package com.atlassian.activeobjects.internal;
   
   import com.atlassian.activeobjects.external.ModelVersion;
   import com.atlassian.sal.api.pluginsettings.PluginSettings;
   import com.atlassian.sal.api.pluginsettings.PluginSettingsFactory;
   
   import java.util.concurrent.locks.Lock;
   import java.util.concurrent.locks.ReadWriteLock;
   import java.util.concurrent.locks.ReentrantReadWriteLock;
  
  import static com.google.common.base.Preconditions.checkNotNull;
  
  /**
   * A model version manager that uses SAL's {@link PluginSettings} to store the actual current version.
   *
   * @see PluginSettingsFactory
   * @see PluginSettings
   */
  public final class SalModelVersionManager implements ModelVersionManager {
      private final ReadWriteLock lock = new ReentrantReadWriteLock();
  
      private final PluginSettingsFactory pluginSettingsFactory;
      private final ActiveObjectsSettingKeys settingKeys;
  
      public SalModelVersionManager(PluginSettingsFactory pluginSettingsFactory, ActiveObjectsSettingKeys settingKeys) {
          this.pluginSettingsFactory = checkNotNull(pluginSettingsFactory);
          this.settingKeys = checkNotNull(settingKeys);
      }
  
      @Override
      public ModelVersion getCurrent(Prefix tableNamePrefix) {
          final Lock read = lock.readLock();
          read.lock();
          try {
              return ModelVersion.valueOf((String) getPluginSettings().get(settingKeys.getModelVersionKey(tableNamePrefix)));
          } finally {
              read.unlock();
          }
      }
  
      @Override
      public void update(Prefix tableNamePrefix, ModelVersion version) {
          final Lock write = lock.writeLock();
          write.lock();
          try {
              getPluginSettings().put(settingKeys.getModelVersionKey(tableNamePrefix), version.toString());
          } finally {
              write.unlock();
          }
      }
  
      private PluginSettings getPluginSettings() {
          return pluginSettingsFactory.createGlobalSettings();
      }
  }