{-# LANGUAGE CPP #-}

--------------------------------------------------

{-# LANGUAGE NoImplicitPrelude #-}

{-# LANGUAGE PackageImports, TypeOperators, LambdaCase, PatternSynonyms #-}
{-# LANGUAGE RankNTypes, PolyKinds, KindSignatures, ConstraintKinds, ScopedTypeVariables #-}
{-# LANGUAGE GeneralizedNewtypeDeriving #-}

-- {-# OPTIONS_HADDOCK not-home #-}

--------------------------------------------------
--------------------------------------------------

{-|

These identifiers are "soft" overrides, they generalize the signatures of their @Prelude@ namesakes:

* 'map': @() => []@ to @(Functor f) => f@
* 'sequence': @Monad@ to @Applicative@
* 'sequence_': @Monad@ to @Applicative@

These symbols are "hard" overrides, they are completely different from @Prelude@:

* '>': forward-composition
* '<': backward-composition (i.e. '(.)')

-}

module Prelude.Spiros.Utilities where

#include <sboo-base-feature-macros.h>

--------------------------------------------------

import Prelude.Spiros.Types
import Prelude.Spiros.Compatibility

--------------------------------------------------
-- Imports ---------------------------------------
--------------------------------------------------

--TODO import "clock" System.Clock

--------------------------------------------------
--------------------------------------------------

import "mtl" Control.Monad.Reader
  (ReaderT,Reader,runReaderT,runReader)

import "mtl" Control.Monad.State
  (StateT,State,runStateT,evalStateT,execStateT,runState,evalState,execState)

--------------------------------------------------

import "deepseq" Control.DeepSeq (NFData,force)

--------------------------------------------------

-- import qualified "text" Data.Text      as TS
-- import qualified "text" Data.Text.Lazy as TL

--------------------------------------------------

-- import qualified "bytestring" Data.ByteString      as BS 
-- import qualified "bytestring" Data.ByteString.Lazy as BL 

--------------------------------------------------

-- import qualified "template-haskell" Language.Haskell.TH.Syntax as TemplateHaskell

--------------------------------------------------

import "base" Data.Function              ((&))
import "base" Control.Arrow              ((>>>),(<<<))
import "base" Control.Exception          (SomeException,evaluate)
import "base" Control.Concurrent         (threadDelay,forkIO,ThreadId)
import "base" Control.Monad              (forever, void, when)
import "base" Data.Proxy
import "base" Data.String                (IsString)
import "base" Numeric.Natural
import "base" Data.Ratio                 (Ratio,(%))
import "base" Data.Foldable              (Foldable(..))

--------------------------------------------------

import           "base" Control.Category (Category)
import qualified "base" Control.Category as Category
import           "base" Data.Typeable

--------------------------------------------------

import qualified "base" Control.Exception   as E
import qualified "base" System.Environment  as IO

import qualified "base" Data.List as List

import           "base" Data.Foldable
-- import           "base" Text.Read

--------------------------------------------------

import qualified "base" Prelude
import           "base" Prelude hiding
  ( (<), (>)
  , map
  , sequence, sequence_
  )

--------------------------------------------------
-- Imports: CPP ----------------------------------
--------------------------------------------------

#if HAS_BASE_NonEmpty
import "base"       Data.List.NonEmpty         (NonEmpty)
--import qualified Data.List.NonEmpty as NonEmpty
#else
import "semigroups" Data.List.NonEmpty         (NonEmpty)
#endif

--------------------------------------------------

#if HAS_BASE_Semigroup
import qualified "base"       Data.Semigroup as Semigroup
import           "base"       Data.Semigroup ((<>))
#else
import qualified "semigroups" Data.Semigroup as Semigroup
import           "semigroups" Data.Semigroup ((<>))
#endif

--------------------------------------------------

#if MIN_VERSION_GLASGOW_HASKELL(8,0,0,0)
import "base" Data.Foldable              (sequenceA_,toList)
import "base" Data.Traversable           (sequenceA)
#else
import "base" Data.Foldable              (sequenceA_)
#endif

--------------------------------------------------

#if IS_COMPILER_ghc
import "base" GHC.Exts                   (IsString(..))
#endif

--------------------------------------------------
-- Values ----------------------------------------
--------------------------------------------------

--------------------------------------------------
-- soft overrides

-- | (generalization)
-- @= 'fmap'@
map :: Functor f => (a -> b) -> f a -> f b
map = fmap

{-# INLINEABLE map #-}

--------------------------------------------------

-- | (generalization)
-- @= 'sequenceA'@
sequence :: (Traversable t, Applicative f) => t (f a) -> f (t a)
sequence = sequenceA

{-# INLINEABLE sequence #-}

--------------------------------------------------

-- | (generalization)
-- @ = 'sequenceA_'@
sequence_ :: (Foldable t, Applicative f) => t (f a) -> f ()
sequence_ = sequenceA_

{-# INLINEABLE sequence_ #-}

--------------------------------------------------
-- hard overrides

{- | forwards composition

e.g. "f, then g, then h"

@
forwards x
 = x
 & f
 > g
 > h
@

same precedence/associativity as '.'

-}
(>) :: (a -> b) -> (b -> c) -> (a -> c)
(>) = (>>>)
infixr 9 >

{-# INLINEABLE (>) #-}

--------------------------------------------------

{- | backwards composition

e.g. "h, after g, after f"

@
backwards x
 = h
 < g
 < f
 $ x
@

same precedence/associativity as '.'

-}
(<) :: (b -> c) -> (a -> b) -> (a -> c)
(<) = (<<<)
infixr 9 <

{-# INLINEABLE (<) #-}

---------------------------------------

-- NOTE
-- infixr 1 <<<
-- infixr 9 .
-- function application (i.e. whitespace juxtaposition) is like: infixl 10 _
-- infixr 0 $
-- infixl 1 &

-- | same precedence/associativity as "Prelude.<"
lessThan :: Ord a => a -> a -> Bool
lessThan = (Prelude.<)
infix 4 `lessThan`

{-# INLINEABLE lessThan #-}

--------------------------------------------------

-- | same precedence/associativity as "Prelude.>"
greaterThan :: Ord a => a -> a -> Bool
greaterThan = (Prelude.>)
infix 4 `greaterThan`

{-# INLINEABLE greaterThan #-}

--------------------------------------------------

{- | @(-:) = (,)@

fake dictionary literal syntax:

@
 [ "a"-: 1
 , "b"-: 2
 , "c"-: 1+2
 ] :: [(String,Integer)]
@

-}
(-:) :: a -> b -> (a,b)
(-:) = (,)
infix 1 -:

--------------------------------------------------
--------------------------------------------------

{-# INLINEABLE (-:) #-}

todo :: a --TODO call stack
todo = error "TODO"
{-# DEPRECATED todo "use { __ERROR__ \"TODO\" }" #-}

--------------------------------------------------

__BUG__ :: SomeException -> a --TODO callstack
__BUG__ = error . show

--------------------------------------------------

__ERROR__ :: String -> a --TODO callstack
__ERROR__ = error

--------------------------------------------------
--------------------------------------------------

-- | @= 'pure' ()@

nothing :: (Applicative m) => m ()
nothing = pure ()

{-# INLINEABLE nothing #-}

{- | Raise a Function Arrow into a Kleisli Arrow.

a convenience function for composing pure functions between "kleislis" in monadic sequences.

Definition:

@= ('pure' .)@

@
returning f ≡ f >>> return

returning f ≡ \x -> return (f x)
@

Usage:

@readFile "example.txt" >>= returning show >>= forceIO
@

-}

returning :: (Applicative m) => (a -> b) -> (a -> m b)
returning f = f > pure

{-# INLINEABLE returning #-}

--------------------------------------------------
--------------------------------------------------

maybe2bool :: Maybe a -> Bool
maybe2bool = maybe False (const True)

{-# INLINEABLE maybe2bool #-}

--------------------------------------------------

maybe2either :: e -> Maybe a -> Either e a
maybe2either e = maybe (Left e) Right

{-# INLINEABLE maybe2either #-}

--------------------------------------------------

either2maybe :: Either e a -> Maybe a
either2maybe = either (const Nothing) Just

{-# INLINEABLE either2maybe #-}

--------------------------------------------------

either2bool :: Either e a -> Bool
either2bool = either (const False) (const True)

{-# INLINEABLE either2bool #-}

--------------------------------------------------

maybe2list :: Maybe a -> [a]
maybe2list = maybe [] (:[])

{-# INLINEABLE maybe2list #-}

--------------------------------------------------

list2maybe :: [a] -> Maybe a
list2maybe = \case
 [] -> Nothing
 (x:_) -> Just x

{-# INLINEABLE list2maybe #-}

--------------------------------------------------

#if HAS_BASE_NonEmpty
nonempty2list :: NonEmpty a -> [a]
nonempty2list = toList
#endif

--------------------------------------------------

list
  :: r -> (a -> [a] -> r)
  -> ([a] -> r)
list y f = \case
  []     -> y
  (x:xs) -> f x xs

--------------------------------------------------
--------------------------------------------------
-- numbers

-- | 
--
-- @
-- unsafeNatural :: Int -> Natural  
-- @
-- 
unsafeNatural :: Integral i => i -> Natural
unsafeNatural = fromIntegral

{-# INLINEABLE unsafeNatural #-}

--------------------------------------------------

-- | an alias, since @(%)@ is prime symbolic real estate. 
ratio :: Integral a => a -> a -> Ratio a
ratio = (%)

infixl 7 `ratio` -- same as (%)

{-# INLINEABLE ratio #-}

--------------------------------------------------
-- etc

--pure1 :: (Applicative f) => f a ->

-- | @($>) = flip ('<$')@
($>) :: (Functor f) => f a -> b -> f b
($>) = flip (<$)

{-# INLINEABLE ($>) #-}

--------------------------------------------------

-- | Infix flipped 'fmap'.
--
-- @
-- ('<&>') = 'flip' 'fmap'
-- @
--
-- NOTE: conflicts with the lens package 
(<&>) :: Functor f => f a -> (a -> b) -> f b
as <&> f = f <$> as

infixl 5 <&>
{-NOTE
  infixl 4 <$>
  infixl 4 <*>
-}

{-# INLINEABLE (<&>) #-}

--------------------------------------------------
-- list/number utilities...

{- | Safely get the @n@-th item in the given list.

>>> nth 1 ['a'..'c']
Just 'b'
>>> nth 1 []
Nothing

-}

nth :: Natural -> [a] -> Maybe a
nth n = go
  where

  go =
    ( List.zip [0..]
    > List.lookup n
    )

{-# INLINEABLE nth #-}

--------------------------------------------------

-- | reverse @cons@
snoc :: [a] -> a -> [a]
snoc xs x = xs ++ [x]

{-# INLINEABLE snoc #-}

--------------------------------------------------

{-|

(NOTE truncates large integral types).

-}
toInt :: (Integral a) => a -> Int
toInt = toInteger >>> (id :: Integer -> Integer) >>> fromIntegral

{-# INLINEABLE toInt #-}

--------------------------------------------------

-- | safely-partial @(!)@
index :: (Integral n) => [a] -> n -> Maybe a
index [] _ = Nothing
index (x:xs) n
 | n == 0         = Just x
 | n `lessThan` 0 = Nothing
 | otherwise      = index xs (n-1)

{-# INLINEABLE index #-}

--------------------------------------------------

strip :: String -> String
strip = rstrip . lstrip

{-# INLINEABLE strip #-}

--------------------------------------------------

lstrip :: String -> String
lstrip = dropWhile (`elem` (" \t\n\r"::String))

{-# INLINEABLE lstrip #-}

--------------------------------------------------

rstrip :: String -> String
rstrip = reverse . lstrip . reverse

{-# INLINEABLE rstrip #-}

--------------------------------------------------

shown :: forall a t.
    ( Show a
    , IsString t
    )
  => a
  -> t
shown = fromString . show

{-# INLINEABLE shown #-}

--------------------------------------------------

{-|

>>> pBool = Proxy :: Proxy Bool
>>> constructors pBool
[False,True]

-}
constructors :: (BoundedEnum a) => proxy a -> [a]
constructors _ = [minBound..maxBound]

{-# INLINEABLE constructors #-}

--------------------------------------------------

{-| like 'constructors', but with an implicit type parameter.

>>> constructors' == [False,True]
True

>> :set -XTypeApplications
>> constructors' @Bool
[False,True]

-}
constructors' :: forall a. (BoundedEnum a) => [a]
constructors' = constructors proxy
  where
  proxy = Proxy :: Proxy a

{-# INLINEABLE constructors' #-}

--------------------------------------------------

identity :: (Category cat) => (a `cat` a)
identity = Category.id

{-# INLINEABLE identity #-}

--------------------------------------------------

-- compose :: (Category (==>)) => (b ==> c) -> (a ==> b) -> (a ==> c)
compose
  :: (Category cat)
  => (b `cat` c)
  -> (a `cat` b)
  -> (a `cat` c)
compose = (Category.<<<)

{-# INLINEABLE compose #-}

--------------------------------------------------

typeName
  :: forall proxy a t.
    ( Typeable a
    , IsString t
    )
  => proxy a
  -> t
typeName proxy = typeRep proxy & show & fromString

{-# INLINEABLE typeName #-}

--------------------------------------------------

whenM :: (Monad m) => m Bool -> m () -> m ()
whenM check action = do

  b <- check

  when b action

{-# INLINEABLE whenM #-}

--------------------------------------------------

unlessM :: (Monad m) => m Bool -> m () -> m ()
unlessM check = whenM (not <$> check)

{-# INLINEABLE unlessM #-}

--------------------------------------------------

-- | @= 'flip' 'runReaderT'@
runReaderT' :: r -> (ReaderT r) m a -> m a
runReaderT' = flip runReaderT

-- | @= 'flip' 'runStateT'@
runStateT' :: s -> (StateT s) m a -> m (a, s)
runStateT' = flip runStateT

-- | @= 'flip' 'evalStateT'@
evalStateT' :: (Monad m) => s -> (StateT s) m a -> m a
evalStateT' = flip evalStateT

-- | @= 'flip' 'execStateT'@
execStateT' :: (Monad m) => s -> (StateT s) m a -> m s
execStateT' = flip execStateT

-- | @= 'flip' 'runReader'@
runReader' :: r -> Reader r a -> a
runReader' = flip runReader

-- | @= 'flip' 'runState'@
runState' :: s -> State s a -> (a, s)
runState' = flip runState

-- | @= 'flip' 'evalState'@
evalState' :: s -> State s a -> a
evalState' = flip evalState

-- | @= 'flip' 'execState'@
execState' :: s -> State s a -> s
execState' = flip execState

--------------------------------------------------
-- Time

{-| A number of microseconds (there are one million microseconds per second). An integral number because it's the smallest resolution for most GHC functions. @Int@ because GHC frequently represents integrals as @Int@s (for efficiency). 

Has smart constructors for common time units; in particular, for thread delays, and for human-scale durations.

* 'microseconds'
* 'milliseconds'
* 'seconds'
* 'minutes'
* 'hours'

Which also act as self-documenting (psuedo-keyword-)arguments for 'threadDelay', via 'delayFor'. 

-}
newtype Time = Time { toMicroseconds :: Int }

--------------------------------------------------

microseconds :: Int -> Time
milliseconds :: Int -> Time
seconds      :: Int -> Time
minutes      :: Int -> Time
hours        :: Int -> Time

{-# INLINEABLE microseconds #-}
{-# INLINEABLE milliseconds #-}
{-# INLINEABLE seconds #-}
{-# INLINEABLE minutes #-}
{-# INLINEABLE hours #-}

microseconds = Time
milliseconds = Time . (\t -> t*1000)
seconds      = Time . (\t -> t*1000*1000)
minutes      = Time . (\t -> t*1000*1000*1000)
hours        = Time . (\t -> t*1000*1000*1000*1000)

--------------------------------------------------

delayFor :: (MonadIO m) => Time -> m ()
delayFor = toMicroseconds >>> threadDelay >>> liftIO

{-# INLINEABLE delayFor #-}

delayMicroseconds :: (MonadIO m) => Int -> m ()
delayMicroseconds i = delayFor (microseconds i)

{-# INLINEABLE delayMicroseconds #-}

delayMilliseconds :: (MonadIO m) => Int -> m ()
delayMilliseconds i = delayFor (milliseconds i)

{-# INLINEABLE delayMilliseconds #-}

delaySeconds :: (MonadIO m) => Int -> m ()
delaySeconds i = delayFor (seconds i)

{-# INLINEABLE delaySeconds #-}

--------------------------------------------------

{-

{-| Normally used time units, for threads and for human-scale durations.

A psuedo-keyword-argument for 'threadDelay'. 

-}
data SimpleTimeUnit
  = Nanoseconds  Double
  | Milliseconds Double
  | Seconds      Double
  | Minutes      Double
  | Hours        Double

toNanoseconds :: SimpleTimeUnit -> Int
toNanoseconds = go > fromIntegral
 where
 go = \case
   Nanoseconds  i -> i
   Milliseconds i -> i * (1000)
   Seconds      i -> i * (1000*1000)
   Minutes      i -> i * (1000*1000*1000)
   Hours        i -> i * (1000*1000*1000*1000)

delayFor :: (MonadIO m) => SimpleTimeUnit -> m ()
delayFor = toNanoseconds >>> threadDelay >>> liftIO 

delayNanoseconds :: (MonadIO m) => Int -> m ()
delayNanoseconds i = delayFor (Nanoseconds i)

delayMilliseconds :: (MonadIO m) => Int -> m ()
delayMilliseconds i = delayFor (Milliseconds i)

delaySeconds :: (MonadIO m) => Int -> m ()
delaySeconds i = delayFor (Seconds i)

-- liftIO . threadDelay . (*1000) . (*1000)
-}

--------------------------------------------------
-- IO

io :: MonadIO m => IO a -> m a
io = liftIO

{-# INLINEABLE io #-}

--------------------------------------------------

forkever_ :: IO () -> IO ()
forkever_ = void . forkever Nothing

{-# INLINEABLE forkever_ #-}

--------------------------------------------------

forkever ::Maybe Int -> IO () -> IO ThreadId
forkever t m = forkIO $ forever $ do
    m
    _delay
    where
    _delay = maybe nothing delayMilliseconds t

{-# INLINEABLE forkever #-}

--------------------------------------------------

--TODO -- | Call once to start, then call repeatedly to get the elapsed time since the first call.
-- --   The time is guaranteed to be monotonic. This function is robust to system time changes.
-- --
-- -- > do f <- offsetTime; xs <- replicateM 10 f; return $ xs == sort xs
-- --
-- -- (inlined from the `extra` package)
-- offsetTime :: IO (IO Seconds)
-- offsetTime = do
--     start <- time
--     return $ do
--         end <- time
--         return $ 1e-9 * fromIntegral (toNanoSecs $ end - start)
--     where time = getTime Monotonic

-- | @= 'evaluate' . 'force'@
forceIO :: NFData a => a -> IO a
forceIO = evaluate . force

{-# INLINEABLE forceIO #-}

--------------------------------------------------

-- | @~ 'forceIO'@
forceIO_ :: NFData a => a -> IO ()
forceIO_ = void . evaluate . force

{-# INLINEABLE forceIO_ #-}

--------------------------------------------------
--------------------------------------------------

--TODO: MonadIO

{-| Return the value of the first environment variable that's been set, or a default value if all are unset.

Examples:

@
> firstSetEnvironmentVariable \"\/usr\/run\" [ \"XDG_RUNTIME_HOME\", \"TMP\" ]
@

Properties:

@
firstSetEnvironmentVariable x [] ≡ return x
@

-}

firstSetEnvironmentVariable :: String -> [String] -> IO String
firstSetEnvironmentVariable =

  firstEnvironmentVariableSatisfying (const True)

{-# INLINEABLE firstSetEnvironmentVariable #-}

--------------------------------------------------

-- {-| Return the first **numerical** (@Int@) value among the given environment variables, or a default number.

-- Examples:

-- @
-- > firstReadableEnvironmentVariable 1 [ "EUID", "UID" ]
-- @

-- Properties:

-- @
-- firstReadableEnvironmentVariable n [] ≈ return n
-- @

-- -}

-- firstIntEnvironmentVariable :: Int -> [String] -> IO Int
-- firstIntEnvironmentVariable = firstReadableEnvironmentVariable

-- {-# INLINEABLE firstIntEnvironmentVariable #-}

--------------------------------------------------

-- {-| Return the first **numerical** value among the given environment variables, or a default number.

-- Properties:

-- @
-- firstReadableEnvironmentVariable x [] ≈ return x
-- @

-- -}

-- firstReadableEnvironmentVariable :: (Read a) => a -> [String] -> IO a
-- firstReadableEnvironmentVariable x variables = to <$>

--   firstEnvironmentVariableSatisfying is (show x) variables

--   where

--   to = readMaybe > maybe x id
--   is = readMaybe > maybe False (const True)

-- {-# INLINEABLE firstReadableEnvironmentVariable #-}

--------------------------------------------------

{-| Return the first **nonempty** value among the given environment variables, or a default value if all are either unset or set-to-empty.

Examples:

@
> firstNonemptyEnvironmentVariable "/usr/run" [ "XDG_RUNTIME_HOME", "TMP" ]
@

Properties:

@
firstNonemptyEnvironmentVariable x [] ≈ return x
@

Notes:

* on Windows, @firstNonemptyEnvironmentVariable@ should be equivalent to 'firstSetEnvironmentVariable'.

-}

firstNonemptyEnvironmentVariable :: String -> [String] -> IO String
firstNonemptyEnvironmentVariable =

  firstEnvironmentVariableSatisfying (/= "")

{-# INLINEABLE firstNonemptyEnvironmentVariable #-}

--------------------------------------------------

firstEnvironmentVariableSatisfying :: (String -> Bool) -> String -> [String] -> IO String
firstEnvironmentVariableSatisfying predicate = \x0 variables -> do

  x' <- foldrM go Nothing variables

  let x = x' & maybe x0 Semigroup.getFirst

  E.evaluate (force x)

  where

  go :: String -> Maybe (Semigroup.First String) -> IO (Maybe (Semigroup.First String))
  go n y = do

    x <- IO.lookupEnv n

    let x'  = x >>= p
    let x'' = Semigroup.First <$> x'

    let z = x'' <> y

    return z

  p :: String -> Maybe String
  p x = if predicate x then Just x else Nothing

{-# INLINEABLE firstEnvironmentVariableSatisfying #-}

--------------------------------------------------
-- EOF -------------------------------------------
--------------------------------------------------