/*
 * Copyright DataStax, Inc.
 *
 * Licensed 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.
 */
package com.datastax.oss.driver.internal.core.metadata;

import com.datastax.oss.driver.api.core.session.Session;
import com.datastax.oss.driver.internal.core.context.InternalDriverContext;
import java.util.Collections;
import java.util.List;

Any update to the driver's metadata. It produces a new metadata instance, and may also trigger
events.
This is modelled as a separate type for modularity, and because we can't send the events while
we are doing the refresh (by contract, the new copy of the metadata needs to be visible before
the events are sent). This also makes unit testing very easy.
This is only instantiated and called from MetadataManager's admin thread, therefore implementations don't need to be thread-safe. 
See Also:
Session.getMetadata()/**
 * Any update to the driver's metadata. It produces a new metadata instance, and may also trigger
 * events.
 *
 * <p>This is modelled as a separate type for modularity, and because we can't send the events while
 * we are doing the refresh (by contract, the new copy of the metadata needs to be visible before
 * the events are sent). This also makes unit testing very easy.
 *
 * <p>This is only instantiated and called from {@link MetadataManager}'s admin thread, therefore
 * implementations don't need to be thread-safe.
 *
 * @see Session#getMetadata()
 */
public interface MetadataRefresh {

  Result compute(
      DefaultMetadata oldMetadata, boolean tokenMapEnabled, InternalDriverContext context);

  class Result {
    public final DefaultMetadata newMetadata;
    public final List<Object> events;

    public Result(DefaultMetadata newMetadata, List<Object> events) {
      this.newMetadata = newMetadata;
      this.events = events;
    }

    public Result(DefaultMetadata newMetadata) {
      this(newMetadata, Collections.emptyList());
    }
  }
}