{-# LANGUAGE AllowAmbiguousTypes #-}

module ZkFold.Base.Protocol.ARK.Protostar.Accumulator where

import           Prelude                         hiding (length)

import           ZkFold.Base.Algebra.Basic.Class

data AccumulatorInstance f c = AccumulatorInstance {
      accPublicInput :: f
    , accCommits     :: [c]
    , accChallenges  :: [f]
    , accError       :: c
    , accMu          :: f
}

newtype AccumulatorWitness m = AccumulatorWitness { accMessages :: [m] }

data Accumulator f c m = Accumulator (AccumulatorInstance f c) (AccumulatorWitness m)

data NARKInstance f c = NARKInstance {
      narkPublicInput :: f
    , narkCommits     :: [c]
}

newtype NARKWitness m = NARKWitness { narkMessages :: [m] }

data NARKPair pi f c m = NARKPair (NARKInstance f c) (NARKWitness m)

toAccumulatorInstance :: (FiniteField f, AdditiveGroup c) => (f -> c -> f) -> NARKInstance f c -> AccumulatorInstance f c
toAccumulatorInstance oracle (NARKInstance i cs) =
      let r0 = oracle i zero
          f acc@(r:_) c = oracle r c : acc
          f []        _ = error "Invalid accumulator instance"
          rs = init $ reverse $ foldl f [r0] cs
      in AccumulatorInstance i cs rs zero one

toAccumulatorWitness :: NARKWitness m -> AccumulatorWitness m
toAccumulatorWitness (NARKWitness ms) = AccumulatorWitness ms

toAccumulator :: (FiniteField f, AdditiveGroup c) => (f -> c -> f) -> NARKPair pi f c m -> Accumulator f c m
toAccumulator oracle (NARKPair i w) = Accumulator (toAccumulatorInstance oracle i) (toAccumulatorWitness w)