#include "dshash.hpp"
#include <fstream>
#include <sstream>
#include <iomanip>
#include <cstring>
#include <algorithm>

const uint32_t DSHash::K[64] = {
    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
};

static inline uint32_t rotr(uint32_t x, uint32_t n) {
    return (x >> n) | (x << (32 - n));
}

static inline uint32_t ch(uint32_t x, uint32_t y, uint32_t z) {
    return (x & y) ^ (~x & z);
}

static inline uint32_t maj(uint32_t x, uint32_t y, uint32_t z) {
    return (x & y) ^ (x & z) ^ (y & z);
}

static inline uint32_t sigma0(uint32_t x) {
    return rotr(x, 2) ^ rotr(x, 13) ^ rotr(x, 22);
}

static inline uint32_t sigma1(uint32_t x) {
    return rotr(x, 6) ^ rotr(x, 11) ^ rotr(x, 25);
}

static inline uint32_t gamma0(uint32_t x) {
    return rotr(x, 7) ^ rotr(x, 18) ^ (x >> 3);
}

static inline uint32_t gamma1(uint32_t x) {
    return rotr(x, 17) ^ rotr(x, 19) ^ (x >> 10);
}

void DSHash::processBlock(const uint8_t* block) {
    uint32_t w[64];
    
    for (int i = 0; i < 16; i++) {
        w[i] = (block[i * 4] << 24) |
               (block[i * 4 + 1] << 16) |
               (block[i * 4 + 2] << 8) |
               (block[i * 4 + 3]);
    }
    
    for (int i = 16; i < 64; i++) {
        w[i] = gamma1(w[i - 2]) + w[i - 7] + gamma0(w[i - 15]) + w[i - 16];
    }
    
    uint32_t a = h[0];
    uint32_t b = h[1];
    uint32_t c = h[2];
    uint32_t d = h[3];
    uint32_t e = h[4];
    uint32_t f = h[5];
    uint32_t g = h[6];
    uint32_t hh = h[7];
    
    for (int i = 0; i < 64; i++) {
        uint32_t t1 = hh + sigma1(e) + ch(e, f, g) + K[i] + w[i];
        uint32_t t2 = sigma0(a) + maj(a, b, c);
        hh = g;
        g = f;
        f = e;
        e = d + t1;
        d = c;
        c = b;
        b = a;
        a = t1 + t2;
    }
    
    h[0] += a;
    h[1] += b;
    h[2] += c;
    h[3] += d;
    h[4] += e;
    h[5] += f;
    h[6] += g;
    h[7] += hh;
}

void DSHash::update(const uint8_t* data, size_t length) {
    if (finalized) return;
    
    total_length += length;
    
    buffer.insert(buffer.end(), data, data + length);
    
    while (buffer.size() >= BLOCK_SIZE) {
        processBlock(buffer.data());
        buffer.erase(buffer.begin(), buffer.begin() + BLOCK_SIZE);
    }
}

void DSHash::update(const std::string& str) {
    update(reinterpret_cast<const uint8_t*>(str.data()), str.size());
}

void DSHash::padMessage() {
    uint64_t bit_length = total_length * 8;
    
    buffer.push_back(0x80);
    
    while ((buffer.size() % 64) != 56) {
        buffer.push_back(0x00);
    }
    
    for (int i = 7; i >= 0; i--) {
        buffer.push_back((bit_length >> (i * 8)) & 0xff);
    }
}

tHash DSHash::finalize() {
    if (finalized) {
        tHash result;
        for (int i = 0; i < 8; i++) {
            result[i * 4] = (h[i] >> 24) & 0xff;
            result[i * 4 + 1] = (h[i] >> 16) & 0xff;
            result[i * 4 + 2] = (h[i] >> 8) & 0xff;
            result[i * 4 + 3] = h[i] & 0xff;
        }
        return result;
    }
    
    padMessage();
    
    while (!buffer.empty()) {
        processBlock(buffer.data());
        buffer.erase(buffer.begin(), buffer.begin() + BLOCK_SIZE);
    }
    
    finalized = true;
    
    tHash result;
    for (int i = 0; i < 8; i++) {
        result[i * 4] = (h[i] >> 24) & 0xff;
        result[i * 4 + 1] = (h[i] >> 16) & 0xff;
        result[i * 4 + 2] = (h[i] >> 8) & 0xff;
        result[i * 4 + 3] = h[i] & 0xff;
    }
    
    return result;
}

std::string DSHash::hashString(const std::string& str) {
    h[0] = 0x6a09e667;
    h[1] = 0xbb67ae85;
    h[2] = 0x3c6ef372;
    h[3] = 0xa54ff53a;
    h[4] = 0x510e527f;
    h[5] = 0x9b05688c;
    h[6] = 0x1f83d9ab;
    h[7] = 0x5be0cd19;
    buffer.clear();
    total_length = 0;
    finalized = false;
    
    update(str);
    tHash hash = finalize();
    
    std::stringstream ss;
    for (uint8_t byte : hash) {
        ss << std::hex << std::setfill('0') << std::setw(2) << static_cast<int>(byte);
    }
    return ss.str();
}

std::string DSHash::hashFile(const std::filesystem::path& filepath) {
    std::ifstream file(filepath, std::ios::binary);
    if (!file) {
        throw std::runtime_error("Cannot open file: " + filepath.string());
    }
    
    h[0] = 0x6a09e667;
    h[1] = 0xbb67ae85;
    h[2] = 0x3c6ef372;
    h[3] = 0xa54ff53a;
    h[4] = 0x510e527f;
    h[5] = 0x9b05688c;
    h[6] = 0x1f83d9ab;
    h[7] = 0x5be0cd19;
    buffer.clear();
    total_length = 0;
    finalized = false;
    
    constexpr size_t BUFFER_SIZE = 8192;
    char buffer[BUFFER_SIZE];
    
    while (file.read(buffer, BUFFER_SIZE) || file.gcount() > 0) {
        update(reinterpret_cast<const uint8_t*>(buffer), file.gcount());
    }
    
    tHash hash = finalize();
    
    std::stringstream ss;
    for (uint8_t byte : hash) {
        ss << std::hex << std::setfill('0') << std::setw(2) << static_cast<int>(byte);
    }
    return ss.str();
}

std::string DSHash::hashDirectory(const std::filesystem::path& dirpath) {
    if (!std::filesystem::is_directory(dirpath)) {
        throw std::runtime_error("Not a directory: " + dirpath.string());
    }
    
    h[0] = 0x6a09e667;
    h[1] = 0xbb67ae85;
    h[2] = 0x3c6ef372;
    h[3] = 0xa54ff53a;
    h[4] = 0x510e527f;
    h[5] = 0x9b05688c;
    h[6] = 0x1f83d9ab;
    h[7] = 0x5be0cd19;
    buffer.clear();
    total_length = 0;
    finalized = false;
    
    std::vector<std::filesystem::path> paths;
    
    for (const auto& entry : std::filesystem::recursive_directory_iterator(dirpath)) {
        if (entry.is_regular_file()) {
            paths.push_back(entry.path());
        }
    }
    
    std::sort(paths.begin(), paths.end());
    
    for (const auto& path : paths) {
        std::string relative = std::filesystem::relative(path, dirpath).string();
        update(relative);
        
        DSHash fileHasher(path);
        std::string fileHashStr = fileHasher.toString();
        update(fileHashStr);
    }
    
    tHash hash = finalize();
    
    std::stringstream ss;
    for (uint8_t byte : hash) {
        ss << std::hex << std::setfill('0') << std::setw(2) << static_cast<int>(byte);
    }
    return ss.str();
}

DSHash::DSHash(const std::filesystem::path& path) {
    h[0] = 0x6a09e667;
    h[1] = 0xbb67ae85;
    h[2] = 0x3c6ef372;
    h[3] = 0xa54ff53a;
    h[4] = 0x510e527f;
    h[5] = 0x9b05688c;
    h[6] = 0x1f83d9ab;
    h[7] = 0x5be0cd19;
    
    if (std::filesystem::is_regular_file(path)) {
        hashFile(path);
    } else if (std::filesystem::is_directory(path)) {
        hashDirectory(path);
    } else {
        throw std::runtime_error("Path is neither file nor directory: " + path.string());
    }
}

DSHash::DSHash(const std::string& str) {
    h[0] = 0x6a09e667;
    h[1] = 0xbb67ae85;
    h[2] = 0x3c6ef372;
    h[3] = 0xa54ff53a;
    h[4] = 0x510e527f;
    h[5] = 0x9b05688c;
    h[6] = 0x1f83d9ab;
    h[7] = 0x5be0cd19;
    
    hashString(str);
}

std::string DSHash::toString() {
    if (!finalized) {
        finalize();
    }
    
    tHash hash = get();
    std::stringstream ss;
    for (uint8_t byte : hash) {
        ss << std::hex << std::setfill('0') << std::setw(2) << static_cast<int>(byte);
    }
    return ss.str();
}

tHash DSHash::get() {
    if (!finalized) {
        return finalize();
    }
    
    tHash result;
    for (int i = 0; i < 8; i++) {
        result[i * 4] = (h[i] >> 24) & 0xff;
        result[i * 4 + 1] = (h[i] >> 16) & 0xff;
        result[i * 4 + 2] = (h[i] >> 8) & 0xff;
        result[i * 4 + 3] = h[i] & 0xff;
    }
    return result;
}