{-# LANGUAGE ConstraintKinds            #-}
{-# LANGUAGE DeriveDataTypeable         #-}
{-# LANGUAGE DeriveFoldable             #-}
{-# LANGUAGE DeriveFunctor              #-}
{-# LANGUAGE DeriveTraversable          #-}
{-# LANGUAGE FlexibleInstances          #-}
{-# LANGUAGE GADTs                      #-}
{-# LANGUAGE TemplateHaskell #-}
{-# LANGUAGE GeneralizedNewtypeDeriving #-}
{-# LANGUAGE MultiParamTypeClasses      #-}
{-# LANGUAGE ScopedTypeVariables        #-}
{-# LANGUAGE TypeFamilies               #-}
{-# LANGUAGE NoMonomorphismRestriction  #-}
{-# LANGUAGE ViewPatterns               #-}

-------------------------------------------------------------------------------------
-- |
-- Copyright   : (c) Hans Hoglund 2012
--
-- License     : BSD-style
--
-- Maintainer  : hans@hanshoglund.se
-- Stability   : experimental
-- Portability : non-portable (TF,GNTD)
--
-- Reactive values, or piecewise functions of time.
--
-- Similar to Conal's definition in <http://conal.net/blog/posts/reactive-normal-form>,
-- but defined in negative time as well. Its semantics function is either 'occs' @&&&@ '?'
-- /or/ 'initial' @&&&@ 'updates', where 'intial' is the value from negative infinity
-- to the first update.
--
-- TODO integrate better in the library
--
-------------------------------------------------------------------------------------

module Music.Time.Reactive (
        Reactive,

        -- * Create, isos etc (TODO)
        initial,
        updates,
        occs,
        -- final,
        -- Future,
        -- Past,
        -- resets,

        -- * Predicates
        isConstant,
        isVariable,

        -- * Combinators
        -- step,

        switch,
        trim,
        -- trimBefore,
        -- trimAfter,

        -- * Semantics
        -- renderR,
        -- renderR',
        -- printR,
  ) where

import           Control.Applicative
import           Control.Arrow
import           Control.Lens
import           Control.Monad
import           Control.Monad.Compose
import           Control.Monad.Plus
import           Data.AffineSpace
import           Data.AffineSpace.Point
import           Data.Foldable          (Foldable)
import qualified Data.Foldable          as F
import qualified Data.List              as List
import           Data.Map               (Map)
import qualified Data.Map               as Map
import           Data.Semigroup
import           Data.Set               (Set)
import qualified Data.Set               as Set
import           Data.String
import           Data.Traversable       (Traversable)
import qualified Data.Traversable       as T
import           Data.Typeable
import           Data.VectorSpace

import           Music.Time.Delayable
import           Music.Time.Span
import           Music.Time.Stretchable
import           Music.Time.Time
import           Music.Time.Time
-- import Music.Score.Note
-- import Music.Score.Track
-- import Music.Score.Pitch
-- import Music.Score.Util
-- import Music.Pitch.Literal
-- import Music.Dynamics.Literal

newtype Reactive a = Reactive { getReactive :: ([Time], Time -> a) }
    deriving (Functor, Semigroup, Monoid)

instance Delayable (Reactive a) where
    delay n (Reactive (t,r)) = Reactive (delay n t, delay n r)

instance Stretchable (Reactive a) where
    stretch n (Reactive (t,r)) = Reactive (stretch n t, stretch n r)

instance Wrapped (Reactive a) where
    type Unwrapped (Reactive a) = ([Time], Time -> a)
    _Wrapped' = iso getReactive Reactive

instance Applicative Reactive where
    pure    = (^. _Unwrapped') . pure . pure
    ((^. _Wrapped') -> (tf, rf)) <*> ((^. _Wrapped') -> (tx, rx)) = (^. _Unwrapped') (tf <> tx, rf <*> rx)

instance HasBehavior Reactive where
    (?) = atTime

instance IsString a => IsString (Reactive a) where
    fromString = pure . fromString

instance Eq (Reactive b) where
    (==) = error "(==)"
    (/=) = error "(/=)"

instance Ord b => Ord (Reactive b) where
    min = liftA2 min
    max = liftA2 max

instance Enum a => Enum (Reactive a) where
    succ           = fmap succ
    pred           = fmap pred
    toEnum         = pure . toEnum
    fromEnum       = error "fromEnum"
    enumFrom       = error "enumFrom"
    enumFromThen   = error "enumFromThen"
    enumFromTo     = error "enumFromTo"
    enumFromThenTo = error "enumFromThenTo"

instance Num a => Num (Reactive a) where
    (+)         = liftA2 (+)
    (*)         = liftA2 (*)
    (-)         = liftA2 (-)
    abs         = fmap abs
    signum      = fmap signum
    fromInteger = pure . fromInteger

instance (Num a, Ord a) => Real (Reactive a) where
  toRational = error "toRational"

instance Integral a => Integral (Reactive a) where
    quot      = liftA2 quot
    rem       = liftA2 rem
    div       = liftA2 div
    mod       = liftA2 mod
    quotRem   = (fmap.fmap) unzip' (liftA2 quotRem)
    divMod    = (fmap.fmap) unzip' (liftA2 divMod)
    toInteger = error "toInteger"

instance Fractional b => Fractional (Reactive b) where
    recip        = fmap recip
    fromRational = pure . fromRational

instance Floating b => Floating (Reactive b) where
    pi    = pure pi
    sqrt  = fmap sqrt
    exp   = fmap exp
    log   = fmap log
    sin   = fmap sin
    cos   = fmap cos
    asin  = fmap asin
    atan  = fmap atan
    acos  = fmap acos
    sinh  = fmap sinh
    cosh  = fmap cosh
    asinh = fmap asinh
    atanh = fmap atanh
    acosh = fmap acosh

instance AdditiveGroup v => AdditiveGroup (Reactive v) where
    zeroV   = pure   zeroV
    (^+^)   = liftA2 (^+^)
    negateV = liftA   negateV

instance VectorSpace v => VectorSpace (Reactive v) where
    type Scalar (Reactive v) = Scalar v
    (*^) s = fmap (s *^)


-- | Get the time of all updatese.
occs :: Reactive a -> [Time]
occs = fst . (^. _Wrapped')

-- | @b ?? t@ returns the value of the reactive at time @t@.
--  Semantic function.
atTime :: Reactive a -> Time -> a
atTime = snd . (^. _Wrapped')

-- | Get the initial value.
initial :: Reactive a -> a
initial r = r ? minB (occs r)
    where
        -- If there are no updates, just use value at time 0
        -- Otherwise pick an arbitrary time /before/ the first value
        -- It looks strange but it works
        minB []    = 0
        minB (x:_) = x - 1

-- | Get the time of all updates and the value switched to at this point.
updates :: Reactive a -> [Future a]
updates r = (\t -> (t, r ? t)) <$> (List.sort . List.nub) (occs r)

-- | Get the final value.
final :: Reactive a -> a
final (renderR -> (i,[])) = i
final (renderR -> (i,xs)) = snd $ last xs

-- | @switch t a b@ behaves as @a@ before time @t@, then as @b@.
switch :: Time -> Reactive a -> Reactive a -> Reactive a
switch t (Reactive (tx, rx)) (Reactive (ty, ry)) = Reactive $ (,)
    (filter (< t) tx <> [t] <> filter (> t) ty)
    (\u -> if u < t then rx u else ry u)



-- TODO separate these with newtype
type Future a = (Time, a)
type Past   a = (Time, a)

isConstant :: Reactive a -> Bool
isConstant = null . occs

isVariable :: Reactive a -> Bool
isVariable = not . isConstant

resets :: Reactive a -> [Past a]
resets = error "resets: Not impl"

-- | The unit step function, which goes from 0 to 1 at 'start'.
step :: (AdditiveGroup a, Fractional a) => Reactive a
step = switch start zeroV 1.0 -- TODO some overloaded unit

-- | Replace everthing outside the given span by `mempty`.
trim :: Monoid a => Span -> Reactive a -> Reactive a
trim (view range -> (t,u)) = trimBefore t . trimAfter u

-- | Replace everthing before the given time by `mempty`.
trimBefore :: Monoid a => Time -> Reactive a -> Reactive a
trimBefore start x = switch start mempty x

-- | Replace everthing after the given time by `mempty`.
trimAfter :: Monoid a => Time -> Reactive a -> Reactive a
trimAfter stop x = switch stop x mempty

-- | Semantic function.
renderR :: Reactive a -> (a, [(Time, a)])
renderR = initial &&& updates

-- | Semantic function.
renderR' :: Reactive a -> ([Time], Time -> a)
renderR' = occs &&& (?)


printR :: Show a => Reactive a -> IO ()
printR r = let (x, xs) = renderR r in do
    print x
    mapM_ print xs

unzip' :: Functor f => f (a, b) -> (f a, f b)
unzip' r = (fst <$> r, snd <$> r)