-- Copyright: 2007-2010 Dino Morelli
-- License: BSD3 (see LICENSE)
-- Author: Dino Morelli <dino@ui3.info>

{-# LANGUAGE FlexibleContexts #-}

import Control.Monad.Error
import Control.Monad.Reader
import Graphics.Exif ( fromFile, getTag, Exif )
import System.Environment ( getArgs )
import System.FilePath
import System.IO.Error
import System.Posix

import Photoname.Date
import Photoname.Opts ( Options (..) , parseOpts, usageText )
import Photoname.Serial ( getSerial )


type Ph a = ReaderT Options IO a


runRename :: Options -> Ph a -> IO a
runRename env action = runReaderT action env


modeDir :: FileMode
modeDir = ownerModes       `unionFileModes`
          groupReadMode    `unionFileModes`
          groupExecuteMode


{- load Exif information from a filename, returning Nothing if libexif
   encounters a NULL instead of raising an IO error.

   This is somewhat bogus because of the error type that is used by
   the EXIF library. We have to compare the error string to see if it
   is the kind of user error that we expect. If we build against an
   EXIF library that raises some other exception, then this build will
   still succeed, and the exception will be propagated instead of
   transformed into a handled photoname error.
-}
safeExif :: FilePath -> IO (Maybe Exif)
safeExif = try . fromFile >=> either handleBadExif (return . Just)
    where
      isBadExif e =
         ioeGetErrorString e == "mkExif: NULL" && isUserError e
      handleBadExif e =
         if isBadExif e then return Nothing else ioError e


{- Get shoot date from the exif information. There are several tags 
   potentially containing dates. Try them in a specific order until we
   find one that has data.
-}
getDate :: (MonadError String m, MonadIO m) => FilePath -> m String
getDate = loadExif >=> getOneOf dateTagNames
    where
      loadExif = (liftIO . safeExif) >=>
                 maybe (throwError "failed EXIF loading") return

      getOneOf [] _ = throwError "has no EXIF date"
      getOneOf (tagName:tagNames) exif =
         maybe (getOneOf tagNames exif) return =<<
            liftIO (getTag exif tagName)

      dateTagNames =
         ["DateTimeDigitized", "DateTimeOriginal", "DateTime"]


{- Take a file path to a JPEG file and use EXIF information available to
   move the file to a new location below the given basedir.
-}
createNewLink :: FilePath -> FilePath -> Ph ()
createNewLink newDir oldPath = do
   opts <- ask
   result <- liftIO $ runErrorT $ do
      newPath <- buildNewPath newDir oldPath

      -- Check for existance of the target file
      exists <- liftIO $ fileExist newPath
      when exists $ throwError $ "Destination " ++ newPath ++ " exists!"

      -- Display what will be done
      unless (optQuiet opts) $
         liftIO $ putStrLn $ oldPath ++ " -> " ++ newPath

      unless (optNoAction opts) $ do
         -- Make the target dir
         liftIO $ makeDirectory $ takeDirectory newPath

         -- Make the new hard link
         liftIO $ createLink oldPath newPath

         -- If user has specified, remove the original link
         when (optMove opts) $
            liftIO $ removeLink oldPath

      return ()

   let errPrefix = "** Processing " ++ oldPath ++ ": "

   case result of
      Left errMsg -> liftIO $ putStrLn $ errPrefix ++ errMsg
      Right _ -> return ()


{- Given a list of lists, make a new list where each sublist element 
   consists of the accumulation of all parts that came before it. 
   Like this:
      before: [[1], [2], [3], [4], [5]]
      after : [[1], [1,2], [1,2,3], [1,2,3,4], [1,2,3,4,5]]

   Many thanks to Betty Diegel for help with this algorithm.

   FIXME Try to rewrite this with a scan or something
-}
listAcc :: [[a]] -> [[a]]
listAcc []     = [[]]
listAcc (x:xs) = listAcc' x xs
   where
      listAcc' l (y:ys) = [l] ++ listAcc' (l ++ y) ys
      listAcc' l []     = [l]


{- Ensuring that a directory with subs exists turned out to be a painful 
   process involving making each parent dir piece by piece but not trying
   to make anything that's already there.
-}
makeDirectory :: FilePath -> IO ()
makeDirectory d =
   let makeOneDir dir = do
         exists <- fileExist dir
         unless exists $ createDirectory dir modeDir
   in  mapM_ makeOneDir $ listAcc $ splitPath d


{- Given a path to a file with EXIF data, construct a new path based on the
   date and some serial number info we can parse out of the filename.
-}
buildNewPath :: (MonadError String m, MonadIO m) =>
   FilePath -> FilePath -> m FilePath
buildNewPath newDir oldPath = do
   dateString <- getDate oldPath
   serial <- getSerial oldPath
   let date = readDate dateString
   let year = formatYear date
   let day = formatDay date
   let prefix = formatPrefix date
   return (newDir </> year </> day </>
      (prefix ++ "_" ++ serial) <.> "jpg")


-- Figure out and execute what the user wants based on the supplied args.
executeCommands :: [String] -> Ph ()

-- User gave no files at all. Display help
executeCommands [] = liftIO $ putStrLn usageText

-- User gave just a dir and no files at all. Display help
executeCommands [_] = liftIO $ putStrLn usageText

-- Normal program operation, process the files with the args.
executeCommands (dir:filePaths) = do
   opts <- ask

   -- Get rid of anything not a regular file from the list of paths
   actualPaths <- liftIO $ filterM
      (\p -> getFileStatus p >>= return . isRegularFile) filePaths

   -- Notify user of the switches that will be in effect.
   when (optNoAction opts) $
      liftIO $ putStrLn "No-action mode, nothing will be changed."

   when (optMove opts) $
      liftIO $ putStrLn 
         "Removing original links after new links are in place."

   -- Do the link manipulations.
   mapM_ (createNewLink dir) actualPaths


main :: IO ()
main = do
   -- Parse the arguments
   (opts, paths) <- getArgs >>= parseOpts

   -- Do the photo naming procedure
   runRename opts $ executeCommands paths

   -- Perhaps we should get an ExitCode back from all this above?