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(* Open Source License                                                       *)
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(* FIXME: https://gitlab.com/tezos/tezos/-/issues/4113

   This file is part of the implementation of the new mempool, which
   uses features of the protocol that only exist since Lima.

   When you modify this file, consider whether you should also change
   the files that implement the legacy mempool for Kathmandu. They all
   start with the "legacy" prefix and will be removed when Lima is
   activated on Mainnet. *)

(* Ordering is important, as it is used below in map keys comparison *)
type priority = [`High | `Medium | `Low of Q.t list]

module Priority_map : Map.S with type key = priority = Map.Make (struct
  type t = priority

  module CompareListQ = Compare.List (Q)

  let compare_low_prio p1 p2 =
    (* A higher priority operation should appear before in the map. So we use
       the pointwise comparison of p2 and p1 *)
    CompareListQ.compare p2 p1

  let compare p1 p2 =
    (* - Explicit comparison, `High is smaller,
       - Avoid fragile patterns in case the type is extended in the future *)
    match (p1, p2) with
    | `High, `High | `Medium, `Medium -> 0
    | `Low p1, `Low p2 -> compare_low_prio p1 p2
    | `High, (`Low _ | `Medium) -> -1
    | (`Low _ | `Medium), `High -> 1
    | `Low _, `Medium -> 1
    | `Medium, `Low _ -> -1
end)

module Map = Operation_hash.Map
module Sized_set = Tezos_base.Sized.MakeSizedSet (Operation_hash.Set)

(*
   The type below is used for representing pending operations data of the
   prevalidator. The functions of this module (should) maintain the
   following invariants:
   1 - Union (preimage(pending(prio))) = hashes, for each prio in dom(pending)
   2 - preimage (priority_of) = hashes
   3 - image(priority_of) = preimage (pending)
   4 - map in pending(priority) => map <> empty
*)
type 'a t = {
  (* The main map *)
  pending : 'a Prevalidation.operation Map.t Priority_map.t;
  (* Used for advertising *)
  hashes : Sized_set.t;
  (* We need to remember the priority of each hash, to be used when removing
     without providing the priority *)
  priority_of : priority Map.t;
}

let empty =
  {
    pending = Priority_map.empty;
    hashes = Sized_set.empty;
    priority_of = Map.empty;
  }

let is_empty {pending = _; priority_of = _; hashes} = Sized_set.is_empty hashes

let hashes {pending = _; priority_of = _; hashes} = Sized_set.to_set hashes

let operations {pending; priority_of = _; hashes = _} =
  (* Build a flag map [oph -> op] from pending. Needed when re-cycling
     operations *)
  Priority_map.fold
    (fun _prio -> Map.union (fun _ _ b -> Some b))
    pending
    Map.empty

let mem oph {hashes; priority_of = _; pending = _} = Sized_set.mem oph hashes

let get_priority_map prio pending =
  match Priority_map.find prio pending with None -> Map.empty | Some mp -> mp

let add op prio {pending; hashes; priority_of} =
  let oph = op.Prevalidation.hash in
  let mp = get_priority_map prio pending |> Map.add oph op in
  {
    pending = Priority_map.add prio mp pending;
    hashes = Sized_set.add oph hashes;
    priority_of = Map.add oph prio priority_of;
  }

let remove oph ({pending; hashes; priority_of} as t) =
  match Map.find oph priority_of with
  | None -> t
  | Some prio ->
      let mp = get_priority_map prio pending |> Map.remove oph in
      {
        pending =
          (if Map.is_empty mp then Priority_map.remove prio pending
          else Priority_map.add prio mp pending);
        hashes = Sized_set.remove oph hashes;
        priority_of = Map.remove oph priority_of;
      }

let cardinal {pending = _; hashes; priority_of = _} = Sized_set.cardinal hashes

let fold_es f {pending; hashes = _; priority_of = _} acc =
  Priority_map.fold_es
    (fun prio mp acc -> Map.fold_es (f prio) mp acc)
    pending
    acc

let fold f {pending; hashes = _; priority_of = _} acc =
  Priority_map.fold (fun prio mp acc -> Map.fold (f prio) mp acc) pending acc

let iter f {pending; hashes = _; priority_of = _} =
  Priority_map.iter (fun prio mp -> Map.iter (f prio) mp) pending