/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set ft=cpp tw=78 sw=2 et ts=8 : */
/* 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"
#include "nsIContentPolicyBase.idl"

interface nsIURI;
interface nsIDOMNode;
interface nsIPrincipal;
interface nsIDOMElement;

/**
 * Interface for content policy mechanism.  Implementations of this
 * interface can be used to control loading of various types of out-of-line
 * content, or processing of certain types of in-line content.
 *
 * This interface differs from nsIContentPolicy in that it offers less control
 * (the DOM node doing the load is not provided) but more flexibility for
 * Gecko. In particular, this interface allows an add-on in the chrome process
 * to block loads without using cross-process wrappers (CPOWs). Add-ons should
 * prefer this interface to nsIContentPolicy because it should be faster in
 * e10s. In the future, it may also be run asynchronously.
 *
 * WARNING: do not block the caller from shouldLoad or shouldProcess (e.g.,
 * by launching a dialog to prompt the user for something).
 */

[scriptable,uuid(b181c97c-9d67-4da1-95a0-e0a202e1807c)]
interface nsISimpleContentPolicy : nsIContentPolicyBase
{
  /**
   * Should the resource at this location be loaded?
   * ShouldLoad will be called before loading the resource at aContentLocation
   * to determine whether to start the load at all.
   *
   * @param aContentType      the type of content being tested. This will be one
   *                          one of the TYPE_* constants.
   *
   * @param aContentLocation  the location of the content being checked; must
   *                          not be null
   *
   * @param aRequestOrigin    OPTIONAL. the location of the resource that
   *                          initiated this load request; can be null if
   *                          inapplicable
   *
   * @param aTopFrameElement  OPTIONAL. The top frame element (typically a
   *                          <xul:browser> element) that initiated the
   *                          request. In a content process, this argument
   *                          will be null.
   *
   * @param aIsTopLevel       OPTIONAL. True iff the request was initiated
   *                          from a frame where |window.top === window|.
   *
   * @param aMimeTypeGuess    OPTIONAL. a guess for the requested content's
   *                          MIME type, based on information available to
   *                          the request initiator (e.g., an OBJECT's type
   *                          attribute); does not reliably reflect the
   *                          actual MIME type of the requested content
   *
   * @param aExtra            an OPTIONAL argument, pass-through for non-Gecko
   *                          callers to pass extra data to callees.
   *
   * @param aRequestPrincipal an OPTIONAL argument, defines the principal that
   *                          caused the load. This is optional only for
   *                          non-gecko code: all gecko code should set this
   *                          argument.  For navigation events, this is
   *                          the principal of the page that caused this load.
   *
   * @return ACCEPT or REJECT_*
   *
   * @note shouldLoad can be called while the DOM and layout of the document
   * involved is in an inconsistent state.  This means that implementors of
   * this method MUST NOT do any of the following:
   * 1)  Modify the DOM in any way (e.g. setting attributes is a no-no).
   * 2)  Query any DOM properties that depend on layout (e.g. offset*
   *     properties).
   * 3)  Query any DOM properties that depend on style (e.g. computed style).
   * 4)  Query any DOM properties that depend on the current state of the DOM
   *     outside the "context" node (e.g. lengths of node lists).
   * 5)  [JavaScript implementations only] Access properties of any sort on any
   *     object without using XPCNativeWrapper (either explicitly or
   *     implicitly).  Due to various DOM0 things, this leads to item 4.
   * If you do any of these things in your shouldLoad implementation, expect
   * unpredictable behavior, possibly including crashes, content not showing
   * up, content showing up doubled, etc.  If you need to do any of the things
   * above, do them off timeout or event.
   */
  short shouldLoad(in nsContentPolicyType aContentType,
                   in nsIURI        aContentLocation,
                   in nsIURI        aRequestOrigin,
                   in nsIDOMElement aTopFrameElement,
                   in boolean       aIsTopLevel,
                   in ACString      aMimeTypeGuess,
                   in nsISupports   aExtra,
                   in nsIPrincipal  aRequestPrincipal);

  /**
   * Should the resource be processed?
   * ShouldProcess will be called once all the information passed to it has
   * been determined about the resource, typically after part of the resource
   * has been loaded.
   *
   * @param aContentType      the type of content being tested. This will be one
   *                          one of the TYPE_* constants.
   *
   * @param aContentLocation  OPTIONAL; the location of the resource being
   *                          requested: MAY be, e.g., a post-redirection URI
   *                          for the resource.
   *
   * @param aRequestOrigin    OPTIONAL. the location of the resource that
   *                          initiated this load request; can be null if
   *                          inapplicable
   *
   * @param aTopFrameElement  OPTIONAL. The top frame element (typically a
   *                          <xul:browser> element) that initiated the
   *                          request. In a content process, this argument
   *                          will be null.
   *
   * @param aIsTopLevel       OPTIONAL. True iff the request was initiated
   *                          from a frame where |window.top === window|.
   *
   * @param aMimeType         the MIME type of the requested resource (e.g.,
   *                          image/png), as reported by the networking library,
   *                          if available (may be empty if inappropriate for
   *                          the type, e.g., TYPE_REFRESH).
   *
   * @param aExtra            an OPTIONAL argument, pass-through for non-Gecko
   *                          callers to pass extra data to callees.
   *
   * @return ACCEPT or REJECT_*
   *
   * @note shouldProcess can be called while the DOM and layout of the document
   * involved is in an inconsistent state.  See the note on shouldLoad to see
   * what this means for implementors of this method.
   */
  short shouldProcess(in nsContentPolicyType aContentType,
                      in nsIURI        aContentLocation,
                      in nsIURI        aRequestOrigin,
                      in nsIDOMElement aTopFrameElement,
                      in boolean       aIsTopLevel,
                      in ACString      aMimeType,
                      in nsISupports   aExtra,
                      in nsIPrincipal  aRequestPrincipal);
};
