Merkle Tree Aeternity with MIMC hash as parameter

merkletree.aes

@compiler >= 6

include "List.aes"

contract interface MIMCSponge =
  entrypoint hasher: list(int) => list(int)

contract MerkleTreeWithHistory =

  record state = {
    field_size: int,
    hashing: MIMCSponge,
    levels: int,
    filled_subtrees: list(int),
    roots: list(int),
    root_history_size: int,
    current_root_index: int,
    next_index: int
   }
  
  stateful entrypoint init(_levels: int, _hasher: MIMCSponge) =
    require(_levels > 0 && _levels < 32, "Levels should be in range 0-32 ('Max-Min' is not included)")
    {
      field_size = 52435875175126190479447740508185965837690552500527637822603658699938581184513,
      levels = _levels,
      hashing = _hasher,
      filled_subtrees = zeros(),
      roots = [14128481056524536957498216347562587505734220138697483515041882766627531681467],
      root_history_size = 30,
      current_root_index = 0,
      next_index = 0
     }

  entrypoint hashLeftRight(_left: int, _right: int) : int =
    // Instead of using Field size in int, using in bytes reduced on conversion here.
    require(_left < state.field_size, "_left should be inside the field")
    require(_right < state.field_size, "_right should be inside the field")
    let outs: list(int) = state.hashing.hasher([_left, 0])
    let out_1 : int = (List.get(0, outs) + _right) mod state.field_size
    List.get(0, state.hashing.hasher([out_1, List.get(1, outs)]))

  stateful entrypoint insert(leaf: int) : int=
    let current_index : int = state.next_index
    require(current_index != (2 ^ state.levels), "Merkle tree is full, No more leaves can be added")
    let current_level_hash : int = _insert_loop(List.filter((x) => x < state.levels, zeros()), current_index, leaf)
    let new_root_index = (state.current_root_index + 1) mod state.root_history_size
    put(state{current_root_index = new_root_index})
    put(state{roots @ r = r ++ [current_level_hash]})
    put(state{next_index = current_index + 1})
    current_index
    
  // levels considered 20
  stateful function _insert_loop(zeros: list(int), current_index: int, _current_level_hash: int) : int =
    switch(zeros)
      [] => 
        _current_level_hash
      (zero :: zeros) =>
        let current_level_hash = 
          if(current_index mod 2 == 0)
            let right = zero
            let new_list = List.replace_at(zero, _current_level_hash, state.filled_subtrees)
            put(state{filled_subtrees = new_list})
            hashLeftRight(_current_level_hash, right)

          else
            let left = List.get(zero, state.filled_subtrees)
            hashLeftRight(left, _current_level_hash)

        let current_index = current_index / 2
        _insert_loop(zeros, current_index, current_level_hash)


  function zeros() : list(int) =
    [
        0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30,31
     ]