Add selection to multiple choice question.

cards/example.txt

@@ -1,3 +1,10 @@
+# Multiple choice question, (only one answer is right)
+- Option 1
+* Option 2 (this is the correct answer)
+- Option 3
+- Option 4
+
+---
 # ipRGC
 intrinsically photosensitive Retinal Ganglion Cell
 
@@ -6,11 +13,3 @@ intrinsically photosensitive Retinal Ganglion Cell
 Part of the eye that turns light into electrical neural impulses.
 
 ---
-
-# Multiple choice question, (only one answer is right)
-- Option 1
-* Option 2 (this is the correct answer)
-- Option 3
-- Option 4
-
----

src/Lib.hs

@@ -1,4 +1,5 @@
 {-# LANGUAGE TemplateHaskell #-}
+
 module Lib where
 
 import System.IO (stdin, hReady, hSetEcho, hSetBuffering, BufferMode(NoBuffering))
@@ -11,16 +12,29 @@ import qualified Brick.Widgets.Border.Style as BS
 import qualified Brick.Widgets.Center as C
 import qualified Graphics.Vty as V
 
+type Event = ()
+type Name = ()
+
+data CardState = 
+    DefinitionState
+  { _flipped        :: Bool }
+  | MultipleChoiceState
+  { _selected       :: Int
+  , _nChoices       :: Int }
+
 data State = State
   { _cards          :: [Card]     -- list of flashcards
   , _index          :: Int        -- current card index
-  , _correct  :: Int      -- not implemented, but for score keeping
+  , _currentCard    :: Card
+  , _cardState      :: CardState
   }
 
+makeLenses ''CardState
 makeLenses ''State
 
-type Event = ()
-type Name = ()
+defaultCardState :: Card -> CardState
+defaultCardState Definition{} = DefinitionState { _flipped = False }
+defaultCardState (MultipleChoice _ _ ics) = MultipleChoiceState { _selected = 0, _nChoices = length ics + 1}
 
 app :: App State Event Name
 app = App 
@@ -44,8 +58,8 @@ drawDescr :: String -> Widget Name
 drawDescr descr = padLeftRight 1 $
                   strWrap descr
 
-listMultipleChoice :: CorrectOption -> [IncorrectOption] -> String
-listMultipleChoice c = concat . reverse . listMultipleChoice' [] 0 c
+listMultipleChoice :: CorrectOption -> [IncorrectOption] -> [String]
+listMultipleChoice c = reverse . listMultipleChoice' [] 0 c
   where listMultipleChoice' opts i c@(CorrectOption j cStr) [] = 
           if i == j
             then cStr : opts
@@ -62,7 +76,14 @@ drawCardUI s =
                               drawHeader title <=> drawDescr descr
                               
     MultipleChoice question correct others -> drawCardBox $
-                                              drawHeader question <=> drawDescr (listMultipleChoice correct others)
+                                              drawHeader question <=> drawOptions (listMultipleChoice correct others) s
+
+drawOptions :: [String] -> State -> Widget Name
+drawOptions options s = case s ^. cardState of
+  MultipleChoiceState i _  -> drawDescr (concat formattedOptions)
+                              -- Add "* " to the beginning of selected option
+                              where formattedOptions = options & ix i %~ ("* "++) 
+  _                        -> error "impossible"
 
 drawCardBox :: Widget Name -> Widget Name
 drawCardBox w = C.center $
@@ -79,6 +100,14 @@ handleEvent s (VtyEvent (V.EvKey V.KEnter []))              = next s
 handleEvent s (VtyEvent (V.EvKey V.KRight []))              = next s
 handleEvent s (VtyEvent (V.EvKey (V.KChar ' ') []))         = next s
 handleEvent s (VtyEvent (V.EvKey V.KLeft  []))              = previous s
+handleEvent s (VtyEvent (V.EvKey V.KUp []))                 = continue $
+  case s ^. cardState of
+    MultipleChoiceState i _ -> if i > 0 then s & (cardState.selected) -~ 1 else s
+    _ -> s
+handleEvent s (VtyEvent (V.EvKey V.KDown []))                 = continue $
+  case s ^. cardState of
+    MultipleChoiceState i nChoices -> if i < nChoices - 1 then s & (cardState.selected) +~ 1 else s
+    _ -> s
 handleEvent s _                                             = continue s
   
 titleAttr :: AttrName
@@ -89,8 +118,8 @@ textboxAttr = attrName "textbox"
 
 theMap :: AttrMap
 theMap = attrMap V.defAttr
-  [(titleAttr, bg V.green `V.withStyle` V.bold `V.withStyle` V.underline)
-  ,(textboxAttr, V.defAttr)
+  [ (titleAttr, bg V.green `V.withStyle` V.bold `V.withStyle` V.underline)
+  , (textboxAttr, V.defAttr)
   ]
  
 handleFilePath :: FilePath -> IO String
@@ -101,7 +130,10 @@ runBrickFlashcards input = do
   let cards = case parseCards input of
               Left parseError -> error (show parseError)
               Right result -> result 
-  let initialState = State cards 0 0
+  let initialState = State { _cards = cards
+                           , _index = 0
+                           , _currentCard = head cards
+                           , _cardState = defaultCardState (head cards)}
   finalState <- defaultMain app initialState
   pure ()
 
@@ -114,3 +146,4 @@ next s = if (s ^. index + 1) < length (s ^. cards)
 previous :: State -> EventM Name (Next State)
 previous s | s ^. index > 0 = continue $ s & index %~ subtract 1
            | otherwise      = continue s
+