// Protocol Buffers - Google's data interchange format
// Copyright 2024 Google LLC.  All rights reserved.
//
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file or at
// https://developers.google.com/open-source/licenses/bsd

#ifndef GOOGLE_PROTOBUF_HPB_EXTENSION_H__
#define GOOGLE_PROTOBUF_HPB_EXTENSION_H__

#include <cstdint>
#include <type_traits>

#include "absl/base/attributes.h"
#include "absl/status/status.h"
#include "absl/status/statusor.h"
#include "google/protobuf/hpb/backend/upb/interop.h"
#include "google/protobuf/hpb/internal/message_lock.h"
#include "google/protobuf/hpb/internal/template_help.h"
#include "google/protobuf/hpb/ptr.h"
#include "google/protobuf/hpb/status.h"
#include "upb/mem/arena.h"
#include "upb/mem/arena.hpp"
#include "upb/message/accessors.h"
#include "upb/message/array.h"
#include "upb/mini_table/extension.h"
#include "upb/mini_table/extension_registry.h"

namespace hpb {
class ExtensionRegistry;

template <typename T>
class RepeatedField;

namespace internal {
template <typename Extendee, typename Extension>
class ExtensionIdentifier;

absl::Status MoveExtension(upb_Message* message, upb_Arena* message_arena,
                           const upb_MiniTableExtension* ext,
                           upb_Message* extension, upb_Arena* extension_arena);

absl::Status SetExtension(upb_Message* message, upb_Arena* message_arena,
                          const upb_MiniTableExtension* ext,
                          const upb_Message* extension);

void SetAliasExtension(upb_Message* message, upb_Arena* message_arena,
                       const upb_MiniTableExtension* ext,
                       upb_Message* extension, upb_Arena* extension_arena);

/**
 * Trait that maps upb extension types to the corresponding
 * return value: ubp_MessageValue.
 *
 * All partial specializations must have:
 * - DefaultType: the type of the default value.
 * - ReturnType: the type of the return value.
 * - kGetter: the corresponding upb_MessageValue upb_Message_GetExtension* func
 */
template <typename T, typename = void>
struct UpbExtensionTrait;

template <typename T>
struct UpbExtensionTrait<hpb::RepeatedField<T>> {
  using ReturnType = typename RepeatedField<T>::CProxy;
  using DefaultType = std::false_type;

  template <typename Msg, typename Id>
  static constexpr ReturnType Get(Msg message, const Id& id) {
    auto upb_arr = upb_Message_GetExtensionArray(
        hpb::interop::upb::GetMessage(message), id.mini_table_ext());
    return ReturnType(upb_arr, hpb::interop::upb::GetArena(message));
  }
};

#define UPB_EXT_PRIMITIVE(CppType, UpbFunc)                              \
  template <>                                                            \
  struct UpbExtensionTrait<CppType> {                                    \
    using DefaultType = CppType;                                         \
    using ReturnType = CppType;                                          \
                                                                         \
    template <typename Msg, typename Id>                                 \
    static constexpr ReturnType Get(Msg message, const Id& id) {         \
      auto default_val = internal::PrivateAccess::GetDefaultValue(id);   \
      return upb_Message_GetExtension##UpbFunc(                          \
          interop::upb::GetMessage(message), id.mini_table_ext(),        \
          default_val);                                                  \
    }                                                                    \
    template <typename Msg, typename Id>                                 \
    static absl::Status Set(Msg message, const Id& id, CppType value) {  \
      bool res = upb_Message_SetExtension##UpbFunc(                      \
          interop::upb::GetMessage(message), id.mini_table_ext(), value, \
          interop::upb::GetArena(message));                              \
      return res ? absl::OkStatus() : MessageAllocationError();          \
    }                                                                    \
  };

UPB_EXT_PRIMITIVE(bool, Bool);
UPB_EXT_PRIMITIVE(int32_t, Int32);
UPB_EXT_PRIMITIVE(int64_t, Int64);
UPB_EXT_PRIMITIVE(uint32_t, UInt32);
UPB_EXT_PRIMITIVE(uint64_t, UInt64);
UPB_EXT_PRIMITIVE(float, Float);
UPB_EXT_PRIMITIVE(double, Double);

#undef UPB_EXT_PRIMITIVE

// TODO: b/375460289 - flesh out non-promotional msg support that does
// not return an error if missing but the default msg
template <typename T>
struct UpbExtensionTrait<T> {
  using DefaultType = std::false_type;
  using ReturnType = Ptr<const T>;
  template <typename Msg, typename Id>
  static constexpr absl::StatusOr<ReturnType> Get(Msg message, const Id& id) {
    upb_MessageValue value;
    const bool ok = internal::GetOrPromoteExtension(
        interop::upb::GetMessage(message), id.mini_table_ext(),
        interop::upb::GetArena(message), &value);
    if (!ok) {
      return ExtensionNotFoundError(
          upb_MiniTableExtension_Number(id.mini_table_ext()));
    }
    return Ptr<const T>(interop::upb::MakeCHandle<T>(
        value.msg_val, hpb::interop::upb::GetArena(message)));
  }

  template <typename Msg, typename Id>
  static absl::Status Set(Msg message, const Id& id, const T& value) {
    return Set(message, id, &value);
  }

  template <typename Msg, typename Id>
  static absl::Status Set(Msg message, const Id& id, T&& value) {
    T local = std::move(value);
    return internal::MoveExtension(
        interop::upb::GetMessage(message), interop::upb::GetArena(message),
        id.mini_table_ext(), interop::upb::GetMessage(&local),
        interop::upb::GetArena(&local));
  }

  template <typename Msg, typename Id>
  static absl::Status Set(Msg message, const Id& id, Ptr<const T> value) {
    return hpb::internal::SetExtension(
        interop::upb::GetMessage(message), interop::upb::GetArena(message),
        id.mini_table_ext(), interop::upb::GetMessage(value));
  }
};

// -------------------------------------------------------------------
// ExtensionIdentifier
// This is the type of actual extension objects.  E.g. if you have:
//   extend Foo {
//     optional MyExtension bar = 1234;
//   }
// then "bar" will be defined in C++ as:
//   ExtensionIdentifier<Foo, MyExtension> bar(&namespace_bar_ext);
template <typename ExtendeeType, typename ExtensionType>
class ExtensionIdentifier {
 public:
  using Extension = ExtensionType;
  using Extendee = ExtendeeType;

  // Placeholder for extant legacy callers, avoid use if possible
  const upb_MiniTableExtension* mini_table_ext() const {
    return mini_table_ext_;
  }

 private:
  constexpr explicit ExtensionIdentifier(
      const upb_MiniTableExtension* mte,
      typename UpbExtensionTrait<ExtensionType>::DefaultType val)
      : mini_table_ext_(mte), default_val_(val) {}

  constexpr uint32_t number() const {
    return upb_MiniTableExtension_Number(mini_table_ext_);
  }

  const upb_MiniTableExtension* mini_table_ext_;

  typename UpbExtensionTrait<ExtensionType>::ReturnType default_value() const {
    if constexpr (IsHpbClass<ExtensionType>) {
      return ExtensionType::default_instance();
    } else {
      return default_val_;
    }
  }

  typename UpbExtensionTrait<ExtensionType>::DefaultType default_val_;

  friend struct PrivateAccess;
};

upb_ExtensionRegistry* GetUpbExtensions(
    const ExtensionRegistry& extension_registry);

}  // namespace internal

class ExtensionRegistry {
 public:
  explicit ExtensionRegistry(const upb::Arena& arena)
      : registry_(upb_ExtensionRegistry_New(arena.ptr())) {}

  template <typename ExtensionIdentifier>
  void AddExtension(const ExtensionIdentifier& id) {
    if (registry_) {
      auto* extension = id.mini_table_ext();
      upb_ExtensionRegistryStatus status =
          upb_ExtensionRegistry_AddArray(registry_, &extension, 1);
      if (status != kUpb_ExtensionRegistryStatus_Ok) {
        registry_ = nullptr;
      }
    }
  }

  static const ExtensionRegistry& generated_registry() {
    static const ExtensionRegistry* r = NewGeneratedRegistry();
    return *r;
  }

  static const ExtensionRegistry& EmptyRegistry() {
    static const ExtensionRegistry* r = new ExtensionRegistry();
    return *r;
  }

 private:
  friend upb_ExtensionRegistry* ::hpb::internal::GetUpbExtensions(
      const ExtensionRegistry& extension_registry);
  upb_ExtensionRegistry* registry_;

  // TODO: b/379100963 - Introduce ShutdownHpbLibrary
  static const ExtensionRegistry* NewGeneratedRegistry() {
    static upb::Arena* global_arena = new upb::Arena();
    ExtensionRegistry* registry = new ExtensionRegistry(*global_arena);
    upb_ExtensionRegistry_AddAllLinkedExtensions(registry->registry_);
    return registry;
  }

  explicit ExtensionRegistry() = default;
};

template <typename T, typename Extendee, typename Extension,
          typename = hpb::internal::EnableIfHpbClassThatHasExtensions<T>>
ABSL_MUST_USE_RESULT bool HasExtension(
    Ptr<T> message,
    const ::hpb::internal::ExtensionIdentifier<Extendee, Extension>& id) {
  return ::hpb::internal::HasExtensionOrUnknown(
      hpb::interop::upb::GetMessage(message), id.mini_table_ext());
}

template <typename T, typename Extendee, typename Extension,
          typename = hpb::internal::EnableIfHpbClassThatHasExtensions<T>>
ABSL_MUST_USE_RESULT bool HasExtension(
    const T* message,
    const ::hpb::internal::ExtensionIdentifier<Extendee, Extension>& id) {
  return HasExtension(Ptr(message), id);
}

template <typename T, typename Extension,
          typename = hpb::internal::EnableIfHpbClassThatHasExtensions<T>,
          typename = hpb::internal::EnableIfMutableProto<T>>
void ClearExtension(
    Ptr<T> message,
    const ::hpb::internal::ExtensionIdentifier<T, Extension>& id) {
  static_assert(!std::is_const_v<T>, "");
  upb_Message_ClearExtension(hpb::interop::upb::GetMessage(message),
                             id.mini_table_ext());
}

template <typename T, typename Extension,
          typename = hpb::internal::EnableIfHpbClassThatHasExtensions<T>>
void ClearExtension(
    T* message, const ::hpb::internal::ExtensionIdentifier<T, Extension>& id) {
  ClearExtension(Ptr(message), id);
}

/**
 * Sets the extension to provided value.
 *
 * `message` is the model and may be passed in as a `T*` or a `Ptr<T>`.
 *
 * `id` is the ExtensionIdentifier provided by hpb gencode.
 *
 * `value` is the value to set the extension to.
 *  For message extension it can bind to `const Input&`, `Input&&`,
 *  or `Ptr<const Input>`.
 *  For rvalue references, if the arenas match, the extension is moved.
 *  If the arenas differ, a deep copy is performed.
 */
template <int&... DeductionBlocker, typename T, typename Extension,
          typename Input>
auto SetExtension(
    hpb::internal::PtrOrRawMutable<T> message,
    const internal::ExtensionIdentifier<internal::RemovePtrT<T>, Extension>& id,
    Input&& value)
    -> decltype(internal::UpbExtensionTrait<Extension>::Set(
        message, id, std::forward<Input>(value))) {
  return internal::UpbExtensionTrait<Extension>::Set(
      message, id, std::forward<Input>(value));
}

template <typename T, typename Extension,
          typename = hpb::internal::EnableIfHpbClassThatHasExtensions<T>,
          typename = hpb::internal::EnableIfMutableProto<T>>
void SetAliasExtension(
    Ptr<T> message,
    const ::hpb::internal::ExtensionIdentifier<T, Extension>& id,
    Ptr<Extension> value) {
  static_assert(!std::is_const_v<T>);
  auto* message_arena = hpb::interop::upb::GetArena(message);
  auto* extension_arena = hpb::interop::upb::GetArena(value);
  return ::hpb::internal::SetAliasExtension(
      hpb::interop::upb::GetMessage(message), message_arena,
      id.mini_table_ext(), hpb::interop::upb::GetMessage(value),
      extension_arena);
}

template <typename T, typename Extendee, typename Extension,
          typename = hpb::internal::EnableIfHpbClassThatHasExtensions<T>>
absl::StatusOr<typename internal::UpbExtensionTrait<Extension>::ReturnType>
GetExtension(
    Ptr<T> message,
    const ::hpb::internal::ExtensionIdentifier<Extendee, Extension>& id) {
  return hpb::internal::UpbExtensionTrait<Extension>::Get(message, id);
}

template <typename T, typename Extendee, typename Extension,
          typename = hpb::internal::EnableIfHpbClassThatHasExtensions<T>>
absl::StatusOr<typename internal::UpbExtensionTrait<Extension>::ReturnType>
GetExtension(
    const T* message,
    const hpb::internal::ExtensionIdentifier<Extendee, Extension>& id) {
  return GetExtension(Ptr(message), id);
}

template <typename T, typename Extension>
constexpr uint32_t ExtensionNumber(
    const internal::ExtensionIdentifier<T, Extension>& id) {
  return internal::PrivateAccess::GetExtensionNumber(id);
}

}  // namespace hpb

#endif  // GOOGLE_PROTOBUF_HPB_EXTENSION_H__