Add a Font class type to allow text rendition schemes other than CMaps

Hufflepdf.cabal

@@ -27,6 +27,7 @@ library
                      , PDF.Update
   other-modules:       Data.ByteString.Char8.Util
                      , PDF.Body
+                     , PDF.Font
   -- other-extensions:    
   build-depends:       attoparsec
                      , base >=4.9 && <4.13

src/PDF/CMap.hs

@@ -1,4 +1,6 @@
 {-# LANGUAGE NamedFieldPuns #-}
+{-# LANGUAGE FlexibleInstances #-}
+{-# LANGUAGE TypeSynonymInstances #-}
 module PDF.CMap (
       CMap
     , CMappers
@@ -19,6 +21,7 @@ import Data.ByteString.Char8.Util (
 import Data.Map (Map, union)
 import qualified Data.Map as Map (adjust, empty, fromList, insertWith)
 import qualified PDF.EOL as EOL (charset, parser)
+import PDF.Font (Font(..))
 import PDF.Object (
       DirectObject(..), Name, StringObject(..)
     , blank, directObject, integer, line, stringObject
@@ -35,6 +38,9 @@ data CRange = CRange {
 type RangeSize = Int
 type CMap = Map RangeSize [CRange]
 
+instance Font CMap where
+  decode = undefined
+
 emptyCMap :: CMap
 emptyCMap = Map.empty
 

src/PDF/Font.hs

@@ -0,0 +1,9 @@
+module PDF.Font (
+    Font(..)
+  ) where
+
+import Data.ByteString (ByteString)
+import PDF.Object (StringObject)
+
+class Font a where
+  decode :: a -> StringObject -> ByteString