// Copyright (C) 2016 Dmitry Chestnykh
// MIT License. See LICENSE file for details.

/**
 * Package sha512 implements SHA-2-512 cryptographic hash function.
 */

import type { SerializableHash } from "@stablelib/hash";
import { readUint32BE, writeUint32BE } from "@stablelib/binary";
import { wipe } from "@stablelib/wipe";

export const DIGEST_LENGTH = 64;
export const BLOCK_SIZE = 128;

/**
 * SHA-2-512 cryptographic hash algorithm.
 */
export class SHA512 implements SerializableHash {
    /** Length of hash output */
    readonly digestLength: number = DIGEST_LENGTH;

    /** Block size */
    readonly blockSize: number = BLOCK_SIZE;

    // Note: Int32Array is used instead of Uint32Array for performance reasons.
    protected _stateHi = new Int32Array(8); // hash state, high bytes
    protected _stateLo = new Int32Array(8); // hash state, low bytes
    private _tempHi = new Int32Array(16); // temporary state, high bytes
    private _tempLo = new Int32Array(16); // temporary state, low bytes
    private _buffer = new Uint8Array(256); // buffer for data to hash
    private _bufferLength = 0; // number of bytes in buffer
    private _bytesHashed = 0; // number of total bytes hashed
    private _finished = false; // indicates whether the hash was finalized

    constructor() {
        this.reset();
    }

    protected _initState() {
        this._stateHi[0] = 0x6a09e667;
        this._stateHi[1] = 0xbb67ae85;
        this._stateHi[2] = 0x3c6ef372;
        this._stateHi[3] = 0xa54ff53a;
        this._stateHi[4] = 0x510e527f;
        this._stateHi[5] = 0x9b05688c;
        this._stateHi[6] = 0x1f83d9ab;
        this._stateHi[7] = 0x5be0cd19;

        this._stateLo[0] = 0xf3bcc908;
        this._stateLo[1] = 0x84caa73b;
        this._stateLo[2] = 0xfe94f82b;
        this._stateLo[3] = 0x5f1d36f1;
        this._stateLo[4] = 0xade682d1;
        this._stateLo[5] = 0x2b3e6c1f;
        this._stateLo[6] = 0xfb41bd6b;
        this._stateLo[7] = 0x137e2179;
    }

    /**
     * Resets hash state making it possible
     * to re-use this instance to hash other data.
     */
    reset(): this {
        this._initState();
        this._bufferLength = 0;
        this._bytesHashed = 0;
        this._finished = false;
        return this;
    }

    /**
     * Cleans internal buffers and resets hash state.
     */
    clean() {
        wipe(this._buffer);
        wipe(this._tempHi);
        wipe(this._tempLo);
        this.reset();
    }

    /**
     * Updates hash state with the given data.
     *
     * Throws error when trying to update already finalized hash:
     * instance must be reset to update it again.
     */
    update(data: Uint8Array, dataLength: number = data.length): this {
        if (this._finished) {
            throw new Error("SHA512: can't update because hash was finished.");
        }
        let dataPos = 0;
        this._bytesHashed += dataLength;
        if (this._bufferLength > 0) {
            while (this._bufferLength < BLOCK_SIZE && dataLength > 0) {
                this._buffer[this._bufferLength++] = data[dataPos++];
                dataLength--;
            }
            if (this._bufferLength === this.blockSize) {
                hashBlocks(this._tempHi, this._tempLo, this._stateHi, this._stateLo,
                    this._buffer, 0, this.blockSize);
                this._bufferLength = 0;
            }
        }
        if (dataLength >= this.blockSize) {
            dataPos = hashBlocks(this._tempHi, this._tempLo, this._stateHi, this._stateLo,
                data, dataPos, dataLength);
            dataLength %= this.blockSize;
        }
        while (dataLength > 0) {
            this._buffer[this._bufferLength++] = data[dataPos++];
            dataLength--;
        }
        return this;
    }

    /**
     * Finalizes hash state and puts hash into out.
     * If hash was already finalized, puts the same value.
     */
    finish(out: Uint8Array): this {
        if (!this._finished) {
            const bytesHashed = this._bytesHashed;
            const left = this._bufferLength;
            const bitLenHi = (bytesHashed / 0x20000000) | 0;
            const bitLenLo = bytesHashed << 3;
            const padLength = (bytesHashed % 128 < 112) ? 128 : 256;

            this._buffer[left] = 0x80;
            for (let i = left + 1; i < padLength - 8; i++) {
                this._buffer[i] = 0;
            }
            writeUint32BE(bitLenHi, this._buffer, padLength - 8);
            writeUint32BE(bitLenLo, this._buffer, padLength - 4);

            hashBlocks(this._tempHi, this._tempLo, this._stateHi, this._stateLo, this._buffer, 0, padLength);

            this._finished = true;
        }

        for (let i = 0; i < this.digestLength / 8; i++) {
            writeUint32BE(this._stateHi[i], out, i * 8);
            writeUint32BE(this._stateLo[i], out, i * 8 + 4);
        }

        return this;
    }

    /**
     * Returns the final hash digest.
     */
    digest(): Uint8Array {
        const out = new Uint8Array(this.digestLength);
        this.finish(out);
        return out;
    }

    /**
     * Function useful for HMAC/PBKDF2 optimization. Returns hash state to be
     * used with restoreState(). Only chain value is saved, not buffers or
     * other state variables.
     */
    saveState(): SavedState {
        if (this._finished) {
            throw new Error("SHA256: cannot save finished state");
        }
        return {
            stateHi: new Int32Array(this._stateHi),
            stateLo: new Int32Array(this._stateLo),
            buffer: this._bufferLength > 0 ? new Uint8Array(this._buffer) : undefined,
            bufferLength: this._bufferLength,
            bytesHashed: this._bytesHashed
        };
    }

    /**
     * Function useful for HMAC/PBKDF2 optimization. Restores state saved by
     * saveState() and sets bytesHashed to the given value.
     */
    restoreState(savedState: SavedState): this {
        this._stateHi.set(savedState.stateHi);
        this._stateLo.set(savedState.stateLo);
        this._bufferLength = savedState.bufferLength;
        if (savedState.buffer) {
            this._buffer.set(savedState.buffer);
        }
        this._bytesHashed = savedState.bytesHashed;
        this._finished = false;
        return this;
    }

    /**
     * Cleans state returned by saveState().
     */
    cleanSavedState(savedState: SavedState) {
        wipe(savedState.stateHi);
        wipe(savedState.stateLo);
        if (savedState.buffer) {
            wipe(savedState.buffer);
        }
        savedState.bufferLength = 0;
        savedState.bytesHashed = 0;
    }
}

export type SavedState = {
    stateHi: Int32Array;
    stateLo: Int32Array;
    buffer: Uint8Array | undefined;
    bufferLength: number;
    bytesHashed: number;
};

// Constants
const K = new Int32Array([
    0x428a2f98, 0xd728ae22, 0x71374491, 0x23ef65cd,
    0xb5c0fbcf, 0xec4d3b2f, 0xe9b5dba5, 0x8189dbbc,
    0x3956c25b, 0xf348b538, 0x59f111f1, 0xb605d019,
    0x923f82a4, 0xaf194f9b, 0xab1c5ed5, 0xda6d8118,
    0xd807aa98, 0xa3030242, 0x12835b01, 0x45706fbe,
    0x243185be, 0x4ee4b28c, 0x550c7dc3, 0xd5ffb4e2,
    0x72be5d74, 0xf27b896f, 0x80deb1fe, 0x3b1696b1,
    0x9bdc06a7, 0x25c71235, 0xc19bf174, 0xcf692694,
    0xe49b69c1, 0x9ef14ad2, 0xefbe4786, 0x384f25e3,
    0x0fc19dc6, 0x8b8cd5b5, 0x240ca1cc, 0x77ac9c65,
    0x2de92c6f, 0x592b0275, 0x4a7484aa, 0x6ea6e483,
    0x5cb0a9dc, 0xbd41fbd4, 0x76f988da, 0x831153b5,
    0x983e5152, 0xee66dfab, 0xa831c66d, 0x2db43210,
    0xb00327c8, 0x98fb213f, 0xbf597fc7, 0xbeef0ee4,
    0xc6e00bf3, 0x3da88fc2, 0xd5a79147, 0x930aa725,
    0x06ca6351, 0xe003826f, 0x14292967, 0x0a0e6e70,
    0x27b70a85, 0x46d22ffc, 0x2e1b2138, 0x5c26c926,
    0x4d2c6dfc, 0x5ac42aed, 0x53380d13, 0x9d95b3df,
    0x650a7354, 0x8baf63de, 0x766a0abb, 0x3c77b2a8,
    0x81c2c92e, 0x47edaee6, 0x92722c85, 0x1482353b,
    0xa2bfe8a1, 0x4cf10364, 0xa81a664b, 0xbc423001,
    0xc24b8b70, 0xd0f89791, 0xc76c51a3, 0x0654be30,
    0xd192e819, 0xd6ef5218, 0xd6990624, 0x5565a910,
    0xf40e3585, 0x5771202a, 0x106aa070, 0x32bbd1b8,
    0x19a4c116, 0xb8d2d0c8, 0x1e376c08, 0x5141ab53,
    0x2748774c, 0xdf8eeb99, 0x34b0bcb5, 0xe19b48a8,
    0x391c0cb3, 0xc5c95a63, 0x4ed8aa4a, 0xe3418acb,
    0x5b9cca4f, 0x7763e373, 0x682e6ff3, 0xd6b2b8a3,
    0x748f82ee, 0x5defb2fc, 0x78a5636f, 0x43172f60,
    0x84c87814, 0xa1f0ab72, 0x8cc70208, 0x1a6439ec,
    0x90befffa, 0x23631e28, 0xa4506ceb, 0xde82bde9,
    0xbef9a3f7, 0xb2c67915, 0xc67178f2, 0xe372532b,
    0xca273ece, 0xea26619c, 0xd186b8c7, 0x21c0c207,
    0xeada7dd6, 0xcde0eb1e, 0xf57d4f7f, 0xee6ed178,
    0x06f067aa, 0x72176fba, 0x0a637dc5, 0xa2c898a6,
    0x113f9804, 0xbef90dae, 0x1b710b35, 0x131c471b,
    0x28db77f5, 0x23047d84, 0x32caab7b, 0x40c72493,
    0x3c9ebe0a, 0x15c9bebc, 0x431d67c4, 0x9c100d4c,
    0x4cc5d4be, 0xcb3e42b6, 0x597f299c, 0xfc657e2a,
    0x5fcb6fab, 0x3ad6faec, 0x6c44198c, 0x4a475817
]);


function hashBlocks(wh: Int32Array, wl: Int32Array, hh: Int32Array, hl: Int32Array,
    m: Uint8Array, pos: number, len: number): number {

    let ah0 = hh[0],
        ah1 = hh[1],
        ah2 = hh[2],
        ah3 = hh[3],
        ah4 = hh[4],
        ah5 = hh[5],
        ah6 = hh[6],
        ah7 = hh[7],

        al0 = hl[0],
        al1 = hl[1],
        al2 = hl[2],
        al3 = hl[3],
        al4 = hl[4],
        al5 = hl[5],
        al6 = hl[6],
        al7 = hl[7];

    let h: number, l: number;
    let th: number, tl: number;
    let a: number, b: number, c: number, d: number;

    while (len >= 128) {
        for (let i = 0; i < 16; i++) {
            const j = 8 * i + pos;
            wh[i] = readUint32BE(m, j);
            wl[i] = readUint32BE(m, j + 4);
        }
        for (let i = 0; i < 80; i++) {
            let bh0 = ah0;
            let bh1 = ah1;
            let bh2 = ah2;
            let bh3 = ah3;
            let bh4 = ah4;
            let bh5 = ah5;
            let bh6 = ah6;
            let bh7 = ah7;

            let bl0 = al0;
            let bl1 = al1;
            let bl2 = al2;
            let bl3 = al3;
            let bl4 = al4;
            let bl5 = al5;
            let bl6 = al6;
            let bl7 = al7;

            // add
            h = ah7;
            l = al7;

            a = l & 0xffff; b = l >>> 16;
            c = h & 0xffff; d = h >>> 16;

            // Sigma1
            h = ((ah4 >>> 14) | (al4 << (32 - 14))) ^ ((ah4 >>> 18) |
                (al4 << (32 - 18))) ^ ((al4 >>> (41 - 32)) | (ah4 << (32 - (41 - 32))));
            l = ((al4 >>> 14) | (ah4 << (32 - 14))) ^ ((al4 >>> 18) |
                (ah4 << (32 - 18))) ^ ((ah4 >>> (41 - 32)) | (al4 << (32 - (41 - 32))));

            a += l & 0xffff; b += l >>> 16;
            c += h & 0xffff; d += h >>> 16;

            // Ch
            h = (ah4 & ah5) ^ (~ah4 & ah6);
            l = (al4 & al5) ^ (~al4 & al6);

            a += l & 0xffff; b += l >>> 16;
            c += h & 0xffff; d += h >>> 16;

            // K
            h = K[i * 2];
            l = K[i * 2 + 1];

            a += l & 0xffff; b += l >>> 16;
            c += h & 0xffff; d += h >>> 16;

            // w
            h = wh[i % 16];
            l = wl[i % 16];

            a += l & 0xffff; b += l >>> 16;
            c += h & 0xffff; d += h >>> 16;

            b += a >>> 16;
            c += b >>> 16;
            d += c >>> 16;

            th = c & 0xffff | d << 16;
            tl = a & 0xffff | b << 16;

            // add
            h = th;
            l = tl;

            a = l & 0xffff; b = l >>> 16;
            c = h & 0xffff; d = h >>> 16;

            // Sigma0
            h = ((ah0 >>> 28) | (al0 << (32 - 28))) ^ ((al0 >>> (34 - 32)) |
                (ah0 << (32 - (34 - 32)))) ^ ((al0 >>> (39 - 32)) | (ah0 << (32 - (39 - 32))));
            l = ((al0 >>> 28) | (ah0 << (32 - 28))) ^ ((ah0 >>> (34 - 32)) |
                (al0 << (32 - (34 - 32)))) ^ ((ah0 >>> (39 - 32)) | (al0 << (32 - (39 - 32))));

            a += l & 0xffff; b += l >>> 16;
            c += h & 0xffff; d += h >>> 16;

            // Maj
            h = (ah0 & ah1) ^ (ah0 & ah2) ^ (ah1 & ah2);
            l = (al0 & al1) ^ (al0 & al2) ^ (al1 & al2);

            a += l & 0xffff; b += l >>> 16;
            c += h & 0xffff; d += h >>> 16;

            b += a >>> 16;
            c += b >>> 16;
            d += c >>> 16;

            bh7 = (c & 0xffff) | (d << 16);
            bl7 = (a & 0xffff) | (b << 16);

            // add
            h = bh3;
            l = bl3;

            a = l & 0xffff; b = l >>> 16;
            c = h & 0xffff; d = h >>> 16;

            h = th;
            l = tl;

            a += l & 0xffff; b += l >>> 16;
            c += h & 0xffff; d += h >>> 16;

            b += a >>> 16;
            c += b >>> 16;
            d += c >>> 16;

            bh3 = (c & 0xffff) | (d << 16);
            bl3 = (a & 0xffff) | (b << 16);

            ah1 = bh0;
            ah2 = bh1;
            ah3 = bh2;
            ah4 = bh3;
            ah5 = bh4;
            ah6 = bh5;
            ah7 = bh6;
            ah0 = bh7;

            al1 = bl0;
            al2 = bl1;
            al3 = bl2;
            al4 = bl3;
            al5 = bl4;
            al6 = bl5;
            al7 = bl6;
            al0 = bl7;

            if (i % 16 === 15) {
                for (let j = 0; j < 16; j++) {
                    // add
                    h = wh[j];
                    l = wl[j];

                    a = l & 0xffff; b = l >>> 16;
                    c = h & 0xffff; d = h >>> 16;

                    h = wh[(j + 9) % 16];
                    l = wl[(j + 9) % 16];

                    a += l & 0xffff; b += l >>> 16;
                    c += h & 0xffff; d += h >>> 16;

                    // sigma0
                    th = wh[(j + 1) % 16];
                    tl = wl[(j + 1) % 16];
                    h = ((th >>> 1) | (tl << (32 - 1))) ^ ((th >>> 8) |
                        (tl << (32 - 8))) ^ (th >>> 7);
                    l = ((tl >>> 1) | (th << (32 - 1))) ^ ((tl >>> 8) |
                        (th << (32 - 8))) ^ ((tl >>> 7) | (th << (32 - 7)));

                    a += l & 0xffff; b += l >>> 16;
                    c += h & 0xffff; d += h >>> 16;

                    // sigma1
                    th = wh[(j + 14) % 16];
                    tl = wl[(j + 14) % 16];
                    h = ((th >>> 19) | (tl << (32 - 19))) ^ ((tl >>> (61 - 32)) |
                        (th << (32 - (61 - 32)))) ^ (th >>> 6);
                    l = ((tl >>> 19) | (th << (32 - 19))) ^ ((th >>> (61 - 32)) |
                        (tl << (32 - (61 - 32)))) ^ ((tl >>> 6) | (th << (32 - 6)));

                    a += l & 0xffff; b += l >>> 16;
                    c += h & 0xffff; d += h >>> 16;

                    b += a >>> 16;
                    c += b >>> 16;
                    d += c >>> 16;

                    wh[j] = (c & 0xffff) | (d << 16);
                    wl[j] = (a & 0xffff) | (b << 16);
                }
            }
        }

        // add
        h = ah0;
        l = al0;

        a = l & 0xffff; b = l >>> 16;
        c = h & 0xffff; d = h >>> 16;

        h = hh[0];
        l = hl[0];

        a += l & 0xffff; b += l >>> 16;
        c += h & 0xffff; d += h >>> 16;

        b += a >>> 16;
        c += b >>> 16;
        d += c >>> 16;

        hh[0] = ah0 = (c & 0xffff) | (d << 16);
        hl[0] = al0 = (a & 0xffff) | (b << 16);

        h = ah1;
        l = al1;

        a = l & 0xffff; b = l >>> 16;
        c = h & 0xffff; d = h >>> 16;

        h = hh[1];
        l = hl[1];

        a += l & 0xffff; b += l >>> 16;
        c += h & 0xffff; d += h >>> 16;

        b += a >>> 16;
        c += b >>> 16;
        d += c >>> 16;

        hh[1] = ah1 = (c & 0xffff) | (d << 16);
        hl[1] = al1 = (a & 0xffff) | (b << 16);

        h = ah2;
        l = al2;

        a = l & 0xffff; b = l >>> 16;
        c = h & 0xffff; d = h >>> 16;

        h = hh[2];
        l = hl[2];

        a += l & 0xffff; b += l >>> 16;
        c += h & 0xffff; d += h >>> 16;

        b += a >>> 16;
        c += b >>> 16;
        d += c >>> 16;

        hh[2] = ah2 = (c & 0xffff) | (d << 16);
        hl[2] = al2 = (a & 0xffff) | (b << 16);

        h = ah3;
        l = al3;

        a = l & 0xffff; b = l >>> 16;
        c = h & 0xffff; d = h >>> 16;

        h = hh[3];
        l = hl[3];

        a += l & 0xffff; b += l >>> 16;
        c += h & 0xffff; d += h >>> 16;

        b += a >>> 16;
        c += b >>> 16;
        d += c >>> 16;

        hh[3] = ah3 = (c & 0xffff) | (d << 16);
        hl[3] = al3 = (a & 0xffff) | (b << 16);

        h = ah4;
        l = al4;

        a = l & 0xffff; b = l >>> 16;
        c = h & 0xffff; d = h >>> 16;

        h = hh[4];
        l = hl[4];

        a += l & 0xffff; b += l >>> 16;
        c += h & 0xffff; d += h >>> 16;

        b += a >>> 16;
        c += b >>> 16;
        d += c >>> 16;

        hh[4] = ah4 = (c & 0xffff) | (d << 16);
        hl[4] = al4 = (a & 0xffff) | (b << 16);

        h = ah5;
        l = al5;

        a = l & 0xffff; b = l >>> 16;
        c = h & 0xffff; d = h >>> 16;

        h = hh[5];
        l = hl[5];

        a += l & 0xffff; b += l >>> 16;
        c += h & 0xffff; d += h >>> 16;

        b += a >>> 16;
        c += b >>> 16;
        d += c >>> 16;

        hh[5] = ah5 = (c & 0xffff) | (d << 16);
        hl[5] = al5 = (a & 0xffff) | (b << 16);

        h = ah6;
        l = al6;

        a = l & 0xffff; b = l >>> 16;
        c = h & 0xffff; d = h >>> 16;

        h = hh[6];
        l = hl[6];

        a += l & 0xffff; b += l >>> 16;
        c += h & 0xffff; d += h >>> 16;

        b += a >>> 16;
        c += b >>> 16;
        d += c >>> 16;

        hh[6] = ah6 = (c & 0xffff) | (d << 16);
        hl[6] = al6 = (a & 0xffff) | (b << 16);

        h = ah7;
        l = al7;

        a = l & 0xffff; b = l >>> 16;
        c = h & 0xffff; d = h >>> 16;

        h = hh[7];
        l = hl[7];

        a += l & 0xffff; b += l >>> 16;
        c += h & 0xffff; d += h >>> 16;

        b += a >>> 16;
        c += b >>> 16;
        d += c >>> 16;

        hh[7] = ah7 = (c & 0xffff) | (d << 16);
        hl[7] = al7 = (a & 0xffff) | (b << 16);

        pos += 128;
        len -= 128;
    }

    return pos;
}

export function hash(data: Uint8Array): Uint8Array {
    const h = new SHA512();
    h.update(data);
    const digest = h.digest();
    h.clean();
    return digest;
}