/**
 * @author Kyi Wong
 * @copyright Crown Copyright 2026
 * @license Apache-2.0
 */

/**
 * ZUC Stream Cipher implementation.
 * Based on the 3GPP ZUC specification.
 */

const S0 = [
    0x3E, 0x72, 0x5B, 0x47, 0xCA, 0xE0, 0x00, 0x33, 0x04, 0xD1, 0x54, 0x98, 0x09, 0xB9, 0x6D, 0xCB,
    0x7B, 0x1B, 0xF9, 0x32, 0xAF, 0x9D, 0x6A, 0xA5, 0xB8, 0x2D, 0xFC, 0x1D, 0x08, 0x53, 0x03, 0x90,
    0x4D, 0x4E, 0x84, 0x99, 0xE4, 0xCE, 0xD9, 0x91, 0xDD, 0xB6, 0x85, 0x48, 0x8B, 0x29, 0x6E, 0xAC,
    0xCD, 0xC1, 0xF8, 0x1E, 0x73, 0x43, 0x69, 0xC6, 0xB5, 0xBD, 0xFD, 0x39, 0x63, 0x20, 0xD4, 0x38,
    0x76, 0x7D, 0xB2, 0xA7, 0xCF, 0xED, 0x57, 0xC5, 0xF3, 0x2C, 0xBB, 0x14, 0x21, 0x06, 0x55, 0x9B,
    0xE3, 0xEF, 0x5E, 0x31, 0x4F, 0x7F, 0x5A, 0xA4, 0x0D, 0x82, 0x51, 0x49, 0x5F, 0xBA, 0x58, 0x1C,
    0x4A, 0x16, 0xD5, 0x17, 0xA8, 0x92, 0x24, 0x1F, 0x8C, 0xFF, 0xD8, 0xAE, 0x2E, 0x01, 0xD3, 0xAD,
    0x3B, 0x4B, 0xDA, 0x46, 0xEB, 0xC9, 0xDE, 0x9A, 0x8F, 0x87, 0xD7, 0x3A, 0x80, 0x6F, 0x2F, 0xC8,
    0xB1, 0xB4, 0x37, 0xF7, 0x0A, 0x22, 0x13, 0x28, 0x7C, 0xCC, 0x3C, 0x89, 0xC7, 0xC3, 0x96, 0x56,
    0x07, 0xBF, 0x7E, 0xF0, 0x0B, 0x2B, 0x97, 0x52, 0x35, 0x41, 0x79, 0x61, 0xA6, 0x4C, 0x10, 0xFE,
    0xBC, 0x26, 0x95, 0x88, 0x8A, 0xB0, 0xA3, 0xFB, 0xC0, 0x18, 0x94, 0xF2, 0xE1, 0xE5, 0xE9, 0x5D,
    0xD0, 0xDC, 0x11, 0x66, 0x64, 0x5C, 0xEC, 0x59, 0x42, 0x75, 0x12, 0xF5, 0x74, 0x9C, 0xAA, 0x23,
    0x0E, 0x86, 0xAB, 0xBE, 0x2A, 0x02, 0xE7, 0x67, 0xE6, 0x44, 0xA2, 0x6C, 0xC2, 0x93, 0x9F, 0xF1,
    0xF6, 0xFA, 0x36, 0xD2, 0x50, 0x68, 0x9E, 0x62, 0x71, 0x15, 0x3D, 0xD6, 0x40, 0xC4, 0xE2, 0x0F,
    0x8E, 0x83, 0x77, 0x6B, 0x25, 0x05, 0x3F, 0x0C, 0x30, 0xEA, 0x70, 0xB7, 0xA1, 0xE8, 0xA9, 0x65,
    0x8D, 0x27, 0x1A, 0xDB, 0x81, 0xB3, 0xA0, 0xF4, 0x45, 0x7A, 0x19, 0xDF, 0xEE, 0x78, 0x34, 0x60
];

const S1 = [
    0x55, 0xC2, 0x63, 0x71, 0x3B, 0xC8, 0x47, 0x86, 0x9F, 0x3C, 0xDA, 0x5B, 0x29, 0xAA, 0xFD, 0x77,
    0x8C, 0xC5, 0x94, 0x0C, 0xA6, 0x1A, 0x13, 0x00, 0xE3, 0xA8, 0x16, 0x72, 0x40, 0xF9, 0xF8, 0x42,
    0x44, 0x26, 0x68, 0x96, 0x81, 0xD9, 0x45, 0x3E, 0x10, 0x76, 0xC6, 0xA7, 0x8B, 0x39, 0x43, 0xE1,
    0x3A, 0xB5, 0x56, 0x2A, 0xC0, 0x6D, 0xB3, 0x05, 0x22, 0x66, 0xBF, 0xDC, 0x0B, 0xFA, 0x62, 0x48,
    0xDD, 0x20, 0x11, 0x06, 0x36, 0xC9, 0xC1, 0xCF, 0xF6, 0x27, 0x52, 0xBB, 0x69, 0xF5, 0xD4, 0x87,
    0x7F, 0x84, 0x4C, 0xD2, 0x9C, 0x57, 0xA4, 0xBC, 0x4F, 0x9A, 0xDF, 0xFE, 0xD6, 0x8D, 0x7A, 0xEB,
    0x2B, 0x53, 0xD8, 0x5C, 0xA1, 0x14, 0x17, 0xFB, 0x23, 0xD5, 0x7D, 0x30, 0x67, 0x73, 0x08, 0x09,
    0xEE, 0xB7, 0x70, 0x3F, 0x61, 0xB2, 0x19, 0x8E, 0x4E, 0xE5, 0x4B, 0x93, 0x8F, 0x5D, 0xDB, 0xA9,
    0xAD, 0xF1, 0xAE, 0x2E, 0xCB, 0x0D, 0xFC, 0xF4, 0x2D, 0x46, 0x6E, 0x1D, 0x97, 0xE8, 0xD1, 0xE9,
    0x4D, 0x37, 0xA5, 0x75, 0x5E, 0x83, 0x9E, 0xAB, 0x82, 0x9D, 0xB9, 0x1C, 0xE0, 0xCD, 0x49, 0x89,
    0x01, 0xB6, 0xBD, 0x58, 0x24, 0xA2, 0x5F, 0x38, 0x78, 0x99, 0x15, 0x90, 0x50, 0xB8, 0x95, 0xE4,
    0xD0, 0x91, 0xC7, 0xCE, 0xED, 0x0F, 0xB4, 0x6F, 0xA0, 0xCC, 0xF0, 0x02, 0x4A, 0x79, 0xC3, 0xDE,
    0xA3, 0xEF, 0xEA, 0x51, 0xE6, 0x6B, 0x18, 0xEC, 0x1B, 0x2C, 0x80, 0xF7, 0x74, 0xE7, 0xFF, 0x21,
    0x5A, 0x6A, 0x54, 0x1E, 0x41, 0x31, 0x92, 0x35, 0xC4, 0x33, 0x07, 0x0A, 0xBA, 0x7E, 0x0E, 0x34,
    0x88, 0xB1, 0x98, 0x7C, 0xF3, 0x3D, 0x60, 0x6C, 0x7B, 0xCA, 0xD3, 0x1F, 0x32, 0x65, 0x04, 0x28,
    0x64, 0xBE, 0x85, 0x9B, 0x2F, 0x59, 0x8A, 0xD7, 0xB0, 0x25, 0xAC, 0xAF, 0x12, 0x03, 0xE2, 0xF2
];

const D = [
    0x44D7, 0x26BC, 0x626B, 0x135E, 0x5789, 0x35E2, 0x7135, 0x09AF,
    0x4D78, 0x2F13, 0x6BC4, 0x1AF1, 0x5E26, 0x3C4D, 0x789A, 0x47AC
];

/**
 *
 */
class ZUC {
    /**
     * @param {Uint8Array} key - 16 bytes
     * @param {Uint8Array} iv - 16 bytes
     */
    constructor(key, iv) {
        if (key.length !== 16 || iv.length !== 16) {
            throw new Error("ZUC requires a 16-byte key and a 16-byte IV.");
        }

        this.LFSR = new Uint32Array(16);
        this.R1 = 0;
        this.R2 = 0;

        // Initialization
        for (let i = 0; i < 16; i++) {
            this.LFSR[i] = ((key[i] << 23) | (D[i] << 8) | iv[i]) >>> 0;
        }

        for (let i = 0; i < 32; i++) {
            this.bitReconstruction();
            const W = this.F();
            this.LFSRWithInitialisationMode(W >>> 1);
        }

        // Discard step before working mode
        this.bitReconstruction();
        this.F();
        this.LFSRWithWorkMode();
    }

    /**
     *
     */
    addM(a, b) {
        const c = Number(a) + Number(b);
        const high = Math.floor(c / 0x80000000);
        const low = c % 0x80000000;
        return (low + high) >>> 0;
    }

    /**
     * @param {number} u
     */
    LFSRWithInitialisationMode(u) {
        let v = this.LFSR[15];
        const f = this.LFSR[13];
        v = this.addM(v * Math.pow(2, 15), f * Math.pow(2, 17));
        v = this.addM(v, this.LFSR[10] * Math.pow(2, 21));
        v = this.addM(v, this.LFSR[4] * Math.pow(2, 20));
        v = this.addM(v, this.LFSR[0] * Math.pow(2, 8));
        v = this.addM(v, this.LFSR[0]);

        let s16 = this.addM(v, u);
        if (s16 === 0) s16 = 0x7fffffff;

        for (let i = 0; i < 15; i++) {
            this.LFSR[i] = this.LFSR[i + 1];
        }
        this.LFSR[15] = s16;
    }

    /**
     * Updates LFSR in work mode
     */
    LFSRWithWorkMode() {
        const v = this.LFSR[15];
        const f = this.LFSR[13];
        let s16 = this.addM(v * Math.pow(2, 15), f * Math.pow(2, 17));
        s16 = this.addM(s16, this.LFSR[10] * Math.pow(2, 21));
        s16 = this.addM(s16, this.LFSR[4] * Math.pow(2, 20));
        s16 = this.addM(s16, this.LFSR[0] * Math.pow(2, 8));
        s16 = this.addM(s16, this.LFSR[0]);

        if (s16 === 0) s16 = 0x7fffffff;

        for (let i = 0; i < 15; i++) {
            this.LFSR[i] = this.LFSR[i + 1];
        }
        this.LFSR[15] = s16;
    }

    /**
     * Bit reconstruction step
     */
    /**
     * Bit reconstruction step
     */
    bitReconstruction() {
        this.X0 = (((this.LFSR[15] >>> 15) << 16) | (this.LFSR[14] & 0xFFFF)) >>> 0;
        this.X1 = (((this.LFSR[11] & 0xFFFF) << 16) | (this.LFSR[9] >>> 15)) >>> 0;
        this.X2 = (((this.LFSR[7] & 0xFFFF) << 16) | (this.LFSR[5] >>> 15)) >>> 0;
        this.X3 = (((this.LFSR[2] & 0xFFFF) << 16) | (this.LFSR[0] >>> 15)) >>> 0;
    }

    /**
     * S-box substitution
     * @param {number} x
     * @returns {number}
     */
    S(x) {
        const x0 = (x >>> 24) & 0xFF;
        const x1 = (x >>> 16) & 0xFF;
        const x2 = (x >>> 8) & 0xFF;
        const x3 = x & 0xFF;

        return ((S0[x0] << 24) | (S1[x1] << 16) | (S0[x2] << 8) | S1[x3]) >>> 0;
    }

    /**
     * Rotate left 32 bit
     * @param {number} x
     * @param {number} k
     * @returns {number}
     */
    rotL32(x, k) {
        return ((x << k) | (x >>> (32 - k))) >>> 0;
    }

    /**
     * Linear transform L1
     * @param {number} x
     * @returns {number}
     */
    L1(x) {
        return (x ^ this.rotL32(x, 2) ^ this.rotL32(x, 10) ^ this.rotL32(x, 18) ^ this.rotL32(x, 24)) >>> 0;
    }

    /**
     * Linear transform L2
     * @param {number} x
     * @returns {number}
     */
    L2(x) {
        return (x ^ this.rotL32(x, 8) ^ this.rotL32(x, 14) ^ this.rotL32(x, 22) ^ this.rotL32(x, 30)) >>> 0;
    }

    /**
     * F function
     * @returns {number}
     */
    F() {
        const W = ((this.X0 ^ this.R1) >>> 0) + this.R2;
        const W1 = (this.R1 + this.X1) >>> 0;
        const W2 = (this.R2 ^ this.X2) >>> 0;

        const u = (((W1 & 0xFFFF) << 16) | (W2 >>> 16)) >>> 0;
        const v = (((W2 & 0xFFFF) << 16) | (W1 >>> 16)) >>> 0;

        this.R1 = this.S(this.L1(u));
        this.R2 = this.S(this.L2(v));

        return W >>> 0;
    }

    /**
     * @returns {number} 32-bit keystream word
     */
    generateKeystreamWord() {
        this.bitReconstruction();
        const W = this.F();
        const Z = (W ^ this.X3) >>> 0;
        this.LFSRWithWorkMode();
        return Z;
    }

    /**
     * Encrypts or decrypts data
     * @param {Uint8Array} data
     * @returns {Uint8Array}
     */
    process(data) {
        const length = data.length;
        const result = new Uint8Array(length);

        for (let i = 0; i < length; i++) {
            if (i % 4 === 0) {
                this.currentZ = this.generateKeystreamWord();
            }
            const shift = 24 - ((i % 4) * 8);
            const keyByte = (this.currentZ >>> shift) & 0xFF;
            result[i] = data[i] ^ keyByte;
        }

        return result;
    }
}

export default ZUC;