/*
    * Copyright (c) 2023. Roland T. Lichti, Kaiserpfalz EDV-Service.
    *
    * This program 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.
    *
    * This program 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 this program.  If not, see <https://www.gnu.org/licenses/>.
   */
  
  package de.kaiserpfalzedv.commons.core.store;
  
  import java.util.HashMap;
  import java.util.Optional;
  import java.util.UUID;
  
  import de.kaiserpfalzedv.commons.api.resources.Resource;
  import de.kaiserpfalzedv.commons.api.store.OptimisticLockStoreException;
  import de.kaiserpfalzedv.commons.api.store.StoreService;
  import lombok.EqualsAndHashCode;
  import lombok.ToString;
  import lombok.extern.slf4j.Slf4j;
  
  /**
   * GenericStoreService -- an ephemeral store for Resources.
   * <p>
   * This is a memory alternative for a persistent data store.
   *
   * @param <T> The resource to be stored inside the data store.
   * @author klenkes74 {@literal <rlichti@kaiserpfalz-edv.de>}
   * @since 2.0.0  2021-05-24
   */
  @ToString
  @EqualsAndHashCode
  @Slf4j
  public abstract class GenericStoreService<T extends Resource<?>> implements StoreService<T> {
      /**
       * The name based memory store for guilds.
       */
      private final HashMap<String, T> namedStore = new HashMap<>(10);
  
      /**
       * The uid based memory store for guilds.
       */
      private final HashMap<UUID, T> uidStore = new HashMap<>(10);
  
  
      @Override
      public Optional<T> findByNameSpaceAndName(final String nameSpace, final String name) {
          final String key = this.generateStoreKey(nameSpace, name);
  
          return Optional.ofNullable(this.namedStore.get(key));
      }
  
      @Override
      public Optional<T> findByUid(final UUID uid) {
          return Optional.ofNullable(this.uidStore.get(uid));
      }
  
      private String generateStoreKey(final String nameSpace, final String name) {
          return nameSpace + "-" + name;
      }
  
      @Override
      public T save(final T object) throws OptimisticLockStoreException {
          log.trace("Saving: {}", object);
  
          final String key = this.generateStoreKey(object.getNameSpace(), object.getName());
  
          @SuppressWarnings("unchecked")
          final
          T data = (!this.namedStore.containsKey(key))
                  ? object
                  : (T) object.increaseGeneration();
  
  
          this.checkOptimisticLocking(key, data);
  
          this.namedStore.put(key, data);
          this.uidStore.put(object.getUid(), data);
          return data;
      }
  
      private void checkOptimisticLocking(final String key, final T object) {
          if (
                  this.namedStore.containsKey(key)
                          && (this.namedStore.get(key).getGeneration() >= object.getGeneration())
          ) {
              throw new OptimisticLockStoreException(this.namedStore.get(key).getGeneration(), object.getGeneration());
          }
      }
  
     @Override
     public void remove(final T object) {
         final String key = this.generateStoreKey(object.getNameSpace(), object.getName());
 
         this.namedStore.remove(key);
         this.uidStore.remove(object.getUid());
     }
 
     @Override
     public void remove(final String nameSpace, final String name) {
         final String key = this.generateStoreKey(nameSpace, name);
 
         if (this.namedStore.containsKey(key)) {
             this.uidStore.remove(this.namedStore.get(key).getUid());
             this.namedStore.remove(key);
         }
     }
 
     @Override
     public void remove(final UUID uid) {
         if (this.uidStore.containsKey(uid)) {
             final T data = this.uidStore.get(uid);
             final String key = this.generateStoreKey(data.getNameSpace(), data.getName());
 
             this.namedStore.remove(key);
             this.uidStore.remove(uid);
         }
     }
 }