module uexpr

import StdEnv

import Data.Functor
import Data.Functor.Identity
import Control.Applicative
import Control.Monad => qualified join
import Control.Monad.State
import Control.Monad.Trans
import Control.Monad.Writer
import Data.Array
import Data.Func
import Data.List
import Text

:: In a b = In infix 0 a b

class uexpr v where
	lit :: a -> v a | toString a
	(+.) infixl 6 :: (v a) (v a) -> v a | + a

class uvar v where
	var :: (u:(v .a) -> v:(In u:(v .a) u:(v b))) -> u:(v b), [v <= u]

class uarr v where
	arr :: *(arr a) -> v *(arr a) | Array arr a & toString a
	(++.) infixr 5 :: (v .(arr a)) (v .(arr a)) -> v .(arr a) | Array arr a
	(!.) infixl 9 :: (v .(arr a)) (v Int) -> v a | Array arr a

:: Printer a = P (WriterT [String] (StateT Int Identity) ())
runPrinter (P a) = concat $ snd $ evalState (runWriterT a) 0
instance uexpr Printer where
	lit a = P $ tell [toString a]
	+. (P l) (P r) = P $ tell ["("] >>| l >>| tell ["+"] >>| r >>| tell [")"]

instance uvar Printer where
	var def = P (
		        liftT (getState)
		>>= \s->liftT (put (s+1))
		>>| let (P i In P b) = def $ P $ tell $ varName s []
		    in  tell ["let ":varName s [" = "]] >>| i >>| tell [" in\n"] >>| b
		)
	where
		varName i c = ["v",toString i:c]

instance uarr Printer where
	arr a = P $ tell ["{",join "," [toString a\\a<-:a],"}"]
	++. (P l) (P r) = P $ tell ["("] >>| l >>| tell ["+++"] >>| r >>| tell [")"]
	!. (P l) (P r) = P $ l >>| tell [".["] >>| r >>| tell ["]"]

:: Eval a = E a
runEval (E a) = a
instance uexpr Eval where
	lit a = E $ pure a
	+. (E l) (E r) = E $ l + r

//instance uvar Eval where
//	var def = let (i In b) = def i in b

instance uarr Eval where
	arr a = E a
	++. (E l) (E r) = E (appendArr l r)
	!. (E l) (E r) = E (select l r)

appendArr :: .(arr a) .(arr a) -> .arr a | Array arr a
appendArr l r = {if (i < size l) l.[i] r.[i rem size l]\\i<-[0..size l + size r - 1]}

//Start = both (var \v=arr {!1,2,3} In v ++. arr {!4,5,6})
Start = runPrinter (var \v=arr {!1,2,3} In v ++. arr {!4,5,6})

//both :: (A.v: v a | uexpr, uarr, uvar v) -> (String, a)
//both f = (runPrinter f, runEval f)

//i :: v Int | uexpr v
//i = lit 41 +. lit 1
//
//ai :: v {Int} | uexpr, uarr v
//ai = arr {1,2,3}
//
//aip :: v {Int} | uexpr, uarr v
//aip = arr {1,2,3} ++. arr {4,5,6}
//
//aii :: v Int | uexpr, uarr v
//aii = ai !. lit 41
//
//somearray :: *{Int}
//somearray = {1,2,3}