module Text.Blaze.Truncate(truncateHtml) where
-- from Blaze 0.4 to 0.5: Html -> Markup; HtmlM -> MarkupM; AddCustomAttribute has an additional first argument
import Text.Blaze(Html)
import Text.Blaze.Internal(HtmlM(..),ChoiceString(..),StaticString(..))
import Data.Char
import qualified Data.Text as T
import qualified Data.ByteString as B
import GHC.Exts (IsString (..))
import Data.List(dropWhileEnd)
data Tagged a = Tagged Int a
instance Functor Tagged where
fmap f (Tagged n a) = Tagged n (f a)
-- type Html = Markup
-- type HtmlM a = MarkupM a
-- | Truncate the given HTML to a certain length, preserving tags. Returns the truncated Html or `Nothing` if no truncation occured.
-- Words are preserved, so if the truncated text ends within some word, that whole word is cut.
truncateHtml :: Int -- ^ The amount of characters (not counting tags) which the truncated text should have at most
-> Html -- ^ The HTML to truncate
-> Maybe Html -- ^ `Just` the truncated HTML or `Nothing` if no truncation occured
truncateHtml n html = case go n html of Tagged n' html' -> if n' /= n then Just html' else Nothing
where
go :: Int -> HtmlM b -> Tagged (HtmlM b)
go i (Parent t open close content) = fmap (Parent t open close) (go i content)
go i (Leaf t begin end) = Tagged i (Leaf t begin end)
go i (AddAttribute t key value h) = fmap (AddAttribute t key value) (go i h)
go i (AddCustomAttribute t key value h) = fmap (AddCustomAttribute t key value) (go i h)
go i (Append h1 h2) = case go i h1 of
Tagged j h1' -> fmap (Append h1') (go j h2)
go i Empty = Tagged i Empty
go i (Content content) = fmap Content (truncateChoiceString i content)
splitAt' :: Int -> ChoiceString -> (ChoiceString, ChoiceString)
splitAt' i (Static str) = case splitAt i ((getString str) "") of (str',str'') -> (Static (fromString str'),Static (fromString str''))
splitAt' i (String str) = case splitAt i str of (str',str'') -> (String str',String str'')
splitAt' i (Text str) = case T.splitAt i str of (str',str'') -> (Text str',Text str'')
splitAt' i (ByteString str) = case B.splitAt i str of (str',str'') -> (ByteString str',ByteString str'')
splitAt' i (PreEscaped str) = case splitAt' i str of (str',str'') -> (PreEscaped str',PreEscaped str'')
splitAt' _ (External str) = (External str,External EmptyChoiceString) -- note: these should not be truncated, so the behavior is a bit special here
splitAt' i (AppendChoiceString str1 str2) = case splitAt' i str1 of
(str1',str1'') ->
if empty' str1'' then case splitAt' (i - (length' str1')) str2 of
(str2',str2'') -> (AppendChoiceString str1' str2',str2'')
else (str1',AppendChoiceString str1'' str2)
splitAt' _ EmptyChoiceString = (EmptyChoiceString,EmptyChoiceString)
length' :: ChoiceString -> Int
length' (Static str) = length ((getString str) "")
length' (String str) = length str
length' (Text str) = T.length str
length' (ByteString str) = B.length str
length' (PreEscaped str) = length' str
length' (External str) = 0 -- note: these should not be truncated, so the behavior is a bit special here
length' (AppendChoiceString str1 str2) = length' str1 + length' str2
length' EmptyChoiceString = 0
empty' :: ChoiceString -> Bool
empty' (Static str) = null ((getString str) "")
empty' (String str) = null str
empty' (Text str) = T.null str
empty' (ByteString str) = B.null str
empty' (PreEscaped str) = empty' str
empty' (External str) = True -- note: these should not be truncated, so the behavior is a bit special here
empty' (AppendChoiceString str1 str2) = empty' str1 && empty' str2
empty' EmptyChoiceString = True
head' :: ChoiceString -> Char
head' (Static str) = head ((getString str) "")
head' (String str) = head str
head' (Text str) = T.head str
head' (ByteString str) = (head . show . B.head) str
head' (PreEscaped str) = head' str
head' (External str) = undefined -- note: these should not be truncated, so the behavior is a bit special here
head' (AppendChoiceString str1 str2) = if empty' str1 then head' str2 else head' str1
head' EmptyChoiceString = undefined
dropWhileEnd' :: (Char -> Bool) -> ChoiceString -> ChoiceString
dropWhileEnd' f (Static str) = Static (fromString (dropWhileEnd f ((getString str) "")))
dropWhileEnd' f (String str) = String (dropWhileEnd f str)
dropWhileEnd' f (Text str) = Text (T.dropWhileEnd f str)
dropWhileEnd' f (ByteString str) = ByteString (fst $ B.spanEnd (f . head . show) str) -- FIXME: inefficient
dropWhileEnd' f (PreEscaped str) = dropWhileEnd' f str
dropWhileEnd' f (External str) = External str -- note: these should not be truncated, so the behavior is a bit special here
dropWhileEnd' f (AppendChoiceString str1 str2) = case dropWhileEnd' f str2 of
str2' -> if empty' str2' then dropWhileEnd' f str1
else (AppendChoiceString str1 str2')
dropWhileEnd' f EmptyChoiceString = EmptyChoiceString
truncateChoiceString :: Int -> ChoiceString -> Tagged ChoiceString
truncateChoiceString i str = case splitAt' i str of
(str',rst) -> if (empty' rst) || (isSpace $ head' rst)
then Tagged (i - (length' str')) str'
else case dropWhileEnd' (not. isSpace) (dropWhileEnd' isSpace str') of
str'' -> Tagged (i - length' str'') str''