Source file qty_repr.ml

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module type QTY = sig
  val id : string

  val name : string
end

module type S = sig
  type qty

  type error +=
    | Addition_overflow of qty * qty (* `Temporary *)
    | Subtraction_underflow of qty * qty (* `Temporary *)
    | Multiplication_overflow of qty * int64 (* `Temporary *)
    | Negative_multiplicator of qty * int64 (* `Temporary *)
    | Invalid_divisor of qty * int64

  (* `Temporary *)

  val id : string

  val zero : qty

  val one_mutez : qty

  val one_cent : qty

  val fifty_cents : qty

  val one : qty

  val ( -? ) : qty -> qty -> qty tzresult

  val ( +? ) : qty -> qty -> qty tzresult

  val ( *? ) : qty -> int64 -> qty tzresult

  val ( /? ) : qty -> int64 -> qty tzresult

  val to_mutez : qty -> int64

  (** [of_mutez n] (micro tez) is None if n is negative *)
  val of_mutez : int64 -> qty option

  (** [of_mutez_exn n] fails if n is negative.
      It should only be used at toplevel for constants. *)
  val of_mutez_exn : int64 -> qty

  (** It should only be used at toplevel for constants. *)
  val add_exn : qty -> qty -> qty

  (** It should only be used at toplevel for constants. *)
  val mul_exn : qty -> int -> qty

  val encoding : qty Data_encoding.t

  val to_int64 : qty -> int64

  include Compare.S with type t := qty

  val pp : Format.formatter -> qty -> unit

  val of_string : string -> qty option

  val to_string : qty -> string
end

module Make (T : QTY) : S = struct
  type qty = int64 (* invariant: positive *)

  type error +=
    | Addition_overflow of qty * qty (* `Temporary *)
    | Subtraction_underflow of qty * qty (* `Temporary *)
    | Multiplication_overflow of qty * int64 (* `Temporary *)
    | Negative_multiplicator of qty * int64 (* `Temporary *)
    | Invalid_divisor of qty * int64

  (* `Temporary *)

  include Compare.Int64

  let zero = 0L

  (* all other constant are defined from the value of one micro tez *)
  let one_mutez = 1L

  let one_cent = Int64.mul one_mutez 10_000L

  let fifty_cents = Int64.mul one_cent 50L

  (* 1 tez = 100 cents = 1_000_000 mutez *)
  let one = Int64.mul one_cent 100L

  let id = T.id

  let of_string s =
    let triplets = function
      | hd :: tl ->
          let len = String.length hd in
          Compare.Int.(
            len <= 3 && len > 0
            && List.for_all (fun s -> String.length s = 3) tl)
      | [] ->
          false
    in
    let integers s = triplets (String.split_on_char ',' s) in
    let decimals s =
      let l = String.split_on_char ',' s in
      if Compare.Int.(List.length l > 2) then false else triplets (List.rev l)
    in
    let parse left right =
      let remove_commas s = String.concat "" (String.split_on_char ',' s) in
      let pad_to_six s =
        let len = String.length s in
        String.init 6 (fun i -> if Compare.Int.(i < len) then s.[i] else '0')
      in
      try
        Some
          (Int64.of_string
             (remove_commas left ^ pad_to_six (remove_commas right)))
      with _ -> None
    in
    match String.split_on_char '.' s with
    | [left; right] ->
        if String.contains s ',' then
          if integers left && decimals right then parse left right else None
        else if
          Compare.Int.(String.length right > 0)
          && Compare.Int.(String.length right <= 6)
        then parse left right
        else None
    | [left] ->
        if (not (String.contains s ',')) || integers left then parse left ""
        else None
    | _ ->
        None

  let pp ppf amount =
    let mult_int = 1_000_000L in
    let rec left ppf amount =
      let (d, r) = (Int64.(div amount 1000L), Int64.(rem amount 1000L)) in
      if d > 0L then Format.fprintf ppf "%a%03Ld" left d r
      else Format.fprintf ppf "%Ld" r
    in
    let right ppf amount =
      let triplet ppf v =
        if Compare.Int.(v mod 10 > 0) then Format.fprintf ppf "%03d" v
        else if Compare.Int.(v mod 100 > 0) then
          Format.fprintf ppf "%02d" (v / 10)
        else Format.fprintf ppf "%d" (v / 100)
      in
      let (hi, lo) = (amount / 1000, amount mod 1000) in
      if Compare.Int.(lo = 0) then Format.fprintf ppf "%a" triplet hi
      else Format.fprintf ppf "%03d%a" hi triplet lo
    in
    let (ints, decs) =
      (Int64.(div amount mult_int), Int64.(to_int (rem amount mult_int)))
    in
    Format.fprintf ppf "%a" left ints ;
    if Compare.Int.(decs > 0) then Format.fprintf ppf ".%a" right decs

  let to_string t = Format.asprintf "%a" pp t

  let ( - ) t1 t2 = if t2 <= t1 then Some (Int64.sub t1 t2) else None

  let ( -? ) t1 t2 =
    match t1 - t2 with
    | None ->
        error (Subtraction_underflow (t1, t2))
    | Some v ->
        ok v

  let ( +? ) t1 t2 =
    let t = Int64.add t1 t2 in
    if t < t1 then error (Addition_overflow (t1, t2)) else ok t

  let ( *? ) t m =
    let open Compare.Int64 in
    let open Int64 in
    let rec step cur pow acc =
      if cur = 0L then ok acc
      else
        pow +? pow
        >>? fun npow ->
        if logand cur 1L = 1L then
          acc +? pow >>? fun nacc -> step (shift_right_logical cur 1) npow nacc
        else step (shift_right_logical cur 1) npow acc
    in
    if m < 0L then error (Negative_multiplicator (t, m))
    else
      match step m t 0L with
      | Ok res ->
          Ok res
      | Error ([Addition_overflow _] as errs) ->
          Error (Multiplication_overflow (t, m) :: errs)
      | Error errs ->
          Error errs

  let ( /? ) t d =
    if d <= 0L then error (Invalid_divisor (t, d)) else ok (Int64.div t d)

  let add_exn t1 t2 =
    let t = Int64.add t1 t2 in
    if t <= 0L then invalid_arg "add_exn" else t

  let mul_exn t m =
    match t *? Int64.(of_int m) with
    | Ok v ->
        v
    | Error _ ->
        invalid_arg "mul_exn"

  let of_mutez t = if t < 0L then None else Some t

  let of_mutez_exn x =
    match of_mutez x with None -> invalid_arg "Qty.of_mutez" | Some v -> v

  let to_int64 t = t

  let to_mutez t = t

  let encoding =
    let open Data_encoding in
    Data_encoding.def
      T.name
      (check_size 10 (conv Z.of_int64 (Json.wrap_error Z.to_int64) n))

  let () =
    let open Data_encoding in
    register_error_kind
      `Temporary
      ~id:(T.id ^ ".addition_overflow")
      ~title:("Overflowing " ^ T.id ^ " addition")
      ~pp:(fun ppf (opa, opb) ->
        Format.fprintf
          ppf
          "Overflowing addition of %a %s and %a %s"
          pp
          opa
          T.id
          pp
          opb
          T.id)
      ~description:("An addition of two " ^ T.id ^ " amounts overflowed")
      (obj1 (req "amounts" (tup2 encoding encoding)))
      (function Addition_overflow (a, b) -> Some (a, b) | _ -> None)
      (fun (a, b) -> Addition_overflow (a, b)) ;
    register_error_kind
      `Temporary
      ~id:(T.id ^ ".subtraction_underflow")
      ~title:("Underflowing " ^ T.id ^ " subtraction")
      ~pp:(fun ppf (opa, opb) ->
        Format.fprintf
          ppf
          "Underflowing subtraction of %a %s and %a %s"
          pp
          opa
          T.id
          pp
          opb
          T.id)
      ~description:("An subtraction of two " ^ T.id ^ " amounts underflowed")
      (obj1 (req "amounts" (tup2 encoding encoding)))
      (function Subtraction_underflow (a, b) -> Some (a, b) | _ -> None)
      (fun (a, b) -> Subtraction_underflow (a, b)) ;
    register_error_kind
      `Temporary
      ~id:(T.id ^ ".multiplication_overflow")
      ~title:("Overflowing " ^ T.id ^ " multiplication")
      ~pp:(fun ppf (opa, opb) ->
        Format.fprintf
          ppf
          "Overflowing multiplication of %a %s and %Ld"
          pp
          opa
          T.id
          opb)
      ~description:
        ("A multiplication of a " ^ T.id ^ " amount by an integer overflowed")
      (obj2 (req "amount" encoding) (req "multiplicator" int64))
      (function Multiplication_overflow (a, b) -> Some (a, b) | _ -> None)
      (fun (a, b) -> Multiplication_overflow (a, b)) ;
    register_error_kind
      `Temporary
      ~id:(T.id ^ ".negative_multiplicator")
      ~title:("Negative " ^ T.id ^ " multiplicator")
      ~pp:(fun ppf (opa, opb) ->
        Format.fprintf
          ppf
          "Multiplication of %a %s by negative integer %Ld"
          pp
          opa
          T.id
          opb)
      ~description:
        ("Multiplication of a " ^ T.id ^ " amount by a negative integer")
      (obj2 (req "amount" encoding) (req "multiplicator" int64))
      (function Negative_multiplicator (a, b) -> Some (a, b) | _ -> None)
      (fun (a, b) -> Negative_multiplicator (a, b)) ;
    register_error_kind
      `Temporary
      ~id:(T.id ^ ".invalid_divisor")
      ~title:("Invalid " ^ T.id ^ " divisor")
      ~pp:(fun ppf (opa, opb) ->
        Format.fprintf
          ppf
          "Division of %a %s by non positive integer %Ld"
          pp
          opa
          T.id
          opb)
      ~description:
        ("Multiplication of a " ^ T.id ^ " amount by a non positive integer")
      (obj2 (req "amount" encoding) (req "divisor" int64))
      (function Invalid_divisor (a, b) -> Some (a, b) | _ -> None)
      (fun (a, b) -> Invalid_divisor (a, b))
end