#pragma once

#include <array>
#include <string>
#include <vector>
#include <cstring>

class SHA512 {
private:
	static constexpr std::array<uint64_t, 8> H0 = {
		0x6a09e667f3bcc908, 0xbb67ae8584caa73b, 0x3c6ef372fe94f82b, 0xa54ff53a5f1d36f1,
		0x510e527fade682d1, 0x9b05688c2b3e6c1f, 0x1f83d9abfb41bd6b, 0x5be0cd19137e2179
	};

	static constexpr std::array<uint64_t, 80> K = {
		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
	};

	std::array<uint64_t, 8> hash;
	std::vector<uint8_t> buffer;
	uint64_t totalLength = 0;

	static uint64_t rotr(uint64_t x, int n) {
		return (x >> n) | (x << (64 - n));
	}

	static uint64_t ch(uint64_t x, uint64_t y, uint64_t z) {
		return (x & y) ^ (~x & z);
	}

	static uint64_t maj(uint64_t x, uint64_t y, uint64_t z) {
		return (x & y) ^ (x & z) ^ (y & z);
	}

	static uint64_t sigma0(uint64_t x) {
		return rotr(x, 28) ^ rotr(x, 34) ^ rotr(x, 39);
	}

	static uint64_t sigma1(uint64_t x) {
		return rotr(x, 14) ^ rotr(x, 18) ^ rotr(x, 41);
	}

	static uint64_t gamma0(uint64_t x) {
		return rotr(x, 1) ^ rotr(x, 8) ^ (x >> 7);
	}

	static uint64_t gamma1(uint64_t x) {
		return rotr(x, 19) ^ rotr(x, 61) ^ (x >> 6);
	}

	void processChunk(const uint8_t* chunk) {
		std::array<uint64_t, 80> w;
		
		for (int i = 0; i < 16; i++) {
			w[i] = 0;
			for (int j = 0; j < 8; j++) {
				w[i] = (w[i] << 8) | chunk[i * 8 + j];
			}
		}

		for (int i = 16; i < 80; i++) {
			w[i] = gamma1(w[i-2]) + w[i-7] + gamma0(w[i-15]) + w[i-16];
		}

		auto [a, b, c, d, e, f, g, h] = hash;

		for (int i = 0; i < 80; i++) {
			uint64_t t1 = h + sigma1(e) + ch(e, f, g) + K[i] + w[i];
			uint64_t t2 = sigma0(a) + maj(a, b, c);
			h = g;
			g = f;
			f = e;
			e = d + t1;
			d = c;
			c = b;
			b = a;
			a = t1 + t2;
		}

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

public:
	SHA512() : hash(H0) {}

	void update(const void* data, size_t length) {
		const uint8_t* bytes = static_cast<const uint8_t*>(data);
		totalLength += length;

		buffer.insert(buffer.end(), bytes, bytes + length);

		while (buffer.size() >= 128) {
			processChunk(buffer.data());
			buffer.erase(buffer.begin(), buffer.begin() + 128);
		}
	}

	std::string hexdigest() {
		std::vector<uint8_t> finalBuffer = buffer;
		finalBuffer.push_back(0x80);

		while ((finalBuffer.size() % 128) != 112) {
			finalBuffer.push_back(0);
		}

		uint64_t bitLength = totalLength * 8;
		for (int i = 15; i >= 8; i--) {
			finalBuffer.push_back(0);
		}
		for (int i = 7; i >= 0; i--) {
			finalBuffer.push_back((bitLength >> (i * 8)) & 0xff);
		}

		for (size_t i = 0; i < finalBuffer.size(); i += 128) {
			processChunk(finalBuffer.data() + i);
		}

		std::string result;
		result.reserve(128);
		
		for (uint64_t h : hash) {
			for (int i = 7; i >= 0; i--) {
				uint8_t byte = (h >> (i * 8)) & 0xff;
				result += "0123456789abcdef"[byte >> 4];
				result += "0123456789abcdef"[byte & 0xf];
			}
		}
		
		return result;
	}

	static std::string hash(const std::string& input) {
		SHA512 sha;
		sha.update(input.data(), input.length());
		return sha.hexdigest();
	}
};