#include <crypto/crypto.h>
#include <lib/string.h>
#include <lib/printf.h>

#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)))

#define ROTATE_LEFT(x, n) (((x) << (n)) | ((x) >> (32 - (n))))

#define FF(a, b, c, d, x, s, ac) { \
    (a) += F((b), (c), (d)) + (x) + (uint32_t)(ac); \
    (a) = ROTATE_LEFT((a), (s)); \
    (a) += (b); \
}
#define GG(a, b, c, d, x, s, ac) { \
    (a) += G((b), (c), (d)) + (x) + (uint32_t)(ac); \
    (a) = ROTATE_LEFT((a), (s)); \
    (a) += (b); \
}
#define HH(a, b, c, d, x, s, ac) { \
    (a) += H((b), (c), (d)) + (x) + (uint32_t)(ac); \
    (a) = ROTATE_LEFT((a), (s)); \
    (a) += (b); \
}
#define II(a, b, c, d, x, s, ac) { \
    (a) += I((b), (c), (d)) + (x) + (uint32_t)(ac); \
    (a) = ROTATE_LEFT((a), (s)); \
    (a) += (b); \
}

static void md5_transform(uint32_t state[4], const uint8_t block[64]) {
    uint32_t a = state[0], b = state[1], c = state[2], d = state[3], x[16];

    for (int i = 0, j = 0; j < 64; i++, j += 4) {
        x[i] = ((uint32_t)block[j]) | (((uint32_t)block[j + 1]) << 8) |
               (((uint32_t)block[j + 2]) << 16) | (((uint32_t)block[j + 3]) << 24);
    }

    // Round 1
    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);

    // Round 2
    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);

    // Round 3
    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);

    // Round 4
    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;
}

void md5_init(md5_ctx_t* ctx) {
    ctx->count[0] = ctx->count[1] = 0;
    ctx->state[0] = 0x67452301;
    ctx->state[1] = 0xefcdab89;
    ctx->state[2] = 0x98badcfe;
    ctx->state[3] = 0x10325476;
}

void md5_update(md5_ctx_t* ctx, const void* input, size_t input_len) {
    uint32_t i, index, part_len;
    const uint8_t* buf = (const uint8_t*)input;

    index = (uint32_t)((ctx->count[0] >> 3) & 0x3F);
    if ((ctx->count[0] += ((uint32_t)input_len << 3)) < ((uint32_t)input_len << 3)) {
        ctx->count[1]++;
    }
    ctx->count[1] += ((uint32_t)input_len >> 29);
    part_len = 64 - index;

    if (input_len >= part_len) {
        memcpy(&ctx->buffer[index], buf, part_len);
        md5_transform(ctx->state, ctx->buffer);
        for (i = part_len; i + 63 < input_len; i += 64) {
            md5_transform(ctx->state, &buf[i]);
        }
        index = 0;
    } else {
        i = 0;
    }

    memcpy(&ctx->buffer[index], &buf[i], input_len - i);
}

void md5_final(uint8_t digest[16], md5_ctx_t* ctx) {
    static const uint8_t PADDING[64] = { 0x80 };
    uint8_t bits[8];
    uint32_t index, pad_len;

    for (int i = 0; i < 4; i++) {
        bits[i] = (uint8_t)((ctx->count[0] >> (i * 8)) & 0xFF);
        bits[i + 4] = (uint8_t)((ctx->count[1] >> (i * 8)) & 0xFF);
    }

    index = (uint32_t)((ctx->count[0] >> 3) & 0x3F);
    pad_len = (index < 56) ? (56 - index) : (120 - index);
    md5_update(ctx, PADDING, pad_len);
    md5_update(ctx, bits, 8);

    for (int i = 0; i < 4; i++) {
        digest[i] = (uint8_t)((ctx->state[0] >> (i * 8)) & 0xFF);
        digest[i + 4] = (uint8_t)((ctx->state[1] >> (i * 8)) & 0xFF);
        digest[i + 8] = (uint8_t)((ctx->state[2] >> (i * 8)) & 0xFF);
        digest[i + 12] = (uint8_t)((ctx->state[3] >> (i * 8)) & 0xFF);
    }
}

void md5_string(const char* str, char output[33]) {
    md5_ctx_t ctx;
    uint8_t digest[16];
    md5_init(&ctx);
    md5_update(&ctx, str, strlen(str));
    md5_final(digest, &ctx);

    for (int i = 0; i < 16; i++) {
        sprintf(output + i * 2, "%02x", digest[i]);
    }
    output[32] = '\0';
}