{-# LANGUAGE CPP #-}
{-# LANGUAGE EmptyDataDecls #-}
{-# LANGUAGE TupleSections #-}
module KeyRing where

import System.Environment
import Control.Monad
import Control.Applicative
import Data.Maybe
import Data.Char
import System.Directory ( getHomeDirectory, doesFileExist )
import Control.Arrow    ( first, second )

data HomeDir =
    HomeDir { homevar :: String
            , appdir :: String
            , optfile_alts :: [String]
            }

home = HomeDir
    { homevar = "GNUPGHOME"
    , appdir  = ".gnupg"
    , optfile_alts = ["keys.conf","gpg.conf-2","gpg.conf"]
    }

data KeyRing

todo = error "unimplemented"

loadKeys :: (Maybe FilePath) -> IO KeyRing
loadKeys = todo

parseOptionFile fname = do
    xs <- fmap lines (readFile fname)
    let ys = filter notComment xs
        notComment ('#':_) = False
        notComment cs      = not (all isSpace cs)
    return ys

getHomeDir protohome = do
        homedir <- envhomedir protohome
        flip (maybe (error "Could not determine home directory."))
             homedir $ \homedir -> do
        -- putStrLn $ "homedir = " ++show homedir
        let secring = homedir ++ "/" ++ "secring.gpg"
            pubring = homedir ++ "/" ++ "pubring.gpg"
        -- putStrLn $ "secring = " ++ show secring
        workingkey <- getWorkingKey homedir
        return (homedir,secring,pubring,workingkey)
 where
    envhomedir opt = do
        gnupghome <- lookupEnv (homevar home) >>=
                  \d -> return $ d >>= guard . (/="") >> d
        homed <- flip fmap getHomeDirectory $
                  \d -> fmap (const d) $ guard (d/="")
        let homegnupg = (++('/':(appdir home))) <$> homed
        let val = (opt `mplus` gnupghome `mplus` homegnupg)
        return $ val
    
    -- TODO: rename this to getGrip
    getWorkingKey homedir = do
        let o = Nothing
            h = Just homedir
        ofile <- fmap listToMaybe . flip (maybe (return [])) h $ \h ->
                let optfiles = map (second ((h++"/")++))
                                   (maybe optfile_alts' (:[]) o')
                    optfile_alts' = zip (False:repeat True) (optfile_alts home)
                    o' = fmap (False,) o
                in filterM (doesFileExist . snd) optfiles
        args <- flip (maybe $ return []) ofile $
            \(forgive,fname) -> parseOptionFile fname
        let config = map (topair . words) args
                        where topair (x:xs) = (x,xs)
        return $ lookup "default-key" config >>= listToMaybe

#if MIN_VERSION_base(4,6,0)
#else
lookupEnv var =
    handleIO_ (return Nothing) $ fmap Just (getEnv var)
#endif