add message parsing module

message.nim

@@ -0,0 +1,47 @@
+import strutils
+from net import IpAddress, parseIpAddress, Port, `$`
+
+proc parseField(input: string, output: var string) =
+  output = input
+
+proc parseField[T: SomeUnsignedInt](input: string, output: var T) =
+  let parsed = parseUInt(input)
+  if parsed > T.high:
+    raise newException(ValueError, "Unsigned integer out of range")
+  output = parsed.T
+
+proc parseField(input: string, output: var IpAddress) =
+  output = parseIpAddress(input)
+
+proc parseField(input: string, output: var Port) =
+  var portNumber: uint16
+  parseField(input, portNumber)
+  output = Port(portNumber)
+
+proc parseField[S, T](input: string, output: var array[S, T]) =
+  let parts = input.split(",", S.high)
+  if parts.len != S.high + 1:
+    raise newException(ValueError, "Array has wrong length")
+  for i in 0 .. S.high:
+    parseField(parts[i], output[i])
+
+proc parseField[T: tuple | object](input: string, output: var T) =
+  var fieldCount = 0
+  for _ in output.fields:
+    fieldCount = fieldCount + 1
+  let args = input.parseArgs(fieldCount)
+  var i = 0
+  for value in output.fields:
+    parseField(args[i], value)
+    i.inc
+
+proc parseArgs*(input: string, count: int, optionalCount = 0): seq[string] =
+  assert(optionalCount <= count)
+  result = input.split("|", count - 1)
+  if result.len < count:
+    if result.len < count - optionalCount:
+      raise newException(ValueError, "invalid message")
+    result.add(repeat("", count - result.len))
+
+proc parseMessage*[T: tuple | object](input: string): T =
+  parseField(input, result)