server: control port (#804)

* server: control port

* do not remove messages when saving via control port

* remove unused record fields

* fix tests

src/Simplex/Messaging/Server/Control.hs

@@ -0,0 +1,36 @@
+{-# LANGUAGE LambdaCase #-}
+{-# LANGUAGE OverloadedStrings #-}
+
+module Simplex.Messaging.Server.Control where
+
+import qualified Data.Attoparsec.ByteString.Char8 as A
+import Simplex.Messaging.Encoding.String
+
+data ControlProtocol
+  = CPSuspend
+  | CPResume
+  | CPClients
+  | CPStats
+  | CPSave
+  | CPHelp
+  | CPQuit
+
+instance StrEncoding ControlProtocol where
+  strEncode = \case
+    CPSuspend -> "suspend"
+    CPResume -> "resume"
+    CPClients -> "clients"
+    CPStats -> "stats"
+    CPSave -> "save"
+    CPHelp -> "help"
+    CPQuit -> "quit"
+  strP =
+    A.takeTill (== ' ') >>= \case
+      "suspend" -> pure CPSuspend
+      "resume" -> pure CPResume
+      "clients" -> pure CPClients
+      "stats" -> pure CPStats
+      "save" -> pure CPSave
+      "help" -> pure CPHelp
+      "quit" -> pure CPQuit
+      _ -> fail "bad ControlProtocol command"