have sand daemon check env for socket fd

.gitignore

@@ -2,3 +2,4 @@
 /release/
 /release.tar.zst
 .direnv/
+__pycache__/

src/Sand/SandDaemon.lean

@@ -190,12 +190,46 @@ def handleClient : CmdHandlerT IO Unit := do
 
 partial def forever (act : IO α) : IO β := act *> forever act
 
+inductive EnvFdError
+ | varNotFound
+ | couldntParse
+
+def EnvFdError.toString : EnvFdError → String
+ | .varNotFound => "SAND_SOCKFD not present in environment"
+ | .couldntParse => "Found SAND_SOCKFD but couldn't parse it as a string"
+
+def envFd : BaseIO (Except EnvFdError UInt32) := do
+ let some str ← IO.getEnv "SAND_SOCKFD"
+ | return .error .varNotFound
+ let some n := str.toNat?
+ | return .error .couldntParse
+ return pure n.toUInt32
+
+def systemdSockFd : UInt32 := 3
+
 def SandDaemon.main (_args : List String) : IO α := do
- let systemdSockFd := 3
- let sock ← Socket.fromFd systemdSockFd
 
- IO.eprintln "sandd started"
- IO.eprintln "listening..."
+ let fd? ← envFd
+ let fd : UInt32 ← match fd? with
+ | .error e@(.couldntParse) => do
+ IO.eprintln s!"Error: {e.toString}"
+ IO.Process.exit 1
+ | .error .varNotFound => do
+ IO.eprintln "SAND_SOCKFD not found, falling back on default."
+ pure systemdSockFd
+ | .ok fd => do
+ IO.eprintln "found SAND_SOCKFD."
+ pure fd
+
+ let sock ← match ← (Socket.fromFd fd).toBaseIO with
+ | .ok sock => pure sock
+ | .error e => do
+ IO.eprintln s!"Error creating socket from file descriptor {fd}:"
+ IO.eprintln s!" {e}"
+ IO.Process.exit 1
+
+
+ IO.eprintln s!"Sand daemon started. listening on fd {fd}"
 
  let state ← DaemonState.initial