package com.atlassian.plugin.servlet.download.plugin;
   
   import com.atlassian.plugin.ModuleDescriptor;
   import com.atlassian.plugin.event.PluginEventListener;
   import com.atlassian.plugin.event.PluginEventManager;
   import com.atlassian.plugin.event.events.PluginModuleDisabledEvent;
   import com.atlassian.plugin.event.events.PluginModuleEnabledEvent;
   import com.atlassian.plugin.servlet.DownloadException;
   import com.atlassian.plugin.servlet.DownloadStrategy;
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  import javax.servlet.http.HttpServletRequest;
  import javax.servlet.http.HttpServletResponse;
  import java.util.Map;
  import java.util.concurrent.ConcurrentHashMap;
  
  /**
   * A download strategy which maintains a list of {@link DownloadStrategyModuleDescriptor}s
   * and delegates to them in order.
   *
   * @see DownloadStrategyModuleDescriptor
   * @see DownloadStrategy
   * @since 2.2.0
   */
  public class PluggableDownloadStrategy implements DownloadStrategy {
      private static final Logger log = LoggerFactory.getLogger(PluggableDownloadStrategy.class);
      private final Map<String, DownloadStrategy> strategies = new ConcurrentHashMap<>();
  
      public PluggableDownloadStrategy(final PluginEventManager pluginEventManager) {
          pluginEventManager.register(this);
      }
  
      public boolean matches(final String urlPath) {
          for (final DownloadStrategy strategy : strategies.values()) {
              if (strategy.matches(urlPath)) {
                  log.debug("Matched plugin download strategy: {}", strategy.getClass().getName());
                  return true;
              }
          }
          return false;
      }
  
      public void serveFile(final HttpServletRequest request, final HttpServletResponse response) throws DownloadException {
          for (final DownloadStrategy strategy : strategies.values()) {
              if (strategy.matches(request.getRequestURI().toLowerCase())) {
                  strategy.serveFile(request, response);
                  return;
              }
          }
          throw new DownloadException(
                  "Found plugin download strategy during matching but not when trying to serve. Enable debug logging for more information.");
      }
  
      public void register(final String key, final DownloadStrategy strategy) {
          if (strategies.containsKey(key)) {
              log.warn("Replacing existing download strategy with module key: {}", key);
          }
          strategies.put(key, strategy);
      }
  
      public void unregister(final String key) {
          strategies.remove(key);
      }
  
      @PluginEventListener
      public void pluginModuleEnabled(final PluginModuleEnabledEvent event) {
          final ModuleDescriptor<?> module = event.getModule();
          if (!(module instanceof DownloadStrategyModuleDescriptor)) {
              return;
          }
  
          register(module.getCompleteKey(), (DownloadStrategy) module.getModule());
      }
  
      @PluginEventListener
      public void pluginModuleDisabled(final PluginModuleDisabledEvent event) {
          final ModuleDescriptor<?> module = event.getModule();
          if (!(module instanceof DownloadStrategyModuleDescriptor)) {
              return;
          }
  
          unregister(module.getCompleteKey());
      }
  }