add amount.mli

src/amount.ml

@@ -1,7 +1,7 @@
 (* TODO
      have safe amount arithmetic
      make type private
-     use config currency option *)
+     redefine an Amount module with currency enforced to be Config.currency? *)
 (* Amounts of currency, serialized as `<Currency>:<IntegerPart>.<FractionalPart>`
      Fixed-precision numbers with 8 decimal places.
      - <Currency> must be at most 11 characters long
@@ -11,9 +11,13 @@
 
      Prefixed with '+' or '-' in certain contexts.
      When no sign is present, the amount is assumed to be positive. *)
+type sign =
+  | Sign_plus
+  | Sign_minus
+
 type t = {
-  sign: [ `Plus | `Minus ] option;
-  currency: [ `Eur ];
+  sign: sign option;
+  currency: string;
   value: Int64.t;
   fraction: Int32.t;
 }
@@ -37,11 +41,12 @@ let make ~sign ~currency ~value ~fraction =
 
 let pp =
   let open Fmt in
-  let pp_sign ppf = function `Plus -> char ppf '+' | `Minus -> char ppf '-' in
-  let pp_currency ppf = function `Eur -> string ppf "EUR" in
+  let pp_sign ppf = function
+    | Sign_plus -> char ppf '+'
+    | Sign_minus -> char ppf '-'
+  in
   fun ppf { sign; currency; value; fraction } ->
-    pf ppf "%a%a:%Ld.%02ld" (Fmt.option pp_sign) sign pp_currency currency value
-      fraction
+    pf ppf "%a%s:%Ld.%02ld" (Fmt.option pp_sign) sign currency value fraction
 
 let to_string = Fmt.str "%a" pp
 
@@ -50,11 +55,16 @@ let of_string =
   let parse_sign =
     choice
       [
-        char '+' *> return (Some `Plus); char '-' *> return (Some `Minus);
-        return None;
+        char '+' *> return (Some Sign_plus);
+        char '-' *> return (Some Sign_minus); return None;
       ]
   in
-  let parse_currency = string "EUR" *> return `Eur in
+  let parse_currency =
+    (* TODO currency string constraint/format *)
+    take_while1 (function
+      | 'a' .. 'z' | 'A' .. 'Z' -> true
+      | _ -> false)
+  in
   let parse_int64 =
     take_while1 (function '0' .. '9' -> true | _ -> false)
     >>| Int64.of_string_opt