// Copyright 2013 The Flutter 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 FLUTTER_IMPELLER_RENDERER_BACKEND_GLES_HANDLE_GLES_H_
#define FLUTTER_IMPELLER_RENDERER_BACKEND_GLES_HANDLE_GLES_H_

#include <cstdint>
#include <optional>
#include <sstream>
#include <string>
#include <thread>
#include <type_traits>

#include "flutter/fml/hash_combine.h"
#include "impeller/base/comparable.h"

namespace impeller {

enum class HandleType {
  kUnknown,
  kTexture,
  kBuffer,
  kProgram,
  kRenderBuffer,
  kFrameBuffer,
  kFence,
};

std::string HandleTypeToString(HandleType type);

// Returns whether this type of handle can be shared across OpenGL contexts.
bool HandleTypeIsShareable(HandleType type);

class ReactorGLES;

//------------------------------------------------------------------------------
/// @brief      Represents a handle to an underlying OpenGL object. Unlike
///             OpenGL object handles, these handles can be collected on any
///             thread as long as their destruction is scheduled in a reactor.
///
class HandleGLES {
 public:
  //----------------------------------------------------------------------------
  /// @brief      Creates a dead handle.
  ///
  /// @return     The handle.
  ///
  static HandleGLES DeadHandle() {
    return HandleGLES{HandleType::kUnknown, std::nullopt};
  }

  //----------------------------------------------------------------------------
  /// @brief      Determines if the handle is dead.
  ///
  /// @return     True if dead, False otherwise.
  ///
  constexpr bool IsDead() const { return !name_.has_value(); }

  //----------------------------------------------------------------------------
  /// @brief      Get the hash value of this handle. Handles can be used as map
  ///             keys.
  ///
  struct Hash {
    std::size_t operator()(const HandleGLES& handle) const {
      return handle.GetHash();
    }
  };

  //----------------------------------------------------------------------------
  /// @brief      A comparer used to test the equality of two handles.
  ///
  struct Equal {
    bool operator()(const HandleGLES& lhs, const HandleGLES& rhs) const {
      return lhs.type_ == rhs.type_ && lhs.name_ == rhs.name_;
    }
  };

  HandleType GetType() const { return type_; }
  const std::optional<UniqueID>& GetName() const { return name_; }
  std::size_t GetHash() const { return hash_; }

 private:
  HandleType type_ = HandleType::kUnknown;
  std::optional<UniqueID> name_;
  std::size_t hash_;
  std::optional<uint64_t> untracked_id_;
  std::optional<std::thread::id> owner_thread_;

  friend class ReactorGLES;

  HandleGLES(HandleType p_type, UniqueID p_name, std::thread::id p_owner_thread)
      : type_(p_type),
        name_(p_name),
        hash_(fml::HashCombine(
            static_cast<std::underlying_type_t<decltype(p_type)>>(p_type),
            p_name)) {}

  HandleGLES(HandleType p_type, std::optional<UniqueID> p_name)
      : type_(p_type),
        name_(p_name),
        hash_(fml::HashCombine(
            static_cast<std::underlying_type_t<decltype(p_type)>>(p_type),
            p_name)) {}

  static HandleGLES Create(HandleType type) {
    HandleGLES handle{type, UniqueID{}};
    if (!HandleTypeIsShareable(type)) {
      handle.owner_thread_ = std::this_thread::get_id();
    }
    return handle;
  }
};

}  // namespace impeller

namespace std {

inline std::ostream& operator<<(std::ostream& out,
                                const impeller::HandleGLES& handle) {
  out << HandleTypeToString(handle.GetType()) << "(";
  if (handle.IsDead()) {
    out << "DEAD";
  } else {
    const std::optional<impeller::UniqueID>& name = handle.GetName();
    if (name.has_value()) {
      out << name.value().id;
    } else {
      out << "UNNAMED";
    }
  }
  out << ")";
  return out;
}

}  // namespace std

#endif  // FLUTTER_IMPELLER_RENDERER_BACKEND_GLES_HANDLE_GLES_H_