feat: experiment with adding custom decoder for tagged

gleam.toml

@@ -8,6 +8,7 @@ repository = { type = "github", user = "Beaudidly", repo = "https://github.com/B
 [dependencies]
 gleam_stdlib = ">= 0.44.0 and < 2.0.0"
 ieee_float = ">= 1.5.0 and < 2.0.0"
+gleam_erlang = ">= 1.2.0 and < 2.0.0"
 
 [dev-dependencies]
 gleeunit = ">= 1.0.0 and < 2.0.0"

src/gbor/decode.gleam

@@ -1,6 +1,9 @@
 import gleam/bit_array
+import gleam/bool
 import gleam/dynamic
 import gleam/dynamic/decode as gdd
+import gleam/erlang/atom
+import gleam/int
 import gleam/list
 import gleam/result
 import gleam/string
@@ -17,6 +20,46 @@ pub type CborDecodeError {
   UnassignedError
 }
 
+pub fn cbor_to_dynamic(cbor: g.CBOR) -> dynamic.Dynamic {
+  case cbor {
+    g.CBInt(v) -> dynamic.int(v)
+    g.CBString(v) -> dynamic.string(v)
+    g.CBFloat(v) -> dynamic.float(v)
+    g.CBMap(v) ->
+      dynamic.properties(
+        list.map(v, fn(v) { #(cbor_to_dynamic(v.0), cbor_to_dynamic(v.1)) }),
+      )
+    g.CBArray(v) -> dynamic.array(list.map(v, cbor_to_dynamic))
+    g.CBBool(v) -> dynamic.bool(v)
+    g.CBNull -> dynamic.nil()
+    g.CBUndefined -> dynamic.nil()
+    g.CBBinary(v) -> dynamic.bit_array(v)
+    g.CBTagged(tag, value) -> ffi_to_tagged(tag, cbor_to_dynamic(value))
+  }
+}
+
+pub fn tagged_decoder(
+  expected_tag: Int,
+  decoder: gdd.Decoder(a),
+  zero: a,
+) -> gdd.Decoder(a) {
+  let error = gdd.failure(zero, "CBOR tagged value")
+
+  use cbor_tag <- gdd.field(0, atom.decoder())
+  use <- bool.guard(
+    cbor_tag != atom.create("cbor_tagged__"),
+    gdd.failure(zero, "CBOR tagged value"),
+  )
+
+  use tag <- gdd.field(1, gdd.int)
+  use <- bool.guard(
+    tag != expected_tag,
+    gdd.failure(zero, int.to_string(expected_tag)),
+  )
+
+  gdd.at([2], decoder)
+}
+
 pub fn decode(data: BitArray) -> Result(#(g.CBOR, BitArray), CborDecodeError) {
   case data {
     <<0:3, min:5, rest:bits>> -> decode_uint(min, rest)
@@ -315,3 +358,11 @@ pub fn decode_tagged(
 
   Ok(#(g.CBTagged(tag_num, tag_value), rest))
 }
+
+@external(erlang, "erl_gbor", "to_tagged")
+pub fn ffi_to_tagged(tag: Int, value: dynamic.Dynamic) -> dynamic.Dynamic
+
+@external(erlang, "erl_gbor", "check_tagged")
+pub fn ffi_check_tagged(
+  tagged: dynamic.Dynamic,
+) -> Result(#(Int, dynamic.Dynamic), String)

src/gbor/erl_gbor.erl

@@ -0,0 +1,15 @@
+-module(erl_gbor).
+
+-export([to_tagged/2, check_tagged/1]).
+
+to_tagged(Tag, Value) ->
+  {cbor_tagged__, Tag, Value}.
+
+
+check_tagged(Tagged) ->
+  case Tagged of
+    {cbor_tagged__, Tag, Value} ->
+      {ok, {Tag, Value}};
+    _ ->
+      {error, invalid_tagged_value}
+  end.

test/round_trip_test.gleam

@@ -1,4 +1,8 @@
 import gleam/bit_array
+import gleam/bool
+import gleam/dynamic/decode as gdd
+import gleam/list
+import gleam/result
 import gleeunit
 
 import gbor as g
@@ -99,3 +103,29 @@ pub fn decode_taggded_test() {
 
   round_trip(g.CBTagged(1, g.CBInt(1_363_896_240)), "c11a514b67b0")
 }
+
+type Cat {
+  Cat(name: String, dob: String)
+}
+
+pub fn decode_dynamic_test() {
+  let assert Ok(bin) =
+    bit_array.base16_decode(
+      "A2646E616D6574323031332D30332D32315432303A30343A30305A63646F62C074323031332D30332D32315432303A30343A30305A",
+    )
+
+  let assert Ok(#(cbor_val, <<>>)) = d.decode(bin)
+  let dyn_val = d.cbor_to_dynamic(cbor_val)
+
+  let decoder = {
+    use name <- gdd.field("name", gdd.string)
+    use dob <- gdd.field("dob", d.tagged_decoder(0, gdd.string, "INVALID"))
+    gdd.success(Cat(name, dob))
+  }
+
+  let assert Ok(v) = gdd.run(dyn_val, decoder)
+  assert v == Cat("2013-03-21T20:04:00Z", "2013-03-21T20:04:00Z")
+
+  let assert Ok(encoded) = e.to_bit_array(cbor_val)
+  assert encoded == bin
+}