBuilder builder) throws Exception {
                        Map<String, Map<String, Map<String, FieldMappingMetadata>>> mappingsByIndex = response.mappings();

                        boolean isPossibleSingleFieldRequest = indices.length == 1 && types.length == 1 && fields.length == 1;
                        if (isPossibleSingleFieldRequest && isFieldMappingMissingField(mappingsByIndex)) {
                            return new BytesRestResponse(OK, builder.startObject().endObject());
                        }

                        RestStatus status = OK;
                        if (mappingsByIndex.isEmpty() && fields.length > 0) {
                            status = NOT_FOUND;
                        }
                        response.toXContent(builder, request);
                        return new BytesRestResponse(status, builder);
                    }
                });
    }

    /**
     * Helper method to find out if the only included fieldmapping metadata is typed NULL, which means
     * that type and index exist, but the field did not
     */
    private boolean isFieldMappingMissingField(Map<String, Map<String, Map<String, FieldMappingMetadata>>> mappingsByIndex) {
        if (mappingsByIndex.size() != 1) {
            return false;
        }

        for (Map<String, Map<String, FieldMappingMetadata>> value : mappingsByIndex.values()) {
            for (Map<String, FieldMappingMetadata> fieldValue : value.values()) {
                for (Map.Entry<String, FieldMappingMetadata> fieldMappingMetadataEntry : fieldValue.entrySet()) {
                    if (fieldMappingMetadataEntry.getValue().isNull()) {
                        return true;
                    }
                }
            }
        }
        return false;
    }
}
