module Micro.Lexer where

import Data.Char (digitToInt)
import Text.Parsec
import Text.Parsec.Language (emptyDef)
import Text.Parsec.String (Parser)
import qualified Text.Parsec.Token as T

scanner :: T.TokenParser ()
scanner = T.makeTokenParser style
  where
    ops = ["+", "*", "-", ";", "="]
    names = ["module", "private", "var", "def", "return", "->", "true", "false"]
    style =
      emptyDef
        { T.commentLine = "#",
          T.reservedOpNames = ops,
          T.reservedNames = names
        }

binNum :: Parser Integer
binNum = do
  _ <- char '0'
  _ <- oneOf "bB"
  digits <- many1 $ oneOf "01"
  let n = foldl (\x d -> 2 * x + toInteger (digitToInt d)) 0 digits
  seq n $ return n

integer :: Parser Integer
integer = try binNum <|> T.integer scanner

parens :: Parser a -> Parser a
parens = T.parens scanner

braces :: Parser a -> Parser a
braces = T.braces scanner

commaSep :: Parser a -> Parser [a]
commaSep = T.commaSep scanner

colonSep :: Parser String
colonSep = T.colon scanner

identifier :: Parser String
identifier = T.identifier scanner

reserved :: String -> Parser ()
reserved = T.reserved scanner

reservedOp :: String -> Parser ()
reservedOp = T.reservedOp scanner

scan :: Parser a -> Parser a
scan p = do
  T.whiteSpace scanner
  r <- p
  eof
  return r