{-# OPTIONS_GHC -fglasgow-exts #-}
module Text.JRegex.Impl where


import Array
import Maybe

-- | instances of this class may be used as regular expressions with this syntax.

class RegexLike r a | r -> a where
    -- | Test whether the regex matches at all
    matchTest :: r -> [a] -> Bool
    -- | Count the number of times the regex matches
    matchCount :: r -> [a] -> Int
    -- | return all matches
    matchAll  :: r -> [a] -> [(Array Int (Int,Int))]
    -- | match once
    matchOnce :: r  -- ^ Regular Expression
            -> [a]  -- ^ String to match
            -> Bool -- ^ Whether we are at the begining of the string (as opposed to continuing a previous match)
            -> Maybe (Array Int (Int,Int))  -- ^ array of matched expression
    matchShow :: r -> String  -- ^ Used for error messages
    matchTest r xs = isJust (matchOnce r xs True)
    matchCount r xs = length (matchAll r xs)
    matchAll r xs = f 0 xs where
        f t xs = case matchOnce r xs (t == 0) of
            Nothing -> []
            Just a  | l == 0 -> [na]
                    | otherwise -> na:f (t + x) (drop x xs) where
                (o,l) = a!0
                x = o + l
                na = fmap (adj t) a
        adj t (x,y) = ((,) $! x + t) $! y
    matchShow _ = "Unknown"