proxy.hs

{-# LANGUAGE RecordWildCards #-}

import Data.Maybe
import Data.List


-- this defines the data type that will be read from the config file, all of the values are optional
data Proxy = Proxy
    { proxyKey  :: Maybe String
    , proxyUser :: Maybe String
    , proxyHost :: Maybe String
    , proxyPort :: Maybe Int
    } deriving Show


-- the mock config, the data we actually load
config = Proxy
    { proxyKey  = Just "/home/.ssh/id_rsa"
    , proxyUser = Just "bob"
    , proxyHost = Just "example.com"
    , proxyPort = Just 8080
    }


-- the actual function
proxyCommand :: Proxy -> Maybe String
proxyCommand Proxy{proxyHost=Nothing} = Nothing
proxyCommand Proxy{..}                = Just $
    intercalate " " ["ssh" ++ key, "-w %h:%p", ("ssh://" ++ user ++ host ++ port)]
  where
    host = fromJust proxyHost
    key  = fromMaybe "" $ (" -i"++)      <$> proxyKey
    user = fromMaybe "" $ (++"@")        <$> proxyUser
    port = fromMaybe "" $ ((":"++).show) <$> proxyPort


-- convert the config data into the command and display it
main = do
    putStrLn $ show $ proxyCommand config