// Copyright 2020 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef UI_GFX_X_PROPERTY_CACHE_H_
#define UI_GFX_X_PROPERTY_CACHE_H_

#include <vector>

#include "base/component_export.h"
#include "base/containers/flat_map.h"
#include "base/memory/ref_counted_memory.h"
#include "base/memory/weak_ptr.h"
#include "third_party/abseil-cpp/absl/types/optional.h"
#include "ui/gfx/x/connection.h"
#include "ui/gfx/x/future.h"
#include "ui/gfx/x/x11_window_event_manager.h"
#include "ui/gfx/x/xproto.h"

namespace x11 {

// Watches properties on an X11 window.  Property values are obtained once upon
// creation and are refreshed after each property change.
class COMPONENT_EXPORT(X11) PropertyCache : public EventObserver {
 public:
  PropertyCache(Connection* connection,
                Window window,
                const std::vector<Atom>& properties);

  PropertyCache(const PropertyCache&) = delete;
  PropertyCache& operator=(const PropertyCache&) = delete;

  ~PropertyCache() override;

  const GetPropertyResponse& Get(Atom atom);

  template <typename T>
  const T* GetAs(Atom atom, size_t* size = nullptr) {
    auto& response = Get(atom);
    if (size)
      *size = 0;
    if (!response || response->format != CHAR_BIT * sizeof(T) ||
        !response->value_len) {
      return nullptr;
    }
    if (size)
      *size = response->value_len;
    return response->value->front_as<T>();
  }

 private:
  friend class PropertyCacheTest;

  struct PropertyValue {
    PropertyValue();

    PropertyValue(PropertyValue&&);
    PropertyValue& operator=(PropertyValue&&);

    ~PropertyValue();

    Future<GetPropertyReply> future;
    // |response| is nullopt if the request hasn't yet finished.
    absl::optional<GetPropertyResponse> response = absl::nullopt;
  };

  // EventObserver:
  void OnEvent(const Event& xev) override;

  void FetchProperty(Atom property, PropertyValue* value);

  void OnGetPropertyResponse(PropertyValue* value,
                             GetPropertyResponse response);

  Connection* connection_;
  Window window_;
  XScopedEventSelector event_selector_;
  base::flat_map<Atom, PropertyValue> properties_;

  base::WeakPtrFactory<PropertyCache> weak_factory_{this};
};

}  // namespace x11

#endif  // UI_GFX_X_PROPERTY_CACHE_H_