{-# LANGUAGE BlockArguments #-}
{-# LANGUAGE LambdaCase #-}
{-# LANGUAGE OverloadedRecordDot #-}
{-# LANGUAGE OverloadedStrings #-}
{-# LANGUAGE RecordWildCards #-}
{-# LANGUAGE NoFieldSelectors #-}
{-# OPTIONS_GHC -fno-warn-name-shadowing #-}

module Main where

import Control.Arrow (second)
import Control.Concurrent.ParallelIO.Local (parallel, withPool)
import Control.Exception (Exception, throw, throwIO)
import Control.Monad (unless, when)
import Data.Aeson qualified as J
import Data.Attoparsec.Text qualified as A
import Data.ByteString.Lazy qualified as LB
import Data.Default
import Data.Digest.Pure.SHA (sha256, showDigest)
import Data.List
import Data.Map qualified as M
import Data.Maybe (fromMaybe)
import Data.String (IsString (fromString))
import Data.Text qualified as T
import Data.Text.Encoding qualified as T
import Data.Text.IO qualified as T
import Debug.Trace
import GHC.Conc (getNumProcessors)
import GHC.Generics (Generic)
import Options.Applicative qualified as O
import System.Directory
import System.Environment (getEnv)
import System.FilePath
import System.IO.LockFile (withLockFile)
import System.IO.Temp (withSystemTempDirectory)
import System.Process.Typed
import Text.Printf (printf)
import Text.Read (readMaybe)

data Args = Args
  { cmd :: Cmd
  }

data Cmd
  = Consume Bool [FilePath]
  | List

args :: O.Parser Args
args =
  Args <$> cmd

cmd :: O.Parser Cmd
cmd =
  O.hsubparser . mconcat $
    [ O.command "consume" . O.info consumeCmd $
        O.progDesc "Consume document(s)",
      O.command "list" . O.info listCmd $
        O.progDesc "List document(s)"
    ]

consumeCmd :: O.Parser Cmd
consumeCmd =
  Consume
    <$> keepArg
    <*> filePathsArg

listCmd :: O.Parser Cmd
listCmd =
  pure List

filePathsArg :: O.Parser [FilePath]
filePathsArg =
  O.many (O.strArgument (O.metavar "FILE" <> O.action "file"))

keepArg :: O.Parser Bool
keepArg =
  O.switch
    ( O.long "keep"
        <> O.help "Keep input document"
    )

main :: IO ()
main = do
  cwd <- getCurrentDirectory
  setCurrentDirectory =<< getEnv "APAPERLESS_STORE_DIR"
  ensureGit
  ensureDir "originals"
  ensureDir "index"

  O.execParser (O.info (args O.<**> O.helper) O.idm) >>= \case
    Args {cmd = Consume keep filePaths} ->
      mapM_ putStrLn
        =<< parMapM (consume1 keep) (map (cwd </>) filePaths)
    Args {cmd = List} -> do
      mapM_
        ( \(iFileName, index) -> do
            putStrLn (takeBaseName iFileName)
            T.putStrLn index.originalText
        )
        =<< parMapM
          ( \iFileName ->
              (,) iFileName <$> decodeFile @Index ("index" </> iFileName)
          )
        =<< sort <$> listDirectory "index"

ensureGit :: IO ()
ensureGit = do
  doesExist <- doesDirectoryExist ".git"
  unless doesExist $ sh_ "git init --initial-branch main"

ensureDir :: FilePath -> IO ()
ensureDir dirName =
  createDirectoryIfMissing False dirName

debug :: Show a => String -> a -> a
debug s x =
  trace (printf "%s: %s\n" s (show x)) x

fileKey :: FilePath -> IO FilePath
fileKey filePath =
  showDigest . sha256 <$> LB.readFile filePath

consume1 :: Bool -> FilePath -> IO FilePath
consume1 keep filePath = do
  fKey <- fileKey filePath
  let oFilePath = "originals" </> fKey <.> takeExtension filePath
  originalExists <- doesFileExist oFilePath
  when originalExists do
    error (printf "error: error adding %s: duplicate of %s\n" filePath oFilePath)
  let iFilePath = "index" </> fKey <.> "json"
  originalText <- do
    originalText' <-
      T.decodeUtf8 . LB.toStrict
        <$> sh (printf "pdftotext '%s' -" filePath)
    let hasText = (not . T.null) . T.strip $ originalText'
    if not hasText
      then ocr filePath
      else pure originalText'
  withGit do
    J.encodeFile iFilePath Index {..}
    if keep
      then copyFile filePath oFilePath
      else renameFile filePath oFilePath
    commitAll
      [iFilePath, oFilePath]
      (printf "add %s" (takeFileName filePath))
  pure (takeBaseName iFilePath)

withGit :: IO a -> IO a
withGit = withLockFile def ".gitlock"

commitAll :: [FilePath] -> String -> IO ()
commitAll fps m = do
  sh_ ("git add -- " ++ intercalate " " (map (printf "'%s'") fps))
  sh_ (printf "git commit -m '%s'" m)

data DecodeException = DecodeException FilePath String
  deriving (Show)

instance Exception DecodeException

decodeFile :: J.FromJSON a => FilePath -> IO a
decodeFile fp =
  either (throwIO . DecodeException fp) pure . J.eitherDecode
    =<< LB.readFile fp

ocr :: FilePath -> IO T.Text
ocr input =
  withSystemTempDirectory (takeBaseName input) $ \tmp -> do
    let fn suffix = tmp </> takeBaseName input <> suffix
    pdfInfo <- parsePdfInfo <$> sh (printf "pdfinfo '%s'" input)
    pdfImages <- parsePdfImages <$> sh (printf "pdfimages -list '%s'" input)
    let isScan =
          length pdfImages == pdfInfo.numPages
            && all ((pdfInfo.pageSize ==) . imageSize) pdfImages
    if isScan
      then sh_ (printf "pdfimages '%s' '%s' -tiff" input (fn ""))
      else sh_ (printf "pdftoppm '%s' '%s' -r 300 -tiff" input (fn "-%d.pdf"))
    imageFiles <- sort <$> listDirectory tmp
    -- XXX add DPI information to image so that resulting pdf preserves DPI
    parMapM_
      ( \(pdfImage, imageFile) ->
          sh_
            ( printf
                "convert -density %dx%d -units PixelsPerInch '%s' '%s'"
                pdfImage.xPpi
                pdfImage.yPpi
                (tmp </> imageFile)
                (tmp </> imageFile)
            )
      )
      (zip pdfImages imageFiles)
    T.unlines <$> mapM (ocr1 tmp . (tmp </>)) imageFiles

ocr1 :: FilePath -> FilePath -> IO T.Text
ocr1 tmp input =
  T.decodeUtf8 . LB.toStrict
    <$> sh (printf "tesseract '%s' -" (tmp </> input))

data Index = Index
  { originalText :: T.Text
  }
  deriving (Show, Generic, Eq)

instance J.ToJSON Index

instance J.FromJSON Index

data PdfInfo = PdfInfo
  { numPages :: Int,
    pageSize :: (Double, Double)
  }
  deriving (Show)

data PdfInfoException = PdfInfoException
  deriving (Show)

instance Exception PdfInfoException

parsePdfInfo :: LB.ByteString -> PdfInfo
parsePdfInfo out' =
  fromMaybe (throw PdfInfoException) $ do
    numPages <- readMaybe . T.unpack =<< M.lookup "Pages" kvs
    pageSize <-
      rightToMaybe . A.parseOnly pageSizeParser
        =<< M.lookup "Page size" kvs
    pure PdfInfo {..}
  where
    out = T.decodeUtf8 (LB.toStrict out')
    kvs =
      M.fromList
        . map (second T.stripStart)
        . map (second T.tail . T.break (== ':'))
        . filter (not . T.null)
        . T.lines
        $ out
    pageSizeParser =
      (,)
        <$> (A.double <* A.string " x ")
        <*> (A.double <* A.string " pts (A4)")
        <* A.endOfInput

type PdfImages = [PdfImage]

data PdfImage = PdfImage
  { page :: Int,
    num :: Int,
    type_ :: String,
    width :: Int,
    height :: Int,
    color :: String,
    comp :: Int,
    bpc :: Int,
    enc :: String,
    interp :: String,
    object :: Int,
    id :: Int,
    xPpi :: Int,
    yPpi :: Int,
    size :: String,
    ratio :: String
  }
  deriving (Show)

imageSize :: PdfImage -> (Double, Double)
imageSize (PdfImage {..}) =
  let f ppi p = 72 * fromIntegral p / fromIntegral ppi
   in (f xPpi width, f yPpi height)

data PdfImagesException = PdfImagesException
  deriving (Show)

instance Exception PdfImagesException

data ProcessException = ProcessException Int LB.ByteString
  deriving (Show)

instance Exception ProcessException

parsePdfImages :: LB.ByteString -> PdfImages
parsePdfImages out' =
  map
    ( \(page' : num' : type_ : width' : height' : color : comp' : bpc' : enc : interp : object' : id' : xPpi' : yPpi' : size : ratio : []) ->
        PdfImage
          { page = read page',
            num = read num',
            width = read width',
            height = read height',
            comp = read comp',
            bpc = read bpc',
            object = read object',
            id = read id',
            xPpi = read xPpi',
            yPpi = read yPpi',
            ..
          }
    )
    . map (map T.unpack)
    . map T.words
    . drop 2
    . filter (not . T.null)
    . T.lines
    $ out
  where
    out = T.decodeUtf8 (LB.toStrict out')

sh :: String -> IO LB.ByteString
sh cmd = do
  (exitCode, out, err) <- readProcess (fromString cmd)
  case exitCode of
    ExitSuccess -> return out
    ExitFailure exitCode' -> throwIO $ ProcessException exitCode' err

sh_ :: String -> IO ()
sh_ = fmap (\_ -> ()) . sh

rightToMaybe :: Either e a -> Maybe a
rightToMaybe = either (const Nothing) Just

parMapM :: (a -> IO b) -> [a] -> IO [b]
parMapM f xs = do
  n <- getNumProcessors
  withPool n $ \pool -> parallel pool (map f xs)

parMapM_ :: (a -> IO b) -> [a] -> IO ()
parMapM_ f = fmap (const ()) . parMapM f