{-

sscan --- text UI for scanning with SANE

Copyright (C) 2017  Sean Whitton

This file is part of sscan.

sscan is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.

sscan is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with sscan.  If not, see <http://www.gnu.org/licenses/>.

-}

{-# LANGUAGE TemplateHaskell #-}

module Types.State where

import           Data.Maybe
import           Lens.Micro    ((&), (.~), (^.))
import           Lens.Micro.TH (makeLenses)

-- | Whether to do colour, grey or b&w scans
data Colour = Lineart | Greyscale | Colour
    deriving (Eq, Show)

cycleColour :: Colour -> Colour
cycleColour Lineart   = Greyscale
cycleColour Greyscale = Colour
cycleColour Colour    = Lineart

-- | Paper size to scan (determines both scanning area and PDF page
-- size)
data Paper = A4 | Letter | Photo | Auto
    deriving (Eq, Show)

cyclePaper :: Paper -> Paper
cyclePaper A4     = Letter
cyclePaper Letter = Photo
cyclePaper Photo  = Auto
cyclePaper Auto   = A4

-- | DPI to scan
type DPI = Int

-- | Output format
data OutputFormat = PDF | PNG
    deriving (Eq, Show)

-- | An active scanning session
data ScanSess = ScanSess
    -- | An action requested by the user, that has not yet been
    -- fulfilled
    Command
    -- | The number of pages scanned so far in this scanning session
    Int
    -- | Temporary directory containing pages scanned in this scanning
    -- session, if any have been scanned, and the session is multi-page
    (Maybe FilePath)

-- | An sscan operation selected by the user in the UI
data Command
    -- | Scan an additional page, or the first page, of a multi-page
    -- scanning session.
    = NextPage
    -- | Scan the final page of a multi-page scanning session, or the
    -- first page of a single-page scanning session
    | FinalPage
    -- | End a multi-page scanning session without scanning anymore
    -- pages, i.e., consider the most recently scanned page the final
    -- page
    | Finalise
    -- | Abandon the current scanning session.  Delete its tmpdir.
    | Abort

-- | Application state
data St =
    --
    St { _stScanSess     :: Maybe ScanSess -- ^ Nothing indicates user
                                           -- wants to quit sscan
       , _stOCR          :: Bool -- ^ whether to use OCRmyPDF
       , _stColour       :: Colour
       , _stPaper        :: Paper -- ^ currently selected paper size
       , _stDefaultPaper :: Paper -- ^ locale's default paper size
       , _stDPI          :: DPI
       , _stOutFormat    :: OutputFormat
       , _stOutdir       :: FilePath -- ^ where to save final PDFs
       }

makeLenses ''St

ifScanSess :: St -> a -> a -> a
ifScanSess st a b = if isJust $ st^.stScanSess then a else b

-- | Update a state when there is no scanning session in progress (the
-- state should not be changed when some pages have already been
-- scanned)
updateSt :: St -> (St -> St) -> St
updateSt st f = ifScanSess st st (f st)

resetScanSess :: St -> St
resetScanSess st = st & stScanSess .~ Nothing

setScanSessDir :: FilePath -> St -> St
setScanSessDir dir st = case st^.stScanSess of
  Nothing -> st
  Just (ScanSess c p _) ->
      st & stScanSess .~ (Just $ ScanSess c p (Just dir))

setScanSessCommand :: Command -> St -> St
setScanSessCommand c st = case st^.stScanSess of
  Just (ScanSess _ p d) ->
      st & stScanSess .~ (Just $ ScanSess c p d)
  Nothing ->
      st & stScanSess .~ (Just $ ScanSess c 0 Nothing)

incrementPages :: St -> St
incrementPages st = case st^.stScanSess of
  Nothing -> st
  Just (ScanSess c p d) ->
      st & stScanSess .~ (Just $ ScanSess c (p+1) d)

getLatestPage :: St -> Int
getLatestPage st = case st^.stScanSess of
  Nothing -> 0
  Just (ScanSess _ p _ ) -> p