Exiv2.hs

module Photoname.Exiv2
  ( getExifDateWithExiv2
  , setArtist
  , setExifDate
  )
  where

import Control.Exception
import Control.Monad (void)
import Control.Monad.IO.Class (MonadIO)
import Data.Char (isSpace)
import GHC.IO.Exception
import System.Process hiding (proc)
import qualified System.Process as Proc
import Text.Printf (printf)

import Photoname.Common (Artist (Artist), DestPath (DestPath),
  NoActionSwitch (NoActionSwitch), Options (artist, noAction), Ph,
  SrcPath (SrcPath), asks, liftIO)
import Photoname.Date (PhDate (FilenameDate), formatDateForExif)
import Photoname.Log (LogFunction, debugM, infoM, lname, noticeM)


data Reading
data Writing

-- For logging purposes we keep the program name separate from its arguments
-- until we need to build a CreateProcess data structure
data Command rw = Command LogFunction FilePath [String]

-- Construct a human-readable command-line from a Command data structure. This
-- is purely for logging.
-- Arguments may contain spaces but be quoted properly when this is used by
-- System.Process.proc BUT they look odd when logged by our code. This function
-- will put quotes around any space-containing arguments purely for human
-- readability.
commandToString :: Command rw -> String
commandToString (Command _ program' arguments) =
  unwords $ program' : map quoteAsNeeded arguments
  where
    quoteAsNeeded str = if ' ' `elem` str
      then "'" <> str <> "'"
      else str

proc :: Command rw -> CreateProcess
proc (Command _ program' arguments) = Proc.proc program' arguments


logCommand :: MonadIO m => Command rw -> m ()
logCommand command@(Command logFunction _ _) =
  liftIO . logFunction lname . commandToString $ command



-- For Writing (or "destructive") commands, we need to check if the user has
-- chosen no-action behavior before executing
execWritingCommand :: Command Writing -> Ph (Either String String)
execWritingCommand command = do
  logCommand command
  (NoActionSwitch noAction') <- asks noAction
  if noAction'
    then pure $ Left ""
    else execCommand command


-- For Reading (or "non-destructive") commands, we just log it and do it
execReadingCommand :: Command Reading -> Ph (Either String String)
execReadingCommand command = logCommand command >> execCommand command


stripTrailingWhitespace :: String -> String
stripTrailingWhitespace = reverse . dropWhile isSpace . reverse


execCommand :: Command rw -> Ph (Either String String)
execCommand command = liftIO $ do
  eResult <- postProcess =<< try (readCreateProcessWithExitCode (proc command) "")
  either (\msg -> debugM lname $ "** Command failed: " <> stripTrailingWhitespace msg)
    (\output -> debugM lname $ "Command succeeded, output: " <> stripTrailingWhitespace output) eResult
  pure eResult


program :: FilePath
program = "exiv2"


postProcess :: Either IOException (ExitCode, String, String) -> IO (Either String String)
postProcess (Left   e                             ) = pure . Left $ printf "%s: %s" program (ioe_description e)
postProcess (Right (ExitSuccess  , stdOut, _     )) = pure . Right $ stdOut
postProcess (Right (ExitFailure 1, _     , ""    )) = pure . Left $ "EXIF tag not found"
postProcess (Right (ExitFailure _, _     , stdErr)) = pure . Left $ stdErr


setArtist :: DestPath -> Ph ()
setArtist (DestPath destFp) = do
  artist' <- asks artist

  case artist' of
    Nothing -> pure ()
    Just (Artist "") -> void $ execWritingCommand $
      Command noticeM program ["--Modify", "del Exif.Image.Artist", destFp]
    Just (Artist artistInfo) -> void $ execWritingCommand $
      Command noticeM program ["--Modify", "set Exif.Image.Artist " <> artistInfo, destFp]


getExifDateWithExiv2 :: SrcPath -> Ph (Maybe String)
getExifDateWithExiv2 (SrcPath srcFp) = do
  let tag = "Exif.Image.DateTime"
  eResult <- execReadingCommand $ Command infoM program ["--Print", "v", "--grep", tag, srcFp]
  pure . either (const Nothing) Just $ eResult


setExifDate :: PhDate -> DestPath -> Ph ()

setExifDate (FilenameDate lt) (DestPath destFp) =
  void $ execWritingCommand . Command noticeM program $
    [ "--Modify", "set Exif.Image.DateTime Ascii " <> formatDateForExif lt
    , "--Modify", "set Exif.Photo.UserComment charset=Ascii DateTime is a guess", destFp
    ]

setExifDate _ _ = pure ()