{-# LANGUAGE Trustworthy #-}

-- | Non-Futhark-specific utilities.  If you find yourself writing
-- general functions on generic data structures, consider putting them
-- here.
--
-- Sometimes it is also preferable to copy a small function rather
-- than introducing a large dependency.  In this case, make sure to
-- note where you got it from (and make sure that the license is
-- compatible).
module Futhark.Util
  ( nubOrd,
    mapAccumLM,
    maxinum,
    chunk,
    chunks,
    dropAt,
    takeLast,
    dropLast,
    mapEither,
    maybeNth,
    maybeHead,
    splitFromEnd,
    splitAt3,
    focusNth,
    hashIntText,
    unixEnvironment,
    isEnvVarAtLeast,
    fancyTerminal,
    runProgramWithExitCode,
    directoryContents,
    roundFloat,
    ceilFloat,
    floorFloat,
    roundDouble,
    ceilDouble,
    floorDouble,
    lgamma,
    lgammaf,
    tgamma,
    tgammaf,
    fromPOSIX,
    toPOSIX,
    trim,
    pmapIO,
    readFileSafely,
    UserString,
    EncodedString,
    zEncodeString,
  )
where

import Control.Concurrent
import Control.Exception
import Control.Monad
import qualified Data.ByteString as BS
import Data.Char
import Data.Either
import Data.List (foldl', genericDrop, genericSplitAt, sort)
import qualified Data.List.NonEmpty as NE
import Data.Maybe
import qualified Data.Text as T
import qualified Data.Text.Encoding as T
import qualified Data.Text.Encoding.Error as T
import qualified Data.Text.IO as T
import Numeric
import qualified System.Directory.Tree as Dir
import System.Environment
import System.Exit
import qualified System.FilePath as Native
import qualified System.FilePath.Posix as Posix
import System.IO (hIsTerminalDevice, stdout)
import System.IO.Error (isDoesNotExistError)
import System.IO.Unsafe
import System.Process.ByteString
import Text.Printf
import Text.Read (readMaybe)

-- | Like 'nub', but without the quadratic runtime.
nubOrd :: Ord a => [a] -> [a]
nubOrd = map NE.head . NE.group . sort

-- | Like 'Data.Traversable.mapAccumL', but monadic.
mapAccumLM ::
  Monad m =>
  (acc -> x -> m (acc, y)) ->
  acc ->
  [x] ->
  m (acc, [y])
mapAccumLM _ acc [] = return (acc, [])
mapAccumLM f acc (x : xs) = do
  (acc', x') <- f acc x
  (acc'', xs') <- mapAccumLM f acc' xs
  return (acc'', x' : xs')

-- | @chunk n a@ splits @a@ into @n@-size-chunks.  If the length of
-- @a@ is not divisible by @n@, the last chunk will have fewer than
-- @n@ elements (but it will never be empty).
chunk :: Int -> [a] -> [[a]]
chunk _ [] = []
chunk n xs =
  let (bef, aft) = splitAt n xs
   in bef : chunk n aft

-- | @chunks ns a@ splits @a@ into chunks determined by the elements
-- of @ns@.  It must hold that @sum ns == length a@, or the resulting
-- list may contain too few chunks, or not all elements of @a@.
chunks :: [Int] -> [a] -> [[a]]
chunks [] _ = []
chunks (n : ns) xs =
  let (bef, aft) = splitAt n xs
   in bef : chunks ns aft

-- | Like 'maximum', but returns zero for an empty list.
maxinum :: (Num a, Ord a, Foldable f) => f a -> a
maxinum = foldl' max 0

-- | @dropAt i n@ drops @n@ elements starting at element @i@.
dropAt :: Int -> Int -> [a] -> [a]
dropAt i n xs = take i xs ++ drop (i + n) xs

-- | @takeLast n l@ takes the last @n@ elements of @l@.
takeLast :: Int -> [a] -> [a]
takeLast n = reverse . take n . reverse

-- | @dropLast n l@ drops the last @n@ elements of @l@.
dropLast :: Int -> [a] -> [a]
dropLast n = reverse . drop n . reverse

-- | A combination of 'map' and 'partitionEithers'.
mapEither :: (a -> Either b c) -> [a] -> ([b], [c])
mapEither f l = partitionEithers $ map f l

-- | Return the list element at the given index, if the index is valid.
maybeNth :: Integral int => int -> [a] -> Maybe a
maybeNth i l
  | i >= 0, v : _ <- genericDrop i l = Just v
  | otherwise = Nothing

-- | Return the first element of the list, if it exists.
maybeHead :: [a] -> Maybe a
maybeHead [] = Nothing
maybeHead (x : _) = Just x

-- | Like 'splitAt', but from the end.
splitFromEnd :: Int -> [a] -> ([a], [a])
splitFromEnd i l = splitAt (length l - i) l

-- | Like 'splitAt', but produces three lists.
splitAt3 :: Int -> Int -> [a] -> ([a], [a], [a])
splitAt3 n m l =
  let (xs, l') = splitAt n l
      (ys, zs) = splitAt m l'
   in (xs, ys, zs)

-- | Return the list element at the given index, if the index is
-- valid, along with the elements before and after.
focusNth :: Integral int => int -> [a] -> Maybe ([a], a, [a])
focusNth i xs
  | (bef, x : aft) <- genericSplitAt i xs = Just (bef, x, aft)
  | otherwise = Nothing

-- | Convert the given integer (implied to be a hash digest) to a
-- hexadecimal non-negative number.
hashIntText :: Int -> T.Text
hashIntText x = T.pack $ printf "%x" (fromIntegral x :: Word)

{-# NOINLINE unixEnvironment #-}

-- | The Unix environment when the Futhark compiler started.
unixEnvironment :: [(String, String)]
unixEnvironment = unsafePerformIO getEnvironment

-- | True if the environment variable, viewed as an integer, has at
-- least this numeric value.  Returns False if variable is unset or
-- not numeric.
isEnvVarAtLeast :: String -> Int -> Bool
isEnvVarAtLeast s x =
  case readMaybe =<< lookup s unixEnvironment of
    Just y -> y >= x
    _ -> False

{-# NOINLINE fancyTerminal #-}

-- | Are we running in a terminal capable of fancy commands and
-- visualisation?
fancyTerminal :: Bool
fancyTerminal = unsafePerformIO $ do
  isTTY <- hIsTerminalDevice stdout
  isDumb <- (Just "dumb" ==) <$> lookupEnv "TERM"
  return $ isTTY && not isDumb

-- | Like 'readProcessWithExitCode', but also wraps exceptions when
-- the indicated binary cannot be launched, or some other exception is
-- thrown.  Also does shenanigans to handle improperly encoded outputs.
runProgramWithExitCode ::
  FilePath ->
  [String] ->
  BS.ByteString ->
  IO (Either IOException (ExitCode, String, String))
runProgramWithExitCode exe args inp =
  (Right . postprocess <$> readProcessWithExitCode exe args inp)
    `catch` \e -> return (Left e)
  where
    decode = T.unpack . T.decodeUtf8With T.lenientDecode
    postprocess (code, out, err) =
      (code, decode out, decode err)

-- | Every non-directory file contained in a directory tree.
directoryContents :: FilePath -> IO [FilePath]
directoryContents dir = do
  _ Dir.:/ tree <- Dir.readDirectoryWith return dir
  case Dir.failures tree of
    Dir.Failed _ err : _ -> throw err
    _ -> return $ mapMaybe isFile $ Dir.flattenDir tree
  where
    isFile (Dir.File _ path) = Just path
    isFile _ = Nothing

foreign import ccall "nearbyint" c_nearbyint :: Double -> Double

foreign import ccall "nearbyintf" c_nearbyintf :: Float -> Float

foreign import ccall "ceil" c_ceil :: Double -> Double

foreign import ccall "ceilf" c_ceilf :: Float -> Float

foreign import ccall "floor" c_floor :: Double -> Double

foreign import ccall "floorf" c_floorf :: Float -> Float

-- | Round a single-precision floating point number correctly.
roundFloat :: Float -> Float
roundFloat = c_nearbyintf

-- | Round a single-precision floating point number upwards correctly.
ceilFloat :: Float -> Float
ceilFloat = c_ceilf

-- | Round a single-precision floating point number downwards correctly.
floorFloat :: Float -> Float
floorFloat = c_floorf

-- | Round a double-precision floating point number correctly.
roundDouble :: Double -> Double
roundDouble = c_nearbyint

-- | Round a double-precision floating point number upwards correctly.
ceilDouble :: Double -> Double
ceilDouble = c_ceil

-- | Round a double-precision floating point number downwards correctly.
floorDouble :: Double -> Double
floorDouble = c_floor

foreign import ccall "lgamma" c_lgamma :: Double -> Double

foreign import ccall "lgammaf" c_lgammaf :: Float -> Float

foreign import ccall "tgamma" c_tgamma :: Double -> Double

foreign import ccall "tgammaf" c_tgammaf :: Float -> Float

-- | The system-level @lgamma()@ function.
lgamma :: Double -> Double
lgamma = c_lgamma

-- | The system-level @lgammaf()@ function.
lgammaf :: Float -> Float
lgammaf = c_lgammaf

-- | The system-level @tgamma()@ function.
tgamma :: Double -> Double
tgamma = c_tgamma

-- | The system-level @tgammaf()@ function.
tgammaf :: Float -> Float
tgammaf = c_tgammaf

-- | Turn a POSIX filepath into a filepath for the native system.
toPOSIX :: Native.FilePath -> Posix.FilePath
toPOSIX = Posix.joinPath . Native.splitDirectories

-- | Some bad operating systems do not use forward slash as
-- directory separator - this is where we convert Futhark includes
-- (which always use forward slash) to native paths.
fromPOSIX :: Posix.FilePath -> Native.FilePath
fromPOSIX = Native.joinPath . Posix.splitDirectories

-- | Remove leading and trailing whitespace from a string.  Not an
-- efficient implementation!
trim :: String -> String
trim = reverse . dropWhile isSpace . reverse . dropWhile isSpace

-- | Run various 'IO' actions concurrently, possibly with a bound on
-- the number of threads.  The list must be finite.  The ordering of
-- the result list is not deterministic - add your own sorting if
-- needed.  If any of the actions throw an exception, then that
-- exception is propagated to this function.
pmapIO :: Maybe Int -> (a -> IO b) -> [a] -> IO [b]
pmapIO concurrency f elems = do
  tasks <- newMVar elems
  results <- newEmptyMVar
  num_threads <- maybe getNumCapabilities pure concurrency
  replicateM_ num_threads $ forkIO $ worker tasks results
  replicateM (length elems) $ getResult results
  where
    worker tasks results = do
      task <- modifyMVar tasks getTask
      case task of
        Nothing -> pure ()
        Just x -> do
          y <- (Right <$> f x) `catch` (pure . Left)
          putMVar results y
          worker tasks results

    getTask [] = pure ([], Nothing)
    getTask (task : tasks) = pure (tasks, Just task)

    getResult results = do
      res <- takeMVar results
      case res of
        Left err -> throw (err :: SomeException)
        Right v -> pure v

-- | Read a file, returning 'Nothing' if the file does not exist, and
-- 'Left' if some other error occurs.
readFileSafely :: FilePath -> IO (Maybe (Either String T.Text))
readFileSafely filepath =
  (Just . Right <$> T.readFile filepath) `catch` couldNotRead
  where
    couldNotRead e
      | isDoesNotExistError e =
        return Nothing
      | otherwise =
        return $ Just $ Left $ show e

-- Z-encoding from https://ghc.haskell.org/trac/ghc/wiki/Commentary/Compiler/SymbolNames
--
-- Slightly simplified as we do not need it to deal with tuples and
-- the like.
--
-- (c) The University of Glasgow, 1997-2006

-- | As the user typed it.
type UserString = String

-- | Encoded form.
type EncodedString = String

-- | Z-encode a string using a slightly simplified variant of GHC
-- Z-encoding.  The encoded string is a valid identifier in most
-- programming languages.
zEncodeString :: UserString -> EncodedString
zEncodeString "" = ""
zEncodeString (c : cs) = encodeDigitChar c ++ concatMap encodeChar cs

unencodedChar :: Char -> Bool -- True for chars that don't need encoding
unencodedChar 'Z' = False
unencodedChar 'z' = False
unencodedChar '_' = True
unencodedChar c =
  isAsciiLower c
    || isAsciiUpper c
    || isDigit c

-- If a digit is at the start of a symbol then we need to encode it.
-- Otherwise names like 9pH-0.1 give linker errors.
encodeDigitChar :: Char -> EncodedString
encodeDigitChar c
  | isDigit c = encodeAsUnicodeCharar c
  | otherwise = encodeChar c

encodeChar :: Char -> EncodedString
encodeChar c | unencodedChar c = [c] -- Common case first

-- Constructors
encodeChar '(' = "ZL" -- Needed for things like (,), and (->)
encodeChar ')' = "ZR" -- For symmetry with (
encodeChar '[' = "ZM"
encodeChar ']' = "ZN"
encodeChar ':' = "ZC"
encodeChar 'Z' = "ZZ"
-- Variables
encodeChar 'z' = "zz"
encodeChar '&' = "za"
encodeChar '|' = "zb"
encodeChar '^' = "zc"
encodeChar '$' = "zd"
encodeChar '=' = "ze"
encodeChar '>' = "zg"
encodeChar '#' = "zh"
encodeChar '.' = "zi"
encodeChar '<' = "zl"
encodeChar '-' = "zm"
encodeChar '!' = "zn"
encodeChar '+' = "zp"
encodeChar '\'' = "zq"
encodeChar '\\' = "zr"
encodeChar '/' = "zs"
encodeChar '*' = "zt"
encodeChar '_' = "zu"
encodeChar '%' = "zv"
encodeChar c = encodeAsUnicodeCharar c

encodeAsUnicodeCharar :: Char -> EncodedString
encodeAsUnicodeCharar c =
  'z' :
  if isDigit (head hex_str)
    then hex_str
    else '0' : hex_str
  where
    hex_str = showHex (ord c) "U"