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module Main where
import Network.CGI (CGIResult, runCGI, getInput, output, redirect, pathInfo, CGI, outputNotFound, liftIO)
import Data.CircularList (CList, fromList, rotR, rotateTo, focus, rotL)
import Data.Maybe(fromJust, fromMaybe)
import Data.Functor ((<&>))
webring :: CList String
webring = fromList
[ "stuebinm.eu"
, "nwex.de"
]
main :: IO ()
main = runCGI $ do
path <- pathInfo
case path of
"/" -> output "nomsable websites"
"/next" -> rotate True
"/previous" -> rotate False
_ -> outputNotFound path
rotate :: Bool -> CGI CGIResult
rotate backwards = do
from <- getInput "from" <&> fromMaybe (focus' webring)
case rotateTo from webring of
Nothing -> redirect ("https://" <> focus' webring)
Just ring -> redirect ("https://" <> focus' (step ring))
where step = if backwards then rotL else rotR
focus' :: CList c -> c
focus' = fromJust . focus
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