/* -*- Mode: C++; tab-width: 3; indent-tabs-mode: nil; c-basic-offset: 2 -*-
 *
 * This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

#include "nsISupports.idl"

interface nsIURI;
interface nsIFile;
interface nsIInterfaceRequestor;
interface nsIHandlerInfo;

/**
 * The external protocol service is used for finding and launching
 * web handlers (a la registerProtocolHandler in the HTML5 draft) or 
 * platform-specific applications for handling particular protocols.
 *
 * You can ask the external protocol service if it has an external
 * handler for a given protocol scheme. And you can ask it to load 
 * the url using the default handler.
 */
[scriptable, uuid(70f93b7a-3ec6-4bcb-b093-92d9984c9f83)]
interface nsIExternalProtocolService : nsISupports
{
  /**
   * Check whether a handler for a specific protocol exists.  Specifically,
   * this looks to see whether there are any known possible application handlers
   * in either the nsIHandlerService datastore or registered with the OS.
   *
   * @param aProtocolScheme The scheme from a url: http, ftp, mailto, etc.
   *
   * @return true if we have a handler and false otherwise.
   *
   * XXX shouldn't aProtocolScheme be an ACString like nsIURI::scheme?
   */
  boolean externalProtocolHandlerExists(in string aProtocolScheme);

  /**
   * Check whether a handler for a specific protocol is "exposed" as a visible
   * feature of the current application.
   *
   * An exposed protocol handler is one that can be used in all contexts.  A
   * non-exposed protocol handler is one that can only be used internally by the
   * application.  For example, a non-exposed protocol would not be loaded by the
   * application in response to a link click or a X-remote openURL command.
   * Instead, it would be deferred to the system's external protocol handler.
   * XXX shouldn't aProtocolScheme be an ACString like nsIURI::scheme?
   */
  boolean isExposedProtocol(in string aProtocolScheme);

  /**
   * Retrieve the handler for the given protocol.  If neither the application
   * nor the OS knows about a handler for the protocol, the object this method
   * returns will represent a default handler for unknown content.
   * 
   * @param aProtocolScheme the scheme from a URL: http, ftp, mailto, etc.
   * 
   * Note: aProtocolScheme should not include a trailing colon, which is part
   * of the URI syntax, not part of the scheme itself (i.e. pass "mailto" not
   * "mailto:").
   * 
   * @return the handler, if any; otherwise a default handler
   */
  nsIHandlerInfo getProtocolHandlerInfo(in ACString aProtocolScheme);

  /**
   * Given a scheme, looks up the protocol info from the OS.  This should be
   * overridden by each OS's implementation.
   *
   * @param aScheme The protocol scheme we are looking for.
   * @param aFound  Was an OS default handler for this scheme found?
   * @return An nsIHanderInfo for the protocol.
   */
  nsIHandlerInfo getProtocolHandlerInfoFromOS(in ACString aProtocolScheme,
                                              out boolean aFound);

  /** 
   * Set some sane defaults for a protocol handler object.
   * 
   * @param aHandlerInfo      nsIHandlerInfo object, as returned by 
   *                          getProtocolHandlerInfoFromOS
   * @param aOSHandlerExists  was the object above created for an extant
   *                          OS default handler?  This is generally the
   *                          value of the aFound out param from
   *                          getProtocolHandlerInfoFromOS.
   */
  void setProtocolHandlerDefaults(in nsIHandlerInfo aHandlerInfo,
                                  in boolean aOSHandlerExists);

  /**
   * Used to load a URI via an external application. Might prompt the user for
   * permission to load the external application.
   *
   * @param aURI
   *        The URI to load
   *
   * @param aWindowContext 
   *        The window to parent the dialog against, and, if a web handler
   *        is chosen, it is loaded in this window as well.  This parameter
   *        may be ultimately passed nsIURILoader.openURI in the case of a
   *        web handler, and aWindowContext is null or not present, web
   *        handlers will fail.  We need to do better than that; bug 394483
   *        filed in order to track.
   * 
   * @note  Embedders that do not expose the http protocol should not currently
   *        use web-based protocol handlers, as handoff won't work correctly
   *        (bug 394479).  
   */
  void loadURI(in nsIURI aURI,
               [optional] in nsIInterfaceRequestor aWindowContext);

  /**
   * Gets a human-readable description for the application responsible for
   * handling a specific protocol.
   *
   * @param aScheme The scheme to look up. For example, "mms".
   *
   * @throw NS_ERROR_NOT_IMPLEMENTED
   *        If getting descriptions for protocol helpers is not supported
   * @throw NS_ERROR_NOT_AVAILABLE
   *        If no protocol helper exists for this scheme, or if it is not
   *        possible to get a description for it.
   */
  AString getApplicationDescription(in AUTF8String aScheme);
};