module DSL where

import Data.Char (isDigit, isSpace)

import Parsers

------------------------------------------------------------------------------
-- Data types / instances
------------------------------------------------------------------------------

data StackData
  = StackInt Integer
  | StackBool Bool

instance Show StackData where
  show (StackInt x)      = show x
  show (StackBool True)  = "true"
  show (StackBool False) = "false"

type Stack = [StackData]

data Intrinsic
  = I_DUMP
    deriving (Show, Eq)

data Operation
  = OpPushData StackData
  | OpIntrinsic Intrinsic
    deriving (Show)

type Program = [Operation]

data TokenData
  = T_WHITESPACE
  | T_INT_LITERAL Integer
  | T_INTRINSIC Intrinsic
    deriving (Show, Eq)

data DSLToken = DSLToken { tStr :: String -- original text
                         , tData :: TokenData -- actual data
                         } deriving (Show)

type DSLLexer  = Parser Char DSLToken
type DSLParser = Parser DSLToken

------------------------------------------------------------------------------
-- Lexing
------------------------------------------------------------------------------

buildDSLLexer :: (Parser Char [Char]) -> ([Char] -> TokenData) -> DSLLexer
buildDSLLexer p f = do
  str <- p
  return DSLToken { tStr=str
                  , tData=f str
                  }

intrinsicL :: String -> Intrinsic -> DSLLexer
intrinsicL s i = buildDSLLexer (list s) (const $ T_INTRINSIC i)

wsL :: DSLLexer
wsL = buildDSLLexer (mult1 $ satisfy isSpace) (const T_WHITESPACE)

intLiteralL :: DSLLexer
intLiteralL = buildDSLLexer (mult1 $ satisfy isDigit) (T_INT_LITERAL . read)

mainLexer :: Parser Char [DSLToken]
mainLexer = phrase $ mult1 $ firstOf subLexers
  where
    subLexers = [wsL] ++ literals ++ intrinsics
    literals = [ intLiteralL
               ]
    intrinsics = map (uncurry intrinsicL) [ (".", I_DUMP)
                                          ]
------------------------------------------------------------------------------
-- Parsing
------------------------------------------------------------------------------

wsP :: DSLParser ()
wsP = do
  t <- anyToken
  case tData t of
    T_WHITESPACE -> result ()
    _            -> flunk

dataLiteralP :: DSLParser StackData
dataLiteralP = do
  t <- anyToken
  case tData t of
    T_INT_LITERAL x -> result $ StackInt x
    _               -> flunk

pushDataP :: DSLParser Operation
pushDataP = OpPushData <$> dataLiteralP

intrinsicP :: DSLParser Operation
intrinsicP = do
  t <- anyToken
  case tData t of
    T_INTRINSIC i -> result $ OpIntrinsic i
    _             -> flunk

operationP :: DSLParser Operation
operationP = firstOf [ pushDataP
                     , intrinsicP
                     ]

programP :: DSLParser Program
programP = do
  optional wsP
  ops <- operationP `sepBy1` wsP
  optional wsP
  eof
  return ops

stringToProgram :: String -> Maybe Program
stringToProgram str = do
  (_, tokens)  <- parse mainLexer str
  (_, program) <- parse programP tokens
  return program