Moved Printout.BBCode to own module

2 files changed, 184 insertions, 0 deletions

diff --git a/tp-bbcode/src/Thermoprint/Printout/BBCode.hs b/tp-bbcode/src/Thermoprint/Printout/BBCode.hs
new file mode 100644
index 0000000..ce2aa43
--- /dev/null
+++ b/tp-bbcode/src/Thermoprint/Printout/BBCode.hs
@@ -0,0 +1,145 @@
+{-# LANGUAGE OverloadedStrings #-}
+{-# LANGUAGE DeriveGeneric #-}
+{-# LANGUAGE GADTs #-}
+
+-- | Use 'Text.BBCode' to parse BBCode
+module Thermoprint.Printout.BBCode
+       ( bbcode
+       , BBCodeError(..)
+       , TreeError(..)
+       , SemanticError(..)
+       ) where
+
+import Data.Text (Text)
+import Data.Map (Map)
+
+import qualified Data.Text.Lazy as Lazy (Text)
+import qualified Data.Text.Lazy as TL (fromStrict)
+
+import Data.Sequence (Seq)
+import qualified Data.Sequence as Seq (fromList, singleton)
+
+import Data.CaseInsensitive (CI)
+import qualified Data.CaseInsensitive as CI
+
+import GHC.Generics (Generic)
+import Control.Exception (Exception)
+import Data.Typeable (Typeable)
+
+import Data.Bifunctor (bimap, first)
+import Control.Monad (join)
+
+import Data.List (groupBy)
+
+import Text.BBCode (DomForest, DomTree(..), TreeError(..))
+import qualified Text.BBCode as Raw (bbcode, BBCodeError(..))
+
+import Thermoprint.Printout
+
+import Thermoprint.Printout.BBCode.Attribute
+
+-- ^ We replicate 'Raw.BBCodeError' but add a new failure mode documenting incompatibly of the parsed syntax tree with our document format
+data BBCodeError = LexerError String -- ^ Error while parsing input to stream of tokens
+                 | TreeError TreeError -- ^ Error while parsing stream of tokens to syntax tree
+                 | SemanticError SemanticError -- ^ Error while mapping syntax tree to document format
+                 deriving (Show, Eq, Generic, Typeable)
+
+instance Exception BBCodeError
+
+morph' :: Raw.BBCodeError -> BBCodeError
+-- ^ Transform 'Raw.BBCodeError' to 'BBCodeError'
+morph' (Raw.LexerError x) = LexerError x
+morph' (Raw.TreeError x)  = TreeError x
+
+-- | An error ocurred while parsing the DOM-Forest (`['DomTree']`)
+data SemanticError = BlockInLineContext -- ^ A 'Block' structure was encountered when a 'Line' was expected
+                   | LineInBlockContext -- ^ A 'Line' structure was encountered when a 'Block' was expected
+                   | UnmappedBlockElement Text -- ^ We encountered an 'Element' that, in a 'Block' context, does not map to any structure
+                   | UnmappedLineElement Text -- ^ We encountered an 'Element' that, in a 'Line' context, does not map to any structure
+  deriving (Show, Eq, Generic, Typeable)
+
+instance Exception SemanticError
+
+-- | Result of parsing a single 'DomTree'
+data ParseResult = RBlock Block -- ^ Parses only as 'Block'
+                 | RLine Line -- ^ Parses only as 'Line'
+                 | RAmbiguous Block Line -- ^ Parses as either 'Block' or 'Line' depending on context
+                 | RNoParse SemanticError SemanticError -- ^ Does not parse as either 'Block' or 'Line'
+                 deriving (Show)
+
+-- | Current parser context
+data Context a where
+  BlockCtx :: Context Block
+  LineCtx  :: Context Line
+
+extract :: Context a -> ParseResult -> Either SemanticError a
+-- ^ Extract information from a 'ParseResult' given 'Context'
+extract BlockCtx (RBlock b)        = Right b
+extract LineCtx  (RLine l)         = Right l
+extract BlockCtx (RAmbiguous b _)  = Right b
+extract LineCtx  (RAmbiguous _ l)  = Right l
+extract BlockCtx (RNoParse bErr _) = Left bErr
+extract LineCtx  (RNoParse _ lErr) = Left lErr
+extract BlockCtx _                 = Left LineInBlockContext
+extract LineCtx  _                 = Left BlockInLineContext
+
+hasBlockCtx :: ParseResult -> Bool
+-- ^ Result can be 'extract'ed in a 'Block' 'Context'
+hasBlockCtx (RLine _) = False
+hasBlockCtx _         = True
+
+hasLineCtx :: ParseResult -> Bool
+-- ^ Result can be 'extract'ed in a 'Line' 'Context'
+hasLineCtx (RBlock _) = False
+hasLineCtx _          = True
+
+bbcode :: Text -> Either BBCodeError Printout
+-- ^ Parse BBCode
+bbcode = join . fmap (first SemanticError) . bimap morph' morph . Raw.bbcode
+
+morph :: DomForest -> Either SemanticError Printout
+-- ^ Parse a list of paragraphs
+--
+-- Since we permit only cooked input via 'Raw' 'Paragraph' is identical to 'Block'
+morph = fmap Seq.fromList . mapM (\t -> Seq.singleton . Cooked <$> parse BlockCtx t)
+
+parseDom :: DomTree -> ParseResult
+-- ^ Invoke 'asLine' and 'asBlock' to parse a single 'DomTree'
+parseDom (Content t) = either RBlock (\l -> RAmbiguous (Line l) l) . text . TL.fromStrict $ t
+parseDom (Element t attrs cs)
+  | Right blockParse' <- blockParse
+  , Right lineParse' <- lineParse   = RAmbiguous blockParse' lineParse'
+  | Right blockParse' <- blockParse = RBlock blockParse'
+  | Right lineParse' <- lineParse   = RLine lineParse'
+  | Left bErr <- blockParse
+  , Left lErr <- lineParse          = RNoParse bErr lErr
+  where
+    blockParse = asBlock t cs attrs
+    lineParse  = asLine t cs attrs
+
+mergeResult :: Monoid a => Context a -> [ParseResult] -> Either SemanticError a
+-- ^ Merge a list of 'ParseResults' in a certain 'Context'
+mergeResult _        []                        = Right mempty
+mergeResult ctx      (amb@(RAmbiguous _ _):xs) = mappend <$> extract ctx amb <*> mergeResult ctx xs 
+mergeResult ctx      (err@(RNoParse _ _):_)    = extract ctx err
+mergeResult ctx      (x:xs)                    = mappend <$> extract ctx x <*> mergeResult ctx xs
+
+parse :: Monoid a => Context a -> [DomTree] -> Either SemanticError a
+-- ^ Parse a list of 'DomTree's in a certain 'Context'
+--
+-- @parse ctx = 'mergeResult' ctx . map 'parseDom'@
+parse BlockCtx = fmap mconcat . mapM mergeResult' . groupBy sameCtx . map parseDom
+  where
+    sameCtx a b = (hasLineCtx a && hasLineCtx b) || (hasBlockCtx a && hasBlockCtx b)
+    mergeResult' xs
+      | hasLineCtx `all` xs = Line <$> mergeResult LineCtx xs
+      | otherwise           = mergeResult BlockCtx xs
+parse ctx      = mergeResult ctx . map parseDom
+
+asBlock :: CI Text -> [DomTree] -> Map (CI Text) Text -> Either SemanticError Block
+asBlock "VSpace" _  = Right . VSpace . lookupAttr "height" True 1
+asBlock t        _  = const $ Left . UnmappedBlockElement . CI.original $ t
+
+asLine :: CI Text -> [DomTree] -> Map (CI Text) Text -> Either SemanticError Line
+asLine "HSpace"  _  = Right . HSpace . lookupAttr "width" True 1
+asLine t         _  = const $ Left . UnmappedLineElement . CI.original $ t
diff --git a/tp-bbcode/src/Thermoprint/Printout/BBCode/Attribute.hs b/tp-bbcode/src/Thermoprint/Printout/BBCode/Attribute.hs
new file mode 100644
index 0000000..538cca2
--- /dev/null
+++ b/tp-bbcode/src/Thermoprint/Printout/BBCode/Attribute.hs
@@ -0,0 +1,39 @@
+{-# LANGUAGE DefaultSignatures #-}
+
+-- | Parsing attributes
+module Thermoprint.Printout.BBCode.Attribute
+       ( Attribute(..)
+       , lookupAttr
+       ) where
+
+import Data.Text (Text)
+import qualified Data.Text as T (unpack, empty)
+
+import Data.Map (Map)
+import qualified Data.Map as Map (lookup)
+
+import Data.CaseInsensitive (CI)
+import qualified Data.CaseInsensitive as CI
+  
+import Text.Read (readMaybe)
+import Data.Maybe (fromMaybe)
+
+import Control.Applicative (Alternative(..))
+
+-- | We build our own version of 'Read' so we can override the presentation used
+--
+-- We provide a default implementation for 'Read a => Attribute a'
+class Attribute a where
+  attrRead :: Text -> Maybe a
+  default attrRead :: Read a => Text -> Maybe a
+  attrRead = readMaybe . T.unpack
+
+instance Attribute Integer
+
+lookupAttr :: Attribute a => CI Text -> Bool -> a -> Map (CI Text) Text -> a
+-- ^ Extract an attribute by name -- the 'Bool' attribute specifies whether we additionally accept the empty string as key
+lookupAttr t emptyOk def attrs = fromMaybe def $ (emptyOk' $ Map.lookup t attrs) >>= attrRead
+  where
+    emptyOk'
+      | emptyOk   = (<|> Map.lookup (CI.mk T.empty) attrs)
+      | otherwise = id