#include <iostream>
#include <string>
#include <cstring>
#include <sstream>
#include <iomanip>
#include <vector>

class SimpleMD5 {
private:
    // 基础函数定义
    #define F(x, y, z) (((x) & (y)) | ((~x) & (z)))
    #define G(x, y, z) (((x) & (z)) | ((y) & (~z)))
    #define H(x, y, z) ((x) ^ (y) ^ (z))
    #define I(x, y, z) ((y) ^ ((x) | (~z)))
    
    // 循环左移
    #define ROTATE_LEFT(x, n) (((x) << (n)) | ((x) >> (32 - (n))))
    
    // 转换函数
    #define FF(a, b, c, d, x, s, ac) { \
        (a) += F((b), (c), (d)) + (x) + (ac); \
        (a) = ROTATE_LEFT((a), (s)); \
        (a) += (b); \
    }
    
    #define GG(a, b, c, d, x, s, ac) { \
        (a) += G((b), (c), (d)) + (x) + (ac); \
        (a) = ROTATE_LEFT((a), (s)); \
        (a) += (b); \
    }
    
    #define HH(a, b, c, d, x, s, ac) { \
        (a) += H((b), (c), (d)) + (x) + (ac); \
        (a) = ROTATE_LEFT((a), (s)); \
        (a) += (b); \
    }
    
    #define II(a, b, c, d, x, s, ac) { \
        (a) += I((b), (c), (d)) + (x) + (ac); \
        (a) = ROTATE_LEFT((a), (s)); \
        (a) += (b); \
    }
    
    uint32_t state[4];  // 状态变量 (A, B, C, D)
    
    // 填充数据
    void pad(std::vector<uint8_t>& data) {
        uint64_t original_bit_length = data.size() * 8;
        
        // 添加 1 bit (0x80 字节)
        data.push_back(0x80);
        
        // 填充 0 直到长度对 64 取模等于 56
        while ((data.size() % 64) != 56) {
            data.push_back(0x00);
        }
        
        // 添加原始消息长度 (小端序)
        for (int i = 0; i < 8; i++) {
            data.push_back(static_cast<uint8_t>(original_bit_length >> (i * 8)));
        }
    }
    
    // 转换 4 字节为 32 位整数 (小端序)
    uint32_t to_int32(const uint8_t* bytes) {
        return (static_cast<uint32_t>(bytes[0])) |
               (static_cast<uint32_t>(bytes[1]) << 8) |
               (static_cast<uint32_t>(bytes[2]) << 16) |
               (static_cast<uint32_t>(bytes[3]) << 24);
    }
    
    // 主转换函数
    void transform(const uint8_t block[64]) {
        uint32_t a = state[0];
        uint32_t b = state[1];
        uint32_t c = state[2];
        uint32_t d = state[3];
        uint32_t x[16];
        
        // 将 64 字节块解码为 16 个 32 位整数
        for (int i = 0, j = 0; i < 16; i++, j += 4) {
            x[i] = to_int32(&block[j]);
        }
        
        /* 第 1 轮 */
        FF(a, b, c, d, x[0], 7, 0xd76aa478);
        FF(d, a, b, c, x[1], 12, 0xe8c7b756);
        FF(c, d, a, b, x[2], 17, 0x242070db);
        FF(b, c, d, a, x[3], 22, 0xc1bdceee);
        FF(a, b, c, d, x[4], 7, 0xf57c0faf);
        FF(d, a, b, c, x[5], 12, 0x4787c62a);
        FF(c, d, a, b, x[6], 17, 0xa8304613);
        FF(b, c, d, a, x[7], 22, 0xfd469501);
        FF(a, b, c, d, x[8], 7, 0x698098d8);
        FF(d, a, b, c, x[9], 12, 0x8b44f7af);
        FF(c, d, a, b, x[10], 17, 0xffff5bb1);
        FF(b, c, d, a, x[11], 22, 0x895cd7be);
        FF(a, b, c, d, x[12], 7, 0x6b901122);
        FF(d, a, b, c, x[13], 12, 0xfd987193);
        FF(c, d, a, b, x[14], 17, 0xa679438e);
        FF(b, c, d, a, x[15], 22, 0x49b40821);
        
        /* 第 2 轮 */
        GG(a, b, c, d, x[1], 5, 0xf61e2562);
        GG(d, a, b, c, x[6], 9, 0xc040b340);
        GG(c, d, a, b, x[11], 14, 0x265e5a51);
        GG(b, c, d, a, x[0], 20, 0xe9b6c7aa);
        GG(a, b, c, d, x[5], 5, 0xd62f105d);
        GG(d, a, b, c, x[10], 9, 0x02441453);
        GG(c, d, a, b, x[15], 14, 0xd8a1e681);
        GG(b, c, d, a, x[4], 20, 0xe7d3fbc8);
        GG(a, b, c, d, x[9], 5, 0x21e1cde6);
        GG(d, a, b, c, x[14], 9, 0xc33707d6);
        GG(c, d, a, b, x[3], 14, 0xf4d50d87);
        GG(b, c, d, a, x[8], 20, 0x455a14ed);
        GG(a, b, c, d, x[13], 5, 0xa9e3e905);
        GG(d, a, b, c, x[2], 9, 0xfcefa3f8);
        GG(c, d, a, b, x[7], 14, 0x676f02d9);
        GG(b, c, d, a, x[12], 20, 0x8d2a4c8a);
        
        /* 第 3 轮 */
        HH(a, b, c, d, x[5], 4, 0xfffa3942);
        HH(d, a, b, c, x[8], 11, 0x8771f681);
        HH(c, d, a, b, x[11], 16, 0x6d9d6122);
        HH(b, c, d, a, x[14], 23, 0xfde5380c);
        HH(a, b, c, d, x[1], 4, 0xa4beea44);
        HH(d, a, b, c, x[4], 11, 0x4bdecfa9);
        HH(c, d, a, b, x[7], 16, 0xf6bb4b60);
        HH(b, c, d, a, x[10], 23, 0xbebfbc70);
        HH(a, b, c, d, x[13], 4, 0x289b7ec6);
        HH(d, a, b, c, x[0], 11, 0xeaa127fa);
        HH(c, d, a, b, x[3], 16, 0xd4ef3085);
        HH(b, c, d, a, x[6], 23, 0x04881d05);
        HH(a, b, c, d, x[9], 4, 0xd9d4d039);
        HH(d, a, b, c, x[12], 11, 0xe6db99e5);
        HH(c, d, a, b, x[15], 16, 0x1fa27cf8);
        HH(b, c, d, a, x[2], 23, 0xc4ac5665);
        
        /* 第 4 轮 */
        II(a, b, c, d, x[0], 6, 0xf4292244);
        II(d, a, b, c, x[7], 10, 0x432aff97);
        II(c, d, a, b, x[14], 15, 0xab9423a7);
        II(b, c, d, a, x[5], 21, 0xfc93a039);
        II(a, b, c, d, x[12], 6, 0x655b59c3);
        II(d, a, b, c, x[3], 10, 0x8f0ccc92);
        II(c, d, a, b, x[10], 15, 0xffeff47d);
        II(b, c, d, a, x[1], 21, 0x85845dd1);
        II(a, b, c, d, x[8], 6, 0x6fa87e4f);
        II(d, a, b, c, x[15], 10, 0xfe2ce6e0);
        II(c, d, a, b, x[6], 15, 0xa3014314);
        II(b, c, d, a, x[13], 21, 0x4e0811a1);
        II(a, b, c, d, x[4], 6, 0xf7537e82);
        II(d, a, b, c, x[11], 10, 0xbd3af235);
        II(c, d, a, b, x[2], 15, 0x2ad7d2bb);
        II(b, c, d, a, x[9], 21, 0xeb86d391);
        
        state[0] += a;
        state[1] += b;
        state[2] += c;
        state[3] += d;
    }
    
public:
    SimpleMD5() {
        reset();
    }
    
    // 重置状态
    void reset() {
        state[0] = 0x67452301;
        state[1] = 0xefcdab89;
        state[2] = 0x98badcfe;
        state[3] = 0x10325476;
    }
    
    // 计算字符串的 MD5
    std::string hash(const std::string& input) {
        return hash(reinterpret_cast<const uint8_t*>(input.c_str()), input.length());
    }
    
    // 计算字节数组的 MD5
    std::string hash(const uint8_t* data, size_t length) {
        reset();
        
        // 将数据复制到 vector 以便填充
        std::vector<uint8_t> buffer(data, data + length);
        
        // 填充数据
        pad(buffer);
        
        // 处理每个 64 字节块
        for (size_t i = 0; i < buffer.size(); i += 64) {
            transform(&buffer[i]);
        }
        
        // 将结果转换为十六进制字符串
        return to_hex_string();
    }
    
    // 计算文件的 MD5
    std::string hash_file(const std::string& filename) {
        reset();
        
        FILE* file = fopen(filename.c_str(), "rb");
        if (!file) {
            return "";
        }
        
        std::vector<uint8_t> buffer;
        uint8_t chunk[1024];
        size_t bytes_read;
        
        while ((bytes_read = fread(chunk, 1, sizeof(chunk), file)) > 0) {
            buffer.insert(buffer.end(), chunk, chunk + bytes_read);
        }
        
        fclose(file);
        
        return hash(buffer.data(), buffer.size());
    }
    
private:
    // 将结果转换为十六进制字符串
    std::string to_hex_string() {
        std::stringstream ss;
        ss << std::hex << std::setfill('0');
        
        // 以小端序输出每个状态变量
        for (int i = 0; i < 4; i++) {
            // 将 32 位整数按字节输出
            for (int j = 0; j < 4; j++) {
                uint8_t byte = (state[i] >> (j * 8)) & 0xFF;
                ss << std::setw(2) << static_cast<int>(byte);
            }
        }
        
        return ss.str();
    }
};