Poseidon.cs

namespace Drm_Mina;

public static class Poseidon
{
    private static int fullRounds;
    private static int partialRounds;
    private static bool hasInitialRoundConstant;
    private static int stateSize;
    private static int rate;
    private static int power;

    private static Field[][] roundConstants;
    private static Field[,] mds;

    static Poseidon()
    {
        fullRounds = Constants.FullRounds;
        partialRounds = Constants.PartialRounds;
        hasInitialRoundConstant = Constants.HasInitialRoundConstant;
        stateSize = Constants.StateSize;
        rate = Constants.Rate;
        power = Constants.Power;
        roundConstants = Constants.RoundConstants;
        mds = Constants.MdsMatrix;

        if (partialRounds != 0)
        {
            throw new ArgumentException("o1js don't support partial rounds");
        }
    }


    public static Field Hash(Field[] input)
    {
        var state = Update(InitialState(), input);
        return state[0];
    }

    private static Field[] InitialState()
    {
        var state = new Field[stateSize];
        for (int i = 0; i < stateSize; i++)
        {
            state[i] = new Field(0);
        }

        return state;
    }


    private static Field[] Update(Field[] state, Field[] input)
    {
        if (input.Length == 0)
        {
            Permutation(state);
            return state;
        }

        int n = (int)Math.Ceiling((double)input.Length / rate) * rate;
        var paddedInput = new Field[n];
        Array.Copy(input, paddedInput, input.Length);
        for (int i = input.Length; i < n; i++)
        {
            paddedInput[i] = new Field(0);
        }

        for (int blockIndex = 0; blockIndex < n; blockIndex += rate)
        {
            for (int i = 0; i < rate; i++)
            {
                state[i] = state[i] + paddedInput[blockIndex + i];
            }

            Permutation(state);
        }

        return state;
    }


    private static void Permutation(Field[] state)
    {
        int offset = 0;
        if (hasInitialRoundConstant)
        {
            for (int i = 0; i < state.Length; i++)
            {
                state[i] = state[i] + roundConstants[0][i];
            }

            offset = 1;
        }

        for (int round = 0; round < fullRounds; round++)
        {
            for (int i = 0; i < state.Length; i++)
            {
                state[i] = Field.Power(state[i], power);
            }

            var oldState = (Field[])state.Clone();
            for (int i = 0; i < state.Length; i++)
            {
                Field[] mdsRow = new Field[state.Length];
                for (int j = 0; j < state.Length; j++)
                {
                    mdsRow[j] = mds[i, j];
                }

                state[i] = Field.Dot(mdsRow, oldState) + roundConstants[round + offset][i];
            }
        }
    }
}