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

(* TODO Test cancelation of a (pending) connection *)

(* TODO do not recompute list_known_points at each requests...  but
        only once in a while, e.g. every minutes or when a point
        or the associated gid is blacklisted. *)

(* TODO allow to track "requested gids" when we reconnect to a point. *)

open P2p_types
open P2p_connection_pool_types

include Logging.Make (struct let name = "p2p.connection-pool" end)

type 'msg encoding = Encoding : {
    tag: int ;
    encoding: 'a Data_encoding.t ;
    wrap: 'a -> 'msg ;
    unwrap: 'msg -> 'a option ;
    max_length: int option ;
  } -> 'msg encoding

module Message = struct

  type 'msg t =
    | Bootstrap
    | Advertise of Point.t list
    | Message of 'msg
    | Disconnect

  let encoding msg_encoding =
    let open Data_encoding in
    union ~tag_size:`Uint16
      ([ case ~tag:0x01 null
           (function Disconnect -> Some () | _ -> None)
           (fun () -> Disconnect);
         case ~tag:0x02 null
           (function Bootstrap -> Some () | _ -> None)
           (fun () -> Bootstrap);
         case ~tag:0x03 (Variable.list Point.encoding)
           (function Advertise points -> Some points | _ -> None)
           (fun points -> Advertise points);
       ] @
       ListLabels.map msg_encoding
         ~f:(function Encoding { tag ; encoding ; wrap ; unwrap } ->
             case ~tag encoding
               (function Message msg -> unwrap msg | _ -> None)
               (fun msg -> Message (wrap msg))))

end


module Answerer = struct

  type 'msg callback = {
    bootstrap: unit -> Point.t list Lwt.t ;
    advertise: Point.t list -> unit Lwt.t ;
    message: int -> 'msg -> unit Lwt.t ;
  }

  type 'msg t = {
    canceler: Canceler.t ;
    conn: 'msg Message.t P2p_connection.t ;
    callback: 'msg callback ;
    mutable worker: unit Lwt.t ;
  }

  let rec worker_loop st =
    Lwt_unix.yield () >>= fun () ->
    Lwt_utils.protect ~canceler:st.canceler begin fun () ->
      P2p_connection.read st.conn
    end >>= function
    | Ok (_, Bootstrap) -> begin
        st.callback.bootstrap () >>= function
        | [] ->
            worker_loop st
        | points ->
            match P2p_connection.write_now st.conn (Advertise points) with
            | Ok _sent ->
                (* if not sent then ?? TODO count dropped message ?? *)
                worker_loop st
            | Error _ ->
                Canceler.cancel st.canceler >>= fun () ->
                Lwt.return_unit
      end
    | Ok (_, Advertise points) ->
        st.callback.advertise points >>= fun () ->
        worker_loop st
    | Ok (size, Message msg) ->
        st.callback.message size msg >>= fun () ->
        worker_loop st
    | Ok (_, Disconnect) | Error [P2p_io_scheduler.Connection_closed] ->
        Canceler.cancel st.canceler >>= fun () ->
        Lwt.return_unit
    | Error [Lwt_utils.Canceled] ->
        Lwt.return_unit
    | Error err ->
        lwt_log_error "@[Answerer unexpected error:@ %a@]"
          Error_monad.pp_print_error err >>= fun () ->
        Canceler.cancel st.canceler >>= fun () ->
        Lwt.return_unit

  let run conn canceler callback =
    let st = {
      canceler ; conn ; callback ;
      worker = Lwt.return_unit ;
    } in
    st.worker <-
      Lwt_utils.worker "answerer"
        (fun () -> worker_loop st)
        (fun () -> Canceler.cancel canceler) ;
    st

  let shutdown st =
    Canceler.cancel st.canceler >>= fun () ->
    st.worker

end

module LogEvent = struct
  type t =
    | Too_few_connections
    | Too_many_connections
    | New_point of Point.t
    | New_peer of Gid.t
    | Incoming_connection of Point.t
    | Outgoing_connection of Point.t
    | Authentication_failed of Point.t
    | Accepting_request of Point.t * Id_point.t * Gid.t
    | Rejecting_request of Point.t * Id_point.t * Gid.t
    | Request_rejected of Point.t * (Id_point.t * Gid.t) option
    | Connection_established of Id_point.t * Gid.t
    | Disconnection of Gid.t
    | External_disconnection of Gid.t

    | Gc_points
    | Gc_gids

  let encoding =
    let open Data_encoding in
    let branch_encoding name obj =
      conv (fun x -> (), x) (fun ((), x) -> x)
        (merge_objs
           (obj1 (req "event" (constant name))) obj) in
    union ~tag_size:`Uint8 [
      case ~tag:0 (branch_encoding "too_few_connections" empty)
        (function Too_few_connections -> Some () | _ -> None)
        (fun () -> Too_few_connections) ;
      case ~tag:1 (branch_encoding "too_many_connections" empty)
        (function Too_many_connections -> Some () | _ -> None)
        (fun () -> Too_many_connections) ;
      case ~tag:2 (branch_encoding "new_point"
                     (obj1 (req "point" Point.encoding)))
        (function New_point p -> Some p | _ -> None)
        (fun p -> New_point p) ;
      case ~tag:3 (branch_encoding "new_peer"
                     (obj1 (req "gid" Gid.encoding)))
        (function New_peer p -> Some p | _ -> None)
        (fun p -> New_peer p) ;
      case ~tag:4 (branch_encoding "incoming_connection"
                     (obj1 (req "point" Point.encoding)))
        (function Incoming_connection p -> Some p | _ -> None)
        (fun p -> Incoming_connection p) ;
      case ~tag:5 (branch_encoding "outgoing_connection"
                     (obj1 (req "point" Point.encoding)))
        (function Outgoing_connection p -> Some p | _ -> None)
        (fun p -> Outgoing_connection p) ;
      case ~tag:6 (branch_encoding "authentication_failed"
                     (obj1 (req "point" Point.encoding)))
        (function Authentication_failed p -> Some p | _ -> None)
        (fun p -> Authentication_failed p) ;
      case ~tag:7 (branch_encoding "accepting_request"
                     (obj3
                        (req "point" Point.encoding)
                        (req "id_point" Id_point.encoding)
                        (req "gid" Gid.encoding)))
        (function Accepting_request (p, id_p, g) -> Some (p, id_p, g) | _ -> None)
        (fun (p, id_p, g) -> Accepting_request (p, id_p, g)) ;
      case ~tag:8 (branch_encoding "rejecting_request"
                     (obj3
                        (req "point" Point.encoding)
                        (req "id_point" Id_point.encoding)
                        (req "gid" Gid.encoding)))
        (function Rejecting_request (p, id_p, g) -> Some (p, id_p, g) | _ -> None)
        (fun (p, id_p, g) -> Rejecting_request (p, id_p, g)) ;
      case ~tag:9 (branch_encoding "request_rejected"
                     (obj2
                        (req "point" Point.encoding)
                        (opt "identity" (tup2 Id_point.encoding Gid.encoding))))
        (function Request_rejected (p, id) -> Some (p, id) | _ -> None)
        (fun (p, id) -> Request_rejected (p, id)) ;
      case ~tag:10 (branch_encoding "connection_established"
                      (obj2
                         (req "id_point" Id_point.encoding)
                         (req "gid" Gid.encoding)))
        (function Connection_established (id_p, g) -> Some (id_p, g) | _ -> None)
        (fun (id_p, g) -> Connection_established (id_p, g)) ;
      case ~tag:11 (branch_encoding "disconnection"
                      (obj1 (req "gid" Gid.encoding)))
        (function Disconnection g -> Some g | _ -> None)
        (fun g -> Disconnection g) ;
      case ~tag:12 (branch_encoding "external_disconnection"
                      (obj1 (req "gid" Gid.encoding)))
        (function External_disconnection g -> Some g | _ -> None)
        (fun g -> External_disconnection g) ;
      case ~tag:13 (branch_encoding "gc_points" empty)
        (function Gc_points -> Some () | _ -> None)
        (fun () -> Gc_points) ;
      case ~tag:14 (branch_encoding "gc_gids" empty)
        (function Gc_gids -> Some () | _ -> None)
        (fun () -> Gc_gids) ;
    ]

  let log watcher event = Watcher.notify watcher event

  let too_few_connections watcher = log watcher Too_few_connections
  let too_many_connections watcher = log watcher Too_many_connections
  let new_point watcher ~point = log watcher (New_point point)
  let new_peer watcher ~gid = log watcher (New_peer gid)
  let incoming_connection watcher ~point = log watcher (Incoming_connection point)
  let outgoing_connection  watcher ~point = log watcher (Outgoing_connection point)
  let authentication_failed watcher ~point = log watcher (Authentication_failed point)
  let accepting_request watcher ~id_point ~point ~gid =
    log watcher (Accepting_request (point, id_point, gid))
  let rejecting_request watcher ~id_point ~point ~gid =
    log watcher (Rejecting_request (point, id_point, gid))
  let request_rejected watcher ?credentials ~point =
    log watcher (Request_rejected (point, credentials))
  let connection_established watcher ~id_point ~gid =
    log watcher (Connection_established (id_point, gid))
  let disconnection watcher ~is_external ~gid =
    log watcher (if is_external then External_disconnection gid
              else Disconnection gid)
  let gc_points watcher = log watcher Gc_points
  let gc_gids watcher = log watcher Gc_gids
end

type config = {

  identity : Identity.t ;
  proof_of_work_target : Crypto_box.target ;

  trusted_points : Point.t list ;
  peers_file : string ;
  closed_network : bool ;

  listening_port : port option ;
  min_connections : int ;
  max_connections : int ;
  max_incoming_connections : int ;
  authentification_timeout : float ;

  incoming_app_message_queue_size : int option ;
  incoming_message_queue_size : int option ;
  outgoing_message_queue_size : int option ;

  known_gids_history_size : int ;
  known_points_history_size : int ;
  max_known_points : (int * int) option ; (* max, gc target *)
  max_known_gids : (int * int) option ; (* max, gc target *)
}

type 'meta meta_config = {
  encoding : 'meta Data_encoding.t;
  initial : 'meta;
  score : 'meta -> float;
}

type 'msg message_config = {
  encoding : 'msg encoding list ;
  versions : P2p_types.Version.t list;
}

type ('msg, 'meta) t = {
  config : config ;
  meta_config : 'meta meta_config ;
  message_config : 'msg message_config ;
  my_id_points : unit Point.Table.t ;
  known_gids : (('msg, 'meta) connection, 'meta) Gid_info.t Gid.Table.t ;
  connected_gids : (('msg, 'meta) connection, 'meta) Gid_info.t Gid.Table.t ;
  known_points : ('msg, 'meta) connection Point_info.t Point.Table.t ;
  connected_points : ('msg, 'meta) connection Point_info.t Point.Table.t ;
  incoming : Canceler.t Point.Table.t ;
  io_sched : P2p_io_scheduler.t ;
  encoding : 'msg Message.t Data_encoding.t ;
  events : events ;
  watcher : LogEvent.t Watcher.input ;
}


and events = {
  too_few_connections : unit Lwt_condition.t ;
  too_many_connections : unit Lwt_condition.t ;
  new_peer : unit Lwt_condition.t ;
  new_connection : unit Lwt_condition.t ;
}

and ('msg, 'meta) connection = {
  canceler : Canceler.t ;
  messages : (int * 'msg) Lwt_pipe.t ;
  conn : 'msg Message.t P2p_connection.t ;
  gid_info : (('msg, 'meta) connection, 'meta) Gid_info.t ;
  point_info : ('msg, 'meta) connection Point_info.t option ;
  answerer : 'msg Answerer.t ;
  mutable wait_close : bool ;
}

type ('msg, 'meta) pool = ('msg, 'meta) t

module PoolEvent = struct
  let wait_too_few_connections pool =
    Lwt_condition.wait pool.events.too_few_connections
  let wait_too_many_connections pool =
    Lwt_condition.wait pool.events.too_many_connections
  let wait_new_peer pool =
    Lwt_condition.wait pool.events.new_peer
  let wait_new_connection pool =
    Lwt_condition.wait pool.events.new_connection
end

let watch { watcher } = Watcher.create_stream watcher

module GcPointSet = Utils.Bounded(struct
    type t = Time.t * Point.t
    let compare (x, _) (y, _) = - (Time.compare x y)
  end)

let gc_points ({ config = { max_known_points } ; known_points } as pool) =
  match max_known_points with
  | None -> ()
  | Some (_, target) ->
      let now = Time.now () in (* TODO: maybe time of discovery? *)
      let table = GcPointSet.create target in
      Point.Table.iter (fun p pi ->
          if Point_info.State.is_disconnected pi then
            let time =
              match Point_info.last_miss pi with
              | None -> now
              | Some t -> t in
            GcPointSet.insert (time, p) table
        ) known_points ;
      let to_remove = GcPointSet.get table in
      ListLabels.iter to_remove ~f:begin fun (_, p) ->
        Point.Table.remove known_points p
      end ;
      LogEvent.gc_points pool.watcher

let register_point pool ?trusted (addr, port as point) =
  match Point.Table.find pool.known_points point with
  | exception Not_found ->
      let pi = Point_info.create ?trusted addr port in
      iter_option pool.config.max_known_points ~f:begin fun (max, _) ->
        if Point.Table.length pool.known_points >= max then gc_points pool
      end ;
      Point.Table.add pool.known_points point pi ;
      LogEvent.new_point pool.watcher point ;
      pi
  | pi -> pi


(* Bounded table used to garbage collect gid infos when needed. The
   strategy used is to remove the info of the gid with the lowest
   score first. In case of equality, the info of the most recent added
   gid is removed. The rationale behind this choice is that in the
   case of a flood attack, the newly added infos will probably belong
   to gids with the same (low) score and removing the most recent ones
   ensure that older (and probably legit) gid infos are kept. *)
module GcGidSet = Utils.Bounded(struct
    type t = float * Time.t * Gid.t
    let compare (s, t, _) (s', t', _) =
      let score_cmp = Pervasives.compare s s' in
      if score_cmp = 0 then Time.compare t t' else - score_cmp
  end)

let gc_gids ({ meta_config = { score } ;
              config = { max_known_gids } ;
              known_gids ; } as pool) =
  match max_known_gids with
  | None -> ()
  | Some (_, target) ->
      let table = GcGidSet.create target in
      Gid.Table.iter (fun gid gid_info ->
          let created = Gid_info.created gid_info in
          let score = score @@ Gid_info.metadata gid_info in
          GcGidSet.insert (score, created, gid) table
        ) known_gids ;
      let to_remove = GcGidSet.get table in
      ListLabels.iter to_remove ~f:begin fun (_, _, gid) ->
        Gid.Table.remove known_gids gid
      end ;
      LogEvent.gc_gids pool.watcher

let register_peer pool gid =
  match Gid.Table.find pool.known_gids gid with
  | exception Not_found ->
      Lwt_condition.broadcast pool.events.new_peer () ;
      let peer = Gid_info.create gid ~metadata:pool.meta_config.initial in
      iter_option pool.config.max_known_gids ~f:begin fun (max, _) ->
        if Gid.Table.length pool.known_gids >= max then gc_gids pool
      end ;
      Gid.Table.add pool.known_gids gid peer ;
      LogEvent.new_peer pool.watcher gid ;
      peer
  | peer -> peer

let register_new_point pool _gid point =
  if not (Point.Table.mem pool.my_id_points point) then
    ignore (register_point pool point)

let register_new_points pool gid points =
  List.iter (register_new_point pool gid) points ;
  Lwt.return_unit

let compare_known_point_info p1 p2 =
  (* The most-recently disconnected peers are greater. *)
  (* Then come long-standing connected peers. *)
  let disconnected1 = Point_info.State.is_disconnected p1
  and disconnected2 = Point_info.State.is_disconnected p2 in
  let compare_last_seen p1 p2 =
    match Point_info.last_seen p1, Point_info.last_seen p2 with
    | None, None -> Random.int 2 * 2 - 1 (* HACK... *)
    | Some _, None -> 1
    | None, Some _ -> -1
    | Some (_, time1), Some (_, time2) ->
        match compare time1 time2 with
        | 0 -> Random.int 2 * 2 - 1 (* HACK... *)
        | x -> x in
  match disconnected1, disconnected2 with
  | false, false -> compare_last_seen p1 p2
  | false, true -> -1
  | true, false -> 1
  | true, true -> compare_last_seen p2 p1

let list_known_points pool _gid () =
  let knowns =
    Point.Table.fold (fun _ pi acc -> pi :: acc) pool.known_points [] in
  let best_knowns =
    Utils.take_n ~compare:compare_known_point_info 50 knowns in
  Lwt.return (List.map Point_info.point best_knowns)

let active_connections pool = Gid.Table.length pool.connected_gids

let create_connection pool conn id_point pi gi _version =
  let gid = Gid_info.gid gi in
  let canceler = Canceler.create () in
  let size =
    map_option pool.config.incoming_app_message_queue_size
      ~f:(fun qs -> qs, fun (size, _) -> (Sys.word_size / 8) * 11 + size) in
  let messages = Lwt_pipe.create ?size () in
  let callback =
    { Answerer.message =
        (fun size msg -> Lwt_pipe.push messages (size, msg)) ;
      advertise = register_new_points pool gid ;
      bootstrap = list_known_points pool gid ;
    } in
  let answerer = Answerer.run conn canceler callback in
  let conn =
    { conn ; point_info = pi ; gid_info = gi ;
      messages ; canceler ; answerer ; wait_close = false } in
  iter_option pi ~f:begin fun pi ->
    let point = Point_info.point pi in
    Point_info.State.set_running pi gid conn ;
    Point.Table.add pool.connected_points point pi ;
  end ;
  LogEvent.connection_established pool.watcher ~id_point ~gid ;
  Gid_info.State.set_running gi id_point conn ;
  Gid.Table.add pool.connected_gids gid gi ;
  Lwt_condition.broadcast pool.events.new_connection () ;
  Canceler.on_cancel canceler begin fun () ->
    lwt_debug "Disconnect: %a (%a)"
      Gid.pp gid Id_point.pp id_point >>= fun () ->
    iter_option ~f:Point_info.State.set_disconnected pi;
    LogEvent.disconnection pool.watcher ~is_external:false ~gid ;
    Gid_info.State.set_disconnected gi ;
    iter_option pi ~f:begin fun pi ->
      Point.Table.remove pool.connected_points (Point_info.point pi) ;
    end ;
    Gid.Table.remove pool.connected_gids gid ;
    if pool.config.max_connections <= active_connections pool then begin
      Lwt_condition.broadcast pool.events.too_many_connections () ;
      LogEvent.too_many_connections pool.watcher ;
    end ;
    P2p_connection.close ~wait:conn.wait_close conn.conn
  end ;
  if active_connections pool < pool.config.min_connections then begin
    Lwt_condition.broadcast pool.events.too_few_connections () ;
    LogEvent.too_few_connections pool.watcher ;
  end ;
  conn

let disconnect ?(wait = false) conn =
  conn.wait_close <- wait ;
  Canceler.cancel conn.canceler >>= fun () ->
  conn.answerer.worker

type error += Rejected of Gid.t
type error += Unexpected_point_state
type error += Unexpected_gid_state

let may_register_my_id_point pool = function
  | [P2p_connection.Myself (addr, Some port)] ->
      Point.Table.add pool.my_id_points (addr, port) () ;
      Point.Table.remove pool.known_points (addr, port)
  | _ -> ()

let authenticate pool ?pi canceler fd point =
  let incoming = pi = None in
  lwt_debug "authenticate: %a%s"
    Point.pp point
    (if incoming then " incoming" else "") >>= fun () ->
  Lwt_utils.protect ~canceler begin fun () ->
    P2p_connection.authenticate
      ~proof_of_work_target:pool.config.proof_of_work_target
      ~incoming (P2p_io_scheduler.register pool.io_sched fd) point
      ?listening_port:pool.config.listening_port
      pool.config.identity pool.message_config.versions
  end ~on_error: begin fun err ->
    (* Authentication incorrect! *)
    (* TODO do something when the error is Not_enough_proof_of_work ?? *)
    lwt_debug "authenticate: %a%s -> failed %a"
      Point.pp point
      (if incoming then " incoming" else "")
      pp_print_error err >>= fun () ->
    may_register_my_id_point pool err ;
    LogEvent.authentication_failed pool.watcher ~point ;
    if incoming then
      Point.Table.remove pool.incoming point
    else
      iter_option Point_info.State.set_disconnected pi ;
    Lwt.return (Error err)
  end >>=? fun (info, auth_fd) ->
  (* Authentication correct! *)
  lwt_debug "authenticate: %a -> auth %a"
    Point.pp point
    Connection_info.pp info >>= fun () ->
  let remote_pi =
    match info.id_point with
    | addr, Some port
      when not (Point.Table.mem pool.my_id_points (addr, port)) ->
        Some (register_point pool (addr, port))
    | _ -> None in
  let connection_pi =
    match pi, remote_pi with
    | None, None -> None
    | Some _ as pi, _ | _, (Some _ as pi) -> pi in
  let gi = register_peer pool info.gid in
  let acceptable_versions =
    Version.common info.versions pool.message_config.versions
  in
  let acceptable_point =
    unopt_map connection_pi
      ~default:(not pool.config.closed_network)
      ~f:begin fun connection_pi ->
      match Point_info.State.get connection_pi with
      | Requested _ -> not incoming
      | Disconnected ->
          not pool.config.closed_network
          || Point_info.trusted connection_pi
      | Accepted _ | Running _ -> false
    end
  in
  let acceptable_gid =
    match Gid_info.State.get gi with
    | Accepted _ ->
        (* TODO: in some circumstances cancel and accept... *)
        false
    | Running _ -> false
    | Disconnected -> true
  in
  if incoming then
    Point.Table.remove pool.incoming point ;
  match acceptable_versions with
  | Some version when acceptable_gid && acceptable_point -> begin
      LogEvent.accepting_request pool.watcher
        ~id_point:info.id_point ~point ~gid:info.gid ;
      iter_option connection_pi
        ~f:(fun pi -> Point_info.State.set_accepted pi info.gid canceler) ;
      Gid_info.State.set_accepted gi info.id_point canceler ;
      lwt_debug "authenticate: %a -> accept %a"
        Point.pp point
        Connection_info.pp info >>= fun () ->
      Lwt_utils.protect ~canceler begin fun () ->
        P2p_connection.accept
          ?incoming_message_queue_size:pool.config.incoming_message_queue_size
          ?outgoing_message_queue_size:pool.config.outgoing_message_queue_size
          auth_fd pool.encoding >>= fun conn ->
        lwt_debug "authenticate: %a -> Connected %a"
          Point.pp point
          Connection_info.pp info >>= fun () ->
        Lwt.return conn
      end ~on_error: begin fun err ->
        if incoming then
          LogEvent.request_rejected pool.watcher
            ~credentials:(info.id_point, info.gid) ~point ;
        lwt_debug "authenticate: %a -> rejected %a"
          Point.pp point
          Connection_info.pp info >>= fun () ->
        iter_option connection_pi ~f:Point_info.State.set_disconnected;
        Gid_info.State.set_disconnected gi ;
        Lwt.return (Error err)
      end >>=? fun conn ->
      let id_point =
        match info.id_point, map_option Point_info.point pi with
        | (addr, _), Some (_, port) -> addr, Some port
        | id_point, None ->  id_point in
      return (create_connection pool conn id_point connection_pi gi version)
    end
  | _ -> begin
      LogEvent.rejecting_request pool.watcher
        ~id_point:info.id_point ~point ~gid:info.gid ;
      lwt_debug "authenticate: %a -> kick %a point: %B gid: %B"
        Point.pp point
        Connection_info.pp info
        acceptable_point acceptable_gid >>= fun () ->
      P2p_connection.kick auth_fd >>= fun () ->
      if not incoming then begin
        iter_option ~f:Point_info.State.set_disconnected pi ;
        (* FIXME Gid_info.State.set_disconnected ~requested:true gi ; *)
      end ;
      fail (Rejected info.gid)
    end

type error += Pending_connection
type error += Connected
type error += Connection_closed = P2p_io_scheduler.Connection_closed
type error += Connection_refused
type error += Closed_network

let fail_unless_disconnected_point pi =
  match Point_info.State.get pi with
  | Disconnected -> return ()
  | Requested _ | Accepted _ -> fail Pending_connection
  | Running _ -> fail Connected

let fail_unless_disconnected_gid gi =
  match Gid_info.State.get gi with
  | Disconnected -> return ()
  | Accepted _ -> fail Pending_connection
  | Running _ -> fail Connected

let raw_connect canceler pool point =
  let pi = register_point pool point in
  let addr, port as point = Point_info.point pi in
  fail_unless
    (not pool.config.closed_network || Point_info.trusted pi)
    Closed_network >>=? fun () ->
  fail_unless_disconnected_point pi >>=? fun () ->
  Point_info.State.set_requested pi canceler ;
  let fd = Lwt_unix.socket PF_INET6 SOCK_STREAM 0 in
  let uaddr =
    Lwt_unix.ADDR_INET (Ipaddr_unix.V6.to_inet_addr addr, port) in
  lwt_debug "connect: %a" Point.pp point >>= fun () ->
  Lwt_utils.protect ~canceler begin fun () ->
    LogEvent.outgoing_connection pool.watcher ~point ;
    Lwt_unix.connect fd uaddr >>= fun () ->
    return ()
  end ~on_error: begin fun err ->
    lwt_debug "connect: %a -> disconnect" Point.pp point >>= fun () ->
    Point_info.State.set_disconnected pi ;
    Lwt_utils.safe_close fd >>= fun () ->
    match err with
    | [Exn (Unix.Unix_error (Unix.ECONNREFUSED, _, _))] ->
        fail Connection_refused
    | err -> Lwt.return (Error err)
  end >>=? fun () ->
  lwt_debug "connect: %a -> authenticate" Point.pp point >>= fun () ->
  authenticate pool ~pi canceler fd point

type error += Too_many_connections

let connect ~timeout pool point =
  fail_unless
    (active_connections pool <= pool.config.max_connections)
    Too_many_connections >>=? fun () ->
  let canceler = Canceler.create () in
  Lwt_utils.with_timeout ~canceler timeout begin fun canceler ->
    raw_connect canceler pool point
  end

let accept pool fd point =
  LogEvent.incoming_connection pool.watcher ~point ;
  if pool.config.max_incoming_connections <= Point.Table.length pool.incoming
  || pool.config.max_connections <= active_connections pool then
    Lwt.async (fun () -> Lwt_utils.safe_close fd)
  else
    let canceler = Canceler.create () in
    Point.Table.add pool.incoming point canceler ;
    Lwt.async begin fun () ->
      Lwt_utils.with_timeout
        ~canceler pool.config.authentification_timeout
        (fun canceler -> authenticate pool canceler fd point)
    end


(***************************************************************************)

let read { messages ; conn } =
  Lwt.catch
    (fun () -> Lwt_pipe.pop messages >>= fun (s, msg) ->
      lwt_debug "%d bytes message popped from queue %a\027[0m"
        s Connection_info.pp (P2p_connection.info conn) >>= fun () ->
      return msg)
    (fun _ (* Closed *) -> fail P2p_io_scheduler.Connection_closed)

let is_readable { messages } =
  Lwt.catch
    (fun () -> Lwt_pipe.values_available messages >>= return)
    (fun _ (* Closed *) -> fail P2p_io_scheduler.Connection_closed)

let write { conn } msg =
  P2p_connection.write conn (Message msg)

let write_sync { conn } msg =
  P2p_connection.write_sync conn (Message msg)

let write_now { conn } msg =
  P2p_connection.write_now conn (Message msg)

let write_all pool msg =
  Gid.Table.iter
    (fun _gid gi ->
       match Gid_info.State.get gi with
       | Running { data = conn } ->
           ignore (write_now conn msg : bool tzresult )
       | _ -> ())
    pool.connected_gids

let broadcast_bootstrap_msg pool =
  Gid.Table.iter
    (fun _gid gi ->
       match Gid_info.State.get gi with
       | Running { data = { conn } } ->
           ignore (P2p_connection.write_now conn Bootstrap : bool tzresult )
       | _ -> ())
    pool.connected_gids


(***************************************************************************)

module Gids = struct

  type ('msg, 'meta) info = (('msg, 'meta) connection, 'meta) Gid_info.t

  let info { known_gids } point =
    try Some (Gid.Table.find known_gids point)
    with Not_found -> None

  let get_metadata pool gid =
    try Some (Gid_info.metadata (Gid.Table.find pool.known_gids gid))
    with Not_found -> None

  let get_score pool gid =
    try Some (pool.meta_config.score @@ Gid_info.metadata (Gid.Table.find pool.known_gids gid))
    with Not_found -> None

  let set_metadata pool gid data =
    Gid_info.set_metadata (register_peer pool gid) data

  let get_trusted pool gid =
    try Gid_info.trusted (Gid.Table.find pool.known_gids gid)
    with Not_found -> false

  let set_trusted pool gid =
    try Gid_info.set_trusted (register_peer pool gid)
    with Not_found -> ()

  let unset_trusted pool gid =
    try Gid_info.unset_trusted (Gid.Table.find pool.known_gids gid)
    with Not_found -> ()

  let find_connection pool gid =
    apply_option
      (info pool gid)
      ~f:(fun p ->
          match Gid_info.State.get p with
          | Running { data } -> Some data
          | _ -> None)

  let fold_known pool ~init ~f =
    Gid.Table.fold f pool.known_gids init
  let fold_connected pool ~init ~f =
    Gid.Table.fold f pool.connected_gids init

end

let fold_connections  pool ~init ~f =
  Gids.fold_connected pool ~init ~f:begin fun gid gi acc ->
    match Gid_info.State.get gi with
    | Running { data } -> f gid data acc
    | _ -> acc
  end

module Points = struct

  type ('msg, 'meta) info = ('msg, 'meta) connection Point_info.t

  let info { known_points } point =
    try Some (Point.Table.find known_points point)
    with Not_found -> None

  let get_trusted pool gid =
    try Point_info.trusted (Point.Table.find pool.known_points gid)
    with Not_found -> false

  let set_trusted pool gid =
    try Point_info.set_trusted (register_point pool gid)
    with Not_found -> ()

  let unset_trusted pool gid =
    try Point_info.unset_trusted (Point.Table.find pool.known_points gid)
    with Not_found -> ()

  let find_connection pool point =
    apply_option
      (info pool point)
      ~f:(fun p ->
          match Point_info.State.get p with
          | Running { data } -> Some data
          | _ -> None)

  let fold_known pool ~init ~f =
  Point.Table.fold f pool.known_points init

  let fold_connected  pool ~init ~f =
    Point.Table.fold f pool.connected_points init

end

let connection_stat { conn } =
  P2p_connection.stat conn

let pool_stat { io_sched } =
  P2p_io_scheduler.global_stat io_sched

let score { meta_config = { score }} meta = score meta

let connection_info { conn } =
  P2p_connection.info conn

(***************************************************************************)

let create config meta_config message_config io_sched =
  let events = {
    too_few_connections = Lwt_condition.create () ;
    too_many_connections = Lwt_condition.create () ;
    new_peer = Lwt_condition.create () ;
    new_connection = Lwt_condition.create () ;
  } in
  let pool = {
    config ; meta_config ; message_config ;
    my_id_points = Point.Table.create 7 ;
    known_gids = Gid.Table.create 53 ;
    connected_gids = Gid.Table.create 53 ;
    known_points = Point.Table.create 53 ;
    connected_points = Point.Table.create 53 ;
    incoming = Point.Table.create 53 ;
    io_sched ;
    encoding = Message.encoding message_config.encoding ;
    events ;
    watcher = Watcher.create_input () ;
  } in
  List.iter (Points.set_trusted pool) config.trusted_points ;
  Gid_info.File.load config.peers_file meta_config.encoding >>= function
  | Ok gids ->
      List.iter
        (fun gi -> Gid.Table.add pool.known_gids (Gid_info.gid gi) gi)
        gids ;
      Lwt.return pool
  | Error err ->
      log_error "@[Failed to parsed peers file:@ %a@]"
        pp_print_error err ;
      Lwt.return pool

let destroy pool =
  Point.Table.fold (fun _point pi acc ->
      match Point_info.State.get pi with
      | Requested { cancel } | Accepted { cancel } ->
          Canceler.cancel cancel >>= fun () -> acc
      | Running { data = conn } ->
          disconnect conn >>= fun () -> acc
      | Disconnected ->  acc)
    pool.known_points @@
  Gid.Table.fold (fun _gid gi acc ->
      match Gid_info.State.get gi with
      | Accepted { cancel } ->
          Canceler.cancel cancel >>= fun () -> acc
      | Running { data = conn } ->
          disconnect conn >>= fun () -> acc
      | Disconnected ->  acc)
    pool.known_gids @@
  Point.Table.fold (fun _point canceler acc ->
      Canceler.cancel canceler >>= fun () -> acc)
    pool.incoming Lwt.return_unit