{-# OPTIONS -Wall #-}


module FontLoaderUtils
  (
    processCmdLine
  , default_font_loader_help
  ) where


import Control.Applicative
import Control.Monad
import System.Directory
import System.Console.GetOpt
import System.Environment
import System.IO.Error


wumpus_gs_font_dir :: String
wumpus_gs_font_dir = "WUMPUS_GS_FONT_DIR"

wumpus_afm_font_dir :: String
wumpus_afm_font_dir = "WUMPUS_AFM_FONT_DIR"


default_font_loader_help :: String
default_font_loader_help = unlines $ 
    [ "This example uses glyph metrics loaded at runtime."
    , "It can use either the metrics files supplied with GhostScript,"
    , "or the AFM v4.1 metrics for the Core 14 fonts available from"
    , "Adobe's website."
    , "" 
    , "To use GhostScripts font metrics set the environemt variable"
    , wumpus_gs_font_dir ++ " to point to the GhostScript fonts"
    , "directory (e.g. /usr/share/ghostscript/fonts) or use the command"
    , "line flag --gs=PATH_TO_GHOSTSCRIPT_FONTS"
    , ""
    , "To use the Adode Core 14 font metrics download the archive from"
    , "the Adobe website and set the environment variable "
    , wumpus_afm_font_dir ++ " to point to it, or use the command line"
    , "flag -- afm=PATH_TO_AFM_CORE14_FONTS"
    ]


data CmdLineFlag = Help
                 | GS_FontDir  String
                 | AFM_FontDir String
  deriving (Eq,Ord,Show)

processCmdLine :: String -> IO (Maybe FilePath, Maybe FilePath)
processCmdLine help_message = 
    let options = makeCmdLineOptions help_message in do
        args <- getArgs
        let (opts, _, _) = getOpt Permute options args
        if Help `elem` opts then failk help_message
                            else succk opts
  where
    failk msg   = putStr msg >> return (Nothing,Nothing) 
    succk flags = (,) <$> gsFontDirectory flags <*> afmFontDirectory flags 
       

makeCmdLineOptions :: String -> [OptDescr CmdLineFlag]
makeCmdLineOptions help_message =
    [ Option ['h'] ["help"]   (NoArg Help)                help_message
    , Option []    ["afm"]    (ReqArg AFM_FontDir "DIR")  "AFM v4.1 metrics dir"
    , Option []    ["gs"]     (ReqArg GS_FontDir  "DIR")  "GhoshScript font dir"
    ]


gsFontDirectory :: [CmdLineFlag] -> IO (Maybe FilePath)
gsFontDirectory = step 
  where
    step (GS_FontDir p:xs)  = doesDirectoryExist p >>= \check -> 
                              if check then return (Just p) else step xs

    step (_:xs)             = step xs
    step []                 = envLookup wumpus_gs_font_dir
 

afmFontDirectory :: [CmdLineFlag] -> IO (Maybe FilePath)
afmFontDirectory = step 
  where
    step (AFM_FontDir p:xs) = doesDirectoryExist p >>= \check -> 
                              if check then return (Just p) else step xs

    step (_:xs)             = step xs
    step []                 = envLookup wumpus_afm_font_dir


envLookup :: String -> IO (Maybe String)
envLookup name = liftM fn $ try $ getEnv name
  where
    fn (Left _)  = Nothing
    fn (Right a) = Just a