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{-# LANGUAGE DeriveFunctor #-}
{-# LANGUAGE LambdaCase #-}
module Connection where
import Control.Applicative
import Control.Arrow
import Control.Concurrent.STM
import qualified Data.Map as Map
;import Data.Map (Map)
import PingMachine
-- | This type indicates the current status of a connection. The type
-- parameter indicates protocol-specific status information. To present
-- information as a user-comprehensible string, use 'showStatus'.
data Status status
= Dormant
| InProgress status
| Established
deriving (Show,Eq,Ord,Functor)
-- | A policy indicates a desired connection status.
data Policy
= RefusingToConnect -- ^ We desire no connection.
| OpenToConnect -- ^ We will cooperate if a remote side initiates.
| TryingToConnect -- ^ We desire to be connected.
deriving (Eq,Ord,Show)
-- | Information obtained via the 'connectionStatus' interface to
-- 'Manager'.
data Connection status = Connection
{ connStatus :: Status status
, connPolicy :: Policy
}
deriving Functor
-- | This is an interface to make or query status information about connections
-- of a specific kind.
--
-- Type parameters:
--
-- /k/ names a connection. It should implement Ord, and can be parsed and
-- displayed using 'stringToKey' and 'showKey'.
--
-- /status/ indicates the progress of a connection. It is intended as a
-- parameter to the 'InProgress' constructor of 'Status'.
--
data Manager status k = Manager
{ -- | Connect or disconnect a connection.
setPolicy :: k -> Policy -> IO ()
-- | Lookup a connection status.
, status :: k -> STM (Connection status)
-- | Obtain a list of all known connections.
, connections :: STM [k]
-- | Parse a connection key out of a string. Inverse of 'showKey'.
, stringToKey :: String -> Maybe k
-- | Convert a progress value to a string.
, showProgress :: status -> String
-- | Show a connection key as a string.
, showKey :: k -> String
}
-- | Present status information (visible in a UI) for a connection.
showStatus :: Manager status k -> Status status -> String
showStatus mgr Dormant = "dormant"
showStatus mgr Established = "established"
showStatus mgr (InProgress s) = "in progress ("++showProgress mgr s++")"
-- | Combine two different species of 'Manager' into a single interface using
-- 'Either' to combine key and status types.
addManagers :: (Ord kA, Ord kB) =>
Manager statusA kA
-> Manager statusB kB
-> Manager (Either statusA statusB) (Either kA kB)
addManagers mgrA mgrB = Manager
{ setPolicy = either (setPolicy mgrA) (setPolicy mgrB)
, status = \case
Left k -> fmap Left <$> status mgrA k
Right k -> fmap Right <$> status mgrB k
, connections = do
as <- connections mgrA
bs <- connections mgrB
return $ map Left as ++ map Right bs
, stringToKey = \str -> Left <$> stringToKey mgrA str
<|> Right <$> stringToKey mgrB str
, showProgress = either (showProgress mgrA) (showProgress mgrB)
, showKey = either (showKey mgrA) (showKey mgrB)
}
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