module Parser.Core where

import Control.Monad
import Control.Monad.State
import Control.Monad.Writer

import Data.Text (Text)
import qualified Data.Text.Lazy as TL
import Data.Typeable
import Data.Void

import Text.Megaparsec hiding (State)
import Text.Megaparsec.Char
import qualified Text.Megaparsec.Char.Lexer as L

import Network ()
import Test

type TestParser = ParsecT Void TestStream (WriterT [ Toplevel ] (State TestParserState))

type TestStream = TL.Text

data Toplevel
    = ToplevelTest Test

data TestParserState = TestParserState
    { testVars :: [(VarName, SomeExprType)]
    , testContext :: SomeExpr
    }

someEmptyVar :: SomeExprType -> SomeVarValue
someEmptyVar (SomeExprType (Proxy :: Proxy a)) = SomeVarValue $ emptyVarValue @a

textSomeExprType :: SomeExprType -> Text
textSomeExprType (SomeExprType p) = textExprType p

instance MonadEval TestParser where
    lookupVar name = maybe (fail $ "variable not in scope: '" ++ unpackVarName name ++ "'") (return . someEmptyVar) =<< gets (lookup name . testVars)
    rootNetwork = return emptyVarValue

skipLineComment :: TestParser ()
skipLineComment = L.skipLineComment $ TL.pack "#"

scn :: TestParser ()
scn = L.space space1 skipLineComment empty

sc :: TestParser ()
sc = L.space hspace1 skipLineComment empty

wordChar :: TestParser (Token TestStream)
wordChar = alphaNumChar <|> char '_'

lexeme :: TestParser a -> TestParser a
lexeme = L.lexeme sc

symbol, osymbol, wsymbol :: String -> TestParser ()
symbol str  = void $       (string (TL.pack str)) <* sc
osymbol str = void $ try $ (string (TL.pack str) <* notFollowedBy operatorChar) <* sc
wsymbol str = void $ try $ (string (TL.pack str) <* notFollowedBy wordChar) <* sc

operatorChar :: (MonadParsec e s m, Token s ~ Char) => m (Token s)
operatorChar = satisfy $ (`elem` ['.', '+', '-', '*', '/', '='])
{-# INLINE operatorChar #-}

localState :: TestParser a -> TestParser a
localState inner = do
    s <- get
    x <- inner
    put s
    return x

toplevel :: (a -> Toplevel) -> TestParser a -> TestParser ()
toplevel f = tell . (: []) . f <=< L.nonIndented scn

block :: (a -> [b] -> TestParser c) -> TestParser a -> TestParser b -> TestParser c
block merge header item = L.indentBlock scn $ do
    h <- header
    choice
        [ do symbol ":"
             return $ L.IndentSome Nothing (merge h) item
        , L.IndentNone <$> merge h []
        ]

listOf :: TestParser a -> TestParser [a]
listOf item = do
    x <- item
    (x:) <$> choice [ symbol "," >> listOf item, return [] ]