wibo/handles.h

#pragma once

#include "common.h"

#include <atomic>
#include <condition_variable>
#include <cstdint>
#include <shared_mutex>
#include <utility>
#include <vector>

enum class ObjectType : uint16_t {
	File,
	Mapped,
	Process,
	Token,
	Mutex,
	Event,
	Semaphore,
	Thread,
	Heap,
	RegistryKey,
};

struct ObjectHeader {
	const ObjectType type;
	std::atomic<uint32_t> pointerCount{1};
	std::atomic<uint32_t> handleCount{0};

	explicit ObjectHeader(ObjectType t) : type(t) {}
	virtual ~ObjectHeader() = default;

	[[nodiscard]] virtual bool isWaitable() const { return false; }
	virtual void onDestroy() {}
};

namespace detail {

inline void ref(ObjectHeader *o) { o->pointerCount.fetch_add(1, std::memory_order_acq_rel); }
inline void deref(ObjectHeader *o) {
	if (o->pointerCount.fetch_sub(1, std::memory_order_acq_rel) == 1) {
		o->onDestroy();
		delete o;
	}
}

} // namespace detail

struct WaitableObject : ObjectHeader {
	std::atomic<bool> signaled{false};
	std::mutex m;
	std::condition_variable_any cv;

	using ObjectHeader::ObjectHeader;
	[[nodiscard]] bool isWaitable() const override { return true; }
};

template <class T> struct Pin {
	enum class Tag { Acquire, Adopt };

	T *obj = nullptr;

	Pin() = default;
	Pin(T *o, Tag t) : obj(o) {
		if (obj && t == Tag::Acquire) {
			detail::ref(obj);
		}
	}

	static Pin acquire(ObjectHeader *o) { return {o, Tag::Acquire}; }
	static Pin adopt(ObjectHeader *o) { return {o, Tag::Adopt}; }

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

	Pin(Pin &&other) noexcept : obj(std::exchange(other.obj, nullptr)) {}
	Pin &operator=(Pin &&other) noexcept {
		if (this != &other) {
			reset();
			obj = std::exchange(other.obj, nullptr);
		}
		return *this;
	}

	~Pin() { reset(); }

	ObjectHeader *release() { return std::exchange(obj, nullptr); }
	void reset() {
		if (obj) {
			detail::deref(obj);
			obj = nullptr;
		}
	}

	T *operator->() const { return obj; }
	T &operator*() const { return *obj; }
	[[nodiscard]] T *get() const { return obj; }
	explicit operator bool() const { return obj != nullptr; }

	template <typename U> Pin<U> downcast() && {
		if (obj && obj->type == U::kType) {
			auto *u = static_cast<U *>(obj);
			obj = nullptr;
			return Pin<U>::adopt(u);
		}
		return Pin<U>{};
	}
};

constexpr DWORD HANDLE_FLAG_INHERIT = 0x1;
constexpr DWORD HANDLE_FLAG_PROTECT_FROM_CLOSE = 0x2;

constexpr DWORD DUPLICATE_CLOSE_SOURCE = 0x1;
constexpr DWORD DUPLICATE_SAME_ACCESS = 0x2;

struct HandleMeta {
	uint32_t grantedAccess;	  // effective access mask for this handle
	uint32_t flags;			  // inherit/protect/etc
	ObjectType typeCache;	  // cached ObjectType for fast getAs
	uint16_t generation;	  // must match handle’s generation
};

// template <typename T>
// struct HandleRef {
// 	Pin<T> obj;
// 	HandleMeta meta;

// 	HandleRef() = default;
// 	HandleRef(Pin<T> o, HandleMeta m) : obj(std::move(o)), meta(m) {}

// 	explicit operator bool() const { return obj.operator bool(); }
// };

class HandleTable {
  public:
	HANDLE create(ObjectHeader *obj, uint32_t grantedAccess, uint32_t flags);
	bool close(HANDLE h);
	bool get(HANDLE h, Pin<ObjectHeader> &pinOut, HandleMeta *metaOut = nullptr);
	template <typename T> Pin<T> getAs(HANDLE h, HandleMeta *metaOut = nullptr) {
		static_assert(std::is_base_of_v<ObjectHeader, T>, "T must derive from ObjectHeader");
		Pin<ObjectHeader> pin;
		HandleMeta metaOutLocal{};
		if (!metaOut) {
			metaOut = &metaOutLocal;
		}
		if (!get(h, pin, metaOut)) {
			return {};
		}
		if constexpr (std::is_same_v<T, ObjectHeader>) {
			return std::move(pin);
		} else if (metaOut->typeCache != T::kType || pin->type != T::kType) {
			return {};
		} else {
			// Cast directly to T* and transfer ownership to Pin<T>
			return Pin<T>::adopt(static_cast<T *>(pin.release()));
		}
	}
	bool setInformation(HANDLE h, uint32_t mask, uint32_t value);
	bool getInformation(HANDLE h, uint32_t *outFlags) const;
	bool duplicateTo(HANDLE src, HandleTable &dst, HANDLE *out, uint32_t desiredAccess, bool inherit, uint32_t options);

  private:
	struct HandleEntry {
		struct ObjectHeader *obj;
		HandleMeta meta;
	};

	std::vector<HandleEntry> slots_;
	std::vector<uint32_t> freeList_;
	mutable std::shared_mutex mu_;
};

namespace wibo {
extern HandleTable &handles();
}