#include <string>
#include <cstring>
#include <fstream>
#include <iostream>
#include <vector>
#include <cassert>
using namespace std;

class SHA256
{
protected:
	typedef unsigned char uint8;
	typedef unsigned int uint32;
	typedef unsigned long long uint64;

	const static uint32 sha256_k[];
	static const unsigned int SHA224_256_BLOCK_SIZE = (512 / 8);

public:
	void init();
	void update(const unsigned char *message, unsigned int len);
	void final(unsigned char *digest);
	static const unsigned int DIGEST_SIZE = (256 / 8);

protected:
	void transform(const unsigned char *message, unsigned int block_nb);
	unsigned int m_tot_len;
	unsigned int m_len;
	unsigned char m_block[2 * SHA224_256_BLOCK_SIZE];
	uint32 m_h[8];
};

std::string sha256(std::string input);

#define SHA2_SHFR(x, n) (x >> n)
#define SHA2_ROTR(x, n) ((x >> n) | (x << ((sizeof(x) << 3) - n)))
#define SHA2_ROTL(x, n) ((x << n) | (x >> ((sizeof(x) << 3) - n)))
#define SHA2_CH(x, y, z) ((x & y) ^ (~x & z))
#define SHA2_MAJ(x, y, z) ((x & y) ^ (x & z) ^ (y & z))
#define SHA256_F1(x) (SHA2_ROTR(x, 2) ^ SHA2_ROTR(x, 13) ^ SHA2_ROTR(x, 22))
#define SHA256_F2(x) (SHA2_ROTR(x, 6) ^ SHA2_ROTR(x, 11) ^ SHA2_ROTR(x, 25))
#define SHA256_F3(x) (SHA2_ROTR(x, 7) ^ SHA2_ROTR(x, 18) ^ SHA2_SHFR(x, 3))
#define SHA256_F4(x) (SHA2_ROTR(x, 17) ^ SHA2_ROTR(x, 19) ^ SHA2_SHFR(x, 10))
#define SHA2_UNPACK32(x, str)              \
	{                                      \
		*((str) + 3) = (uint8)((x));       \
		*((str) + 2) = (uint8)((x) >> 8);  \
		*((str) + 1) = (uint8)((x) >> 16); \
		*((str) + 0) = (uint8)((x) >> 24); \
	}
#define SHA2_PACK32(str, x)                                                                                                                \
	{                                                                                                                                      \
		*(x) = ((uint32) * ((str) + 3)) | ((uint32) * ((str) + 2) << 8) | ((uint32) * ((str) + 1) << 16) | ((uint32) * ((str) + 0) << 24); \
	}

const unsigned int SHA256::sha256_k[64] = //UL = uint32
	{0x428a2f98, 0x71374491, 0xb5c0fbcf, 0xe9b5dba5,
	 0x3956c25b, 0x59f111f1, 0x923f82a4, 0xab1c5ed5,
	 0xd807aa98, 0x12835b01, 0x243185be, 0x550c7dc3,
	 0x72be5d74, 0x80deb1fe, 0x9bdc06a7, 0xc19bf174,
	 0xe49b69c1, 0xefbe4786, 0x0fc19dc6, 0x240ca1cc,
	 0x2de92c6f, 0x4a7484aa, 0x5cb0a9dc, 0x76f988da,
	 0x983e5152, 0xa831c66d, 0xb00327c8, 0xbf597fc7,
	 0xc6e00bf3, 0xd5a79147, 0x06ca6351, 0x14292967,
	 0x27b70a85, 0x2e1b2138, 0x4d2c6dfc, 0x53380d13,
	 0x650a7354, 0x766a0abb, 0x81c2c92e, 0x92722c85,
	 0xa2bfe8a1, 0xa81a664b, 0xc24b8b70, 0xc76c51a3,
	 0xd192e819, 0xd6990624, 0xf40e3585, 0x106aa070,
	 0x19a4c116, 0x1e376c08, 0x2748774c, 0x34b0bcb5,
	 0x391c0cb3, 0x4ed8aa4a, 0x5b9cca4f, 0x682e6ff3,
	 0x748f82ee, 0x78a5636f, 0x84c87814, 0x8cc70208,
	 0x90befffa, 0xa4506ceb, 0xbef9a3f7, 0xc67178f2};

void SHA256::transform(const unsigned char *message, unsigned int block_nb)
{
	uint32 w[64];
	uint32 wv[8];
	uint32 t1, t2;
	const unsigned char *sub_block;
	int i;
	int j;
	for (i = 0; i < (int)block_nb; i++)
	{
		sub_block = message + (i << 6);
		for (j = 0; j < 16; j++)
		{
			SHA2_PACK32(&sub_block[j << 2], &w[j]);
		}
		for (j = 16; j < 64; j++)
		{
			w[j] = SHA256_F4(w[j - 2]) + w[j - 7] + SHA256_F3(w[j - 15]) + w[j - 16];
		}
		for (j = 0; j < 8; j++)
		{
			wv[j] = m_h[j];
		}
		for (j = 0; j < 64; j++)
		{
			t1 = wv[7] + SHA256_F2(wv[4]) + SHA2_CH(wv[4], wv[5], wv[6]) + sha256_k[j] + w[j];
			t2 = SHA256_F1(wv[0]) + SHA2_MAJ(wv[0], wv[1], wv[2]);
			wv[7] = wv[6];
			wv[6] = wv[5];
			wv[5] = wv[4];
			wv[4] = wv[3] + t1;
			wv[3] = wv[2];
			wv[2] = wv[1];
			wv[1] = wv[0];
			wv[0] = t1 + t2;
		}
		for (j = 0; j < 8; j++)
		{
			m_h[j] += wv[j];
		}
	}
}

void SHA256::init()
{
	m_h[0] = 0x6a09e667;
	m_h[1] = 0xbb67ae85;
	m_h[2] = 0x3c6ef372;
	m_h[3] = 0xa54ff53a;
	m_h[4] = 0x510e527f;
	m_h[5] = 0x9b05688c;
	m_h[6] = 0x1f83d9ab;
	m_h[7] = 0x5be0cd19;
	m_len = 0;
	m_tot_len = 0;
}

void SHA256::update(const unsigned char *message, unsigned int len)
{
	unsigned int block_nb;
	unsigned int new_len, rem_len, tmp_len;
	const unsigned char *shifted_message;
	tmp_len = SHA224_256_BLOCK_SIZE - m_len;
	rem_len = len < tmp_len ? len : tmp_len;
	memcpy(&m_block[m_len], message, rem_len);
	if (m_len + len < SHA224_256_BLOCK_SIZE)
	{
		m_len += len;
		return;
	}
	new_len = len - rem_len;
	block_nb = new_len / SHA224_256_BLOCK_SIZE;
	shifted_message = message + rem_len;
	transform(m_block, 1);
	transform(shifted_message, block_nb);
	rem_len = new_len % SHA224_256_BLOCK_SIZE;
	memcpy(m_block, &shifted_message[block_nb << 6], rem_len);
	m_len = rem_len;
	m_tot_len += (block_nb + 1) << 6;
}

void SHA256::final(unsigned char *digest)
{
	unsigned int block_nb;
	unsigned int pm_len;
	unsigned int len_b;
	int i;
	block_nb = (1 + ((SHA224_256_BLOCK_SIZE - 9) < (m_len % SHA224_256_BLOCK_SIZE)));
	len_b = (m_tot_len + m_len) << 3;
	pm_len = block_nb << 6;
	memset(m_block + m_len, 0, pm_len - m_len);
	m_block[m_len] = 0x80;
	SHA2_UNPACK32(len_b, m_block + pm_len - 4);
	transform(m_block, block_nb);
	for (i = 0; i < 8; i++)
	{
		SHA2_UNPACK32(m_h[i], &digest[i << 2]);
	}
}

std::string sha256(std::string input)
{
	unsigned char digest[SHA256::DIGEST_SIZE];
	memset(digest, 0, SHA256::DIGEST_SIZE);

	SHA256 ctx = SHA256();
	ctx.init();
	ctx.update((unsigned char *)input.c_str(), input.length());
	ctx.final(digest);

	char buf[2 * SHA256::DIGEST_SIZE + 1];
	buf[2 * SHA256::DIGEST_SIZE] = 0;
	for (int i = 0; i < SHA256::DIGEST_SIZE; i++)
		sprintf(buf + i * 2, "%02x", digest[i]);
	return std::string(buf);
}

std::string sha256_vector(vector<std::string> inputs)
{
	unsigned char digest[SHA256::DIGEST_SIZE];
	memset(digest, 0, SHA256::DIGEST_SIZE);

	SHA256 ctx = SHA256();
	ctx.init();
	for (string &input : inputs)
	{
		ctx.update((unsigned char *)input.c_str(), input.length());
	}
	ctx.final(digest);

	char buf[2 * SHA256::DIGEST_SIZE + 1];
	buf[2 * SHA256::DIGEST_SIZE] = 0;
	for (int i = 0; i < SHA256::DIGEST_SIZE; i++)
		sprintf(buf + i * 2, "%02x", digest[i]);
	return std::string(buf);
}
typedef vector<string> Words;
typedef vector<string> Hashes;

Hashes compute_hash(Words words)
{
	Hashes h;
	for (auto &a : words)
	{
		auto hash = sha256(a);
		h.push_back(hash);
	}
	return h;
}
void show_hash(Hashes h)
{
	for (auto &a : h)
	{
		cout << a << endl;
	}
}

string compute_merkle(Hashes src)
{
	............
}
int main()
{
	string input = "grape";
	string output1 = sha256(input);
	cout << output1 << endl;

	Words w;
	w.push_back("apple");
	w.push_back("pear");
	w.push_back("strawberry");
	w.push_back("banana");
	auto hashes = compute_hash(w);
	show_hash(hashes);
	auto final = compute_merkle(hashes);
	cout << "final hash =" << final << endl;
	return 0;
}


final hash =f763dd68d4be72ce37b7f55356e24f958eab69eae59e7ed6d932bacd21d23835