package com.atlassian.vcache.internal.core;
   
   import org.slf4j.Logger;
   import org.slf4j.LoggerFactory;
   
   import static com.atlassian.vcache.internal.NameValidator.requireValidProductIdentifier;
   
   /**
    * Represents the ability to generate the keys used with an external cache.
   *
   * @since 1.0.0
   */
  public abstract class ExternalCacheKeyGenerator {
      private static final Logger log = LoggerFactory.getLogger(ExternalCacheKeyGenerator.class);
  
      private static final String SEPARATOR = "::";
      private static final String CACHE_VERSION_KEY = "cache-version";
  
      private final String productIdentifier;
  
      public ExternalCacheKeyGenerator(String productIdentifier) {
          this.productIdentifier = requireValidProductIdentifier(productIdentifier);
      }
  
      /**
       * Generates the key for an individual entry.
       */
      public String entryKey(String partition, String cacheName, long cacheVersion, String entryKey) {
          final String plain = productIdentifier + SEPARATOR + partition + SEPARATOR + cacheName
                  + SEPARATOR + cacheVersion + SEPARATOR + entryKey;
          final String encoded = encode(plain);
          log.trace("Encoded cacheKey {} to {}", plain, encoded);
          return encoded;
      }
  
      /**
       * Generates the key used to hold the cache version number.
       */
      public String cacheVersionKey(String partition, String cacheName) {
          final String plain = productIdentifier + SEPARATOR + partition + SEPARATOR + cacheName
                  + SEPARATOR + CACHE_VERSION_KEY;
          final String encoded = encode(plain);
          log.trace("Encoded cacheVersionKey {} to {}", plain, encoded);
          return encoded;
      }
  
      /**
       * Responsible for encoding the plain key using the appropriate algorithm.
       *
       * @param plain the plain key to be encoded
       * @return the key encoded
       */
      protected abstract String encode(String plain);
  }