feat(users/Profpatsch): init haskell arglib-netencode

Mirrors the rust exec-helpers

Change-Id: I96f211d6545e228b8ae0c1dce4e60e6f6867690c
Reviewed-on: https://cl.tvl.fyi/c/depot/+/6117
Tested-by: BuildkiteCI
Reviewed-by: Profpatsch <mail@profpatsch.de>

users/Profpatsch/arglib/ArglibNetencode.hs

@@ -0,0 +1,25 @@
+{-# LANGUAGE LambdaCase #-}
+{-# LANGUAGE OverloadedStrings #-}
+{-# LANGUAGE QuasiQuotes #-}
+
+module ArglibNetencode where
+
+import qualified Data.Attoparsec.ByteString as Atto
+import Data.Maybe (fromMaybe)
+import ExecHelpers
+import MyPrelude
+import Netencode
+import qualified System.Environment as Env
+import qualified System.Posix.Env.ByteString as ByteEnv
+
+arglibNetencode :: CurrentProgramName -> Maybe Text -> IO T
+arglibNetencode progName mEnvvar = do
+  let envvar = mEnvvar & fromMaybe "ARGLIB_NETENCODE" & textToBytesUtf8
+  ByteEnv.getEnv envvar >>= \case
+    Nothing -> dieUserError progName [fmt|could not read args, envvar {envvar} not set|]
+    Just bytes ->
+      case Atto.parseOnly (Netencode.netencodeParser <* Atto.endOfInput) bytes of
+        Left err -> dieEnvironmentProblem progName [fmt|arglib parsing error: {err}|]
+        Right t -> do
+          ByteEnv.unsetEnv envvar
+          pure t

users/Profpatsch/arglib/arglib-netencode.cabal

@@ -0,0 +1,17 @@
+cabal-version:      2.4
+name:               arglib-netencode
+version:            0.1.0.0
+author:             Profpatsch
+maintainer:         mail@profpatsch.de
+
+library
+    exposed-modules:          ArglibNetencode
+
+    build-depends:
+        base ^>=4.15.1.0,
+        my-prelude,
+        netencode,
+        exec-helpers,
+        attoparsec,
+        unix
+    default-language: Haskell2010

users/Profpatsch/arglib/netencode.nix

@@ -36,6 +36,28 @@ let
           t
       }
     '';
+
+    haskell = pkgs.haskellPackages.mkDerivation {
+      pname = "arglib-netencode";
+      version = "0.1.0";
+
+      src = depot.users.Profpatsch.exactSource ./. [
+        ./arglib-netencode.cabal
+        ./ArglibNetencode.hs
+      ];
+
+      libraryHaskellDepends = [
+        depot.users.Profpatsch.my-prelude
+        depot.users.Profpatsch.netencode.netencode-hs
+        depot.users.Profpatsch.execline.exec-helpers-hs
+      ];
+
+      isLibrary = true;
+      license = lib.licenses.mit;
+
+
+    };
+
   };
 
 in