feat: Redesign flashcard study screen with live shuffle toggle

src/components/flashcards/FlashcardViewer.tsx

@@ -28,7 +28,7 @@ type CardResult = "correct" | "missed";
 
 export function FlashcardViewer({ cards, deckId, isShared = false, initialProgress }: FlashcardViewerProps) {
   const [order, setOrder] = useState<string[]>(
-    initialProgress ? JSON.parse(initialProgress.orderJson) : []
+    initialProgress ? JSON.parse(initialProgress.orderJson) : cards.map((c) => c.id)
   );
   const [currentIndex, setCurrentIndex] = useState(
     initialProgress ? initialProgress.currentIndex : 0
@@ -40,10 +40,10 @@ export function FlashcardViewer({ cards, deckId, isShared = false, initialProgre
       ? JSON.parse(initialProgress.cardResultsJson) 
       : {}
   );
-  const [mode, setMode] = useState<"SEQUENTIAL" | "SHUFFLED">(
+  const [isShuffled, setIsShuffled] = useState<boolean>(
-    initialProgress ? initialProgress.mode : "SEQUENTIAL"
+    initialProgress ? initialProgress.mode === "SHUFFLED" : false
   );
-  const [started, setStarted] = useState(!!initialProgress);
+  const [toastMessage, setToastMessage] = useState<string | null>(null);
   
   // If progress is provided and index is already at or past the end, it means completed
   const [completed, setCompleted] = useState(
@@ -62,29 +62,33 @@ export function FlashcardViewer({ cards, deckId, isShared = false, initialProgre
   const missedCount = Object.values(results).filter((r) => r === "missed").length;
   const totalGraded = correctCount + missedCount;
 
-  // Start a study session
+  // Auto-hide toast
-  function startSession(selectedMode: "SEQUENTIAL" | "SHUFFLED") {
+  useEffect(() => {
-    setMode(selectedMode);
+    if (toastMessage) {
-    let newOrder: string[];
+      const timer = setTimeout(() => setToastMessage(null), 3000);
-    if (selectedMode === "SHUFFLED") {
+      return () => clearTimeout(timer);
-      newOrder = [...cards.map((c) => c.id)];
-      for (let i = newOrder.length - 1; i > 0; i--) {
-        const j = Math.floor(Math.random() * (i + 1));
-        [newOrder[i], newOrder[j]] = [newOrder[j], newOrder[i]];
     }
-    } else {
+  }, [toastMessage]);
-      newOrder = cards.map((c) => c.id);
-    }
-    setOrder(newOrder);
-    setCurrentIndex(0);
-    setResults({});
-    setIsFlipped(false);
-    setHasFlippedOnce(false);
-    setCompleted(false);
-    setStarted(true);
 
-    // Save initial progress
+  function toggleShuffle() {
-    saveProgress(newOrder, 0, {}, selectedMode);
+    const newShuffled = !isShuffled;
+    setIsShuffled(newShuffled);
+    
+    const remainingIds = order.slice(currentIndex);
+    let newRemaining: string[];
+    
+    if (newShuffled) {
+      newRemaining = [...remainingIds].sort(() => Math.random() - 0.5);
+      setToastMessage("Card shuffle on");
+    } else {
+      const originalIndices = new Map(cards.map((c, i) => [c.id, i]));
+      newRemaining = [...remainingIds].sort((a, b) => (originalIndices.get(a) || 0) - (originalIndices.get(b) || 0));
+      setToastMessage("Card shuffle off");
+    }
+    
+    const newOrder = [...order.slice(0, currentIndex), ...newRemaining];
+    setOrder(newOrder);
+    saveProgress(newOrder, currentIndex, results, newShuffled ? "SHUFFLED" : "SEQUENTIAL");
   }
 
   // Grade the current card
@@ -92,6 +96,7 @@ export function FlashcardViewer({ cards, deckId, isShared = false, initialProgre
     (grade: CardResult) => {
       if (!currentCard || !hasFlippedOnce) return;
 
+      setToastMessage(null);
       const newResults = { ...results, [currentCard.id]: grade };
       setResults(newResults);
 
@@ -105,21 +110,21 @@ export function FlashcardViewer({ cards, deckId, isShared = false, initialProgre
 
         if (currentIndex + 1 >= order.length) {
           setCompleted(true);
-          saveProgress(order, currentIndex, newResults, mode);
+          saveProgress(order, currentIndex, newResults, isShuffled ? "SHUFFLED" : "SEQUENTIAL");
         } else {
           const nextIndex = currentIndex + 1;
           setCurrentIndex(nextIndex);
-          saveProgress(order, nextIndex, newResults, mode);
+          saveProgress(order, nextIndex, newResults, isShuffled ? "SHUFFLED" : "SEQUENTIAL");
         }
       }, 350);
     },
-    [currentCard, hasFlippedOnce, results, currentIndex, order, mode]
+    [currentCard, hasFlippedOnce, results, currentIndex, order, isShuffled]
   );
 
   // Keyboard shortcuts
   useEffect(() => {
     function handleKeyDown(e: KeyboardEvent) {
-      if (!started || completed) return;
+      if (completed) return;
 
       if (e.key === " " || e.key === "Enter" || e.key === "ArrowUp" || e.key === "ArrowDown") {
         e.preventDefault();
@@ -136,7 +141,7 @@ export function FlashcardViewer({ cards, deckId, isShared = false, initialProgre
 
     window.addEventListener("keydown", handleKeyDown);
     return () => window.removeEventListener("keydown", handleKeyDown);
-  }, [started, completed, isFlipped, gradeCard]);
+  }, [completed, isFlipped, gradeCard]);
 
   // Touch handlers for swipe
   function handleTouchStart(e: React.TouchEvent) {
@@ -196,7 +201,19 @@ export function FlashcardViewer({ cards, deckId, isShared = false, initialProgre
 
   // Restart handlers
   function restartFullSet() {
-    startSession(mode);
+    let newOrder: string[];
+    if (isShuffled) {
+      newOrder = [...cards.map((c) => c.id)].sort(() => Math.random() - 0.5);
+    } else {
+      newOrder = cards.map((c) => c.id);
+    }
+    setOrder(newOrder);
+    setCurrentIndex(0);
+    setResults({});
+    setIsFlipped(false);
+    setHasFlippedOnce(false);
+    setCompleted(false);
+    saveProgress(newOrder, 0, {}, isShuffled ? "SHUFFLED" : "SEQUENTIAL");
   }
 
   function redoMissed() {
@@ -206,15 +223,8 @@ export function FlashcardViewer({ cards, deckId, isShared = false, initialProgre
 
     if (missedIds.length === 0) return;
 
-    const newOrder = mode === "SHUFFLED"
+    const newOrder = isShuffled
-      ? (() => {
+      ? [...missedIds].sort(() => Math.random() - 0.5)
-          const arr = [...missedIds];
-          for (let i = arr.length - 1; i > 0; i--) {
-            const j = Math.floor(Math.random() * (i + 1));
-            [arr[i], arr[j]] = [arr[j], arr[i]];
-          }
-          return arr;
-        })()
       : missedIds;
 
     setOrder(newOrder);
@@ -223,42 +233,7 @@ export function FlashcardViewer({ cards, deckId, isShared = false, initialProgre
     setIsFlipped(false);
     setHasFlippedOnce(false);
     setCompleted(false);
-    saveProgress(newOrder, 0, {}, mode);
+    saveProgress(newOrder, 0, {}, isShuffled ? "SHUFFLED" : "SEQUENTIAL");
-  }
-
-  // Mode selection (not yet started)
-  if (!started) {
-    return (
-      <div className="flex flex-col items-center justify-center py-16">
-        <div className="bg-bg-surface rounded-2xl border border-border-light shadow-[var(--shadow-card)] p-8 max-w-md w-full text-center">
-          <div className="inline-flex items-center justify-center w-14 h-14 rounded-xl bg-bg-callout mb-4">
-            <svg className="w-7 h-7 text-primary" fill="none" stroke="currentColor" viewBox="0 0 24 24">
-              <path strokeLinecap="round" strokeLinejoin="round" strokeWidth={1.5} d="M19 11H5m14 0a2 2 0 012 2v6a2 2 0 01-2 2H5a2 2 0 01-2-2v-6a2 2 0 012-2m14 0V9a2 2 0 00-2-2M5 11V9a2 2 0 012-2m0 0V5a2 2 0 012-2h6a2 2 0 012 2v2M7 7h10" />
-            </svg>
-          </div>
-          <h3 className="text-lg font-semibold text-text-heading mb-1">
-            {cards.length} cards ready
-          </h3>
-          <p className="text-sm text-text-secondary mb-6">
-            Choose how you&apos;d like to study
-          </p>
-          <div className="flex flex-col gap-3">
-            <button
-              onClick={() => startSession("SEQUENTIAL")}
-              className="w-full py-3 px-4 rounded-lg bg-primary text-white font-medium hover:bg-primary-hover transition-all duration-200 cursor-pointer"
-            >
-              Sequential Order
-            </button>
-            <button
-              onClick={() => startSession("SHUFFLED")}
-              className="w-full py-3 px-4 rounded-lg border border-border text-text-heading font-medium hover:bg-bg-surface-alt transition-all duration-200 cursor-pointer"
-            >
-              Shuffle Cards
-            </button>
-          </div>
-        </div>
-      </div>
-    );
   }
 
   // Completed summary
@@ -410,6 +385,15 @@ export function FlashcardViewer({ cards, deckId, isShared = false, initialProgre
                 </span>
               </div>
             )}
+
+            {/* Toast Notification */}
+            {toastMessage && (
+              <div className="absolute bottom-6 left-1/2 -translate-x-1/2 z-30 animate-fade-in pointer-events-none">
+                <div className="bg-bg-surface-alt/95 backdrop-blur shadow-[var(--shadow-card)] text-text-heading text-sm font-semibold px-6 py-2.5 rounded-full whitespace-nowrap">
+                  {toastMessage}
+                </div>
+              </div>
+            )}
           </div>
 
           <div className="relative w-full mt-6">
@@ -425,7 +409,7 @@ export function FlashcardViewer({ cards, deckId, isShared = false, initialProgre
                   const newResults = { ...results };
                   delete newResults[prevId];
                   setResults(newResults);
-                  saveProgress(order, prevIndex, newResults, mode);
+                  saveProgress(order, prevIndex, newResults, isShuffled ? "SHUFFLED" : "SEQUENTIAL");
                 }}
                 className="absolute left-0 top-0 p-2 rounded-full text-text-muted hover:bg-bg-surface-alt hover:text-text-heading transition-all duration-200 cursor-pointer z-10"
                 title="Previous Card"
@@ -461,6 +445,18 @@ export function FlashcardViewer({ cards, deckId, isShared = false, initialProgre
               )}
             </div>
 
+            <button
+              onClick={toggleShuffle}
+              className={`absolute right-0 top-1 p-2 rounded-full hover:bg-bg-surface-alt transition-all duration-200 cursor-pointer z-10 ${
+                isShuffled ? "text-primary" : "text-text-muted hover:text-text-heading"
+              }`}
+              title={isShuffled ? "Turn shuffle off" : "Turn shuffle on"}
+            >
+              <svg className={`w-5 h-5 ${isShuffled ? "stroke-[3]" : "stroke-2"}`} fill="none" stroke="currentColor" viewBox="0 0 24 24">
+                <path strokeLinecap="round" strokeLinejoin="round" d="M8 7h12m0 0l-4-4m4 4l-4 4m0 6H4m0 0l4 4m-4-4l4-4" />
+              </svg>
+            </button>
+
             <div className="text-center mt-4 text-xs text-text-muted">
               {hasFlippedOnce
                 ? "← Missed · Got It →"