#!/usr/bin/env stack
> -- stack script --resolver nightly-2025-12-01

whoami.lhs: what IP does Venusia think you are?
===============================================

A throwaway diagnostic applet. The worry it answers: when an `.lhs`
is invoked, `routes.toml` substitutes `$remote_ip` into the argv —
but if Venusia is sitting behind `xinetd` (or any other inetd-style
super-server) the connection it sees may come from `127.0.0.1`, so
`$remote_ip` would echo *localhost* rather than the real visitor.

This script doesn't try to be clever. It dumps every positional
argument it was handed, numbered, plus the relevant connection
environment variables, as gophermap info-lines. Whatever Venusia
actually puts in the `$remote_ip` slot shows up verbatim — if it
reads `127.0.0.1`, the fear is confirmed.

argv layout
-----------

`routes.toml`'s `[[files.script_extension]]` for `lhs` runs:

    run-cached-lhs  $file $selector $search $pathinfo $remote_ip

`run-cached-lhs` shifts off `$file` (the script path) before exec'ing
the compiled binary, so *this* program's argv is:

    argv[0] = $selector
    argv[1] = $search
    argv[2] = $pathinfo
    argv[3] = $remote_ip   <-- the value under suspicion

We print them all rather than hard-coding "index 3 is the IP", so the
output is self-checking: you can see which slot the address landed in.

> import System.Environment (getArgs, lookupEnv)
> import System.IO          (BufferMode (..), hSetBuffering, stdout)

Gophermap helpers. An info-line is item type `i`; the display field
is the only one that matters, and it must not contain a tab or CRLF
or it'll parse as multiple fields / rows on the wire. We replace any
such byte with a space.

> sanitize :: String -> String
> sanitize = map (\c -> if c `elem` "\t\r\n" then ' ' else c)

> infoLine :: String -> IO ()
> infoLine msg = putStr ("i" <> sanitize msg <> "\t\t\t0\r\n")

> main :: IO ()
> main = do
>   hSetBuffering stdout NoBuffering
>   args <- getArgs
>   -- argv[3] is $remote_ip per routes.toml; guard in case it's absent.
>   let remoteIp = case drop 3 args of (ip:_) -> ip; [] -> "(no argv[3]!)"
>   infoLine "whoami.lhs — Venusia connection diagnostic"
>   infoLine ""
>   infoLine ("Venusia says your IP is:  " <> remoteIp)
>   infoLine ""
>   infoLine "--- raw argv (script side, post run-cached-lhs shift) ---"
>   mapM_ (\(n, a) -> infoLine ("  argv[" <> show n <> "] = " <> show a))
>         (zip [0 :: Int ..] args)
>   infoLine ""
>   infoLine "--- connection environment variables ---"
>   mapM_ dumpEnv ["REMOTE_ADDR", "REMOTE_HOST", "TCPREMOTEIP", "GOPHER_REMOTE_IP", "SSH_CONNECTION"]
>   putStr ".\r\n"

> dumpEnv :: String -> IO ()
> dumpEnv k = do
>   v <- lookupEnv k
>   infoLine ("  " <> k <> " = " <> maybe "(unset)" show v)