defmodule ExWeb3EcRecover.RecoverPersonalSignature do
  @moduledoc """
  Documentation for `RecoverPersonalSignature`.
  """


  def recover_personal_signature( %{sig: signature_hex, msg: message }) do

        {r,s,v_num } = convert_sig_to_components(signature_hex)
        bin_message =  create_hash_from_personal_message(message)
        {:ok, recovered_key} =  ExSecp256k1.recover(bin_message, r, s,v_num)
    
        get_address_from_recovered_key(recovered_key)
  end


  def get_address_from_recovered_key(key) do

        address= key
        |> binary_part(1, 64)
        |> ExKeccak.hash_256()
        |> Base.encode16(case: :lower)
        |> String.slice(-40..-1)
        "0x#{address}"
  end


  def convert_sig_to_components(signature_hex) do
    sig_binary = 
    String.trim_leading(signature_hex, "0x")
    |>Base.decode16!(case: :lower)

    r = binary_part(sig_binary, 0, 32)
    s = binary_part(sig_binary, 32, 32)
    v_num = binary_part(sig_binary, 64, 1) 
    |> :binary.decode_unsigned()


    {r,s,v_num - 27}

  end


  def create_hash_from_personal_message(orig_message) do

       "\u0019Ethereum Signed Message:\n#{byte_size(orig_message)}" <> orig_message
       |> ExKeccak.hash_256()


  end

  def legacyToBuffer(binary) do
    case Base.decode16(binary) do
      {:ok, result} -> result
      _ -> binary

    end
end




end