using System;

namespace Org.BouncyCastle.Crypto.Digests
{
    /**
     * SHA-224 as described in RFC 3874
     * <pre>
     *         block  word  digest
     * SHA-1   512    32    160
     * SHA-224 512    32    224
     * SHA-256 512    32    256
     * SHA-384 1024   64    384
     * SHA-512 1024   64    512
     * </pre>
     */
    public class Sha224Digest
        : GeneralDigest
    {
        private const int DigestLength = 28;

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

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

		/**
         * Standard constructor
         */
        public Sha224Digest()
        {
            Reset();
        }

		/**
         * Copy constructor.  This will copy the state of the provided
         * message digest.
         */
         public Sha224Digest(
			 Sha224Digest t)
			 : base(t)
        {
            H1 = t.H1;
            H2 = t.H2;
            H3 = t.H3;
            H4 = t.H4;
            H5 = t.H5;
            H6 = t.H6;
            H7 = t.H7;
            H8 = t.H8;

            Array.Copy(t.X, 0, X, 0, t.X.Length);
            xOff = t.xOff;
        }

		public override string AlgorithmName
		{
			get { return "SHA-224"; }
		}

		public override int GetDigestSize()
		{
			return DigestLength;
		}

		internal override void ProcessWord(
            byte[]  input,
            int     inOff)
        {
            X[xOff++] = ((input[inOff] & 0xff) << 24) | ((input[inOff + 1] & 0xff) << 16)
                        | ((input[inOff + 2] & 0xff) << 8) | ((input[inOff + 3] & 0xff));

            if (xOff == 16)
            {
                ProcessBlock();
            }
        }

		private void UnpackWord(
            int     word,
            byte[]  outBytes,
            int     outOff)
        {
            outBytes[outOff]     = (byte)((uint) word >> 24);
            outBytes[outOff + 1] = (byte)((uint) word >> 16);
            outBytes[outOff + 2] = (byte)((uint) word >> 8);
            outBytes[outOff + 3] = (byte)word;
        }

		internal override void ProcessLength(
            long bitLength)
        {
            if (xOff > 14)
            {
                ProcessBlock();
            }

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

        public override int DoFinal(
            byte[]	output,
            int		outOff)
        {
            Finish();

			UnpackWord(H1, output, outOff);
            UnpackWord(H2, output, outOff + 4);
            UnpackWord(H3, output, outOff + 8);
            UnpackWord(H4, output, outOff + 12);
            UnpackWord(H5, output, outOff + 16);
            UnpackWord(H6, output, outOff + 20);
            UnpackWord(H7, output, outOff + 24);

			Reset();

			return DigestLength;
        }

		/**
         * reset the chaining variables
         */
        public override void Reset()
        {
            base.Reset();

            /* SHA-224 initial hash value
             */

            unchecked
            {
                H1 = (int) 0xc1059ed8;
                H2 = (int) 0x367cd507;
                H3 = (int) 0x3070dd17;
                H4 = (int) 0xf70e5939;
                H5 = (int) 0xffc00b31;
                H6 = (int) 0x68581511;
                H7 = (int) 0x64f98fa7;
                H8 = (int) 0xbefa4fa4;
            }

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

        internal override void ProcessBlock()
        {
            //
            // expand 16 word block into 64 word blocks.
            //
            for (int ti = 16; ti <= 63; ti++)
            {
                X[ti] = Theta1(X[ti - 2]) + X[ti - 7] + Theta0(X[ti - 15]) + X[ti - 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) + (int)K[t] + X[t++];
				d += h;
				h += Sum0(a) + Maj(a, b, c);

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

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

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

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

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

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

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

			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;

			Array.Clear(X, 0, 16);
		}

		/* SHA-224 functions */
        private static int Ch(
            int    x,
            int    y,
            int    z)
        {
            return ((x & y) ^ ((~x) & z));
        }

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

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

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

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

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

		/* SHA-224 Constants
         * (represent the first 32 bits of the fractional parts of the
         * cube roots of the first sixty-four prime numbers)
         */
        internal static readonly uint[] 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
        };
    }
}