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(* Open Source License                                                       *)
(* Copyright (c) 2019-2020 Nomadic Labs <contact@nomadic-labs.com>           *)
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open Client_keys_v0
open Tezos_sapling.Core.Client

module Mnemonic = struct
  let new_random = Bip39.of_entropy (Tezos_crypto.Hacl.Rand.gen 32)

  let to_sapling_key mnemonic =
    (* Z-cash needs 32 bytes and BIP-39 gives 64 bytes of entropy.
       We xor the two halves in case the entropy is not well distributed. *)
    let seed_64_to_seed_32 (seed_64 : bytes) : bytes =
      assert (Bytes.length seed_64 = 64) ;
      let first_32 = Bytes.sub seed_64 0 32 in
      let second_32 = Bytes.sub seed_64 32 32 in
      let seed_32 = Bytes.create 32 in
      for i = 0 to 31 do
        Bytes.set
          seed_32
          i
          (Char.chr
             (Char.code (Bytes.get first_32 i)
             lxor Char.code (Bytes.get second_32 i)))
      done ;
      seed_32
    in
    Spending_key.of_seed (seed_64_to_seed_32 (Bip39.to_seed mnemonic))

  let words_pp = Format.(pp_print_list ~pp_sep:pp_print_space pp_print_string)
end

(* Transform a spending key to an uri, encrypted or not. *)
let to_uri unencrypted cctxt sapling_key =
  if unencrypted then
    Lwt.return (Tezos_signer_backends.Unencrypted.make_sapling_key sapling_key)
  else Tezos_signer_backends.Encrypted.encrypt_sapling_key cctxt sapling_key

(** Transform an uri into a spending key, asking for a password if the uri was
    encrypted. *)
let from_uri (cctxt : #Client_context.full) uri =
  Tezos_signer_backends.Encrypted.decrypt_sapling_key cctxt uri

let register (cctxt : #Client_context.full) ?(force = false)
    ?(unencrypted = false) mnemonic name =
  let sk = Mnemonic.to_sapling_key mnemonic in
  to_uri unencrypted cctxt sk >>=? fun sk_uri ->
  let key =
    {
      sk = sk_uri;
      path = [Spending_key.child_index sk];
      address_index = Viewing_key.default_index;
    }
  in
  Sapling_key.add ~force cctxt name key >>=? fun () ->
  return @@ Viewing_key.of_sk sk

let derive (cctxt : #Client_context.full) ?(force = false)
    ?(unencrypted = false) src_name dst_name child_index =
  Sapling_key.find cctxt src_name >>=? fun k ->
  from_uri cctxt k.sk >>=? fun src_sk ->
  let child_index = Int32.of_int child_index in
  let dst_sk = Spending_key.derive_key src_sk child_index in
  to_uri unencrypted cctxt dst_sk >>=? fun dst_sk_uri ->
  let dst_key =
    {
      sk = dst_sk_uri;
      path = child_index :: k.path;
      address_index = Viewing_key.default_index;
    }
  in
  (* TODO check this force *)
  let _ = force in
  Sapling_key.add ~force:true cctxt dst_name dst_key >>=? fun () ->
  let path =
    String.concat "/" (List.map Int32.to_string (List.rev dst_key.path))
  in
  return (path, Viewing_key.of_sk dst_sk)

let find_vk cctxt name =
  Sapling_key.find cctxt name >>=? fun k ->
  from_uri cctxt k.sk >>=? fun sk -> return (Viewing_key.of_sk sk)

let new_address (cctxt : #Client_context.full) name index_opt =
  Sapling_key.find cctxt name >>=? fun k ->
  let index =
    match index_opt with
    | None -> k.address_index
    | Some i -> Viewing_key.index_of_int64 (Int64.of_int i)
  in
  from_uri cctxt k.sk >>=? fun sk ->
  return (Viewing_key.of_sk sk) >>=? fun vk ->
  (* Viewing_key.new_address finds the smallest index greater or equal to
     [index] that generates a correct address. *)
  let corrected_index, address = Viewing_key.new_address vk index in
  Sapling_key.update
    cctxt
    name
    {k with address_index = Viewing_key.index_succ corrected_index}
  >>=? fun () -> return (sk, corrected_index, address)

let export_vk cctxt name =
  find_vk cctxt name >>=? fun vk ->
  return (Data_encoding.Json.construct Viewing_key.encoding vk)