From 9372506c45811ad50f82c0c031432b64f341cf64 Mon Sep 17 00:00:00 2001
From: swrup <swrup@protonmail.com>
Date: Thu, 26 Feb 2026 16:20:20 +0100
Subject: [PATCH] better module for BytesXX

---
 src/api.ml            | 30 +++++++++++++++++++++++++++++-
 src/pg.ml             |  2 +-
 src/pg_type.ml        |  2 +-
 src/signatures.ml     | 34 +++++++++++++++++++++++++++++-----
 tools/offline_impl.ml |  6 +-----
 5 files changed, 61 insertions(+), 13 deletions(-)

diff --git a/src/api.ml b/src/api.ml
index f6b87cc3..821aac27 100644
--- a/src/api.ml
+++ b/src/api.ml
@@ -62,6 +62,34 @@ module B32 = struct
       ~decode:B32.decode Caqti_type.string
 end
 
+module Bytes32 = struct
+  include Signatures.Bytes32
+
+  let jsont =
+    let decode s = Result.bind (B32.decode s) of_octets in
+    let encode b = to_octets b |> B32.encode in
+    Jsont.of_of_string ~kind:"Bytes32" decode ~enc:encode
+
+  let caqti =
+    Caqti_type.custom
+      ~encode:(fun v -> Ok (to_octets v))
+      ~decode:of_octets Caqti_type.octets
+end
+
+module Bytes64 = struct
+  include Signatures.Bytes64
+
+  let jsont =
+    let decode s = Result.bind (B32.decode s) of_octets in
+    let encode b = to_octets b |> B32.encode in
+    Jsont.of_of_string ~kind:"Bytes64" decode ~enc:encode
+
+  let caqti =
+    Caqti_type.custom
+      ~encode:(fun v -> Ok (to_octets v))
+      ~decode:of_octets Caqti_type.octets
+end
+
 (* TODO error response
    - use GANA error codes
      https://git.gnunet.org/gana.git/tree/gnu-taler-error-codes/registry.rec *)
@@ -676,7 +704,7 @@ module DrainProfitsMessage = struct
     map ~kind:"DrainProfitsMessage" make
     |> mem "debit_account_section" Jsont.string ~enc:debit_account_section
     |> mem "credit_payto_uri" Jsont.string ~enc:credit_payto_uri
-    |> mem "wtid" B32.jsont ~enc:wtid
+    |> mem "wtid" Bytes32.jsont ~enc:wtid
     |> mem "master_sig" MasterDrainProfit.jsont ~enc:master_sig
     |> mem "date" Timestamp.jsont ~enc:date
     |> mem "amount" Amount.jsont ~enc:amount
diff --git a/src/pg.ml b/src/pg.ml
index 749d9d46..ee45ab99 100644
--- a/src/pg.ml
+++ b/src/pg.ml
@@ -290,7 +290,7 @@ let get_wire_accounts =
 
 let find_drain_profit =
   let req =
-    Caqti_type.(octets ->? drain_profit_message)
+    Caqti_type.(Bytes32.caqti ->? drain_profit_message)
       "SELECT wtid, account_section, payto_uri, trigger_date, (amount).*, \
        master_sig FROM profit_drains WHERE wtid=$1"
   in
diff --git a/src/pg_type.ml b/src/pg_type.ml
index 57865968..032a64a2 100644
--- a/src/pg_type.ml
+++ b/src/pg_type.ml
@@ -265,7 +265,7 @@ let drain_profit_message =
           amount;
           master_sig;
         })
-    Caqti_type.(t6 octets string string time amount master_sig)
+    Caqti_type.(t6 Bytes32.caqti string string time amount master_sig)
 
 let aml_officer_setup =
   let master_sig = Signatures.MasterAmlOfficerStatus.caqti in
diff --git a/src/signatures.ml b/src/signatures.ml
index 8fa4c5d3..af9c7b6a 100644
--- a/src/signatures.ml
+++ b/src/signatures.ml
@@ -33,16 +33,40 @@ open Aliases
 
 let size_of_int32 = 4
 
-module Bytes32 = struct
-  type t = string
+module type BYTES = sig
+  type t
 
-  let bin = Bin.bytes 32
+  val of_octets : string -> (t, string) result
+  val to_octets : t -> string
+  val bin : t Bin.t
 end
 
-module Bytes64 = struct
+module Bytes32 : BYTES = struct
+  let n = 32
+
   type t = string
 
-  let bin = Bin.bytes 64
+  let of_octets s =
+    match String.length s = n with
+    | false -> Error "invalid bytes length"
+    | true -> Ok s
+
+  let to_octets = Fun.id
+  let bin = Bin.bytes n
+end
+
+module Bytes64 : BYTES = struct
+  let n = 64
+
+  type t = string
+
+  let of_octets s =
+    match String.length s = n with
+    | false -> Error "invalid bytes length"
+    | true -> Ok s
+
+  let to_octets = Fun.id
+  let bin = Bin.bytes n
 end
 
 module TransferSecretP = Bytes64
diff --git a/tools/offline_impl.ml b/tools/offline_impl.ml
index cc681153..68e45ea7 100644
--- a/tools/offline_impl.ml
+++ b/tools/offline_impl.ml
@@ -411,11 +411,7 @@ let disable_wire ~output ~master_key ~payto_uri =
 let drain ~output ~master_key ~debit_account_section ~credit_payto_uri ~wtid
     ~date ~amount =
   let* key = read_master_key_file master_key in
-  let* () =
-    match String.length wtid = 32 with
-    | false -> Error "invalid wtid: must be 32 bytes"
-    | true -> Ok ()
-  in
+  let* wtid = Api.Bytes32.of_octets wtid in
   let master_sig =
     let open Signatures.MasterDrainProfit in
     signf (EddsaSignature.sign ~key)