-- This file contains code that is common to modules System.Console.ANSI.Unix,
-- System.Console.ANSI.Windows and System.Console.ANSI.Windows.Emulator, such as
-- type signatures and the definition of functions specific to stdout in terms
-- of the corresponding more general functions, inclduding the related Haddock
-- documentation.

import System.Environment
#if !MIN_VERSION_base(4,8,0)
import Control.Applicative
#endif

import Control.Monad (void)
import Data.Char (isDigit)
import Text.ParserCombinators.ReadP (char, many1, ReadP, satisfy)

hCursorUp, hCursorDown, hCursorForward, hCursorBackward
    :: Handle
    -> Int -- ^ Number of lines or characters to move
    -> IO ()
cursorUp, cursorDown, cursorForward, cursorBackward
    :: Int -- ^ Number of lines or characters to move
    -> IO ()
cursorUp = hCursorUp stdout
cursorDown = hCursorDown stdout
cursorForward = hCursorForward stdout
cursorBackward = hCursorBackward stdout

hCursorDownLine, hCursorUpLine :: Handle
                               -> Int -- ^ Number of lines to move
                               -> IO ()
cursorDownLine, cursorUpLine :: Int -- ^ Number of lines to move
                             -> IO ()
cursorDownLine = hCursorDownLine stdout
cursorUpLine = hCursorUpLine stdout

hSetCursorColumn :: Handle
                 -> Int -- ^ 0-based column to move to
                 -> IO ()
setCursorColumn :: Int -- ^ 0-based column to move to
                -> IO ()
setCursorColumn = hSetCursorColumn stdout

hSetCursorPosition :: Handle
                   -> Int -- ^ 0-based row to move to
                   -> Int -- ^ 0-based column to move to
                   -> IO ()
setCursorPosition :: Int -- ^ 0-based row to move to
                  -> Int -- ^ 0-based column to move to
                  -> IO ()
setCursorPosition = hSetCursorPosition stdout

hSaveCursor, hRestoreCursor, hReportCursorPosition :: Handle -> IO ()

-- | Save the cursor position in memory. The only way to access the saved value
-- is with the 'restoreCursor' command.
saveCursor :: IO ()
-- | Restore the cursor position from memory. There will be no value saved in
-- memory until the first use of the 'saveCursor' command.
restoreCursor :: IO ()
-- | Looking for a way to get the cursors position? See
-- 'getCursorPosition'.
--
-- Emit the cursor position into the console input stream, immediately after
-- being recognised on the output stream, as:
-- @ESC [ \<cursor row> ; \<cursor column> R@
--
-- In isolation of 'getReportedCursorPosition' or 'getCursorPosition', this
-- function may be of limited use on Windows operating systems because of
-- difficulties in obtaining the data emitted into the console input stream.
-- The function 'hGetBufNonBlocking' in module "System.IO" does not work on
-- Windows. This has been attributed to the lack of non-blocking primatives in
-- the operating system (see the GHC bug report #806 at
-- <https://ghc.haskell.org/trac/ghc/ticket/806>).
reportCursorPosition :: IO ()

saveCursor = hSaveCursor stdout
restoreCursor = hRestoreCursor stdout
reportCursorPosition = hReportCursorPosition stdout

hHideCursor, hShowCursor :: Handle
                         -> IO ()
hideCursor, showCursor :: IO ()
hideCursor = hHideCursor stdout
showCursor = hShowCursor stdout

-- | Set the terminal window title
hSetTitle :: Handle
          -> String -- ^ New title
          -> IO ()
-- | Set the terminal window title
setTitle :: String -- ^ New title
         -> IO ()
setTitle = hSetTitle stdout

-- | Use heuristics to determine whether the functions defined in this
-- package will work with a given handle.
--
-- The current implementation checks that the handle is a terminal, and
-- that the @TERM@ environment variable doesn't say @dumb@ (which is what
-- Emacs sets for its own terminal).
hSupportsANSI :: Handle -> IO Bool
-- Borrowed from an HSpec patch by Simon Hengel
-- (https://github.com/hspec/hspec/commit/d932f03317e0e2bd08c85b23903fb8616ae642bd)
hSupportsANSI h = (&&) <$> hIsTerminalDevice h <*> (not <$> isDumb)
  where
    -- cannot use lookupEnv since it only appeared in GHC 7.6
    isDumb = maybe False (== "dumb") . lookup "TERM" <$> getEnvironment

-- | Parses the characters emitted by 'reportCursorPosition' into the console
-- input stream. Returns the cursor row and column as a tuple.
--
-- For example, if the characters emitted by 'reportCursorPosition' are in
-- 'String' @input@ then the parser could be applied like this:
--
-- > let result = readP_to_S cursorPosition input
-- > case result of
-- >     [] -> putStrLn $ "Error: could not parse " ++ show input
-- >     [((row, column), _)] -> putStrLn $ "The cursor was at row " ++ show row
-- >         ++ " and column" ++ show column ++ "."
-- >     (_:_) -> putStrLn $ "Error: parse not unique"
--
cursorPosition :: ReadP (Int, Int)
cursorPosition = do
    void $ char '\ESC'
    void $ char '['
    row <- decimal -- A non-negative whole decimal number
    void $ char ';'
    col <- decimal -- A non-negative whole decimal number
    void $ char 'R'
    return (read row, read col)
  where
    digit = satisfy isDigit
    decimal = many1 digit

-- | Attempts to get the reported cursor position data from the console input
-- stream. The function is intended to be called immediately after
-- 'reportCursorPosition' (or related functions) have caused characters to be
-- emitted into the stream.
--
-- For example, on a Unix-like operating system:
--
-- > hSetBuffering stdin NoBuffering -- set no buffering (the contents of the
-- >                                 -- buffer will be discarded, so this needs
-- >                                 -- to be done before the cursor positon is
-- >                                 -- emitted)
-- > reportCursorPosition
-- > hFlush stdout -- ensure the report cursor position code is sent to the
-- >               -- operating system
-- > input <- getReportedCursorPosition
--
-- On Windows operating systems, the function is not supported on consoles, such
-- as mintty, that are not based on the Win32 console of the Windows API.
-- (Command Prompt and PowerShell are based on the Win32 console.)
getReportedCursorPosition :: IO String

-- | Attempts to get the reported cursor position, combining the functions
-- 'reportCursorPosition', 'getReportedCursorPosition' and 'cursorPosition'.
-- Returns 'Nothing' if any data emitted by 'reportCursorPosition', obtained by
-- 'getReportedCursorPosition', cannot be parsed by 'cursorPosition'.
--
-- On Windows operating systems, the function is not supported on consoles, such
-- as mintty, that are not based on the Win32 console of the Windows API.
-- (Command Prompt and PowerShell are based on the Win32 console.)
getCursorPosition :: IO (Maybe (Int, Int))