/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
/* vim: set ts=8 sts=4 et sw=4 tw=99: */
/* 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/. */

#ifndef xpcObjectHelper_h
#define xpcObjectHelper_h

// Including 'windows.h' will #define GetClassInfo to something else.
#ifdef XP_WIN
#ifdef GetClassInfo
#undef GetClassInfo
#endif
#endif

#include "mozilla/Attributes.h"
#include <stdint.h>
#include "nsCOMPtr.h"
#include "nsIClassInfo.h"
#include "nsISupports.h"
#include "nsIXPCScriptable.h"
#include "nsWrapperCache.h"

class xpcObjectHelper {
 public:
  explicit xpcObjectHelper(nsISupports* aObject,
                           nsWrapperCache* aCache = nullptr)
      : mCanonical(nullptr), mObject(aObject), mCache(aCache) {
    if (!mCache) {
      if (aObject)
        CallQueryInterface(aObject, &mCache);
      else
        mCache = nullptr;
    }
  }

  nsISupports* Object() { return mObject; }

  nsISupports* GetCanonical() {
    if (!mCanonical) {
      mCanonicalStrong = do_QueryInterface(mObject);
      mCanonical = mCanonicalStrong;
    }
    return mCanonical;
  }

  already_AddRefed<nsISupports> forgetCanonical() {
    MOZ_ASSERT(mCanonical, "Huh, no canonical to forget?");

    if (!mCanonicalStrong) mCanonicalStrong = mCanonical;
    mCanonical = nullptr;
    return mCanonicalStrong.forget();
  }

  nsIClassInfo* GetClassInfo() {
    if (mXPCClassInfo) return mXPCClassInfo;
    if (!mClassInfo) mClassInfo = do_QueryInterface(mObject);
    return mClassInfo;
  }
  nsXPCClassInfo* GetXPCClassInfo() {
    if (!mXPCClassInfo) {
      CallQueryInterface(mObject, getter_AddRefs(mXPCClassInfo));
    }
    return mXPCClassInfo;
  }

  already_AddRefed<nsXPCClassInfo> forgetXPCClassInfo() {
    GetXPCClassInfo();

    return mXPCClassInfo.forget();
  }

  // We assert that we can reach an nsIXPCScriptable somehow.
  uint32_t GetScriptableFlags() {
    // Try getting an nsXPCClassInfo - this handles DOM scriptable helpers.
    nsCOMPtr<nsIXPCScriptable> sinfo = GetXPCClassInfo();

    // If that didn't work, try just QI-ing. This handles BackstagePass.
    if (!sinfo) sinfo = do_QueryInterface(GetCanonical());

    // We should have something by now.
    MOZ_ASSERT(sinfo);

    // Grab the flags.
    return sinfo->GetScriptableFlags();
  }

  nsWrapperCache* GetWrapperCache() { return mCache; }

 protected:
  xpcObjectHelper(nsISupports* aObject, nsISupports* aCanonical,
                  nsWrapperCache* aCache)
      : mCanonical(aCanonical), mObject(aObject), mCache(aCache) {
    if (!mCache && aObject) CallQueryInterface(aObject, &mCache);
  }

  nsCOMPtr<nsISupports> mCanonicalStrong;
  nsISupports* MOZ_UNSAFE_REF(
      "xpcObjectHelper has been specifically optimized "
      "to avoid unnecessary AddRefs and Releases. "
      "(see bug 565742)") mCanonical;

 private:
  xpcObjectHelper(xpcObjectHelper& aOther) = delete;

  nsISupports* MOZ_UNSAFE_REF(
      "xpcObjectHelper has been specifically optimized "
      "to avoid unnecessary AddRefs and Releases. "
      "(see bug 565742)") mObject;
  nsWrapperCache* mCache;
  nsCOMPtr<nsIClassInfo> mClassInfo;
  RefPtr<nsXPCClassInfo> mXPCClassInfo;
};

#endif
