Working prototype

1 files changed, 96 insertions, 0 deletions

diff --git a/bbcode/src/BBCode.hs b/bbcode/src/BBCode.hs
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+{-# LANGUAGE OverloadedStrings, OverloadedLists, RankNTypes, ImpredicativeTypes #-}
+
+module BBCode
+       ( parse
+       ) where
+
+import Thermoprint
+
+import BBCode.Tokenizer
+import BBCode.Syntax
+
+import Data.Maybe
+import Data.Monoid
+import Data.Either
+import Data.Bifunctor
+import Data.List
+import Data.Ord
+import Data.Foldable
+
+import Data.Function (on)
+
+import           Data.CaseInsensitive  ( CI )
+import qualified Data.CaseInsensitive as CI
+
+import           Data.Map  ( Map )
+import qualified Data.Map as Map
+
+import Prelude hiding (takeWhile)
+
+import Debug.Trace
+
+knownTags :: Map (CI String) (Either (Block String -> Block String) (Inline String -> Inline String))
+knownTags = [ ("center", Left Center)
+            , ("u", Right Underline)
+            ]
+
+isBlock, isInline :: String -> Bool
+isBlock = testTag isLeft
+isInline = testTag isRight
+testTag f k = fromMaybe False (f <$> Map.lookup (CI.mk k) knownTags)
+
+data Decorated c = Decorated c [String]
+                 deriving (Show, Eq)
+
+parse :: String -> Either String (Block String)
+parse input = (remerge . blockify <$> (tokenize input >>= treeify)) >>= semantics
+
+blockify :: ContentForest -> [Decorated String]
+blockify = map sortDeco . concat . map (blockify' [])
+  where
+    blockify' _ Empty = []
+    blockify' initial (Content str) = [str `Decorated` initial]
+    blockify' initial (Tagged cs tag) = concat $ map (blockify' $ tag : initial) cs
+    sortDeco :: Decorated c -> Decorated c
+    sortDeco (Decorated c tags) = Decorated c $ (nubBy ((==) `on` CI.mk) . sortBy blockiness) tags
+    blockiness :: String -> String -> Ordering
+    blockiness a b = comparing isBlock a b <> comparing CI.mk a b -- sort also alphabetically for the benefit of remerge
+
+remerge :: [Decorated String] -> ContentForest
+remerge [] = []
+remerge [(Decorated c deco)] = [appEndo applyDeco $ Content c]
+  where
+    applyDeco = foldMap (\t -> Endo (\c -> Tagged [c] t)) $ reverse deco
+remerge xs = concat $ map toTree $ groupLasts xs
+  where
+    groupLasts = groupBy ((==) `on` (listToMaybe . reverse . (\(Decorated _ ds) -> ds)))
+    -- toTree :: [Decorated String] -> [ContentTree]
+    toTree [] = []
+    toTree (x@(Decorated _ []):xs) = map (Content . (\(Decorated c []) -> c)) (x:xs)
+    toTree (x@(Decorated _ ds):xs) = [Tagged content tag]
+      where
+        tag = last ds
+        content = toTree $ map stripLast (x:xs)
+        stripLast (Decorated c ds) = Decorated c (init ds)
+
+unknownTag :: forall a. String -> Either String a
+unknownTag tag = Left $ "Unknown tag: " ++ tag
+
+semantics :: ContentForest -> Either String (Block String)
+semantics forest = Over <$> mapM semantics' forest
+
+semantics' :: ContentTree -> Either String (Block String)
+semantics' Empty = Right $ Over []
+semantics' (Content str) = Right $ Paragraph (Cooked str)
+semantics' (Tagged cs tag) = case Map.lookup (CI.mk tag) knownTags of
+  Nothing -> unknownTag tag
+  Just (Left f) -> Over . map f <$> mapM semantics' cs
+  Just (Right f) -> Paragraph . Beside . map f<$> mapM iSemantics cs
+
+iSemantics :: ContentTree -> Either String (Inline String)
+iSemantics Empty = Right $ Beside []
+iSemantics (Content str) = Right $ Cooked str
+iSemantics (Tagged cs tag) = case Map.lookup (CI.mk tag) knownTags of
+  Nothing -> unknownTag tag
+  Just (Left f) -> error "Known inline tag sorted within block"
+  Just (Right f) -> Beside . map f <$> mapM iSemantics cs