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(* This file replaces the implementation of Tezos_crypto.BLS12_381

   The dependency bls12-381 used by Tezos_crypto before V4 started was
   considering Fq12 as a field. bls12-381.1.0.0 introduced a breaking API
   changes, changing Fq12 signature to a group. Functions like
   check_bytes, add, one, negate and order have been removed from the API
   (https://gitlab.com/dannywillems/ocaml-bls12-381/-/commit/1dfb8bd813d12539b4007af095f3125646477319).

   Removed values cited above can be mocked with anything because it was not
   used in the environment. Only Fq12.eq and Fq12.one is required to be
   correctly implemented. Therefore, the implementation is replaced with a
   `failwith "Not implemented".

   Also, bls12-381.1.0.0 added Bls12_381.Pairing.pairing_check which does
   exactly the same job than the Michelson instruction IPairing_check_bls12_381
   is expected to do. Therefore, the complete module Pairing is not required
   anymore in Tezos_crypto.
*)

module Fr = Bls12_381.Fr
module G1 = Bls12_381.G1
module G2 = Bls12_381.G2

module Fq12 = struct
  include Bls12_381.Fq12

  let check_bytes _x = failwith "Not implemented"

  let add _x _y = failwith "Not implemented"

  let negate _x = failwith "Not implemented"
end

(* bls12-381.3.0.0 introduces GT as the prime subgroup of Fq12 of order
   Fr.order. These two modules are algebraically different. However, in
   environments < V4, GT was considered to be Fq12, and the implementation of
   pairing was returning a point in Fq12, which is not algebraically strict
   enough. It should be in GT.
   Therefore, we must serialize a point in GT and deserialize it in Fq12.

   The conversions are not required for further environments as
   Bls12_381.Pairing.pairing_check is used and abstract the algebraic
   structures.
   Using F12.of_bytes_exn is not problematic as GT is a subgroup of Fq12.
   Therefore any serialized value of GT will give a valid point by
   Fq12.of_bytes_exn, supposing they follow the same serialisation rules.
*)
module Gt = Fq12

let gt_to_fq12 x = Bls12_381.GT.to_bytes x |> Fq12.of_bytes_exn

let final_exponentiation_opt x =
  Bls12_381.Pairing.final_exponentiation_opt x |> Option.map gt_to_fq12

let pairing g1 g2 = Bls12_381.Pairing.pairing g1 g2 |> gt_to_fq12

let miller_loop = Bls12_381.Pairing.miller_loop