array support!

src/kmer.gleam

@@ -1,4 +1,5 @@
 import gleam/bit_array
+import gleam/list.{reverse}
 import gleam/result.{try}
 import ieee_float.{
   type IEEEFloat, from_bytes_16_be, from_bytes_32_be, from_bytes_64_be,
@@ -10,6 +11,7 @@ pub type DecodedValue {
   Boolean(value: Bool)
   Bytes(value: BitArray)
   String(value: String)
+  Array(List(DecodedValue))
   Null
   Undefined
 }
@@ -42,6 +44,9 @@ pub fn decode(bits: BitArray) -> DecodeResult {
     <<3:3, rest:bits>> ->
       decode_string(rest)
       |> map_decoded(String)
+    <<4:3, rest:bits>> ->
+      decode_array(rest)
+      |> map_decoded(Array)
     <<7:3, x:5, rest:bits>> if x < 25 -> decode_simple(<<x:5, rest:bits>>)
     <<7:3, x:5, rest:bits>> if x >= 25 ->
       decode_float(<<x:5, rest:bits>>)
@@ -83,6 +88,11 @@ fn decode_string(bits: BitArray) -> DecoderResult(String) {
   }
 }
 
+fn decode_array(bits: BitArray) -> DecoderResult(List(DecodedValue)) {
+  use #(length, rest) <- try(decode_int(bits))
+  decode_next_n([], rest, length)
+}
+
 fn decode_float(bits: BitArray) -> DecoderResult(IEEEFloat) {
   case bits {
     <<25:5, float16:bytes-size(2), rest:bits>> ->
@@ -105,6 +115,22 @@ fn decode_simple(bits: BitArray) -> DecodeResult {
   }
 }
 
+fn decode_next_n(
+  retrieved: List(DecodedValue),
+  rest: BitArray,
+  n: Int,
+) -> DecoderResult(List(DecodedValue)) {
+  // Due to how Gleam handles lists, we build it in reverse
+  // and then reverse it at the end before returning
+  case n {
+    0 -> Ok(#(reverse(retrieved), rest))
+    n -> {
+      use #(next, rest) <- try(decode(rest))
+      decode_next_n([next, ..retrieved], rest, n - 1)
+    }
+  }
+}
+
 fn map_decoded(
   result: DecoderResult(t),
   map_fn: fn(t) -> DecodedValue,

test/kmer_test.gleam

@@ -3,8 +3,8 @@ import gleeunit
 import gleeunit/should
 import ieee_float.{finite, nan, positive_infinity}
 import kmer.{
-  type DecodeResult, type DecodedValue, Boolean, Bytes, Float, Integer, Null,
+  type DecodeResult, type DecodedValue, Array, Boolean, Bytes, Float, Integer,
-  String, Undefined,
+  Null, String, Undefined,
 }
 
 pub fn main() {
@@ -122,6 +122,20 @@ pub fn decode_string_test() {
   |> table_fn(table_test_decode)
 }
 
+pub fn decode_list_test() {
+  [
+    #(
+      <<4:3, 5:5, 1, 2, 3, 4, 5>>,
+      Array([Integer(1), Integer(2), Integer(3), Integer(4), Integer(5)]),
+    ),
+    #(
+      <<4:3, 24:5, 3:8, 3:3, 11:5, "Hello world", 1:3, 24:5, 123:8, 3>>,
+      Array([String("Hello world"), Integer(-124), Integer(3)]),
+    ),
+  ]
+  |> table_fn(table_test_decode)
+}
+
 fn table_fn(tests: List(#(a, b)), test_fn: fn(a, b) -> Nil) {
   list.map(tests, fn(t) {
     let #(test_case, expected) = t