module ExprLexer where

import ParseDecorate
import ParseHelper
import qualified Token as T
import ParseTree
import Data.Maybe (fromJust)

data Token
  = Num Int
  | Plus
  | Minus
  | Star
  | Slash
  | POpen
  | PClose
  | Space String
  deriving Eq

instance Symbol Token where
  symbolSize = length . show
  spaceBeforeSize _ = 0
  spaceAfterSize _ = 0

instance Show Token where
  showsPrec _ tok = case tok of
    Num n -> (show n ++)
    Space s -> (s ++)
    _ -> (fromJust (lookup tok statics) ++)

statics :: [(Token, String)]
statics =
  [ (Plus, "+")
  , (Minus, "-")
  , (Star, "*")
  , (Slash, "/")
  , (POpen, "(")
  , (PClose, ")")
  ]

pStaticToken :: Parser Char Token w
pStaticToken = choice $ map (\(tok, syn) -> const tok <$> token syn) statics

pSpace :: Parser Char Token w
pSpace = Space <$> many1 (oneOf " \n\r\t\f")

isSpace :: Token -> Bool
isSpace (Space _) = True
isSpace _ = False

isNum :: Token -> Bool
isNum (Num _) = True
isNum _ = False

pToken :: Parser Char Token w
pToken = pStaticToken <|> Num <$> pInt <|> pSpace

pInt :: Parser Char Int w
pInt = (\d ds -> read (d:ds)) <$> oneOf ['1'..'9'] <*> many (oneOf ['0'..'9'])

pTokens :: Parser Char [T.Token Token] w
pTokens = T.collapse isSpace <$> many pToken