gallery/make-pages/BuilderQQ.hs

190 lines
5.4 KiB
Haskell

{-# LANGUAGE TemplateHaskell #-}
module BuilderQQ
(b,
Builder, toLazyText, fromText, fromString, fromChar,
textMap, ifJust, escId, escAttr)
where
import Data.Char (isLower, isSpace, isDigit, isAlphaNum)
import Language.Haskell.TH
import Language.Haskell.TH.Quote
import Data.List (intersperse)
import Data.Maybe (mapMaybe)
import Data.Text.Lazy.Builder
(Builder, fromText, fromLazyText, fromString, singleton, toLazyText)
import Text.Read (readMaybe)
import Data.Text (Text)
import qualified Data.Text as Text
import qualified Data.Text.Lazy as LText
import Data.Text.Lazy (toStrict)
import Data.Foldable
import Data.Semigroup
data ChunkType = Lit | Var VarType deriving Show
data VarType =
Plain
| Reindent !Int
deriving Show
type Chunk = (ChunkType, Text)
indent :: Int -> LText.Text -> Builder
indent i str
| LText.all isSpace str = ""
| otherwise = replicateB i ' ' <> fromLazyText str
reindentB :: Int -> Builder -> Builder
reindentB i (toLazyText -> str) =
fold $ intersperse "\n" $
map2 (fromLazyText . dropIndent) (indent i . dropIndent) ls
where
ls = dropWhile (LText.all isSpace) $ LText.lines str
ls' = filter (LText.any $ not . isSpace) ls
dropIndent = LText.drop minIndent
minIndent =
getMin $ option 0 id $ foldMap (Option . Just . Min . indentOf) ls'
indentOf = go 0 where
go n (' ' :.. cs) = go (n + 1) cs
go n ('\t' :.. cs) = go (((n `mod` 8) + 1) * 8) cs
go n _ = n
map2 _ _ [] = []
map2 f g (x:xs) = f x : map g xs
chunks :: Text -> [Chunk]
chunks = reverse . go "" [] . trimEnd where
go acc cs NilT = if Text.null acc' then cs else (Lit, acc') : cs
where acc' = toStrictText acc
-- $&: expands to nothing
go acc cs ('$' :. '&' :. rest) = go acc cs rest
-- $$: expands to one $
go acc cs ('$' :. '$' :. rest) = go (acc <> "$") cs rest
-- $n.var (n a number): expands to builder var indented by n
go acc cs ('$' :. rest@(d :. _)) | isDigit d =
go "" ((Var (Reindent n), var) : lit acc : cs) rest3
where
((read . Text.unpack -> n), '.' :. rest2) = Text.span isDigit rest
(var, rest3) = splitVar rest2
-- $var: expands to that var's contents
go acc cs ('$' :. rest) =
go "" ((Var Plain, var) : lit acc : cs) rest2
where (var, rest2) = splitVar rest
go acc cs (c :. rest) = go (acc <> singleton c) cs rest
splitVar s
| (var@(v :. _), s') <- Text.span isIdChar s,
isLower v || v == '_'
= (var, s')
splitVar _ = error "invalid variable name"
isIdChar c = isAlphaNum c || c `elem` ("_'" :: String)
lit s = (Lit, toStrictText s)
trimEnd = Text.dropWhileEnd isSpace
chunksWithReindent :: String -> [Chunk]
chunksWithReindent ('@':str)
| [(n',rest)] <- lex str,
Just n <- readMaybe n'
= chunks $ toStrictText $ reindent n $ Text.pack rest
chunksWithReindent str = chunks $ Text.pack str
toStrictText :: Builder -> Text
toStrictText = toStrict . toLazyText
chunksToExpQ :: [Chunk] -> ExpQ
chunksToExpQ cs = [|mconcat $es :: Builder|] where
es = listE $ mapMaybe chunk1 cs
chunk1 (Lit, "") = Nothing
chunk1 (Lit, lit) = Just $ stringE $ Text.unpack lit
chunk1 (Var t, name) = Just $ case t of
Plain -> [|build $var|]
Reindent n -> [|reindent n $var|]
where var = varE (mkName $ Text.unpack name)
replicateB :: Int -> Char -> Builder
replicateB n c = fromText $ Text.replicate n $ Text.singleton c
b :: QuasiQuoter
b = QuasiQuoter {
quoteExp = chunksToExpQ . chunksWithReindent,
quotePat = error "can't use in a pattern",
quoteType = error "can't use in a type",
quoteDec = error "can't use at top level"
}
pattern NilT :: Text
pattern NilT <- (Text.null -> True)
where NilT = ""
infixr 5 :.
pattern (:.) :: Char -> Text -> Text
pattern c :. t <- (Text.uncons -> Just (c, t))
where c :. t = Text.cons c t
{-# COMPLETE NilT, (:.) :: Text #-}
infixr 5 :..
pattern (:..) :: Char -> LText.Text -> LText.Text
pattern c :.. t <- (LText.uncons -> Just (c, t))
where c :.. t = LText.cons c t
fromChar :: Char -> Builder
fromChar = singleton
textMap :: (Char -> Builder) -> Text -> Builder
textMap f = Text.foldl' (\buf c -> buf <> f c) mempty
ifJust :: Monoid b => Maybe a -> (a -> b) -> b
ifJust x f = maybe mempty f x
escId :: Text -> Builder
escId = foldMap esc1 . Text.unpack where
esc1 c | isSpace c = ""
| latin1Special c = "_"
| otherwise = fromChar c
latin1Special c =
c <= 'ÿ' && not (isAlphaNum c) && c /= '-'
escAttr :: Text -> Builder
escAttr = foldMap esc1 . Text.unpack where
esc1 '<' = "&lt;"
esc1 '>' = "&gt;"
esc1 '"' = "&quot;"
esc1 '\'' = "&apos;"
esc1 c = fromChar c
class CanBuild a where
build :: a -> Builder
reindent :: Int -> a -> Builder
reindent i = reindentB i . build
instance CanBuild Builder where build = id
instance CanBuild Text where build = fromText
instance CanBuild LText.Text where build = fromLazyText
instance CanBuild Char where build = singleton
instance CanBuild String where build = fromString
newtype ShowBuild a = ShowBuild a deriving newtype Show
instance Show a => CanBuild (ShowBuild a) where build = build . show
deriving via ShowBuild Int instance CanBuild Int
deriving via ShowBuild Integer instance CanBuild Integer
instance {-# OVERLAPPABLE #-} CanBuild a => CanBuild [a] where
build = foldMap \x -> build x <> "\n"
reindent n = fold . intersperse ("\n" <> replicateB n ' ') . map build