module Reanimate.Misc
  ( requireExecutable,
    runCmd,
    runCmd_,
    runCmdLazy,
    withTempDir,
    withTempFile,
    renameOrCopyFile,
    getReanimateCacheDirectory,
  )
where

import           Control.Concurrent (forkIO)
import           Control.Exception  (catch, evaluate, finally, throw)
import qualified Data.Text          as T
import qualified Data.Text.IO       as T
import           Foreign.C.Error    (Errno (Errno), eXDEV)
import           GHC.IO.Exception   (ExitCode (ExitFailure, ExitSuccess), IOException (ioe_errno))
import           System.Directory   (XdgDirectory (XdgCache), copyFile, createDirectoryIfMissing,
                                     findExecutable, getXdgDirectory, removeFile, renameFile)
import           System.FilePath    ((<.>), (</>))
import           System.IO          (hClose, hGetContents, hIsEOF, hPutStr, stderr)
import           System.IO.Temp     (withSystemTempDirectory, withSystemTempFile)
import           System.Process     (readProcessWithExitCode, runInteractiveProcess,
                                     showCommandForUser, terminateProcess, waitForProcess)

requireExecutable :: String -> IO FilePath
requireExecutable exec = do
  mbPath <- findExecutable exec
  case mbPath of
    Nothing   -> error $ "Couldn't find executable: " ++ exec
    Just path -> return path

runCmd :: FilePath -> [String] -> IO ()
runCmd exec args = do
  ret <- runCmd_ exec args
  case ret of
    Left err -> error $ showCommandForUser exec args ++ ":\n" ++ err
    Right {} -> return ()

runCmd_ :: FilePath -> [String] -> IO (Either String String)
runCmd_ exec args = do
  (ret, stdout, errMsg) <- readProcessWithExitCode exec args ""
  _ <- evaluate (length stdout + length errMsg)
  case ret of
    ExitSuccess -> return (Right stdout)
    ExitFailure err
      | False ->
        return $
          Left $
            "Failed to run: "
              ++ showCommandForUser exec args
              ++ "\n"
              ++ "Error code: "
              ++ show err
              ++ "\n"
              ++ "stderr: "
              ++ errMsg
    ExitFailure {}
      | null errMsg -> -- LaTeX prints errors to stdout. :(
        return $ Left stdout
    ExitFailure {} -> return $ Left errMsg

runCmdLazy ::
  FilePath -> [String] -> (IO (Either String T.Text) -> IO a) -> IO a
runCmdLazy exec args handler = do
  (inp, out, err, pid) <- runInteractiveProcess exec args Nothing Nothing
  hClose inp
  errOutput <- hGetContents err
  _ <- forkIO $ hPutStr stderr errOutput
  let fetch = do
        eof <- hIsEOF out
        if eof
          then do
            _ <- evaluate (length errOutput)
            ret <- waitForProcess pid
            case ret of
              ExitSuccess    -> return (Left "")
              ExitFailure {} -> return (Left errOutput)
          else {-ExitFailure errMsg -> do
                 return $ Left $
                   "Failed to run: " ++ showCommandForUser exec args ++ "\n" ++
                   "Error code: " ++ show errMsg ++ "\n" ++
                   "stderr: " ++ stderr-}
          do
            line <- T.hGetLine out
            return (Right line)
  handler fetch `finally` do
    terminateProcess pid
    _ <- waitForProcess pid
    return ()

-- renameFile fails if we're crossing filesystem boundaries. If this happens,
-- revert back to copyFile + removeFile.
renameOrCopyFile :: FilePath -> FilePath -> IO ()
renameOrCopyFile src dst = renameFile src dst `catch` exdev
  where
    exdev e =
      if fmap Errno (ioe_errno e) == Just eXDEV
        then copyFile src dst >> removeFile src
        else throw e

withTempDir :: (FilePath -> IO a) -> IO a
withTempDir = withSystemTempDirectory "reanimate"

withTempFile :: String -> (FilePath -> IO a) -> IO a
withTempFile ext action =
  withSystemTempFile ("reanimate" <.> ext) $ \path hd ->
    hClose hd >> action path

getReanimateCacheDirectory :: IO FilePath
getReanimateCacheDirectory = do
  root <- getXdgDirectory XdgCache "reanimate"
  let path = root </> show cacheVersion
  createDirectoryIfMissing True path
  return path
  where
    -- Incrementing this value invalidates all cached results.
    cacheVersion :: Int
    cacheVersion = 0