/*
 *  Chocobo1/Hash
 *
 *   Copyright 2017-2020 by Mike Tzou (Chocobo1)
 *     https://github.com/Chocobo1/Hash
 *
 *   Licensed under GNU General Public License 3 or later.
 *
 *  @license GPL3 <https://www.gnu.org/licenses/gpl-3.0-standalone.html>
 */

#ifndef CHOCOBO1_SHA2_384_H
#define CHOCOBO1_SHA2_384_H

#include <array>
#include <cassert>
#include <climits>
#include <cmath>
#include <cstdint>
#include <initializer_list>
#include <string>
#include <type_traits>
#include <vector>

#if (__cplusplus > 201703L)
#include <version>
#endif

#ifndef USE_STD_SPAN_CHOCOBO1_HASH
#if (__cpp_lib_span >= 202002L)
#define USE_STD_SPAN_CHOCOBO1_HASH 1
#else
#define USE_STD_SPAN_CHOCOBO1_HASH 0
#endif
#endif

#if (USE_STD_SPAN_CHOCOBO1_HASH == 1)
#include <span>
#else
#include "gsl/span"
#endif


namespace Chocobo1
{
	// Use these!!
	// SHA2_384();
}


namespace Chocobo1
{
// users should ignore things in this namespace

namespace Hash
{
#ifndef CONSTEXPR_CPP17_CHOCOBO1_HASH
#if __cplusplus >= 201703L
#define CONSTEXPR_CPP17_CHOCOBO1_HASH constexpr
#else
#define CONSTEXPR_CPP17_CHOCOBO1_HASH
#endif
#endif

#if (USE_STD_SPAN_CHOCOBO1_HASH == 1)
	using IndexType = std::size_t;
#else
	using IndexType = gsl::index;
#endif

#ifndef CHOCOBO1_HASH_BUFFER_IMPL
#define CHOCOBO1_HASH_BUFFER_IMPL
	template <typename T, IndexType N>
	class Buffer
	{
		public:
			using value_type = T;
			using index_type = IndexType;
			using size_type = std::size_t;

			constexpr Buffer() = default;
			constexpr Buffer(const Buffer &) = default;

			CONSTEXPR_CPP17_CHOCOBO1_HASH Buffer(const std::initializer_list<T> initList)
			{
#if !defined(NDEBUG)
				// check if out-of-bounds
				static_cast<void>(m_array.at(m_dataEndIdx + initList.size() - 1));
#endif

				for (const auto &i : initList)
				{
					m_array[m_dataEndIdx] = i;
					++m_dataEndIdx;
				}
			}

			template <typename InputIt>
			constexpr Buffer(const InputIt first, const InputIt last)
			{
				for (InputIt iter = first; iter != last; ++iter)
				{
					this->fill(*iter);
				}
			}

			constexpr T& operator[](const index_type pos)
			{
				return m_array[pos];
			}

			constexpr T operator[](const index_type pos) const
			{
				return m_array[pos];
			}

			CONSTEXPR_CPP17_CHOCOBO1_HASH void fill(const T &value, const index_type count = 1)
			{
#if !defined(NDEBUG)
				// check if out-of-bounds
				static_cast<void>(m_array.at(m_dataEndIdx + count - 1));
#endif

				for (index_type i = 0; i < count; ++i)
				{
					m_array[m_dataEndIdx] = value;
					++m_dataEndIdx;
				}
			}

			template <typename InputIt>
			constexpr void push_back(const InputIt first, const InputIt last)
			{
				for (InputIt iter = first; iter != last; ++iter)
				{
					this->fill(*iter);
				}
			}

			constexpr void clear()
			{
				m_array = {};
				m_dataEndIdx = 0;
			}

			constexpr bool empty() const
			{
				return (m_dataEndIdx == 0);
			}

			constexpr size_type size() const
			{
				return m_dataEndIdx;
			}

			constexpr const T* data() const
			{
				return m_array.data();
			}

		private:
			std::array<T, N> m_array {};
			index_type m_dataEndIdx = 0;
	};
#endif

#ifndef CHOCOBO1_HASH_UINT128_IMPL
#define CHOCOBO1_HASH_UINT128_IMPL
	class Uint128
	{
		public:
			constexpr Uint128()
				: m_lo(0), m_hi(0)
			{
			}

			constexpr Uint128& operator= (const uint64_t n)
			{
				this->m_lo = n;
				this->m_hi = 0;
				return (*this);
			}

			constexpr Uint128 operator+ (const uint64_t n)
			{
				Uint128 ret = *this;
				ret += n;
				return ret;
			}

			constexpr Uint128& operator* (const unsigned int n)
			{
				// only handle `*8` case
				assert(n == 8);

				const uint8_t msb = static_cast<uint8_t>(m_lo >> 61);
				m_hi = (m_hi << 3) | msb;
				m_lo = m_lo << 3;

				return (*this);
			}

			constexpr Uint128& operator+= (const uint64_t n)
			{
				const uint64_t newLo = (m_lo + n);
				if (newLo < m_lo)
					++m_hi;
				m_lo = newLo;

				return (*this);
			}

			constexpr uint64_t low() const
			{
				return m_lo;
			}

			constexpr uint64_t high() const
			{
				return m_hi;
			}

		private:
			uint64_t m_lo;
			uint64_t m_hi;
	};
#endif


namespace SHA2_384_NS
{
	class SHA2_384
	{
		// https://tools.ietf.org/html/rfc6234

		public:
			using Byte = uint8_t;
			using ResultArrayType = std::array<Byte, 48>;

#if (USE_STD_SPAN_CHOCOBO1_HASH == 1)
			template <typename T, std::size_t Extent = std::dynamic_extent>
			using Span = std::span<T, Extent>;
#else
			template <typename T, std::size_t Extent = gsl::dynamic_extent>
			using Span = gsl::span<T, Extent>;
#endif


			constexpr SHA2_384();

			constexpr void reset();
			CONSTEXPR_CPP17_CHOCOBO1_HASH SHA2_384& finalize();  // after this, only `toArray()`, `toString()`, `toVector()`, `reset()` are available

			std::string toString() const;
			std::vector<Byte> toVector() const;
			CONSTEXPR_CPP17_CHOCOBO1_HASH ResultArrayType toArray() const;

			CONSTEXPR_CPP17_CHOCOBO1_HASH SHA2_384& addData(const Span<const Byte> inData);
			CONSTEXPR_CPP17_CHOCOBO1_HASH SHA2_384& addData(const void *ptr, const std::size_t length);
			template <std::size_t N>
			CONSTEXPR_CPP17_CHOCOBO1_HASH SHA2_384& addData(const Byte (&array)[N]);
			template <typename T, std::size_t N>
			SHA2_384& addData(const T (&array)[N]);
			template <typename T>
			SHA2_384& addData(const Span<T> inSpan);

		private:
			CONSTEXPR_CPP17_CHOCOBO1_HASH void addDataImpl(const Span<const Byte> data);

			static constexpr int BLOCK_SIZE = 128;

			Buffer<Byte, (BLOCK_SIZE * 2)> m_buffer;  // x2 for paddings
			Uint128 m_sizeCounter;

			uint64_t m_h[8] = {};

			static constexpr uint64_t kTable[80] =
			{
				0x428a2f98d728ae22, 0x7137449123ef65cd, 0xb5c0fbcfec4d3b2f, 0xe9b5dba58189dbbc,
				0x3956c25bf348b538, 0x59f111f1b605d019, 0x923f82a4af194f9b, 0xab1c5ed5da6d8118,
				0xd807aa98a3030242, 0x12835b0145706fbe, 0x243185be4ee4b28c, 0x550c7dc3d5ffb4e2,
				0x72be5d74f27b896f, 0x80deb1fe3b1696b1, 0x9bdc06a725c71235, 0xc19bf174cf692694,
				0xe49b69c19ef14ad2, 0xefbe4786384f25e3, 0x0fc19dc68b8cd5b5, 0x240ca1cc77ac9c65,
				0x2de92c6f592b0275, 0x4a7484aa6ea6e483, 0x5cb0a9dcbd41fbd4, 0x76f988da831153b5,
				0x983e5152ee66dfab, 0xa831c66d2db43210, 0xb00327c898fb213f, 0xbf597fc7beef0ee4,
				0xc6e00bf33da88fc2, 0xd5a79147930aa725, 0x06ca6351e003826f, 0x142929670a0e6e70,
				0x27b70a8546d22ffc, 0x2e1b21385c26c926, 0x4d2c6dfc5ac42aed, 0x53380d139d95b3df,
				0x650a73548baf63de, 0x766a0abb3c77b2a8, 0x81c2c92e47edaee6, 0x92722c851482353b,
				0xa2bfe8a14cf10364, 0xa81a664bbc423001, 0xc24b8b70d0f89791, 0xc76c51a30654be30,
				0xd192e819d6ef5218, 0xd69906245565a910, 0xf40e35855771202a, 0x106aa07032bbd1b8,
				0x19a4c116b8d2d0c8, 0x1e376c085141ab53, 0x2748774cdf8eeb99, 0x34b0bcb5e19b48a8,
				0x391c0cb3c5c95a63, 0x4ed8aa4ae3418acb, 0x5b9cca4f7763e373, 0x682e6ff3d6b2b8a3,
				0x748f82ee5defb2fc, 0x78a5636f43172f60, 0x84c87814a1f0ab72, 0x8cc702081a6439ec,
				0x90befffa23631e28, 0xa4506cebde82bde9, 0xbef9a3f7b2c67915, 0xc67178f2e372532b,
				0xca273eceea26619c, 0xd186b8c721c0c207, 0xeada7dd6cde0eb1e, 0xf57d4f7fee6ed178,
				0x06f067aa72176fba, 0x0a637dc5a2c898a6, 0x113f9804bef90dae, 0x1b710b35131c471b,
				0x28db77f523047d84, 0x32caab7b40c72493, 0x3c9ebe0a15c9bebc, 0x431d67c49c100d4c,
				0x4cc5d4becb3e42b6, 0x597f299cfc657e2a, 0x5fcb6fab3ad6faec, 0x6c44198c4a475817
			};
	};

	constexpr uint64_t SHA2_384::kTable[80];


	// helpers
	template <typename T>
	class Loader
	{
		// this class workaround loading data from unaligned memory boundaries
		// also eliminate endianness issues
		public:
			explicit constexpr Loader(const uint8_t *ptr)
				: m_ptr(ptr)
			{
			}

			constexpr T operator[](const IndexType idx) const
			{
				static_assert(std::is_same<T, uint64_t>::value, "");
				// handle specific endianness here
				const uint8_t *ptr = m_ptr + (sizeof(T) * idx);
				return  ( (static_cast<T>(*(ptr + 0)) << 56)
						| (static_cast<T>(*(ptr + 1)) << 48)
						| (static_cast<T>(*(ptr + 2)) << 40)
						| (static_cast<T>(*(ptr + 3)) << 32)
						| (static_cast<T>(*(ptr + 4)) << 24)
						| (static_cast<T>(*(ptr + 5)) << 16)
						| (static_cast<T>(*(ptr + 6)) <<  8)
						| (static_cast<T>(*(ptr + 7)) <<  0));
			}

		private:
			const uint8_t *m_ptr;
	};

	template <typename R, typename T>
	constexpr R ror(const T x, const unsigned int s)
	{
		static_assert(std::is_unsigned<R>::value, "");
		static_assert(std::is_unsigned<T>::value, "");
		return static_cast<R>(x >> s);
	}

	template <typename T>
	constexpr T rotr(const T x, const unsigned int s)
	{
		static_assert(std::is_unsigned<T>::value, "");
		if (s == 0)
			return x;
		return ((x >> s) | (x << ((sizeof(T) * 8) - s)));
	}


	//
	constexpr SHA2_384::SHA2_384()
	{
		static_assert((CHAR_BIT == 8), "Sorry, we don't support exotic CPUs");
		reset();
	}

	constexpr void SHA2_384::reset()
	{
		m_buffer.clear();
		m_sizeCounter = 0;

		m_h[0] = 0xcbbb9d5dc1059ed8;
		m_h[1] = 0x629a292a367cd507;
		m_h[2] = 0x9159015a3070dd17;
		m_h[3] = 0x152fecd8f70e5939;
		m_h[4] = 0x67332667ffc00b31;
		m_h[5] = 0x8eb44a8768581511;
		m_h[6] = 0xdb0c2e0d64f98fa7;
		m_h[7] = 0x47b5481dbefa4fa4;
	}

	CONSTEXPR_CPP17_CHOCOBO1_HASH SHA2_384& SHA2_384::finalize()
	{
		m_sizeCounter += m_buffer.size();

		// append 1 bit
		m_buffer.fill(1 << 7);

		// append paddings
		const auto len = static_cast<int>(((2 * BLOCK_SIZE) - (m_buffer.size() + 16)) % BLOCK_SIZE);
		m_buffer.fill(0, (len + 16));

		// append size in bits
		const Uint128 sizeCounterBits = m_sizeCounter * 8;
		const uint64_t sizeCounterBitsL = sizeCounterBits.low();
		const uint64_t sizeCounterBitsH = sizeCounterBits.high();
		for (int i = 0; i < 8; ++i)
		{
			m_buffer[m_buffer.size() - 16 + i] = ror<Byte>(sizeCounterBitsH, (8 * (7 - i)));
			m_buffer[m_buffer.size() - 8 + i] = ror<Byte>(sizeCounterBitsL, (8 * (7 - i)));
		}

		addDataImpl({m_buffer.data(), m_buffer.size()});
		m_buffer.clear();

		return (*this);
	}

	std::string SHA2_384::toString() const
	{
		const auto a = toArray();
		std::string ret;
		ret.resize(2 * a.size());

		auto retPtr = &ret.front();
		for (const auto c : a)
		{
			const Byte upper = ror<Byte>(c, 4);
			*(retPtr++) = static_cast<char>((upper < 10) ? (upper + '0') : (upper - 10 + 'a'));

			const Byte lower = c & 0xf;
			*(retPtr++) = static_cast<char>((lower < 10) ? (lower + '0') : (lower - 10 + 'a'));
		}

		return ret;
	}

	std::vector<SHA2_384::Byte> SHA2_384::toVector() const
	{
		const auto a = toArray();
		return {a.begin(), a.end()};
	}

	CONSTEXPR_CPP17_CHOCOBO1_HASH SHA2_384::ResultArrayType SHA2_384::toArray() const
	{
		const Span<const uint64_t> state(std::begin(m_h), (std::end(m_h) - 2));
		const int dataSize = sizeof(decltype(state)::value_type);

		ResultArrayType ret {};
		auto retPtr = ret.data();
		for (const auto i : state)
		{
			for (int j = (dataSize - 1); j >= 0; --j)
				*(retPtr++) = ror<Byte>(i, (j * 8));
		}

		return ret;
	}

	CONSTEXPR_CPP17_CHOCOBO1_HASH SHA2_384& SHA2_384::addData(const Span<const Byte> inData)
	{
		Span<const Byte> data = inData;

		if (!m_buffer.empty())
		{
			const size_t len = std::min<size_t>((BLOCK_SIZE - m_buffer.size()), data.size());  // try fill to BLOCK_SIZE bytes
			m_buffer.push_back(data.begin(), (data.begin() + len));

			if (m_buffer.size() < BLOCK_SIZE)  // still doesn't fill the buffer
				return (*this);

			addDataImpl({m_buffer.data(), m_buffer.size()});
			m_buffer.clear();

			data = data.subspan(len);
		}

		const size_t dataSize = data.size();
		if (dataSize < BLOCK_SIZE)
		{
			m_buffer = {data.begin(), data.end()};
			return (*this);
		}

		const size_t len = dataSize - (dataSize % BLOCK_SIZE);  // align on BLOCK_SIZE bytes
		addDataImpl(data.first(len));

		if (len < dataSize)  // didn't consume all data
			m_buffer = {(data.begin() + len), data.end()};

		return (*this);
	}

	CONSTEXPR_CPP17_CHOCOBO1_HASH SHA2_384& SHA2_384::addData(const void *ptr, const std::size_t length)
	{
		// Span::size_type = std::size_t
		return addData({static_cast<const Byte*>(ptr), length});
	}

	template <std::size_t N>
	CONSTEXPR_CPP17_CHOCOBO1_HASH SHA2_384& SHA2_384::addData(const Byte (&array)[N])
	{
		return addData({array, N});
	}

	template <typename T, std::size_t N>
	SHA2_384& SHA2_384::addData(const T (&array)[N])
	{
		return addData({reinterpret_cast<const Byte*>(array), (sizeof(T) * N)});
	}

	template <typename T>
	SHA2_384& SHA2_384::addData(const Span<T> inSpan)
	{
		return addData({reinterpret_cast<const Byte*>(inSpan.data()), inSpan.size_bytes()});
	}

	CONSTEXPR_CPP17_CHOCOBO1_HASH void SHA2_384::addDataImpl(const Span<const Byte> data)
	{
		assert((data.size() % BLOCK_SIZE) == 0);

		m_sizeCounter += data.size();

		for (size_t iter = 0, iend = static_cast<size_t>(data.size() / BLOCK_SIZE); iter < iend; ++iter)
		{
			const Loader<uint64_t> m(static_cast<const Byte *>(data.data() + (iter * BLOCK_SIZE)));

			// TODO: kTable was here, move it back when static variable in constexpr function is allowed

			const auto ssig0 = [](const uint64_t x) -> uint64_t
			{
				return (rotr(x, 1) ^ rotr(x, 8) ^ ror<uint64_t>(x, 7));
			};
			const auto ssig1 = [](const uint64_t x) -> uint64_t
			{
				return (rotr(x, 19) ^ rotr(x, 61) ^ ror<uint64_t>(x, 6));
			};
			uint64_t wTable[80] {};
			for (int t = 0; t < 16; ++t)
				wTable[t] = m[t];
			for (int t = 16; t < 80; ++t)
				wTable[t] = ssig1(wTable[t - 2]) + wTable[t - 7] + ssig0(wTable[t - 15]) + wTable[t - 16];

			uint64_t a = m_h[0];
			uint64_t b = m_h[1];
			uint64_t c = m_h[2];
			uint64_t d = m_h[3];
			uint64_t e = m_h[4];
			uint64_t f = m_h[5];
			uint64_t g = m_h[6];
			uint64_t h = m_h[7];

			const auto round = [&wTable](uint64_t &a, uint64_t &b, uint64_t &c, uint64_t &d, uint64_t &e, uint64_t &f, uint64_t &g, uint64_t &h, const unsigned int t) -> void
			{
				const auto ch = [](const uint64_t x, const uint64_t y, const uint64_t z) -> uint64_t
				{
					return ((x & (y ^ z)) ^ z);  // alternative
				};
				const auto maj = [](const uint64_t x, const uint64_t y, const uint64_t z) -> uint64_t
				{
					return ((x & (y | z)) | (y & z));  // alternative
				};
				const auto bsig0 = [](const uint64_t x) -> uint64_t
				{
					return (rotr(x, 28) ^ rotr(x, 34) ^ rotr(x, 39));
				};
				const auto bsig1 = [](const uint64_t x) -> uint64_t
				{
					return (rotr(x, 14) ^ rotr(x, 18) ^ rotr(x, 41));
				};

				const uint64_t t1 = h + bsig1(e) + ch(e, f, g) + kTable[t] + wTable[t];
				const uint64_t t2 = bsig0(a) + maj(a, b, c);

				h = t1;
				d += h;
				h += t2;
			};
			for (int t = 0; t < 10; ++t)
			{
				round(a, b, c, d, e, f, g, h, (8 * t) + 0);
				round(h, a, b, c, d, e, f, g, (8 * t) + 1);
				round(g, h, a, b, c, d, e, f, (8 * t) + 2);
				round(f, g, h, a, b, c, d, e, (8 * t) + 3);
				round(e, f, g, h, a, b, c, d, (8 * t) + 4);
				round(d, e, f, g, h, a, b, c, (8 * t) + 5);
				round(c, d, e, f, g, h, a, b, (8 * t) + 6);
				round(b, c, d, e, f, g, h, a, (8 * t) + 7);
			}

			m_h[0] += a;
			m_h[1] += b;
			m_h[2] += c;
			m_h[3] += d;
			m_h[4] += e;
			m_h[5] += f;
			m_h[6] += g;
			m_h[7] += h;
		}
	}
}
}
	using SHA2_384 = Hash::SHA2_384_NS::SHA2_384;
}

#endif  // CHOCOBO1_SHA2_384_H
