{-# LANGUAGE OverloadedStrings #-}
module ConfigFiles where

import Data.ByteString.Lazy.Char8 as L
import System.Posix.User
import System.Posix.Files (fileExist)
import System.FilePath
import System.Directory
import System.IO
-- import System.IO.Strict
import System.IO.Error
import Control.Exception
import Control.Monad
import Control.DeepSeq
import ByteStringOperators () -- For NFData instance
import ControlMaybe
import Data.List (partition)
import Data.Maybe (catMaybes,isJust)

type User = ByteString

configDir = ".presence"
buddyFile = "buddies"
subscriberFile = "subscribers"
otherFile = "others"
pendingFile = "pending"
solicitedFile = "solicited"


configPath :: User -> String -> IO String
configPath user filename = do
    ue <- getUserEntryForName (unpack user)
    return $ (++("/"++configDir++"/"++filename)) $ homeDirectory ue


createConfigFile tag path = do
    let dir = dropFileName path
    doesDirectoryExist dir >>= flip unless (do
            createDirectory dir 
        )
    withFile path WriteMode $ \h -> do
        L.hPutStrLn h tag

addItem item tag path =
    let doit = do
         handle (\e -> when (isDoesNotExistError e) 
                       (createConfigFile tag path >> doit))
           $ do exists <- fileExist path
                if exists
                  then withFile path AppendMode $ \h ->
                         L.hPutStrLn h item
                  else withFile path WriteMode $ \h -> do
                         L.hPutStrLn h tag
                         L.hPutStrLn h item
    in doit


modifyFile ::
  (ByteString,FilePath)
  -> ByteString
  -> (ByteString -> IO (Maybe ByteString))
  -> Maybe ByteString
  -> IO Bool -- Returns True if test function ever returned Nothing
modifyFile (tag,file) user test appending = configPath user file >>= doit
    where
        doit path = do
         handle (\e -> if (isDoesNotExistError e) 
                        then (createConfigFile tag path >> doit path)
                        else return False)
           $ do exists <- fileExist path
                if exists
                  then do
                    xs <- withFile path ReadMode $ \h -> do
                             contents <- L.hGetContents h
                             case L.lines contents of
                              x:xs -> mapM test xs
                              _    -> return []
                    let (keepers,deleted) = partition isJust xs
                    withFile path WriteMode $ \h -> do
                        L.hPutStrLn h tag
                        forM_ (catMaybes keepers) (L.hPutStrLn h)
                        withJust appending (L.hPutStrLn h)
                    return . not . Prelude.null $ deleted
                  else do
                    withFile path WriteMode $ \h -> do
                        L.hPutStrLn h tag
                        withJust appending (L.hPutStrLn h)
                    return False 


modifySolicited  = modifyFile ("<? solicited ?>" , solicitedFile)
modifyBuddies    = modifyFile ("<? buddies ?>"   , buddyFile)
modifyOthers     = modifyFile ("<? others ?>"    , otherFile)
modifyPending    = modifyFile ("<? pending ?>"   , pendingFile)
modifySubscribers = modifyFile ("<? subscribers ?>", subscriberFile)

addBuddy :: User -> ByteString -> IO ()
addBuddy user buddy =
    configPath user buddyFile >>= addItem buddy "<? buddies ?>"

addSubscriber :: User -> ByteString -> IO ()
addSubscriber user subscriber =
    configPath user subscriberFile >>= addItem subscriber "<? subscribers ?>"

addSolicited :: User -> ByteString -> IO ()
addSolicited user solicited =
    configPath user solicitedFile >>= addItem solicited "<? solicited ?>"


getConfigList path = 
  handle (\e -> if isDoesNotExistError e then (return []) else throw e)
    $ withFile path ReadMode $
        L.hGetContents 
        >=> return . Prelude.tail . L.lines 
        >=> (\a -> seq (rnf a) (return a))

getBuddies :: User -> IO [ByteString]
getBuddies user = configPath user buddyFile >>= getConfigList

getSubscribers :: User -> IO [ByteString]
getSubscribers user = configPath user subscriberFile >>= getConfigList

getOthers :: User -> IO [ByteString]
getOthers user = configPath user otherFile >>= getConfigList

getPending :: User -> IO [ByteString]
getPending user = configPath user pendingFile >>= getConfigList

getSolicited :: User -> IO [ByteString]
getSolicited user = configPath user solicitedFile >>= getConfigList