/* 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 nsIHandlerInfo;
interface nsISimpleEnumerator;

[scriptable, uuid(53f0ad17-ec62-46a1-adbc-efccc06babcd)]
interface nsIHandlerService : nsISupports
{
  /**
   * Asynchronously performs any IO that the nsIHandlerService needs to do
   * before it can be of use.
   */
  void asyncInit();

  /**
   * Retrieve a list of all handlers in the datastore.  This list is not
   * guaranteed to be in any particular order, and callers should not assume
   * it will remain in the same order in the future.
   *
   * @returns a list of all handlers in the datastore
   */
  nsISimpleEnumerator enumerate();

  /**
   * Fill a handler info object with information from the datastore.
   *
   * Note: because of the way the external helper app service currently mixes
   * OS and user handler info in the same handler info object, this method
   * takes an existing handler info object (probably retrieved from the OS)
   * and "fills it in" with information from the datastore, overriding any
   * existing properties on the object with properties from the datastore.
   *
   * Ultimately, however, we're going to separate OS and user handler info
   * into separate objects, at which point this method should be renamed to
   * something like "get" or "retrieve", take a class and type (or perhaps
   * a type whose class can be determined by querying the type, for example
   * an nsIContentType which is also an nsIMIMEType or an nsIProtocolScheme),
   * and return a handler info object representing only the user info.
   *
   * Note: if you specify an override type, then the service will fill in
   * the handler info object with information about that type instead of
   * the type specified by the object's nsIHandlerInfo::type attribute.
   *
   * This is useful when you are trying to retrieve information about a MIME
   * type that doesn't exist in the datastore, but you have a file extension
   * for that type, and nsIHandlerService::getTypeFromExtension returns another
   * MIME type that does exist in the datastore and can handle that extension.
   *
   * For example, the user clicks on a link, and the content has a MIME type
   * that isn't in the datastore, but the link has a file extension, and that
   * extension is associated with another MIME type in the datastore (perhaps
   * an unofficial MIME type preceded an official one, like with image/x-png
   * and image/png).
   *
   * In that situation, you can call this method to fill in the handler info
   * object with information about that other type by passing the other type
   * as the aOverrideType parameter.
   *
   * @param aHandlerInfo   the handler info object
   * @param aOverrideType  a type to use instead of aHandlerInfo::type
   *
   * Note: if there is no information in the datastore about this type,
   * this method throws NS_ERROR_NOT_AVAILABLE. Callers are encouraged to
   * check exists() before calling fillHandlerInfo(), to prevent spamming the
   * console with XPCOM exception errors.
   */
  void fillHandlerInfo(in nsIHandlerInfo aHandlerInfo,
                       in ACString aOverrideType);

  /**
   * Save the preferred action, preferred handler, possible handlers, and
   * always ask properties of the given handler info object to the datastore.
   * Updates an existing record or creates a new one if necessary.
   *
   * Note: if preferred action is undefined or invalid, then we assume
   * the default value nsIHandlerInfo::useHelperApp.
   *
   * @param aHandlerInfo  the handler info object
   */
  void store(in nsIHandlerInfo aHandlerInfo);

  /**
   * Whether or not a record for the given handler info object exists
   * in the datastore. If the datastore is corrupt (or some other error
   * is caught in the implementation), false will be returned.
   *
   * @param aHandlerInfo  a handler info object
   *
   * @returns whether or not a record exists
   */
  boolean exists(in nsIHandlerInfo aHandlerInfo);

  /**
   * Remove the given handler info object from the datastore.  Deletes all
   * records associated with the object, including the preferred handler, info,
   * and type records plus the entry in the list of types, if they exist.
   * Otherwise, it does nothing and does not return an error.
   *
   * @param aHandlerInfo  the handler info object
   */
  void remove(in nsIHandlerInfo aHandlerInfo);

  /**
   * Get the MIME type mapped to the given file extension in the datastore.
   *
   * XXX If we ever support extension -> protocol scheme mappings, then this
   * method should work for those as well.
   *
   * Note: in general, you should use nsIMIMEService::getTypeFromExtension
   * to get a MIME type from a file extension, as that method checks a variety
   * of other sources besides just the datastore.  Use this only when you want
   * to specifically get only the mapping available in the datastore.
   *
   * @param aFileExtension  the file extension
   *
   * @returns the MIME type, if any; otherwise returns an empty string ("").
   */
  ACString getTypeFromExtension(in ACString aFileExtension);

  /**
   * Whether or not there is a handler known to the OS for the
   * specified protocol type.
   *
   * @param aProtocolScheme scheme to check for support
   *
   * @returns whether or not a handler exists
   */
  boolean existsForProtocol(in ACString aProtocolScheme);
};