const hexChars = '0123456789abcdef';

function add(x, y) {
    return (x + y) >>> 0;
}

function rol(x, n) {
    return (x << n) | (x >>> (32 - n));
}

function cmn(q, a, b, x, s, t) {
    return add(rol(add(add(a, q), add(x, t)), s), b);
}

function ff(a, b, c, d, x, s, t) {
    return cmn((b & c) | (~b & d), a, b, x, s, t);
}

function gg(a, b, c, d, x, s, t) {
    return cmn((b & d) | (c & ~d), a, b, x, s, t);
}

function hh(a, b, c, d, x, s, t) {
    return cmn(b ^ c ^ d, a, b, x, s, t);
}

function ii(a, b, c, d, x, s, t) {
    return cmn(c ^ (b | ~d), a, b, x, s, t);
}

function toHex(n) {
    let out = '';
    for (let i = 0; i < 4; i++) {
        const byte = (n >>> (i * 8)) & 0xff;
        out += hexChars.charAt((byte >>> 4) & 0x0f) + hexChars.charAt(byte & 0x0f);
    }
    return out;
}

export function md5ArrayBuffer(buffer) {
    const bytes = new Uint8Array(buffer);
    const words = [];
    for (let i = 0; i < bytes.length; i++) {
        words[i >> 2] |= bytes[i] << ((i % 4) * 8);
    }

    const bitLen = bytes.length * 8;
    words[bitLen >> 5] |= 0x80 << (bitLen % 32);
    words[(((bitLen + 64) >>> 9) << 4) + 14] = bitLen;

    const totalLen = (((bitLen + 64) >>> 9) << 4) + 16;
    for (let i = 0; i < totalLen; i++) {
        if (words[i] === undefined) {
            words[i] = 0;
        }
    }

    let a = 0x67452301;
    let b = 0xefcdab89;
    let c = 0x98badcfe;
    let d = 0x10325476;

    for (let i = 0; i < words.length; i += 16) {
        const oa = a;
        const ob = b;
        const oc = c;
        const od = d;

        a = ff(a, b, c, d, words[i + 0], 7, 0xd76aa478);
        d = ff(d, a, b, c, words[i + 1], 12, 0xe8c7b756);
        c = ff(c, d, a, b, words[i + 2], 17, 0x242070db);
        b = ff(b, c, d, a, words[i + 3], 22, 0xc1bdceee);
        a = ff(a, b, c, d, words[i + 4], 7, 0xf57c0faf);
        d = ff(d, a, b, c, words[i + 5], 12, 0x4787c62a);
        c = ff(c, d, a, b, words[i + 6], 17, 0xa8304613);
        b = ff(b, c, d, a, words[i + 7], 22, 0xfd469501);
        a = ff(a, b, c, d, words[i + 8], 7, 0x698098d8);
        d = ff(d, a, b, c, words[i + 9], 12, 0x8b44f7af);
        c = ff(c, d, a, b, words[i + 10], 17, 0xffff5bb1);
        b = ff(b, c, d, a, words[i + 11], 22, 0x895cd7be);
        a = ff(a, b, c, d, words[i + 12], 7, 0x6b901122);
        d = ff(d, a, b, c, words[i + 13], 12, 0xfd987193);
        c = ff(c, d, a, b, words[i + 14], 17, 0xa679438e);
        b = ff(b, c, d, a, words[i + 15], 22, 0x49b40821);

        a = gg(a, b, c, d, words[i + 1], 5, 0xf61e2562);
        d = gg(d, a, b, c, words[i + 6], 9, 0xc040b340);
        c = gg(c, d, a, b, words[i + 11], 14, 0x265e5a51);
        b = gg(b, c, d, a, words[i + 0], 20, 0xe9b6c7aa);
        a = gg(a, b, c, d, words[i + 5], 5, 0xd62f105d);
        d = gg(d, a, b, c, words[i + 10], 9, 0x02441453);
        c = gg(c, d, a, b, words[i + 15], 14, 0xd8a1e681);
        b = gg(b, c, d, a, words[i + 4], 20, 0xe7d3fbc8);
        a = gg(a, b, c, d, words[i + 9], 5, 0x21e1cde6);
        d = gg(d, a, b, c, words[i + 14], 9, 0xc33707d6);
        c = gg(c, d, a, b, words[i + 3], 14, 0xf4d50d87);
        b = gg(b, c, d, a, words[i + 8], 20, 0x455a14ed);
        a = gg(a, b, c, d, words[i + 13], 5, 0xa9e3e905);
        d = gg(d, a, b, c, words[i + 2], 9, 0xfcefa3f8);
        c = gg(c, d, a, b, words[i + 7], 14, 0x676f02d9);
        b = gg(b, c, d, a, words[i + 12], 20, 0x8d2a4c8a);

        a = hh(a, b, c, d, words[i + 5], 4, 0xfffa3942);
        d = hh(d, a, b, c, words[i + 8], 11, 0x8771f681);
        c = hh(c, d, a, b, words[i + 11], 16, 0x6d9d6122);
        b = hh(b, c, d, a, words[i + 14], 23, 0xfde5380c);
        a = hh(a, b, c, d, words[i + 1], 4, 0xa4beea44);
        d = hh(d, a, b, c, words[i + 4], 11, 0x4bdecfa9);
        c = hh(c, d, a, b, words[i + 7], 16, 0xf6bb4b60);
        b = hh(b, c, d, a, words[i + 10], 23, 0xbebfbc70);
        a = hh(a, b, c, d, words[i + 13], 4, 0x289b7ec6);
        d = hh(d, a, b, c, words[i + 0], 11, 0xeaa127fa);
        c = hh(c, d, a, b, words[i + 3], 16, 0xd4ef3085);
        b = hh(b, c, d, a, words[i + 6], 23, 0x04881d05);
        a = hh(a, b, c, d, words[i + 9], 4, 0xd9d4d039);
        d = hh(d, a, b, c, words[i + 12], 11, 0xe6db99e5);
        c = hh(c, d, a, b, words[i + 15], 16, 0x1fa27cf8);
        b = hh(b, c, d, a, words[i + 2], 23, 0xc4ac5665);

        a = ii(a, b, c, d, words[i + 0], 6, 0xf4292244);
        d = ii(d, a, b, c, words[i + 7], 10, 0x432aff97);
        c = ii(c, d, a, b, words[i + 14], 15, 0xab9423a7);
        b = ii(b, c, d, a, words[i + 5], 21, 0xfc93a039);
        a = ii(a, b, c, d, words[i + 12], 6, 0x655b59c3);
        d = ii(d, a, b, c, words[i + 3], 10, 0x8f0ccc92);
        c = ii(c, d, a, b, words[i + 10], 15, 0xffeff47d);
        b = ii(b, c, d, a, words[i + 1], 21, 0x85845dd1);
        a = ii(a, b, c, d, words[i + 8], 6, 0x6fa87e4f);
        d = ii(d, a, b, c, words[i + 15], 10, 0xfe2ce6e0);
        c = ii(c, d, a, b, words[i + 6], 15, 0xa3014314);
        b = ii(b, c, d, a, words[i + 13], 21, 0x4e0811a1);
        a = ii(a, b, c, d, words[i + 4], 6, 0xf7537e82);
        d = ii(d, a, b, c, words[i + 11], 10, 0xbd3af235);
        c = ii(c, d, a, b, words[i + 2], 15, 0x2ad7d2bb);
        b = ii(b, c, d, a, words[i + 9], 21, 0xeb86d391);

        a = add(a, oa);
        b = add(b, ob);
        c = add(c, oc);
        d = add(d, od);
    }

    return toHex(a) + toHex(b) + toHex(c) + toHex(d);
}