(*****************************************************************************)
(*                                                                           *)
(* Open Source License                                                       *)
(* Copyright (c) 2018 Dynamic Ledger Solutions, Inc. <contact@tezos.com>     *)
(* Copyright (c) 2018 Nomadic Labs, <contact@nomadic-labs.com>               *)
(*                                                                           *)
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(* copy of this software and associated documentation files (the "Software"),*)
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(*****************************************************************************)

open Block_validator_worker_state
open Block_validator_errors

type limits = {
  protocol_timeout : Time.System.Span.t;
  worker_limits : Worker_types.limits;
}

module Name = struct
  type t = unit

  let encoding = Data_encoding.empty

  let base = ["validator"; "block"]

  let pp _ () = ()
end

module Types = struct
  include Worker_state

  type state = {
    protocol_validator : Protocol_validator.t;
    validation_process : Block_validator_process.t;
    limits : limits;
    start_testchain : bool;
  }

  type parameters =
    limits * bool * Distributed_db.t * Block_validator_process.t

  let view _state _parameters = ()
end

module Request = struct
  include Request

  type 'a t =
    | Request_validation : {
        chain_db : Distributed_db.chain_db;
        notify_new_block : State.Block.t -> unit;
        canceler : Lwt_canceler.t option;
        peer : P2p_peer.Id.t option;
        hash : Block_hash.t;
        header : Block_header.t;
        operations : Operation.t list list;
      }
        -> State.Block.t option tzresult t

  let view : type a. a t -> view =
   fun (Request_validation {chain_db; peer; hash; _}) ->
    let chain_id = chain_db |> Distributed_db.chain_state |> State.Chain.id in
    {chain_id; block = hash; peer}
end

module Logger = Worker_logger.Make (Event) (Request)
module Worker = Worker.Make (Name) (Event) (Request) (Types) (Logger)

type t = Worker.infinite Worker.queue Worker.t

let debug w = Format.kasprintf (fun msg -> Worker.record_event w (Debug msg))

let check_chain_liveness chain_db hash (header : Block_header.t) =
  let chain_state = Distributed_db.chain_state chain_db in
  match State.Chain.expiration chain_state with
  | Some eol when Time.Protocol.(eol <= header.shell.timestamp) ->
      fail @@ invalid_block hash
      @@ Expired_chain
           {
             chain_id = State.Chain.id chain_state;
             expiration = eol;
             timestamp = header.shell.timestamp;
           }
  | None | Some _ ->
      return_unit

let should_validate_block w chain_state hash =
  State.Block.read_opt chain_state hash
  >>= function
  | None ->
      Lwt.return_none
  | Some block ->
      State.Block.context_exists block
      >>= fun context_exists ->
      if not context_exists then
        debug w "could not find context for block %a" Block_hash.pp_short hash ;
      let should_validate = not context_exists in
      Lwt.return_some (block, should_validate)

let on_request : type r. t -> r Request.t -> r tzresult Lwt.t =
 fun w
     (Request.Request_validation
       {chain_db; notify_new_block; canceler; peer; hash; header; operations}) ->
  let bv = Worker.state w in
  let chain_state = Distributed_db.chain_state chain_db in
  should_validate_block w chain_state hash
  >>= function
  | Some (block, false) ->
      debug
        w
        "previously validated block %a (after pipe)"
        Block_hash.pp_short
        hash ;
      Protocol_validator.prefetch_and_compile_protocols
        bv.protocol_validator
        ?peer
        ~timeout:bv.limits.protocol_timeout
        block ;
      return (Ok None)
  | Some (_, true) | None -> (
      State.Block.read_invalid chain_state hash
      >>= function
      | Some {errors; _} ->
          return (Error errors)
      | None -> (
          State.Chain.save_point chain_state
          >>= fun (save_point_lvl, _) ->
          (* Safety and late workers in partial mode. *)
          if Compare.Int32.(header.shell.level < save_point_lvl) then
            return (Ok None)
          else
            ( debug w "validating block %a" Block_hash.pp_short hash ;
              State.Block.read chain_state header.shell.predecessor
              >>=? fun pred ->
              Worker.protect w (fun () ->
                  protect ?canceler (fun () ->
                      Block_validator_process.apply_block
                        bv.validation_process
                        ~predecessor:pred
                        header
                        operations
                      >>= function
                      | Ok x ->
                          return x
                      | Error (Missing_test_protocol protocol :: _) ->
                          Protocol_validator.fetch_and_compile_protocol
                            bv.protocol_validator
                            ?peer
                            ~timeout:bv.limits.protocol_timeout
                            protocol
                          >>=? fun _ ->
                          Block_validator_process.apply_block
                            bv.validation_process
                            ~predecessor:pred
                            header
                            operations
                      | Error _ as x ->
                          Lwt.return x)
                  >>=? fun { validation_store;
                             block_metadata;
                             ops_metadata;
                             forking_testchain } ->
                  let validation_store =
                    ( {
                        context_hash = validation_store.context_hash;
                        message = validation_store.message;
                        max_operations_ttl =
                          validation_store.max_operations_ttl;
                        last_allowed_fork_level =
                          validation_store.last_allowed_fork_level;
                      }
                      : Block_validation.validation_store )
                  in
                  Distributed_db.commit_block
                    chain_db
                    hash
                    header
                    block_metadata
                    operations
                    ops_metadata
                    validation_store
                    ~forking_testchain
                  >>=? function
                  | None ->
                      (* This case can be reached if the block was
                         previously validated but its associated
                         context has not been written on disk and
                         therefore it means that it already exists in
                         the store. *)
                      State.Block.read chain_state hash
                  | Some block ->
                      return block) )
            >>= function
            | Ok block ->
                Protocol_validator.prefetch_and_compile_protocols
                  bv.protocol_validator
                  ?peer
                  ~timeout:bv.limits.protocol_timeout
                  block ;
                notify_new_block block ;
                return (Ok (Some block))
            | Error err as error ->
                if
                  List.exists
                    (function Invalid_block _ -> true | _ -> false)
                    err
                then (
                  Worker.protect w (fun () ->
                      Distributed_db.commit_invalid_block
                        chain_db
                        hash
                        header
                        err)
                  >>=? fun commited ->
                  assert commited ;
                  return error )
                else (
                  debug
                    w
                    "Error during %a block validation: %a"
                    Block_hash.pp_short
                    hash
                    Error_monad.pp_print_error
                    err ;
                  return error ) ) )

let on_launch _ _ (limits, start_testchain, db, validation_process) =
  let protocol_validator = Protocol_validator.create db in
  return
    {Types.protocol_validator; validation_process; limits; start_testchain}

let on_error w r st errs =
  Worker.record_event w (Validation_failure (r, st, errs)) ;
  Lwt.return_error errs

let on_completion :
    type a. t -> a Request.t -> a -> Worker_types.request_status -> unit Lwt.t
    =
 fun w (Request.Request_validation _ as r) v st ->
  match v with
  | Ok (Some _) ->
      Worker.record_event w (Event.Validation_success (Request.view r, st)) ;
      Lwt.return_unit
  | Ok None ->
      Lwt.return_unit
  | Error errs ->
      Worker.record_event
        w
        (Event.Validation_failure (Request.view r, st, errs)) ;
      Lwt.return_unit

let on_close w =
  let bv = Worker.state w in
  Block_validator_process.close bv.validation_process

let table = Worker.create_table Queue

let create limits db validation_process ~start_testchain =
  let module Handlers = struct
    type self = t

    let on_launch = on_launch

    let on_request = on_request

    let on_close = on_close

    let on_error = on_error

    let on_completion = on_completion

    let on_no_request _ = return_unit
  end in
  Worker.launch
    table
    limits.worker_limits
    ()
    (limits, start_testchain, db, validation_process)
    (module Handlers)

let shutdown = Worker.shutdown

let validate w ?canceler ?peer ?(notify_new_block = fun _ -> ()) chain_db hash
    (header : Block_header.t) operations =
  let bv = Worker.state w in
  let chain_state = Distributed_db.chain_state chain_db in
  should_validate_block w chain_state hash
  >>= function
  | Some (block, false) ->
      debug
        w
        "previously validated block %a (before pipe)"
        Block_hash.pp_short
        hash ;
      Protocol_validator.prefetch_and_compile_protocols
        bv.protocol_validator
        ?peer
        ~timeout:bv.limits.protocol_timeout
        block ;
      return_none
  | Some (_, true) | None ->
      map_p
        (map_p (fun op ->
             let op_hash = Operation.hash op in
             return op_hash))
        operations
      >>=? fun hashes ->
      let computed_hash =
        Operation_list_list_hash.compute
          (List.map Operation_list_hash.compute hashes)
      in
      fail_when
        ( Operation_list_list_hash.compare
            computed_hash
            header.shell.operations_hash
        <> 0 )
        (Inconsistent_operations_hash
           {
             block = hash;
             expected = header.shell.operations_hash;
             found = computed_hash;
           })
      >>=? fun () ->
      check_chain_liveness chain_db hash header
      >>=? fun () ->
      Worker.Queue.push_request_and_wait
        w
        (Request_validation
           {
             chain_db;
             notify_new_block;
             canceler;
             peer;
             hash;
             header;
             operations;
           })
      >>=? fun result -> Lwt.return result

let fetch_and_compile_protocol w =
  let bv = Worker.state w in
  Protocol_validator.fetch_and_compile_protocol bv.protocol_validator

let status = Worker.status

let running_worker () =
  match Worker.list table with
  | [(_, single)] ->
      single
  | [] ->
      raise Not_found
  | _ :: _ :: _ ->
      (* NOTE: names of workers must be unique, [Name.t = unit] which has only
         one inhabitant. *)
      assert false

let pending_requests t = Worker.Queue.pending_requests t

let current_request t = Worker.current_request t

let last_events = Worker.last_events