#pragma once

#include <exception>
#include <string>

#include "Platform.h"
#include "types.h"

namespace fmt
{
	template<typename... Args>
	static std::string format(const char*, const Args&...);
}

template<typename T, typename>
struct fmt_unveil
{
	static_assert(sizeof(T) > 0, "fmt_unveil<>: cannot pass forward-declared object");

	using type = T;

	static inline u64 get(const T& arg)
	{
		return reinterpret_cast<std::uintptr_t>(&arg);
	}
};

template<typename T>
struct fmt_unveil<T, std::enable_if_t<std::is_integral<T>::value && sizeof(T) <= 8 && alignof(T) <= 8>>
{
	using type = T;

	static inline u64 get(T arg)
	{
		return static_cast<T>(arg);
	}
};

template<typename T>
struct fmt_unveil<T, std::enable_if_t<std::is_floating_point<T>::value && sizeof(T) <= 8 && alignof(T) <= 8>>
{
	using type = T;

	// Convert FP to f64 and reinterpret (TODO?)
	static inline u64 get(f64 arg)
	{
		return reinterpret_cast<u64&>(arg);
	}
};

template<typename T>
struct fmt_unveil<T, std::enable_if_t<std::is_enum<T>::value>>
{
	using type = T;

	static inline u64 get(T arg)
	{
		return static_cast<std::underlying_type_t<T>>(arg);
	}
};

template<typename T>
struct fmt_unveil<T*, void>
{
	using type = const T*;

	static inline u64 get(const T* arg)
	{
		return reinterpret_cast<std::uintptr_t>(arg);
	}
};

template<typename T, std::size_t N>
struct fmt_unveil<T[N], void>
{
	using type = const T*;

	static inline u64 get(const T* arg)
	{
		return reinterpret_cast<std::uintptr_t>(arg);
	}
};

template<>
struct fmt_unveil<b8, void>
{
	using type = bool;

	static inline u64 get(const b8& value)
	{
		return fmt_unveil<bool>::get(value);
	}
};

// String type format provider, also type classifier (format() called if an argument is formatted as "%s")
template<typename T, typename = void>
struct fmt_class_string
{
	// Formatting function (must be explicitly specialized)
	static void format(std::string& out, u64 arg);

	// Helper typedef (visible in format())
	using type = T;

	// Helper function (converts arg to object reference)
	static SAFE_BUFFERS FORCE_INLINE const T& get_object(u64 arg)
	{
		return *reinterpret_cast<const T*>(static_cast<std::uintptr_t>(arg));
	}

	// Helper function (safely converts arg to enum value)
	static SAFE_BUFFERS FORCE_INLINE void format_enum(std::string& out, u64 arg, const char*(*get)(T value))
	{
		const auto value = static_cast<std::underlying_type_t<T>>(arg);

		// Check narrowing
		if (static_cast<u64>(value) == arg)
		{
			if (const char* str = get(static_cast<T>(value)))
			{
				out += str;
				return;
			}
		}

		// Fallback to underlying type formatting
		fmt_class_string<std::underlying_type_t<T>>::format(out, static_cast<u64>(value));
	}

	// Helper constant (may be used in format_enum as lambda return value)
	static constexpr const char* unknown = nullptr;
};

template<>
struct fmt_class_string<const void*, void>
{
	static void format(std::string& out, u64 arg);
};

template<typename T>
struct fmt_class_string<T*, void> : fmt_class_string<const void*, void>
{
	// Classify all pointers as const void*
};

template<>
struct fmt_class_string<const char*, void>
{
	static void format(std::string& out, u64 arg);
};

template<>
struct fmt_class_string<char*, void> : fmt_class_string<const char*>
{
	// Classify char* as const char*
};

struct fmt_type_info
{
	decltype(&fmt_class_string<int>::format) fmt_string;

	template<typename T>
	static constexpr fmt_type_info make()
	{
		return fmt_type_info
		{
			&fmt_class_string<T>::format,
		};
	}

	template<typename... Args>
	static inline const fmt_type_info* get()
	{
		// Constantly initialized null-terminated list of type-specific information
		static constexpr fmt_type_info result[sizeof...(Args) + 1]
		{
			make<Args>()...
		};

		return result;
	}
};

template<typename Arg>
using fmt_unveil_t = typename fmt_unveil<Arg>::type;

// Argument array type (each element generated via fmt_unveil<>)
template<typename... Args>
using fmt_args_t = const u64(&&)[sizeof...(Args) + 1];

namespace fmt
{
	// Internal formatting function
	void raw_append(std::string& out, const char*, const fmt_type_info*, const u64*) noexcept;

	// Formatting function
	template<typename... Args>
	static SAFE_BUFFERS void append(std::string& out, const char* fmt, const Args&... args)
	{
		raw_append(out, fmt, fmt_type_info::get<fmt_unveil_t<Args>...>(), fmt_args_t<Args...>{fmt_unveil<Args>::get(args)...});
	}

	// Formatting function
	template<typename... Args>
	static SAFE_BUFFERS std::string format(const char* fmt, const Args&... args)
	{
		std::string result;
		append<Args...>(result, fmt, args...);
		return result;
	}

	// Internal helper function
	char* alloc_format(const char*, const fmt_type_info*, const u64*) noexcept;

	// Exception type with formatting constructor
	template<typename Base>
	class exception_t : public Base
	{
		using base = Base;

	public:
		template<typename... Args>
		SAFE_BUFFERS exception_t(const char* fmt, const Args&... args)
			: base((fmt = alloc_format(fmt, fmt_type_info::get<fmt_unveil_t<Args>...>(), fmt_args_t<Args...>{fmt_unveil<Args>::get(args)...})))
		{
			std::free(const_cast<char*>(fmt));
		}
	};

	// Exception type derived from std::runtime_error with formatting constructor
	using exception = exception_t<std::runtime_error>;
}