module Database.Berkeley.Util
    where

import Data.List

locate :: (Eq a) => [a] -> [a] -> Maybe Int
locate needle haystack = locate_ needle haystack 0 where
    locate_ _ [] _ = Nothing
    locate_ needle haystack idx =
        if isPrefixOf needle haystack
            then Just idx
            else locate_ needle (tail haystack) (idx+1)

maybeRead :: Read a => String -> Maybe a 
maybeRead s = case reads s of
    [(x, "")] -> Just x
    _         -> Nothing

toDelim :: String -> Int -> [Char] -> String
toDelim line idx delims = takeWhile (flip notElem delims) (drop idx line)

extract :: String -> String -> [Char] -> Maybe String
extract tag line delims =
    case locate tag line of
        Just idx -> Just $ toDelim line (idx+(length tag)) delims
        _        -> Nothing