package at.gv.egovernment.moa.util;

import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;
import java.util.MissingResourceException;
import java.util.ResourceBundle;

/**
 * A class to chain <code>ResourceBundle</code>s.
 * 
 * @author Patrick Peck
 * @version $Id$
 */
public class ResourceBundleChain {
  /** Error message indicating the resource is not available. */
  private static final String ERROR_MISSING_RESOURCE = "Missing resource";
  /** The <code>ResourceBundle</code>s contained in this chain. */
  private List resourceBundles = new ArrayList();

  /**
   * Add a <code>ResourceBundle</code> to the chain.
   * 
   * @param resourceBundle The <code>ResourceBundle</code> to add.
   */
  public void addResourceBundle(ResourceBundle resourceBundle) {
    resourceBundles.add(resourceBundle);
  }

  /**
   * Return the value of the resource.
   * 
   * @param key The key to access the <code>String</code> resource.
   * @return The resource value. All the registered <code>ResourceBundle</code>s
   * are searched in the order in which they have previously been added to this
   * <code>ResourceBundleChain</code>.
   * @throws MissingResourceException The resource coult not be found in any of
   * the bundles.
   */
  public String getString(String key) throws MissingResourceException {
    MissingResourceException lastException = null;
    Iterator iter;

    // handle case where no resource bundles have been added
    if (resourceBundles.size() == 0) {
      throw new MissingResourceException(
        ERROR_MISSING_RESOURCE,
        this.getClass().getName(),
        key);
    }

    // try to find the resource in one of the bundles; if it cannot be found,
    // return the exception thrown by the last bundle in the list
    for (iter = resourceBundles.iterator(); iter.hasNext();) {
      ResourceBundle resourceBundle = (ResourceBundle) iter.next();
      try {
        String value = resourceBundle.getString(key);
        return value;
      } catch (MissingResourceException e) {
        lastException = e;
      }
    }
    throw lastException;
  }

}