#ifndef UTIL_H
#define UTIL_H

#include <cassert>
#include <cstring>
#include <memory>
#include <stdexcept>
#include <string>
#include <type_traits>
#include <windows.h>

#define CONCAT_IMPL(a, b) a##b
#define CONCAT(a, b) CONCAT_IMPL(a, b)
#define _ CONCAT(unused_, __LINE__)

/* Scope guard. */
template <typename F>
struct Finally
{
	F f;
	inline Finally(F f) noexcept : f(f) {}
	inline ~Finally() { f(); }
};
#define FINALLY Finally _ = [=]()

/* Unique is similar to unique_ptr, but it is designed for pointers
 * and handles of type T, where T is not an RAII class. Further, the
 * managed object is assumed to be in an invalid state until checked
 * with Good or Bad. Upon destruction, the object, if valid, is passed
 * to a given destructor function F. */
template <typename T, auto F>
struct Unique
{
	union { T v; };
	bool ok = false;
	Unique() noexcept {}
	Unique(T v) noexcept : v(v) {}
	Unique& operator =(T v_) noexcept
	{
		Destroy();
		v = v_;
		ok = false;
		return *this;
	}
	Unique(Unique&& other) noexcept : v(std::move(other.v)), ok(other.ok)
	{
		other.ok = false;
	}
	Unique& operator =(Unique&& other) noexcept
	{
		Destroy();
		v = std::move(other.v);
		ok = other.ok;
		other.ok = false;
		return *this;
	}
	bool Good(T u) noexcept
	{
		return !(ok = v == u);
	}
	bool Bad(T u) noexcept
	{
		return !(ok = v != u);
	}
	template <typename, auto> class UniqueOk;
	template <auto E>
	UniqueOk<T, F> ThrowIf(T u) noexcept
	{
		if (v == u)
			throw E;
		return std::move(*this);
	}
	~Unique()
	{
		Destroy();
	}
private:
	void Destroy()
	{
		if (ok) {
			if constexpr (F) F(v);
			v.~T();
		}
	}
};

/* UniqueOk contains a Unique that has already been validated. */
template <typename T, auto F>
struct UniqueOk
{
	T v;
	UniqueOk(Unique<T, F>&& u) : v(std::move(u.v))
	{
		assert(u.ok);
		u.ok = false;
	}
	UniqueOk& operator =(Unique<T, F>&& u)
	{
		assert(u.ok);
		F(v);
		v = std::move(u.v);
		u.ok = false;
		return *this;
	}
	~UniqueOk()
	{
		F(v);
	}
};

/* Buf is a span-like structure of a buffer and its size. */
template <typename T>
struct Buf
{
	using U = std::remove_const_t<T>;

	T* data;
	size_t c;

	Buf(T* data, size_t c) noexcept : data(data), c(c) {}
	Buf(std::enable_if<!std::is_same_v<T, U>, U*> data, size_t c) noexcept
		: data(data), c(c) {}

	Buf(std::basic_string<U>& s) noexcept : data(s.data()), c(s.capacity()+1) {}

	template <size_t N> inline Buf(T (&data)[N]) noexcept : data(data), c(N) {}

	operator T*() const noexcept { return data; }
	T& operator *() const noexcept { return *data; }
	T& operator [](size_t i) const noexcept { return data[i]; }
	Buf<T> operator +(size_t i) const noexcept { return {data+i, c-i}; }
	//T operator -(size_t i) { return {data-i, c+i}; }
};

inline int Cmp(const int a, const int b)
{
	if (a == b) return 0;
	if (a > b) return 1;
	return -1;
}

inline size_t Min(size_t a, size_t b)
{
	return a < b? a: b;
}

template <typename T, size_t N>
inline size_t Len(T (&)[N])
{
	return N-1;
}

template <typename T>
inline size_t Len(Buf<T> buf)
{
	return buf.c-1;
}

/* Format wide string. */
template<typename... T>
inline std::enable_if_t<!std::disjunction_v<std::is_class<T>...>, int>
Swprintf(Buf<wchar_t> buf, const wchar_t* const fmt, T... xs)
{
	return _snwprintf_s(buf, buf.c, _TRUNCATE, fmt, xs...);
}

/* Format static narrow string. */
template<typename... T>
inline std::enable_if_t<!std::disjunction_v<std::is_class<T>...>, int>
Sprintf(Buf<char> buf, const char* const fmt, T... xs)
{
	return _snprintf_s(buf, buf.c, _TRUNCATE, fmt, xs...);
}

/* Copy to static wide string buffer. */
inline wchar_t* Wcscpy(Buf<wchar_t> dst, const wchar_t* const src)
{
	const size_t len = Min(dst.c, wcslen(src)+1);
	memcpy(dst, src, len*sizeof(wchar_t));
	dst[len-1] = 0;
	return dst;
}

/* Copy to static narrow string buffer. */
inline char* Strcpy(Buf<char> dst, const char* const src)
{
	const size_t len = Min(dst.c, strlen(src)+1);
	memcpy(dst, src, len);
	dst[len-1] = 0;
	return dst;
}

#endif