/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set ts=8 sts=2 et sw=2 tw=80: */
/* 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 mozilla_a11y_LazyInstantiator_h
#define mozilla_a11y_LazyInstantiator_h

#include "IUnknownImpl.h"
#include "mozilla/Maybe.h"
#include "mozilla/RefPtr.h"
#include "nsString.h"

#include <oleacc.h>

class nsIFile;

namespace mozilla {
namespace a11y {

class MsaaRootAccessible;

/**
 * LazyInstantiator is an IAccessible that initially acts as a placeholder.
 * The a11y service is not actually started until two conditions are met:
 *
 * (1) A method is called on the LazyInstantiator that would require a11y
 *     services in order to fulfill; and
 * (2) LazyInstantiator::ShouldInstantiate returns true.
 */
class LazyInstantiator final : public IAccessible, public IServiceProvider {
 public:
  [[nodiscard]] static already_AddRefed<IAccessible> GetRootAccessible(
      HWND aHwnd);
  static void EnableBlindAggregation(HWND aHwnd);

  // IUnknown
  STDMETHODIMP QueryInterface(REFIID aIid, void** aOutInterface) override;
  STDMETHODIMP_(ULONG) AddRef() override;
  STDMETHODIMP_(ULONG) Release() override;

  // IDispatch
  STDMETHODIMP GetTypeInfoCount(UINT* pctinfo) override;
  STDMETHODIMP GetTypeInfo(UINT iTInfo, LCID lcid,
                           ITypeInfo** ppTInfo) override;
  STDMETHODIMP GetIDsOfNames(REFIID riid, LPOLESTR* rgszNames, UINT cNames,
                             LCID lcid, DISPID* rgDispId) override;
  STDMETHODIMP Invoke(DISPID dispIdMember, REFIID riid, LCID lcid, WORD wFlags,
                      DISPPARAMS* pDispParams, VARIANT* pVarResult,
                      EXCEPINFO* pExcepInfo, UINT* puArgErr) override;

  // IAccessible
  STDMETHODIMP get_accParent(IDispatch** ppdispParent) override;
  STDMETHODIMP get_accChildCount(long* pcountChildren) override;
  STDMETHODIMP get_accChild(VARIANT varChild, IDispatch** ppdispChild) override;
  STDMETHODIMP get_accName(VARIANT varChild, BSTR* pszName) override;
  STDMETHODIMP get_accValue(VARIANT varChild, BSTR* pszValue) override;
  STDMETHODIMP get_accDescription(VARIANT varChild,
                                  BSTR* pszDescription) override;
  STDMETHODIMP get_accRole(VARIANT varChild, VARIANT* pvarRole) override;
  STDMETHODIMP get_accState(VARIANT varChild, VARIANT* pvarState) override;
  STDMETHODIMP get_accHelp(VARIANT varChild, BSTR* pszHelp) override;
  STDMETHODIMP get_accHelpTopic(BSTR* pszHelpFile, VARIANT varChild,
                                long* pidTopic) override;
  STDMETHODIMP get_accKeyboardShortcut(VARIANT varChild,
                                       BSTR* pszKeyboardShortcut) override;
  STDMETHODIMP get_accFocus(VARIANT* pvarChild) override;
  STDMETHODIMP get_accSelection(VARIANT* pvarChildren) override;
  STDMETHODIMP get_accDefaultAction(VARIANT varChild,
                                    BSTR* pszDefaultAction) override;
  STDMETHODIMP accSelect(long flagsSelect, VARIANT varChild) override;
  STDMETHODIMP accLocation(long* pxLeft, long* pyTop, long* pcxWidth,
                           long* pcyHeight, VARIANT varChild) override;
  STDMETHODIMP accNavigate(long navDir, VARIANT varStart,
                           VARIANT* pvarEndUpAt) override;
  STDMETHODIMP accHitTest(long xLeft, long yTop, VARIANT* pvarChild) override;
  STDMETHODIMP accDoDefaultAction(VARIANT varChild) override;
  STDMETHODIMP put_accName(VARIANT varChild, BSTR szName) override;
  STDMETHODIMP put_accValue(VARIANT varChild, BSTR szValue) override;

  // IServiceProvider
  STDMETHODIMP QueryService(REFGUID aServiceId, REFIID aServiceIid,
                            void** aOutInterface) override;

  /**
   * We cache the result of UIA detection because it could be expensive if a
   * client repeatedly queries us. This function is called to reset that cache
   * when one of our windows comes to the foreground. If there is a new UIA
   * client that isn't blocked, instantiation will subsequently be allowed. The
   * hope is that a user will probably need to switch apps in order to start a
   * new client.
   */
  static void ResetUiaDetectionCache() { sShouldBlockUia = Nothing(); }

 private:
  explicit LazyInstantiator(HWND aHwnd);
  ~LazyInstantiator();

  bool IsBlockedInjection();
  bool ShouldInstantiate(const DWORD aClientPid);
  bool ShouldInstantiate();

  DWORD GetRemoteMsaaClientPid();

  /**
   * @return S_OK if we have a valid mRealRoot to invoke methods on
   */
  HRESULT MaybeResolveRoot();

  /**
   * @return S_OK if we have a valid mWeakDispatch to invoke methods on
   */
  HRESULT ResolveDispatch();

  MsaaRootAccessible* ResolveMsaaRoot();
  void TransplantRefCnt();
  void ClearProp();

 private:
  mozilla::a11y::AutoRefCnt mRefCnt;
  HWND mHwnd;
  bool mAllowBlindAggregation;
  RefPtr<IUnknown> mRealRootUnk;
  RefPtr<IUnknown> mStdDispatch;
  /**
   * mWeakMsaaRoot, mWeakAccessible and mWeakDispatch are weak because they
   * are interfaces that come from objects that we aggregate. Aggregated object
   * interfaces share refcount methods with ours, so if we were to hold strong
   * references to them, we would be holding strong references to ourselves,
   * creating a cycle.
   */
  MsaaRootAccessible* mWeakMsaaRoot;
  IAccessible* mWeakAccessible;
  IDispatch* mWeakDispatch;
  static Maybe<bool> sShouldBlockUia;
};

}  // namespace a11y
}  // namespace mozilla

#endif  // mozilla_a11y_LazyInstantiator_h