#!/usr/bin/env stack
> -- stack script --resolver lts-22.6 --package http-client --package http-client-tls --package bytestring

Icecast → Gopher relay. Always streams; emits no gophermap and no
terminator. Pair this with a sibling icecast.txt that explains how to
pipe it (`nc gopher.someodd.zip 70 <<< /applets/icecast.lhs | mpv -`).

The default upstream is `https://radio.someodd.zip/` (port 443 implicit).
Override with the GOPHER_RADIO_URL env var if needed without editing.

Important details inside `main`:

  - hSetBinaryMode stdout True   →  audio bytes; no UTF-8 translation
  - Icy-MetaData: 0               →  Icecast must not interleave metadata
                                     into the audio (would corrupt MP3
                                     for non-icy-aware players)
  - responseTimeoutNone           →  http-client's default ~30 s timeout
                                     would kill the unbounded stream
  - withResponse                  →  bracket-style; on stdout broken-pipe
                                     (gopher client disconnects) the
                                     exception unwinds and the upstream
                                     TLS connection closes. venusia's
                                     child-process bracket then reaps.

> {-# LANGUAGE OverloadedStrings #-}
> module Main (main) where
>
> import qualified Data.ByteString         as BS
> import           Data.Maybe              (fromMaybe)
> import           Network.HTTP.Client     (brRead, parseRequest,
>                                           requestHeaders, responseBody,
>                                           responseTimeout,
>                                           responseTimeoutNone,
>                                           withResponse)
> import           Network.HTTP.Client.TLS (newTlsManager)
> import           System.Environment      (lookupEnv)
> import           System.IO               (BufferMode (..), hSetBinaryMode,
>                                           hSetBuffering, stdout)
>
> defaultUrl :: String
> defaultUrl = "https://radio.someodd.zip/"
>
> main :: IO ()
> main = do
>   hSetBinaryMode stdout True
>   hSetBuffering  stdout NoBuffering
>   url  <- fromMaybe defaultUrl <$> lookupEnv "GOPHER_RADIO_URL"
>   mgr  <- newTlsManager
>   req0 <- parseRequest url
>   let req = req0
>         { requestHeaders  = ("Icy-MetaData", "0") : requestHeaders req0
>         , responseTimeout = responseTimeoutNone
>         }
>   withResponse req mgr $ \res -> pump (responseBody res)
>
> -- | Read chunks from the upstream body and write them to stdout until
> -- either upstream closes (empty chunk) or stdout breaks (gopher client
> -- disconnects → exception propagates out, withResponse cleans up).
> pump :: (IO BS.ByteString) -> IO ()
> pump body = go
>   where
>     go = do
>       chunk <- brRead body
>       if BS.null chunk
>         then pure ()
>         else BS.hPut stdout chunk >> go