(**************************************************************************)
(*                                                                        *)
(*    Copyright (c) 2014 - 2016.                                          *)
(*    Dynamic Ledger Solutions, Inc. <contact@tezos.com>                  *)
(*                                                                        *)
(*    All rights reserved. No warranty, explicit or implicit, provided.   *)
(*                                                                        *)
(**************************************************************************)

open Tezos_context

let select_winning_proposal proposals =
  let merge proposal vote winners =
    match winners with
    | None -> Some ([proposal], vote)
    | Some (winners, winners_vote) as previous ->
        if Compare.Int32.(vote = winners_vote) then
          Some (proposal :: winners, winners_vote)
        else if Compare.Int32.(vote >= winners_vote) then
          Some ([proposal], vote)
        else
          previous in
  match Protocol_hash.Map.fold merge proposals None with
  | None -> None
  | Some ([proposal], _) -> Some proposal
  | Some _ -> None (* in case of a tie, lets do nothing. *)

let check_approval_and_update_quorum ctxt =
  Vote.get_ballots ctxt >>=? fun ballots ->
  Vote.listing_size ctxt >>=? fun maximum_vote ->
  Vote.get_current_quorum ctxt >>=? fun expected_quorum ->
  (* FIXME check overflow ??? *)
  let casted_vote = Int32.add ballots.yay ballots.nay in
  let actual_vote = Int32.add casted_vote ballots.pass in
  let actual_quorum =
    Int32.div (Int32.mul actual_vote 100_00l) maximum_vote in
  let supermajority = Int32.div (Int32.mul 8l casted_vote) 10l in
  let updated_quorum =
    Int32.div
      (Int32.add (Int32.mul 8l expected_quorum)
                 (Int32.mul 2l actual_quorum))
      10l in
  Vote.set_current_quorum ctxt updated_quorum >>=? fun ctxt ->
  return
    (ctxt,
     Compare.Int32.(actual_quorum >= expected_quorum
                    && ballots.yay >= supermajority))

let start_new_voting_cycle ctxt =
  Vote.get_current_period_kind ctxt >>=? function
  | Proposal -> begin
      Vote.get_proposals ctxt >>=? fun proposals ->
      Vote.clear_proposals ctxt >>=? fun ctxt ->
      Vote.clear_listings ctxt >>=? fun ctxt ->
      match select_winning_proposal proposals with
      | None ->
          Vote.freeze_listings ctxt >>=? fun ctxt ->
          return ctxt
      | Some proposal ->
          Vote.init_current_proposal ctxt proposal >>=? fun ctxt ->
          Vote.freeze_listings ctxt >>=? fun ctxt ->
          Vote.set_current_period_kind ctxt Testing_vote >>=? fun ctxt ->
          return ctxt
    end
  | Testing_vote ->
      check_approval_and_update_quorum ctxt >>=? fun (ctxt, approved) ->
      Vote.clear_ballots ctxt >>= fun ctxt ->
      Vote.clear_listings ctxt >>=? fun ctxt ->
      if approved then
        let expiration = (* in two days maximum... *)
          Time.add (Timestamp.current ctxt) (Int64.mul 48L 3600L) in
        Vote.get_current_proposal ctxt >>=? fun proposal ->
        fork_test_network ctxt proposal expiration >>= fun ctxt ->
        Vote.set_current_period_kind ctxt Testing >>=? fun ctxt ->
        return ctxt
      else
        Vote.clear_current_proposal ctxt >>=? fun ctxt ->
        Vote.freeze_listings ctxt >>=? fun ctxt ->
        Vote.set_current_period_kind ctxt Proposal >>=? fun ctxt ->
        return ctxt
  | Testing ->
      Vote.freeze_listings ctxt >>=? fun ctxt ->
      Vote.set_current_period_kind ctxt Promotion_vote >>=? fun ctxt ->
      return ctxt
  | Promotion_vote ->
      check_approval_and_update_quorum ctxt >>=? fun (ctxt, approved) ->
      begin
        if approved then
          Vote.get_current_proposal ctxt >>=? fun proposal ->
          activate ctxt proposal >>= fun ctxt ->
          return ctxt
        else
          return ctxt
      end >>=? fun ctxt ->
      Vote.clear_ballots ctxt >>= fun ctxt ->
      Vote.clear_listings ctxt >>=? fun ctxt ->
      Vote.clear_current_proposal ctxt >>=? fun ctxt ->
      Vote.freeze_listings ctxt >>=? fun ctxt ->
      Vote.set_current_period_kind ctxt Proposal >>=? fun ctxt ->
      return ctxt

type error +=
  | Invalid_proposal
  | Unexpected_proposal
  | Unauthorized_proposal
  | Unexpected_ballot
  | Unauthorized_ballot

let record_proposals ctxt delegate proposals =
  Vote.get_current_period_kind ctxt >>=? function
  | Proposal ->
      Vote.in_listings ctxt delegate >>= fun in_listings ->
      if in_listings then
        fold_left_s
          (fun ctxt proposal ->
             Vote.record_proposal ctxt proposal delegate)
          ctxt proposals
      else
        fail Unauthorized_proposal
  | Testing_vote | Testing | Promotion_vote ->
      fail Unexpected_proposal

let record_ballot ctxt delegate proposal ballot =
  Vote.get_current_period_kind ctxt >>=? function
  | Testing_vote | Promotion_vote ->
      Vote.get_current_proposal ctxt >>=? fun current_proposal ->
      fail_unless (Protocol_hash.equal proposal current_proposal)
        Invalid_proposal >>=? fun () ->
      Vote.in_listings ctxt delegate >>= fun in_listings ->
      if in_listings then
        Vote.record_ballot ctxt delegate ballot
      else
        fail Unauthorized_ballot
  | Testing | Proposal ->
      fail Unexpected_ballot

let last_of_a_voting_period ctxt l =
  Compare.Int32.(Int32.succ l.Level.voting_period_position =
                 Constants.voting_period_length ctxt )

let may_start_new_voting_cycle ctxt =
  let level = Level.current ctxt in
  if last_of_a_voting_period ctxt level then
    start_new_voting_cycle ctxt
  else
    return ctxt