/**
 * 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 org.apache.aurora.scheduler;

import java.util.Map;

import javax.inject.Inject;

import com.google.common.annotations.VisibleForTesting;
import com.google.common.base.Strings;
import com.google.common.collect.ImmutableMap;

import org.apache.aurora.scheduler.storage.entities.ITaskConfig;
import org.codehaus.jackson.annotate.JsonCreator;
import org.codehaus.jackson.annotate.JsonProperty;

import static java.util.Objects.requireNonNull;

import static com.google.common.base.Preconditions.checkArgument;

/**
 * Translates job tier configuration into a set of task traits/attributes.
 */
public interface TierManager {

  /**
   * Gets {@link TierInfo} instance representing task's tier details.
   *
   * @param taskConfig Task configuration to get tier for.
   * @return {@link TierInfo} for the given {@code taskConfig}.
   */
  TierInfo getTier(ITaskConfig taskConfig);

  /**
   * Gets name of the default tier.
   *
   * @return Name for the default tier.
   */
  String getDefaultTierName();

  /**
   * Gets the map of tier name to {@link TierInfo} instance.
   *
   * @return A readonly view of all tiers.
   */
  Map<String, TierInfo> getTiers();

  class TierManagerImpl implements TierManager {
    private final TierConfig tierConfig;

    @VisibleForTesting
    public static class TierConfig {
      private final String defaultTier;
      private final Map<String, TierInfo> tiers;

      @VisibleForTesting
      @JsonCreator
      public TierConfig(
          @JsonProperty("default") String defaultTier,
          @JsonProperty("tiers") Map<String, TierInfo> tiers) {

        checkArgument(!Strings.isNullOrEmpty(defaultTier), "Default tier name cannot be empty.");
        checkArgument(!tiers.isEmpty(), "Tiers cannot be empty.");
        checkArgument(
            tiers.containsKey(defaultTier),
            "Default tier name should match supplied tiers.");
        this.defaultTier = defaultTier;
        this.tiers = ImmutableMap.copyOf(tiers);
      }

      @VisibleForTesting
      public String getDefault() {
        return defaultTier;
      }

      @VisibleForTesting
      public Map<String, TierInfo> getTiers() {
        return tiers;
      }
    }

    @VisibleForTesting
    @Inject
    public TierManagerImpl(TierConfig tierConfig) {
      this.tierConfig = requireNonNull(tierConfig);
    }

    @Override
    public TierInfo getTier(ITaskConfig taskConfig) {
      checkArgument(
          !taskConfig.isSetTier() || tierConfig.tiers.containsKey(taskConfig.getTier()),
          "Invalid tier '%s' in TaskConfig.", taskConfig.getTier());

      return tierConfig.tiers.get(taskConfig.getTier());
    }

    @Override
    public String getDefaultTierName() {
      return tierConfig.defaultTier;
    }

    @Override
    public Map<String, TierInfo> getTiers() {
      return tierConfig.tiers;
    }
  }
}