From 7f1f2b46ba140d25ffed4832c3fec52585f4a9bc Mon Sep 17 00:00:00 2001
From: Martin Ashby <martin@ashbysoft.com>
Date: Fri, 24 Nov 2023 20:04:26 +0000
Subject: Add list decoding

---
 main.roc | 130 +++++++++++++++++++++++++++++++++++++++++++++++++--------------
 1 file changed, 102 insertions(+), 28 deletions(-)

diff --git a/main.roc b/main.roc
index a1c3e38..3d48fcd 100644
--- a/main.roc
+++ b/main.roc
@@ -4,13 +4,6 @@ app "roctorrent"
     provides [main] to pf
 
 
-BVal: [
-  BStr  Str,
-  BNum  I64,
-  BList (List BVal),
-  # TODO add dict! 
-]
-
 # Decodes an exact string, errors if there is remaining unused data
 bDecodeStr: List U8 -> Result (List U8) [Malformatted]
 bDecodeStr = \i ->
@@ -110,29 +103,110 @@ expect
     res = bDecodeNum (Str.toUtf8 case)
     res == Err (Malformatted msg)
 
-bDecodeList: (List U8) -> Result (List BVal) [Malformatted]
-bDecodeList = \_i -> 
-  Ok [BNum 64, BStr "foo"]
-  #when i is
-  #  ['l', .., 'e'] -> 
-  #  _ -> Err Malformatted
-
-#bDecodeListInner: (List U8, List BVal) -> Result {res: (List BVal), others: (List U8)} [Malformatted]
-#bDecodeListInner = \i, o ->
-#  when (List.first i) is
-#    Ok first -> 
-#      when first is
-#      '0'|'1'|'2'|'3'|'4'|'5'|'6'|'7'|'8'|'9' -> 
-#        when bDecodeStringAndRemainder first is
-#          Ok {before, others} -> 
-#          Err _err -> Err Malformatted
-#      'i' ->
-#        bDecode
-#    Err _err -> Err Malformatted
+# Tags for storing heterogenous collections
+BVal: [
+  BStr  (List U8),
+  BNum  I64,
+  BList (List BVal),
+]
+
+# Detects and decodes any kind of element.
+bDecodeValueAndRem: (List U8) -> Result {res: BVal, others: (List U8)} [Malformatted, End (List U8)]
+bDecodeValueAndRem = \i ->
+  when (List.first i) is
+    Ok first -> 
+      when first is
+        '0'|'1'|'2'|'3'|'4'|'5'|'6'|'7'|'8'|'9' -> 
+          when bDecodeStrAndRemainder i is
+            Ok {before, others} -> 
+              Ok {res: BStr before, others: others}
+            Err _err -> 
+              Err Malformatted
+        'i' ->
+          when bDecodeNumAndRem i is
+            Ok {num, rem} -> 
+              Ok {res: BNum num, others: rem}
+            Err _err -> 
+              Err Malformatted
+        'l' ->
+          when bDecodeListAndRem i is
+            Ok {res, others} ->
+              Ok {res: BList res, others: others}
+            Err _err -> 
+              Err Malformatted
+        'e' ->
+          {before, others} = List.split i 1
+          Err (End others)
+        _ -> 
+          Err Malformatted
+    Err _err -> Err Malformatted
+
+expect
+  res = bDecodeValueAndRem (Str.toUtf8 "i64efoo")
+  res == Ok {res: BNum 64, others: (Str.toUtf8 "foo")}
+
+expect
+  res = bDecodeValueAndRem (Str.toUtf8 "3:foo3:foo")
+  res == Ok {res: BStr (Str.toUtf8 "foo"), others: (Str.toUtf8 "3:foo")}
+
+expect
+  res = bDecodeValueAndRem (Str.toUtf8 "efoo")
+  res == Err (End (Str.toUtf8 "foo"))
 
 expect
-  res = bDecodeList (Str.toUtf8 "li64e3:fooe")
-  res == Ok [BNum 64, BStr "foo"]
+  res = bDecodeValueAndRem (Str.toUtf8 "z")
+  res == Err Malformatted
+
+# Decodes a list. List elements can be any 
+bDecodeList: (List U8) -> Result {res: (List BVal)} [Malformatted]
+bDecodeList = \i ->
+  when bDecodeListAndRem i is
+    Ok {res, others} ->
+      if (List.len others) == 0 then
+        Ok {res: res}
+      else 
+        Err Malformatted
+    Err e -> 
+      Err e
+
+bDecodeListAndRem: (List U8) -> Result {res: (List BVal), others: (List U8)} [Malformatted]
+bDecodeListAndRem = \i -> 
+  when List.first i is
+    Ok f -> 
+      if f == 'l' then 
+        {before, others} = List.split i 1
+        bDecodeListAndRemInternal [] others
+      else 
+        Err Malformatted
+    Err _e -> Err Malformatted
+
+bDecodeListAndRemInternal: List BVal, List U8 -> Result {res: (List BVal), others: (List U8)} [Malformatted]
+bDecodeListAndRemInternal = \l, i ->
+  when bDecodeValueAndRem i is
+    Ok {res, others} ->
+      l2 = List.append l res
+      bDecodeListAndRemInternal l2 others
+    Err e -> when e is
+      End others -> 
+        Ok {res: l, others: others}
+      Malformatted -> 
+        Err Malformatted
+
+expect 
+  res = bDecodeList (Str.toUtf8 "le")
+  res == Ok { res: []}
+
+expect 
+  res = bDecodeList (Str.toUtf8 "li123e3:fooe")
+  res == Ok { res: [BNum 123i64, BStr (Str.toUtf8 "foo")] }
+
+expect 
+  res = bDecodeList (Str.toUtf8 "li123e3:fooe123")
+  res == Err Malformatted
+
+expect 
+  res = bDecodeList (Str.toUtf8 "lli123eee")
+  res == Ok { res: [BList [BNum 123i64]]}
 
 main = 
   Stdout.line "Hello, World"
\ No newline at end of file
-- 
cgit v1.2.3-ZIG