/**
 * This file is part of Graylog.
 *
 * Graylog is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * Graylog is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with Graylog.  If not, see <http://www.gnu.org/licenses/>.
 */
package org.graylog2.rest.resources.system;

import com.codahale.metrics.annotation.Timed;
import com.google.common.collect.ImmutableMap;
import com.google.common.collect.Sets;
import io.swagger.annotations.Api;
import io.swagger.annotations.ApiOperation;
import io.swagger.annotations.ApiParam;
import org.apache.shiro.authz.annotation.RequiresAuthentication;
import org.apache.shiro.authz.annotation.RequiresPermissions;
import org.graylog2.indexer.IndexSetRegistry;
import org.graylog2.indexer.indices.Indices;
import org.graylog2.plugin.Message;
import org.graylog2.shared.rest.resources.RestResource;
import org.graylog2.shared.security.RestPermissions;

import javax.inject.Inject;
import javax.ws.rs.GET;
import javax.ws.rs.Path;
import javax.ws.rs.Produces;
import javax.ws.rs.QueryParam;
import java.util.Map;
import java.util.Set;

import static javax.ws.rs.core.MediaType.APPLICATION_JSON;

@RequiresAuthentication
@Api(value = "System/Fields", description = "Get list of message fields that exist.")
@Path("/system/fields")
public class SystemFieldsResource extends RestResource {
    private final Indices indices;
    private final IndexSetRegistry indexSetRegistry;

    @Inject
    public SystemFieldsResource(Indices indices, IndexSetRegistry indexSetRegistry) {
        this.indices = indices;
        this.indexSetRegistry = indexSetRegistry;
    }

    @GET
    @Timed
    @ApiOperation(value = "Get list of message fields that exist",
            notes = "This operation is comparably fast because it reads directly from the indexer mapping.")
    @RequiresPermissions(RestPermissions.FIELDNAMES_READ)
    @Produces(APPLICATION_JSON)
    public Map<String, Set<String>> fields(@ApiParam(name = "limit", value = "Maximum number of fields to return. Set to 0 for all fields.", required = false)
                                           @QueryParam("limit") int limit) {
        boolean unlimited = limit <= 0;

        final String[] writeIndexWildcards = indexSetRegistry.getIndexWildcards();

        final Set<String> fields;
        if (unlimited) {
            fields = indices.getAllMessageFields(writeIndexWildcards);
        } else {
            fields = Sets.newHashSetWithExpectedSize(limit);
            addStandardFields(fields);
            int i = 0;
            for (String field : indices.getAllMessageFields(writeIndexWildcards)) {
                if (i == limit) {
                    break;
                }

                fields.add(field);
                i++;
            }
        }
        return ImmutableMap.of("fields", fields);
    }

    private void addStandardFields(Set<String> fields) {
        fields.add(Message.FIELD_SOURCE);
        fields.add(Message.FIELD_MESSAGE);
        fields.add(Message.FIELD_TIMESTAMP);
    }
}