1 files changed, 23 insertions, 0 deletions
diff --git a/src/Terminal.hs b/src/Terminal.hs
index 84dfb91..aa7335c 100644
--- a/src/Terminal.hs
+++ b/src/Terminal.hs
@@ -1,9 +1,11 @@
 module Terminal (
     TerminalOutput,
     TerminalLine,
+    TerminalFootnote(..),
     initTerminalOutput,
     newLine,
     redrawLine,
+    newFootnote,
     terminalBlinkStatus,
 ) where
 
@@ -11,6 +13,7 @@ import Control.Concurrent
 import Control.Concurrent.STM
 import Control.Monad
 
+import Data.Function
 import Data.Text (Text)
 import Data.Text qualified as T
 import Data.Text.IO qualified as T
@@ -20,17 +23,30 @@ import System.IO
 
 data TerminalOutput = TerminalOutput
     { outNumLines :: MVar Int
+    , outNextFootnote :: MVar Int
     , outBlinkVar :: TVar Bool
     }
 
+instance Eq TerminalOutput where
+    (==) = (==) `on` outNumLines
+
 data TerminalLine = TerminalLine
     { lineOutput :: TerminalOutput
     , lineNum :: Int
     }
+    deriving (Eq)
+
+data TerminalFootnote = TerminalFootnote
+    { footnoteLine :: TerminalLine
+    , footnoteNumber :: Int
+    , footnoteText :: Text
+    }
+    deriving (Eq)
 
 initTerminalOutput :: IO TerminalOutput
 initTerminalOutput = do
     outNumLines <- newMVar 0
+    outNextFootnote <- newMVar 1
     outBlinkVar <- newTVarIO False
     void $ forkIO $ forever $ do
         threadDelay 500000
@@ -52,5 +68,12 @@ redrawLine TerminalLine {..} text = do
         T.putStr $ "\ESC[s\ESC[" <> T.pack (show moveBy) <> "F" <> text <> "\ESC[u"
         hFlush stdout
 
+newFootnote :: TerminalOutput -> Text -> IO TerminalFootnote
+newFootnote tout@TerminalOutput {..} footnoteText = do
+    modifyMVar outNextFootnote $ \footnoteNumber -> do
+        footnoteLine <- newLine tout $ "[" <> T.pack (show footnoteNumber) <> "] " <> footnoteText
+        hFlush stdout
+        return ( footnoteNumber + 1, TerminalFootnote {..} )
+
 terminalBlinkStatus :: TerminalOutput -> STM Bool
 terminalBlinkStatus TerminalOutput {..} = readTVar outBlinkVar