Implement encoder for good

src/PDF/CMap.hs

@@ -18,12 +18,12 @@ import Data.ByteString.Char8 (unpack)
 import Data.ByteString.Char8.Util (
     B16Int(..), b16ToBytes, b16ToInt, toBytes, utf16BEToutf8
   )
-import Data.Map (Map, union)
+import Data.Map (Map, mapWithKey, union)
 import qualified Data.Map as Map (
     adjust, empty, fromList, insert, insertWith, lookup, toList
   )
 import Data.Text (Text)
-import qualified Data.Text as Text (length)
+import qualified Data.Text as Text (length, null, splitAt)
 import qualified PDF.EOL as EOL (charset, parser)
 import PDF.Font (Decoder, Encoder, Font(..))
 import PDF.Object (
@@ -72,7 +72,16 @@ decoder rangesBySize input
         outputSequence -> outputSequence
 
 encoder :: Map Size FromUnicode -> Encoder
-encoder = undefined
+encoder fromUnicodes input
+  | Text.null input = Right ""
+  | otherwise =
+    foldl (<>) (Left "No encoding found") $ mapWithKey tryOn fromUnicodes
+    where
+      tryOn size fromUnicode =
+        let (prefix, end) = Text.splitAt size input in
+        case Map.lookup prefix fromUnicode of
+          Nothing -> Left ""
+          Just code -> (code <>) <$> encoder fromUnicodes end
 
 matches :: ByteString -> CRange -> Bool
 matches code (CRange {fromSequence, toSequence}) =