/*
 * Copyright (c) 2000-2021 The Legion of the Bouncy Castle Inc. (https://www.bouncycastle.org)
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy of this software 
 * and associated documentation files (the "Software"), to deal in the Software without restriction, 
 * including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, 
 * and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so,
 * subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in all copies or substantial
 * portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED,
 * INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR
 * PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
 * LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
 * OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
 * DEALINGS IN THE SOFTWARE.
 * 
 */

package net.lax1dude.eaglercraft.v1_8.crypto;

public class SHA256Digest extends GeneralDigest {

	private static final int DIGEST_LENGTH = 32;

	private int H1, H2, H3, H4, H5, H6, H7, H8;

	private int[] X = new int[64];
	private int xOff;

	public SHA256Digest() {
		reset();
	}

	public static int bigEndianToInt(byte[] bs, int off) {
		int n = bs[off] << 24;
		n |= (bs[++off] & 0xff) << 16;
		n |= (bs[++off] & 0xff) << 8;
		n |= (bs[++off] & 0xff);
		return n;
	}

	public static void bigEndianToInt(byte[] bs, int off, int[] ns) {
		for (int i = 0; i < ns.length; ++i) {
			ns[i] = bigEndianToInt(bs, off);
			off += 4;
		}
	}

	public static byte[] intToBigEndian(int n) {
		byte[] bs = new byte[4];
		intToBigEndian(n, bs, 0);
		return bs;
	}

	public static void intToBigEndian(int n, byte[] bs, int off) {
		bs[off] = (byte) (n >>> 24);
		bs[++off] = (byte) (n >>> 16);
		bs[++off] = (byte) (n >>> 8);
		bs[++off] = (byte) (n);
	}

	protected void processWord(byte[] in, int inOff) {
		X[xOff] = bigEndianToInt(in, inOff);

		if (++xOff == 16) {
			processBlock();
		}
	}

	protected void processLength(long bitLength) {
		if (xOff > 14) {
			processBlock();
		}

		X[14] = (int) (bitLength >>> 32);
		X[15] = (int) (bitLength & 0xffffffff);
	}

	public int doFinal(byte[] out, int outOff) {
		finish();

		intToBigEndian(H1, out, outOff);
		intToBigEndian(H2, out, outOff + 4);
		intToBigEndian(H3, out, outOff + 8);
		intToBigEndian(H4, out, outOff + 12);
		intToBigEndian(H5, out, outOff + 16);
		intToBigEndian(H6, out, outOff + 20);
		intToBigEndian(H7, out, outOff + 24);
		intToBigEndian(H8, out, outOff + 28);

		reset();

		return DIGEST_LENGTH;
	}

	/**
	 * reset the chaining variables
	 */
	public void reset() {
		super.reset();

		/*
		 * SHA-256 initial hash value The first 32 bits of the fractional parts of the
		 * square roots of the first eight prime numbers
		 */

		H1 = 0x6a09e667;
		H2 = 0xbb67ae85;
		H3 = 0x3c6ef372;
		H4 = 0xa54ff53a;
		H5 = 0x510e527f;
		H6 = 0x9b05688c;
		H7 = 0x1f83d9ab;
		H8 = 0x5be0cd19;

		xOff = 0;
		for (int i = 0; i != X.length; i++) {
			X[i] = 0;
		}
	}

	protected void processBlock() {
		//
		// expand 16 word block into 64 word blocks.
		//
		for (int t = 16; t <= 63; t++) {
			X[t] = Theta1(X[t - 2]) + X[t - 7] + Theta0(X[t - 15]) + X[t - 16];
		}

		//
		// set up working variables.
		//
		int a = H1;
		int b = H2;
		int c = H3;
		int d = H4;
		int e = H5;
		int f = H6;
		int g = H7;
		int h = H8;

		int t = 0;
		for (int i = 0; i < 8; i++) {
			// t = 8 * i
			h += Sum1(e) + Ch(e, f, g) + K[t] + X[t];
			d += h;
			h += Sum0(a) + Maj(a, b, c);
			++t;

			// t = 8 * i + 1
			g += Sum1(d) + Ch(d, e, f) + K[t] + X[t];
			c += g;
			g += Sum0(h) + Maj(h, a, b);
			++t;

			// t = 8 * i + 2
			f += Sum1(c) + Ch(c, d, e) + K[t] + X[t];
			b += f;
			f += Sum0(g) + Maj(g, h, a);
			++t;

			// t = 8 * i + 3
			e += Sum1(b) + Ch(b, c, d) + K[t] + X[t];
			a += e;
			e += Sum0(f) + Maj(f, g, h);
			++t;

			// t = 8 * i + 4
			d += Sum1(a) + Ch(a, b, c) + K[t] + X[t];
			h += d;
			d += Sum0(e) + Maj(e, f, g);
			++t;

			// t = 8 * i + 5
			c += Sum1(h) + Ch(h, a, b) + K[t] + X[t];
			g += c;
			c += Sum0(d) + Maj(d, e, f);
			++t;

			// t = 8 * i + 6
			b += Sum1(g) + Ch(g, h, a) + K[t] + X[t];
			f += b;
			b += Sum0(c) + Maj(c, d, e);
			++t;

			// t = 8 * i + 7
			a += Sum1(f) + Ch(f, g, h) + K[t] + X[t];
			e += a;
			a += Sum0(b) + Maj(b, c, d);
			++t;
		}

		H1 += a;
		H2 += b;
		H3 += c;
		H4 += d;
		H5 += e;
		H6 += f;
		H7 += g;
		H8 += h;

		//
		// reset the offset and clean out the word buffer.
		//
		xOff = 0;
		for (int i = 0; i < 16; i++) {
			X[i] = 0;
		}
	}

	/* SHA-256 functions */
	private static int Ch(int x, int y, int z) {
		return (x & y) ^ ((~x) & z);
//        return z ^ (x & (y ^ z));
	}

	private static int Maj(int x, int y, int z) {
//        return (x & y) ^ (x & z) ^ (y & z);
		return (x & y) | (z & (x ^ y));
	}

	private static int Sum0(int x) {
		return ((x >>> 2) | (x << 30)) ^ ((x >>> 13) | (x << 19)) ^ ((x >>> 22) | (x << 10));
	}

	private static int Sum1(int x) {
		return ((x >>> 6) | (x << 26)) ^ ((x >>> 11) | (x << 21)) ^ ((x >>> 25) | (x << 7));
	}

	private static int Theta0(int x) {
		return ((x >>> 7) | (x << 25)) ^ ((x >>> 18) | (x << 14)) ^ (x >>> 3);
	}

	private static int Theta1(int x) {
		return ((x >>> 17) | (x << 15)) ^ ((x >>> 19) | (x << 13)) ^ (x >>> 10);
	}

	/*
	 * SHA-256 Constants (represent the first 32 bits of the fractional parts of the
	 * cube roots of the first sixty-four prime numbers)
	 */
	static final int K[] = { 0x428a2f98, 0x71374491, 0xb5c0fbcf, 0xe9b5dba5, 0x3956c25b, 0x59f111f1, 0x923f82a4,
			0xab1c5ed5, 0xd807aa98, 0x12835b01, 0x243185be, 0x550c7dc3, 0x72be5d74, 0x80deb1fe, 0x9bdc06a7, 0xc19bf174,
			0xe49b69c1, 0xefbe4786, 0x0fc19dc6, 0x240ca1cc, 0x2de92c6f, 0x4a7484aa, 0x5cb0a9dc, 0x76f988da, 0x983e5152,
			0xa831c66d, 0xb00327c8, 0xbf597fc7, 0xc6e00bf3, 0xd5a79147, 0x06ca6351, 0x14292967, 0x27b70a85, 0x2e1b2138,
			0x4d2c6dfc, 0x53380d13, 0x650a7354, 0x766a0abb, 0x81c2c92e, 0x92722c85, 0xa2bfe8a1, 0xa81a664b, 0xc24b8b70,
			0xc76c51a3, 0xd192e819, 0xd6990624, 0xf40e3585, 0x106aa070, 0x19a4c116, 0x1e376c08, 0x2748774c, 0x34b0bcb5,
			0x391c0cb3, 0x4ed8aa4a, 0x5b9cca4f, 0x682e6ff3, 0x748f82ee, 0x78a5636f, 0x84c87814, 0x8cc70208, 0x90befffa,
			0xa4506ceb, 0xbef9a3f7, 0xc67178f2 };

}
