import System.File
import System.Directory
import Data.String

check : Either FileError a -> IO a
check (Left err) = putStrLn ("Error: " ++ show err) >> exitFailure
check (Right val) = pure val

main : IO ()
main = do
    -- The easiest way to create a temporary file is by using
    -- openTempFile. It creates a file and opens it for reading
    -- and writing. We provide Nothing as the first argument,
    -- so openTempFile will create the file in the default
    -- location for our OS.
    (tmpPath, tmpHandle) <- check $ openTempFile Nothing "sample"
    
    -- Display the name of the temporary file. On
    -- Unix-based OSes the directory will likely be /tmp.
    -- The file name starts with the prefix given as the
    -- second argument to openTempFile and the rest
    -- is chosen automatically to ensure that concurrent
    -- calls will always create different file names.
    putStrLn $ "Temp file name: " ++ tmpPath
    
    -- Clean up the file after we're done. The OS is
    -- likely to clean up temporary files by itself after
    -- some time, but it's good practice to do this
    -- explicitly.
    closeFile tmpHandle
    removeFile tmpPath
    
    -- We can write some data to the file.
    let content = "1234"
    check $ writeFile tmpPath content
    
    -- If we intend to write many temporary files, we may
    -- prefer to create a temporary directory.
    -- createTempDirectory's arguments are similar to
    -- openTempFile's, but it returns a directory name
    -- rather than an open file.
    tmpDir <- check $ createTempDirectory Nothing "sampledir"
    putStrLn $ "Temp dir name: " ++ tmpDir
    
    -- Now we can synthesize temporary file names by
    -- prefixing them with our temporary directory.
    let fname = tmpDir ++ "/file1"
    check $ writeFile fname "12"
    
    -- Clean up the directory and its contents
    removeDirectory tmpDir