(*****************************************************************************)
(*                                                                           *)
(* Open Source License                                                       *)
(* Copyright (c) 2018 Dynamic Ledger Solutions, Inc. <contact@tezos.com>     *)
(*                                                                           *)
(* Permission is hereby granted, free of charge, to any person obtaining a   *)
(* copy of this software and associated documentation files (the "Software"),*)
(* to deal in the Software without restriction, including without limitation *)
(* the rights to use, copy, modify, merge, publish, distribute, sublicense,  *)
(* and/or sell copies of the Software, and to permit persons to whom the     *)
(* Software is furnished to do so, subject to the following conditions:      *)
(*                                                                           *)
(* The above copyright notice and this permission notice shall be included   *)
(* in all copies or substantial portions of the Software.                    *)
(*                                                                           *)
(* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR*)
(* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,  *)
(* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL   *)
(* THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER*)
(* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING   *)
(* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER       *)
(* DEALINGS IN THE SOFTWARE.                                                 *)
(*                                                                           *)
(*****************************************************************************)

open Misc

type error +=
  | Unknown of {
      oldest : Cycle_repr.t;
      cycle : Cycle_repr.t;
      latest : Cycle_repr.t;
    }

(* `Permanent *)

let () =
  register_error_kind
    `Permanent
    ~id:"seed.unknown_seed"
    ~title:"Unknown seed"
    ~description:"The requested seed is not available"
    ~pp:(fun ppf (oldest, cycle, latest) ->
      if Cycle_repr.(cycle < oldest) then
        Format.fprintf
          ppf
          "The seed for cycle %a has been cleared from the context  (oldest \
           known seed is for cycle %a)"
          Cycle_repr.pp
          cycle
          Cycle_repr.pp
          oldest
      else
        Format.fprintf
          ppf
          "The seed for cycle %a has not been computed yet  (latest known \
           seed is for cycle %a)"
          Cycle_repr.pp
          cycle
          Cycle_repr.pp
          latest)
    Data_encoding.(
      obj3
        (req "oldest" Cycle_repr.encoding)
        (req "requested" Cycle_repr.encoding)
        (req "latest" Cycle_repr.encoding))
    (function
      | Unknown {oldest; cycle; latest} ->
          Some (oldest, cycle, latest)
      | _ ->
          None)
    (fun (oldest, cycle, latest) -> Unknown {oldest; cycle; latest})

let compute_for_cycle c ~revealed cycle =
  match Cycle_repr.pred cycle with
  | None ->
      assert false (* should not happen *)
  | Some previous_cycle ->
      let levels = Level_storage.levels_with_commitments_in_cycle c revealed in
      let combine (c, random_seed, unrevealed) level =
        Storage.Seed.Nonce.get c level
        >>=? function
        | Revealed nonce ->
            Storage.Seed.Nonce.delete c level
            >>=? fun c ->
            return (c, Seed_repr.nonce random_seed nonce, unrevealed)
        | Unrevealed u ->
            Storage.Seed.Nonce.delete c level
            >>=? fun c -> return (c, random_seed, u :: unrevealed)
      in
      Storage.Seed.For_cycle.get c previous_cycle
      >>=? fun prev_seed ->
      let seed = Seed_repr.deterministic_seed prev_seed in
      fold_left_s combine (c, seed, []) levels
      >>=? fun (c, seed, unrevealed) ->
      Storage.Seed.For_cycle.init c cycle seed
      >>=? fun c -> return (c, unrevealed)

let for_cycle ctxt cycle =
  let preserved = Constants_storage.preserved_cycles ctxt in
  let current_level = Level_storage.current ctxt in
  let current_cycle = current_level.cycle in
  let latest =
    if Cycle_repr.(current_cycle = root) then
      Cycle_repr.add current_cycle (preserved + 1)
    else Cycle_repr.add current_cycle preserved
  in
  let oldest =
    match Cycle_repr.sub current_cycle preserved with
    | None ->
        Cycle_repr.root
    | Some oldest ->
        oldest
  in
  fail_unless
    Cycle_repr.(oldest <= cycle && cycle <= latest)
    (Unknown {oldest; cycle; latest})
  >>=? fun () -> Storage.Seed.For_cycle.get ctxt cycle

let clear_cycle c cycle = Storage.Seed.For_cycle.delete c cycle

let init ctxt =
  let preserved = Constants_storage.preserved_cycles ctxt in
  List.fold_left2
    (fun ctxt c seed ->
      ctxt
      >>=? fun ctxt ->
      let cycle = Cycle_repr.of_int32_exn (Int32.of_int c) in
      Storage.Seed.For_cycle.init ctxt cycle seed)
    (return ctxt)
    (0 --> (preserved + 1))
    (Seed_repr.initial_seeds (preserved + 2))

let cycle_end ctxt last_cycle =
  let preserved = Constants_storage.preserved_cycles ctxt in
  ( match Cycle_repr.sub last_cycle preserved with
  | None ->
      return ctxt
  | Some cleared_cycle ->
      clear_cycle ctxt cleared_cycle )
  >>=? fun ctxt ->
  match Cycle_repr.pred last_cycle with
  | None ->
      return (ctxt, [])
  | Some revealed ->
      (* cycle with revelations *)
      let inited_seed_cycle = Cycle_repr.add last_cycle (preserved + 1) in
      compute_for_cycle ctxt ~revealed inited_seed_cycle