module Error where

import Data.List (sort)
import Text.Parsec (SourcePos, errorPos)
import Text.Parsec.Error (ParseError, errorMessages, showErrorMessages)

data ErrorType = GenericError | TypeError | UnexpectedReturn | AlreadyDefined | NonCallable deriving (Show)

instance Enum ErrorType where
  fromEnum GenericError = 0
  fromEnum TypeError = 1
  fromEnum UnexpectedReturn = 2
  fromEnum AlreadyDefined = 3
  fromEnum NonCallable = 4
  toEnum _ = error "toEnum is undefined for Error"

data Error = Error ErrorType String SourcePos
  deriving (Eq)

instance Show Error where
  show (Error _ message pos) =
    show pos ++ " error: " ++ message

showParserError :: ParseError -> String
showParserError error =
  show (errorPos error) ++ " error: syntax error"
    ++ showErrorMessages "or" "unknown parser error" "  expected:" "     found:" "end of input" (errorMessages error)

instance Ord Error where
  compare (Error _ _ pos1) (Error _ _ pos2) = compare pos1 pos2

instance Eq ErrorType where
  e1 == e2 = fromEnum e1 == fromEnum e2

showErrorList :: [Error] -> String
showErrorList errs = unlines $ map show (sort errs)