package com.atlassian.plugin.osgi.container.impl;
   
   import com.atlassian.plugin.osgi.container.OsgiContainerException;
   import com.atlassian.plugin.osgi.container.OsgiPersistentCache;
   import com.google.common.base.Charsets;
   import com.google.common.hash.Hashing;
   import org.apache.commons.io.FileUtils;
   import org.slf4j.Logger;
   import org.slf4j.LoggerFactory;
  
  import java.io.File;
  import java.io.IOException;
  
  import static com.google.common.base.Preconditions.checkNotNull;
  import static com.google.common.base.Preconditions.checkState;
  
  /**
   * Default implementation of persistent cache. Handles clearing of directories if an upgrade has been detected.
   *
   * @since 2.2.0
   */
  public class DefaultOsgiPersistentCache implements OsgiPersistentCache {
      private final File osgiBundleCache;
      private final File frameworkBundleCache;
      private final File transformedPluginCache;
      private final Logger log = LoggerFactory.getLogger(DefaultOsgiPersistentCache.class);
  
      /**
       * Constructs a cache, using the passed file as the base directory for cache subdirectories
       *
       * @param baseDir The base directory
       */
      public DefaultOsgiPersistentCache(final File baseDir) {
          checkState(checkNotNull(baseDir).exists(), "The base directory for OSGi persistent caches should exist, %s", baseDir);
          osgiBundleCache = new File(baseDir, "felix");
          frameworkBundleCache = new File(baseDir, "framework-bundles");
          transformedPluginCache = new File(baseDir, "transformed-plugins");
          validate(null);
      }
  
      public File getFrameworkBundleCache() {
          return frameworkBundleCache;
      }
  
      public File getOsgiBundleCache() {
          return osgiBundleCache;
      }
  
      public File getTransformedPluginCache() {
          return transformedPluginCache;
      }
  
      public void clear() throws OsgiContainerException {
          try {
              FileUtils.cleanDirectory(frameworkBundleCache);
              FileUtils.cleanDirectory(osgiBundleCache);
              FileUtils.cleanDirectory(transformedPluginCache);
          } catch (final IOException e) {
              throw new OsgiContainerException("Unable to clear OSGi caches", e);
          }
      }
  
      public void validate(final String cacheValidationKey) {
          ensureDirectoryExists(frameworkBundleCache);
          ensureDirectoryExists(osgiBundleCache);
          ensureDirectoryExists(transformedPluginCache);
  
          try {
              FileUtils.cleanDirectory(osgiBundleCache);
          } catch (final IOException e) {
              throw new OsgiContainerException("Unable to clean the cache directory: " + osgiBundleCache, e);
          }
  
          if (cacheValidationKey != null) {
              final String newHash = Hashing.sha1().hashString(cacheValidationKey, Charsets.UTF_8).toString();
              final File versionFile = new File(transformedPluginCache, "cache.key");
              if (versionFile.exists()) {
                  String oldVersion = null;
                  try {
                      oldVersion = FileUtils.readFileToString(versionFile);
                  } catch (final IOException e) {
                      log.debug("Unable to read cache key file", e);
                  }
                  if (!newHash.equals(oldVersion)) {
                      log.info("Application upgrade detected, clearing OSGi cache directories");
                      clear();
                  } else {
                      return;
                  }
              }
  
              try {
                  FileUtils.writeStringToFile(versionFile, newHash);
              } catch (final IOException e) {
                  log.warn("Unable to write cache key file, so will be unable to detect upgrades", e);
              }
          }
      }
  
     private void ensureDirectoryExists(final File dir) {
         if (dir.exists() && !dir.isDirectory()) {
             throw new IllegalArgumentException("'" + dir + "' is not a directory");
         }
 
         if (!dir.exists() && !dir.mkdir()) {
             throw new IllegalArgumentException("Directory '" + dir + "' cannot be created");
         }
     }
 }