module Exercise04 where

{-WETT-}
xmlLight :: String -> Bool
xmlLight str = helper str [] ""

helper :: String -> [String] -> String -> Bool
helper "" lastTags nextTag = null lastTags && null nextTag
helper (char:str) lastTags nextTag
    | char == '<' = null nextTag && helper str lastTags (nextTag ++ [char])
    | char == '>' = not (null nextTag) && isValidTag newNextTag False && 
                    if isClosingTag newNextTag 
                    then not (null lastTags) && (getTagId (last lastTags) == getTagId newNextTag) && helper str (init lastTags) ""
                    else helper str (lastTags ++ [newNextTag]) "" 
    | otherwise = if null nextTag then helper str lastTags nextTag else helper str lastTags newNextTag
    where 
        newNextTag = nextTag ++ [char]
        isClosingTag xs = xs !! 1 == '/'
        getTagId xs = [x | x <- xs, x /= '/', x /= ' ', x /= '<', x /= '>']

isValidTag :: String -> Bool -> Bool
isValidTag "" _ = True
isValidTag (char:str) whiteSpace
    | char == ' ' = isValidTag str True
    | char == '>' = True
    | otherwise = not whiteSpace && isValidTag str whiteSpace
{-TTEW-}

-- 1st Iteration:
-- xmlLight2 :: String -> Bool
-- xmlLight2 "" = True
-- xmlLight2 str = length potentialTags == lengthActualTags && lengthActualTags == length validTags && isValidTagOrder validTags []
--     where
--         parsedToList = parseToList str "" []
--         potentialTags = [xs | xs<- parsedToList, head xs == '<' || last xs == '>']
--         actualTags = [ys | ys <- potentialTags, head ys == '<', last ys == '>']
--         validTags = [zs | zs <- actualTags, isValidTag zs False]
--         lengthActualTags = length actualTags
        
-- parseToList :: String -> String -> [String] -> [String]
-- parseToList [] accList list = if null accList then list else list ++ [accList]
-- parseToList (char:str) accList list
--     | char == '<' = if null accList then parseToList str "<" list else parseToList str "<" (list ++ [accList])
--     | char == '>' = parseToList str "" (list ++ [accList ++ ">"])
--     | otherwise = parseToList str (accList ++ [char]) list

-- isValidTagOrder :: [String] -> [String] -> Bool
-- isValidTagOrder [] accList = null accList
-- isValidTagOrder (tag:list) accList 
--     | isOpeningTag tag = isValidTagOrder list (accList ++ [tag])
--     | otherwise = not (null accList) && (getTagId tag == getTagId (last accList)) && isValidTagOrder list (init accList)
--     where
--         getTagId str = [char | char <- str, char /= '/', char /= ' ', char /= '<', char /= '>']
--         isOpeningTag str = str !! 1 == '/'

-- 2nd Iteration:
-- helper :: String -> [String] -> String -> Bool
-- helper "" _ _ = True
-- helper (char:"") lastTags nextTag
--     | char == '<' = False
--     | char == '>' = let newTag = nextTag ++ [char] in 
--                     not (null nextTag) && not (null lastTags) && null (init lastTags) &&
--                     isValidTag newTag False && 
--                     isClosingTag newTag && (getTagId (last lastTags) == getTagId newTag) 
--     | otherwise = null lastTags && null nextTag
-- helper (char:str) lastTags nextTag
--     | char == '<' = null nextTag && helper str lastTags (nextTag ++ [char])
--     | char == '>' = let newTag = nextTag ++ [char] in 
--                     not (null nextTag) && isValidTag newTag False && 
--                     if isClosingTag newTag then not (null lastTags) && (getTagId (last lastTags) == getTagId newTag) && helper str (init lastTags) ""
--                     else helper str (lastTags ++ [newTag]) "" 
--     | otherwise = if null nextTag then helper str lastTags nextTag else helper str lastTags (nextTag ++ [char])