Generate RSS feed from list of Git references and timestamps

NixRSS.hs

{-# LANGUAGE RecordWildCards #-}
{-# LANGUAGE ViewPatterns #-}
module Main where

import Data.Maybe
import Data.Time.Clock
import Data.Time.Clock.POSIX
import Network.URI
import Text.RSS

data Record = Record
  { ref :: String
  , time :: UTCTime
  }

parseRecord :: String -> Maybe Record
parseRecord s = case words s of
  [ref, posixSecondsToUTCTime . realToFrac . read -> time] -> Just Record {..}
  _ -> Nothing

recordItem :: Record -> Item
recordItem Record{..} =
  [ Title $ "nixos-19.03-small " ++ ref
  , Link $ fromJust $ parseURI "https://releases.nixos.org/nixos/19.03-small"
  , Description ref
  , PubDate time
  ]

main :: IO ()
main = interact $
  showXML .
  rssToXML .
  RSS "nixos-19.03-small" (fromJust $ parseURI "https://channels.nix.gsc.io/nixos-19.03-small") "nixos-19.03-small" [TTL 15] .
  map recordItem .
  mapMaybe parseRecord .
  lines