From a20ce36876487b48dbbd18a38570f4ade522118e Mon Sep 17 00:00:00 2001
From: Martin Ashby <martin@ashbysoft.com>
Date: Thu, 23 Nov 2023 23:56:10 +0000
Subject: Adaptations to allow reading sequential values

---
 main.roc | 116 ++++++++++++++++++++++++++++++++++++++++++++++++---------------
 1 file changed, 89 insertions(+), 27 deletions(-)

diff --git a/main.roc b/main.roc
index c90531f..a1c3e38 100644
--- a/main.roc
+++ b/main.roc
@@ -4,16 +4,35 @@ 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 ->
+  when bDecodeStrAndRemainder i is
+    Ok {before, others} -> 
+      if List.len others == 0 then
+        Ok before
+      else 
+        Err Malformatted
+    Err _ -> Err Malformatted
+
+# Decodes a string and returns the remainder of the input as well if there was any
+bDecodeStrAndRemainder: List U8 -> Result {before: List U8, others: List U8} [Malformatted]
+bDecodeStrAndRemainder = \i -> 
   when (List.splitFirst i ':') is
     Ok {before, after} -> 
       when (Str.fromUtf8 before) is 
       Ok ls -> 
-        when (Str.toU32 ls) is
+        when (Str.toNat ls) is
         Ok l -> 
-          if Num.toU32 (List.len after) == l then 
-            Ok after
+          if List.len after >= l then 
+            Ok (List.split after l)
           else 
             Err Malformatted
         Err _err -> Err Malformatted
@@ -39,18 +58,37 @@ expect
     res = bDecodeStr (Str.toUtf8 t)
     res == Err Malformatted
 
-bDecodeNum: List U8 -> Result I64 [Malformatted]
+# Decodes an exact number, exta input causes an error
+bDecodeNum: List U8 -> Result I64 [Malformatted Str]
 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
+  when bDecodeNumAndRem i is
+    Ok {num, rem} -> 
+      if (List.len rem) == 0 then
+        Ok num
+      else 
+        Err (Malformatted "remaining characters after number")
+    Err e -> Err e
+
+# Decodes a number and returns the number and any unused input
+bDecodeNumAndRem: List U8 -> Result {num: I64, rem: (List U8)} [Malformatted Str]
+bDecodeNumAndRem = \i ->
+  when (List.first i) is
+    Ok f -> 
+      if f == 'i' then
+        when List.findFirstIndex i (\j -> j == 'e') is
+          Ok ix -> 
+            {before, others} = List.split i (ix+1)
+            numl = List.sublist before {start: 1, len: ix-1}
+            when (Str.fromUtf8 numl) is
+              Ok nums ->
+                when (Str.toI64 nums) is
+                  Ok num -> Ok {num: num, rem: others}
+                  Err _e -> Err (Malformatted "failed to parse number from \(nums)")
+              Err _e -> Err (Malformatted "failed to parse utf8")
+          Err _e -> Err (Malformatted "failed to find number end char 'e'")
+      else 
+        Err (Malformatted "number didn't start with 'i'")
+    Err _e -> Err (Malformatted "number string was empty")
 
 expect 
   res = bDecodeNum (Str.toUtf8 "i32e")
@@ -58,19 +96,43 @@ expect
 
 expect 
   errCases = [
-    "", 
-    "foo", 
-    "i32", 
-    "32e", 
-    "ifooe", 
-    "ie", 
-    "i", 
-    "e", 
-    "i522222222222222222343423432434322e",
+    {case: "", msg: "number string was empty"}, 
+    {case: "foo", msg: "number didn't start with 'i'"},
+    {case: "i32", msg: "failed to find number end char 'e'"},
+    {case: "32e", msg: "number didn't start with 'i'"},
+    {case: "ifooe", msg: "failed to parse number from foo"},
+    {case: "ie", msg: "failed to parse number from "},
+    {case: "i", msg: "failed to find number end char 'e'"}, 
+    {case: "e", msg: "number didn't start with 'i'"},
+    {case: "i522222222222222222343423432434322e", msg: "failed to parse number from 522222222222222222343423432434322"},
   ]
-  List.all errCases \t -> 
-    res = bDecodeNum (Str.toUtf8 t)
-    res == Err Malformatted
+  List.all errCases \{case, msg} -> 
+    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
+
+expect
+  res = bDecodeList (Str.toUtf8 "li64e3:fooe")
+  res == Ok [BNum 64, BStr "foo"]
 
 main = 
-  Stdout.line "Hello, World"
+  Stdout.line "Hello, World"
\ No newline at end of file
-- 
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