module File where
import Control.Monad
import System.Directory
import System.FilePath
import Paths_lambdabot (getDataFileName)
-- | Constants.
lambdabot, local, state :: FilePath
lambdabot = ".lambdabot"
state = lambdabot </> local
local = "State"
maybeFileExists :: FilePath -> IO (Maybe FilePath)
maybeFileExists path =
do b <- doesFileExist path
return $ if b then Just path else Nothing
-- | For a given file, look locally under State/. That is, suppose one is
-- running out of a Lambdabot darcs repository in /home/cale/lambdabot. Then
--
-- > lookLocally "fact" ~> "/home/cale/lambdabot/State/fact"
lookLocally :: FilePath -> IO (Maybe String)
lookLocally file = maybeFileExists $ local </> file
-- | For a given file, look at the home directory. By default, we stash files in
-- ~/.lambdabot. So, running Lambdabot normally would let us do:
--
-- > lookHome "fact" ~> "/home/cale/lambdabot/State/fact"
--
-- (Note that for convenience we preserve the "State/foo" address pattern.)
lookHome :: FilePath -> IO (Maybe String)
lookHome f = do home <- getHomeDirectory
maybeFileExists $ home </> state </> f
-- | Do ~/.lambdabot & ~/.lambdabot/State exist?
isHome :: IO Bool
isHome = do home <- getHomeDirectory
fmap and . mapM (doesDirectoryExist . (home </>)) $ [lambdabot, state]
-- | Create ~/.lambdabot and ~/.lambdabot/State
mkdirL :: IO ()
mkdirL = do home <- getHomeDirectory
mapM_ (createDirectory . (home </>)) $ [lambdabot, state]
-- | Ask Cabal for the read-only copy of a file, and copy it into ~/.lambdabot/State.
cpDataToHome :: FilePath -> IO ()
cpDataToHome f = do rofile <- getDataFileName (local </> f)
home <- getHomeDirectory
-- cp /.../lambdabot-4.foo/State/foo ~/.lambdabot/State/foo
copyFile rofile (home </> state </> f)
-- | Complicated. If a file exists locally, we return that. If a file exists in
-- ~/lambdabot/State, we return that. If neither the file nor ~/lambdabot/State
-- exist, we create the directories and then copy the file into it.
-- Note that the return type is simple so we can just do a binding and stuff it
-- into the conventional functions easily; unfortunately, this removes
-- error-checking, as an error is now just \"\".
findFile :: FilePath -> IO String
findFile f = do first <- lookLocally f
case first of
-- With any luck we can exit quickly
Just a -> return a
Nothing -> do second <- lookHome f
case second of
-- OK, we didn't get lucky with local, so
-- hopefully it's in ~/.lambdabot
Just a -> return a
-- Uh oh. We didn't find it locally, nor did we
-- find it in ~/.lambdabot/State. So now we
-- need to make ~/.lambdabot/State and copy it in.
Nothing -> do exists <- isHome
when (not exists) mkdirL
cpDataToHome f
-- With the file copied/created,
-- a second attempt should work.
g <- lookHome f
case g of
Just a -> return a
Nothing ->
do home <- getHomeDirectory
fail $ "File.findFile: couldn't find file "
++ f ++ " in " ++ home </> state