Add bencoded number decoding

1 files changed, 43 insertions, 1 deletions

diff --git a/main.roc b/main.roc
index 033ff1d..c90531f 100644
--- a/main.roc
+++ b/main.roc
@@ -25,10 +25,52 @@ expect
   res == Ok (Str.toUtf8 "foo")
 
 expect 
-  errCases = ["foo", "1:foo", "4:foo", ":", "foo:", "1:", "::"]
+  errCases = [
+    "", 
+    "foo", 
+    "1:foo", 
+    "4:foo",
+    ":", 
+    "foo:", 
+    "1:",
+    "::",
+  ]
   List.all errCases \t -> 
     res = bDecodeStr (Str.toUtf8 t)
     res == Err Malformatted
 
+bDecodeNum: List U8 -> Result I64 [Malformatted]
+bDecodeNum = \i ->
+  when i is
+    ['i', .., 'e'] -> 
+      ii = List.sublist i {start: 1, len: ((List.len i) - 2)}
+      when (Str.fromUtf8 ii) is
+        Ok iii ->
+          when (Str.toI64 iii) is
+            Ok res -> Ok res
+            Err _err -> Err Malformatted
+        Err _err -> Err Malformatted
+    _ -> Err Malformatted
+
+expect 
+  res = bDecodeNum (Str.toUtf8 "i32e")
+  res == Ok 32i64
+
+expect 
+  errCases = [
+    "", 
+    "foo", 
+    "i32", 
+    "32e", 
+    "ifooe", 
+    "ie", 
+    "i", 
+    "e", 
+    "i522222222222222222343423432434322e",
+  ]
+  List.all errCases \t -> 
+    res = bDecodeNum (Str.toUtf8 t)
+    res == Err Malformatted
+
 main = 
   Stdout.line "Hello, World"