using System;
using System.Diagnostics;

namespace Org.BouncyCastle.Math.EC.Custom.Sec
{
    internal class SecP384R1Field
    {
            // 2^384 - 2^128 - 2^96 + 2^32 - 1
        internal static readonly uint[] P = new uint[]{ 0xFFFFFFFF, 0x00000000, 0x00000000, 0xFFFFFFFF, 0xFFFFFFFE, 0xFFFFFFFF,
            0xFFFFFFFF, 0xFFFFFFFF, 0xFFFFFFFF, 0xFFFFFFFF, 0xFFFFFFFF, 0xFFFFFFFF };
        private const uint P11 = 0xFFFFFFFF;
        private static readonly uint[] PExt = new uint[]{ 0x00000001, 0xFFFFFFFE, 0x00000000, 0x00000002, 0x00000000, 0xFFFFFFFE,
            0x00000000, 0x00000002, 0x00000001, 0x00000000, 0x00000000, 0x00000000, 0xFFFFFFFE, 0x00000001, 0x00000000,
            0xFFFFFFFE, 0xFFFFFFFD, 0xFFFFFFFF, 0xFFFFFFFF, 0xFFFFFFFF, 0xFFFFFFFF, 0xFFFFFFFF, 0xFFFFFFFF, 0xFFFFFFFF };
        private const uint PExt23 = 0xFFFFFFFF;

        public static void Add(uint[] x, uint[] y, uint[] z)
        {
            uint c = Nat.Add(12, x, y, z);
            if (c != 0 || (z[11] == P11 && Nat.Gte(12, z, P)))
            {
                Nat.Sub(12, z, P, z);
            }
        }

        public static void AddExt(uint[] xx, uint[] yy, uint[] zz)
        {
            uint c = Nat.Add(24, xx, yy, zz);
            if (c != 0 || (zz[23] == PExt23 && Nat.Gte(24, zz, PExt)))
            {
                Nat.Sub(24, zz, PExt, zz);
            }
        }

        public static void AddOne(uint[] x, uint[] z)
        {
            Nat.Copy(12, x, z);
            uint c = Nat.Inc(12, z, 0);
            if (c != 0 || (z[11] == P11 && Nat.Gte(12, z, P)))
            {
                Nat.Sub(12, z, P, z);
            }
        }

        public static uint[] FromBigInteger(BigInteger x)
        {
            uint[] z = Nat.FromBigInteger(384, x);
            if (z[11] == P11 && Nat.Gte(12, z, P))
            {
                Nat.Sub(12, z, P, z);
            }
            return z;
        }

        public static void Half(uint[] x, uint[] z)
        {
            if ((x[0] & 1) == 0)
            {
                Nat.ShiftDownBit(12, x, 0, z);
            }
            else
            {
                uint c = Nat.Add(12, x, P, z);
                Nat.ShiftDownBit(12, z, c);
            }
        }

        public static void Multiply(uint[] x, uint[] y, uint[] z)
        {
            uint[] tt = Nat.Create(24);
            Nat384.Mul(x, y, tt);
            Reduce(tt, z);
        }

        public static void Negate(uint[] x, uint[] z)
        {
            if (Nat.IsZero(12, x))
            {
                Nat.Zero(12, z);
            }
            else
            {
                Nat.Sub(12, P, x, z);
            }
        }

        public static void Reduce(uint[] xx, uint[] z)
        {
            long xx12 = xx[12], xx13 = xx[13], xx14 = xx[14], xx15 = xx[15];
            long xx16 = xx[16], xx17 = xx[17], xx18 = xx[18], xx19 = xx[19];
            long xx20 = xx[20], xx21 = xx[21], xx22 = xx[22], xx23 = xx[23];

            long cc = 0;
            cc += (long)xx[0] + xx12 + xx20 + xx21 - xx23;
            z[0] = (uint)cc;
            cc >>= 32;
            cc += (long)xx[1] + xx13 + xx22 + xx23 - xx12 - xx20;
            z[1] = (uint)cc;
            cc >>= 32;
            cc += (long)xx[2] + xx14 + xx23 - xx13 - xx21;
            z[2] = (uint)cc;
            cc >>= 32;
            cc += (long)xx[3] + xx12 + xx15 + xx20 + xx21 - xx14 - xx22 - xx23;
            z[3] = (uint)cc;
            cc >>= 32;
            cc += (long)xx[4] + xx12 + xx13 + xx16 + xx20 + ((xx21 - xx23) << 1) + xx22 - xx15;
            z[4] = (uint)cc;
            cc >>= 32;
            cc += (long)xx[5] + xx13 + xx14 + xx17 + xx21 + (xx22 << 1) + xx23 - xx16;
            z[5] = (uint)cc;
            cc >>= 32;
            cc += (long)xx[6] + xx14 + xx15 + xx18 + xx22 + (xx23 << 1) - xx17;
            z[6] = (uint)cc;
            cc >>= 32;
            cc += (long)xx[7] + xx15 + xx16 + xx19 + xx23 - xx18;
            z[7] = (uint)cc;
            cc >>= 32;
            cc += (long)xx[8] + xx16 + xx17 + xx20 - xx19;
            z[8] = (uint)cc;
            cc >>= 32;
            cc += (long)xx[9] + xx17 + xx18 + xx21 - xx20;
            z[9] = (uint)cc;
            cc >>= 32;
            cc += (long)xx[10] + xx18 + xx19 + xx22 - xx21;
            z[10] = (uint)cc;
            cc >>= 32;
            cc += (long)xx[11] + xx19 + xx20 + xx23 - xx22;
            z[11] = (uint)cc;
            cc >>= 32;

            int c = (int)cc;
            if (c > 0)
            {
                Reduce32((uint)c, z);
            }
            else
            {
                while (c < 0)
                {
                    c += (int)Nat256.Add(z, P, z);
                }
            }
        }

        public static void Reduce32(uint x, uint[] z)
        {
            long xx12 = x;

            long cc = 0;
            cc += (long)z[0] + xx12;
            z[0] = (uint)cc;
            cc >>= 32;
            cc += (long)z[1] - xx12;
            z[1] = (uint)cc;
            cc >>= 32;
            cc += (long)z[2];
            z[2] = (uint)cc;
            cc >>= 32;
            cc += (long)z[3] + xx12;
            z[3] = (uint)cc;
            cc >>= 32;
            cc += (long)z[4] + xx12;
            z[4] = (uint)cc;
            cc >>= 32;

            Debug.Assert(cc >= 0);

            if (cc > 0)
            {
                uint c = Nat.AddWord(12, (uint)cc, z, 5);
                if (c != 0 || (z[11] == P11 && Nat.Gte(12, z, P)))
                {
                    Nat.Sub(12, z, P, z);
                }
            }
        }

        public static void Square(uint[] x, uint[] z)
        {
            uint[] tt = Nat.Create(24);
            Nat384.Square(x, tt);
            Reduce(tt, z);
        }

        public static void SquareN(uint[] x, int n, uint[] z)
        {
            Debug.Assert(n > 0);

            uint[] tt = Nat.Create(24);
            Nat384.Square(x, tt);
            Reduce(tt, z);

            while (--n > 0)
            {
                Nat384.Square(z, tt);
                Reduce(tt, z);
            }
        }

        public static void Subtract(uint[] x, uint[] y, uint[] z)
        {
            int c = Nat.Sub(12, x, y, z);
            if (c != 0)
            {
                Nat.Add(12, z, P, z);
            }
        }

        public static void SubtractExt(uint[] xx, uint[] yy, uint[] zz)
        {
            int c = Nat.Sub(24, xx, yy, zz);
            if (c != 0)
            {
                Nat.Add(24, zz, PExt, zz);
            }
        }

        public static void Twice(uint[] x, uint[] z)
        {
            uint c = Nat.ShiftUpBit(12, x, 0, z);
            if (c != 0 || (z[11] == P11 && Nat.Gte(12, z, P)))
            {
                Nat.Sub(12, z, P, z);
            }
        }
    }
}