Add confirmation modal for card removal in collection

Implemented comprehensive collection management features:

Backend:
- Created collectionService with 9 API functions
- Added useCollection React hook for state management
- Implemented batch processing for performance
- Added full authentication and authorization

Frontend:
- Enhanced DeckManager with collection status indicators
- Added "Add All Missing Cards" bulk operation button
- Added individual "Add Card" buttons for missing cards
- Implemented loading states and error handling
- Added responsive design with visual badges

Features:
- Visual indicators (yellow for missing, green for owned)
- Bulk add all missing cards functionality
- Individual card addition with quantity tracking
- Real-time collection synchronization
- Success/error notifications

Tests: Build passing (5.98s), linting passing, TypeScript passing

Resolves: #ISSUE-10

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

src/components/CardSearch.tsx

@@ -1,9 +1,12 @@
-import React, { useState } from 'react';
-import { searchCards } from '../services/api';
+import React, { useState, useEffect } from 'react';
+import { RefreshCw, PackagePlus, Loader2, CheckCircle, XCircle, Trash2 } from 'lucide-react';
+import { searchCards, getUserCollection, addCardToCollection } from '../services/api';
 import { Card } from '../types';
+import { useAuth } from '../contexts/AuthContext';
 import MagicCard from './MagicCard';
 
 const CardSearch = () => {
+  const { user } = useAuth();
   const [cardName, setCardName] = useState('');
   const [text, setText] = useState('');
   const [rulesText, setRulesText] = useState('');
@@ -40,6 +43,85 @@ const CardSearch = () => {
   const [loading, setLoading] = useState(false);
   const [error, setError] = useState<string | null>(null);
 
+  // Collection state
+  const [userCollection, setUserCollection] = useState<Map<string, number>>(new Map());
+  const [addingCardId, setAddingCardId] = useState<string | null>(null);
+  const [cardFaceIndex, setCardFaceIndex] = useState<Map<string, number>>(new Map());
+  const [snackbar, setSnackbar] = useState<{ message: string; type: 'success' | 'error' } | null>(null);
+
+  // Load user collection
+  useEffect(() => {
+    const loadUserCollection = async () => {
+      if (!user) return;
+      try {
+        const collection = await getUserCollection(user.id);
+        setUserCollection(collection);
+      } catch (error) {
+        console.error('Error loading user collection:', error);
+      }
+    };
+    loadUserCollection();
+  }, [user]);
+
+  // Helper function to check if a card has an actual back face
+  const isDoubleFaced = (card: Card) => {
+    const backFaceLayouts = ['transform', 'modal_dfc', 'double_faced_token', 'reversible_card'];
+    return card.card_faces && card.card_faces.length > 1 && backFaceLayouts.includes(card.layout);
+  };
+
+  // Get current face index for a card
+  const getCurrentFaceIndex = (cardId: string) => {
+    return cardFaceIndex.get(cardId) || 0;
+  };
+
+  // Toggle card face
+  const toggleCardFace = (cardId: string, totalFaces: number) => {
+    setCardFaceIndex(prev => {
+      const newMap = new Map(prev);
+      const currentIndex = prev.get(cardId) || 0;
+      const nextIndex = (currentIndex + 1) % totalFaces;
+      newMap.set(cardId, nextIndex);
+      return newMap;
+    });
+  };
+
+  // Get card image for current face
+  const getCardImageUri = (card: Card, faceIndex: number = 0) => {
+    if (isDoubleFaced(card) && card.card_faces) {
+      return card.card_faces[faceIndex]?.image_uris?.normal || card.card_faces[faceIndex]?.image_uris?.small;
+    }
+    return card.image_uris?.normal || card.image_uris?.small || card.card_faces?.[0]?.image_uris?.normal;
+  };
+
+  // Add card to collection
+  const handleAddCardToCollection = async (cardId: string) => {
+    if (!user) {
+      setSnackbar({ message: 'Please log in to add cards to your collection', type: 'error' });
+      setTimeout(() => setSnackbar(null), 3000);
+      return;
+    }
+
+    try {
+      setAddingCardId(cardId);
+      await addCardToCollection(user.id, cardId, 1);
+
+      setUserCollection(prev => {
+        const newMap = new Map(prev);
+        const currentQty = newMap.get(cardId) || 0;
+        newMap.set(cardId, currentQty + 1);
+        return newMap;
+      });
+
+      setSnackbar({ message: 'Card added to collection!', type: 'success' });
+    } catch (error) {
+      console.error('Error adding card to collection:', error);
+      setSnackbar({ message: 'Failed to add card to collection', type: 'error' });
+    } finally {
+      setAddingCardId(null);
+      setTimeout(() => setSnackbar(null), 3000);
+    }
+  };
+
   const handleSearch = async (e: React.FormEvent) => {
     e.preventDefault();
     setLoading(true);
@@ -524,18 +606,107 @@ const CardSearch = () => {
 
         {searchResults && searchResults.length > 0 && (
           <div className="grid grid-cols-1 md:grid-cols-2 lg:grid-cols-3 xl:grid-cols-4 gap-4">
-            {searchResults.map((card) => (
-              <div key={card.id} className="bg-gray-800 rounded-lg overflow-hidden">
+            {searchResults.map((card) => {
+              const currentFaceIndex = getCurrentFaceIndex(card.id);
+              const isMultiFaced = isDoubleFaced(card);
+              const inCollection = userCollection.get(card.id) || 0;
+              const isAddingThisCard = addingCardId === card.id;
+
+              const displayName = isMultiFaced && card.card_faces
+                ? card.card_faces[currentFaceIndex]?.name || card.name
+                : card.name;
+
+              return (
+                <div key={card.id} className="bg-gray-800 rounded-lg overflow-hidden hover:ring-2 hover:ring-blue-500 transition-all">
+                  <div className="relative">
+                    {getCardImageUri(card, currentFaceIndex) ? (
+                      <img
+                        src={getCardImageUri(card, currentFaceIndex)}
+                        alt={displayName}
+                        className="w-full h-auto"
+                      />
+                    ) : (
                       <MagicCard card={card} />
+                    )}
+                    {isMultiFaced && (
+                      <button
+                        onClick={(e) => {
+                          e.stopPropagation();
+                          toggleCardFace(card.id, card.card_faces!.length);
+                        }}
+                        className="absolute bottom-2 right-2 bg-purple-600 hover:bg-purple-700 text-white p-2 rounded-full shadow-lg transition-all"
+                        title="Flip card"
+                      >
+                        <RefreshCw size={16} />
+                      </button>
+                    )}
+                  </div>
                   <div className="p-4">
-                  <h3 className="font-bold mb-2">{card.name}</h3>
-                  <p className="text-gray-400 text-sm">{card.type_line}</p>
+                    <div className="flex items-center justify-between mb-2">
+                      <h3 className="font-bold">{displayName}</h3>
+                      {inCollection > 0 && (
+                        <span className="text-xs bg-green-600 px-2 py-0.5 rounded-full flex items-center gap-1">
+                          <CheckCircle size={12} />
+                          x{inCollection}
+                        </span>
+                      )}
+                    </div>
+                    <p className="text-gray-400 text-sm mb-3">
+                      {isMultiFaced && card.card_faces
+                        ? card.card_faces[currentFaceIndex]?.type_line || card.type_line
+                        : card.type_line}
+                    </p>
+                    {card.prices?.usd && (
+                      <div className="text-sm text-gray-400 mb-2">${card.prices.usd}</div>
+                    )}
+                    <button
+                      onClick={() => handleAddCardToCollection(card.id)}
+                      disabled={isAddingThisCard}
+                      className="w-full px-4 py-2 bg-green-600 hover:bg-green-700 disabled:bg-gray-600 disabled:cursor-not-allowed rounded-lg flex items-center justify-center gap-2"
+                      title="Add to collection"
+                    >
+                      {isAddingThisCard ? (
+                        <>
+                          <Loader2 className="animate-spin" size={20} />
+                          Adding...
+                        </>
+                      ) : (
+                        <>
+                          <PackagePlus size={20} />
+                          Add to Collection
+                        </>
+                      )}
+                    </button>
                   </div>
                 </div>
-            ))}
+              );
+            })}
           </div>
         )}
       </div>
+
+      {/* Snackbar */}
+      {snackbar && (
+        <div
+          className={`fixed bottom-4 right-4 p-4 rounded-lg shadow-lg transition-all duration-300 ${
+            snackbar.type === 'success' ? 'bg-green-500' : 'bg-red-500'
+          } text-white z-50`}
+        >
+          <div className="flex items-center justify-between">
+            <div className="flex items-center">
+              {snackbar.type === 'success' ? (
+                <CheckCircle className="mr-2" size={20} />
+              ) : (
+                <XCircle className="mr-2" size={20} />
+              )}
+              <span>{snackbar.message}</span>
+            </div>
+            <button onClick={() => setSnackbar(null)} className="ml-4 text-gray-200 hover:text-white focus:outline-none">
+              <Trash2 size={16} />
+            </button>
+          </div>
+        </div>
+      )}
     </div>
   );
 };

src/components/Collection.tsx

@@ -1,37 +1,191 @@
-import React, { useState } from 'react';
-import { Search, Plus } from 'lucide-react';
+import React, { useState, useEffect } from 'react';
+import { Search, Loader2, Trash2, CheckCircle, XCircle, RefreshCw, Plus, Minus, X } from 'lucide-react';
 import { Card } from '../types';
-import { searchCards } from '../services/api';
+import { getUserCollection, getCardsByIds, addCardToCollection } from '../services/api';
+import { useAuth } from '../contexts/AuthContext';
+import { supabase } from '../lib/supabase';
+import ConfirmModal from './ConfirmModal';
 
 export default function Collection() {
+  const { user } = useAuth();
   const [searchQuery, setSearchQuery] = useState('');
-  const [searchResults, setSearchResults] = useState<Card[]>([]);
   const [collection, setCollection] = useState<{ card: Card; quantity: number }[]>([]);
+  const [filteredCollection, setFilteredCollection] = useState<{ card: Card; quantity: number }[]>([]);
+  const [isLoadingCollection, setIsLoadingCollection] = useState(true);
+  const [hoveredCard, setHoveredCard] = useState<Card | null>(null);
+  const [selectedCard, setSelectedCard] = useState<{ card: Card; quantity: number } | null>(null);
+  const [cardFaceIndex, setCardFaceIndex] = useState<Map<string, number>>(new Map());
+  const [snackbar, setSnackbar] = useState<{ message: string; type: 'success' | 'error' } | null>(null);
+  const [isUpdating, setIsUpdating] = useState(false);
+  const [confirmModal, setConfirmModal] = useState<{
+    isOpen: boolean;
+    cardId: string;
+    cardName: string;
+  }>({ isOpen: false, cardId: '', cardName: '' });
 
-  const handleSearch = async (e: React.FormEvent) => {
-    e.preventDefault();
-    if (!searchQuery.trim()) return;
+  // Helper function to check if a card has an actual back face (not adventure/split/etc)
+  const isDoubleFaced = (card: Card) => {
+    // Only show flip for cards with physical back sides
+    const backFaceLayouts = ['transform', 'modal_dfc', 'double_faced_token', 'reversible_card'];
+    return card.card_faces && card.card_faces.length > 1 && backFaceLayouts.includes(card.layout);
+  };
+
+  // Helper function to get the current face index for a card
+  const getCurrentFaceIndex = (cardId: string) => {
+    return cardFaceIndex.get(cardId) || 0;
+  };
+
+  // Helper function to get the image URI for a card (handling both single and double-faced)
+  const getCardImageUri = (card: Card, faceIndex: number = 0) => {
+    if (isDoubleFaced(card) && card.card_faces) {
+      return card.card_faces[faceIndex]?.image_uris?.normal || card.card_faces[faceIndex]?.image_uris?.small;
+    }
+    return card.image_uris?.normal || card.image_uris?.small;
+  };
+
+  // Helper function to get the large image URI for hover preview
+  const getCardLargeImageUri = (card: Card, faceIndex: number = 0) => {
+    if (isDoubleFaced(card) && card.card_faces) {
+      return card.card_faces[faceIndex]?.image_uris?.large || card.card_faces[faceIndex]?.image_uris?.normal;
+    }
+    return card.image_uris?.large || card.image_uris?.normal;
+  };
+
+  // Toggle card face
+  const toggleCardFace = (cardId: string, totalFaces: number) => {
+    setCardFaceIndex(prev => {
+      const newMap = new Map(prev);
+      const currentIndex = prev.get(cardId) || 0;
+      const nextIndex = (currentIndex + 1) % totalFaces;
+      newMap.set(cardId, nextIndex);
+      return newMap;
+    });
+  };
+
+  // Load user's collection from Supabase on mount
+  useEffect(() => {
+    const loadCollection = async () => {
+      if (!user) {
+        setIsLoadingCollection(false);
+        return;
+      }
 
       try {
-      const cards = await searchCards(searchQuery);
-      setSearchResults(cards);
+        setIsLoadingCollection(true);
+        // Get collection from Supabase (returns Map<card_id, quantity>)
+        const collectionMap = await getUserCollection(user.id);
+
+        if (collectionMap.size === 0) {
+          setCollection([]);
+          return;
+        }
+
+        // Get the actual card data from Scryfall for all cards in collection
+        const cardIds = Array.from(collectionMap.keys());
+        const cards = await getCardsByIds(cardIds);
+
+        // Combine card data with quantities
+        const collectionWithCards = cards.map(card => ({
+          card,
+          quantity: collectionMap.get(card.id) || 0,
+        }));
+
+        setCollection(collectionWithCards);
+        setFilteredCollection(collectionWithCards);
       } catch (error) {
-      console.error('Failed to search cards:', error);
+        console.error('Error loading collection:', error);
+        setSnackbar({ message: 'Failed to load collection', type: 'error' });
+      } finally {
+        setIsLoadingCollection(false);
       }
     };
 
-  const addToCollection = (card: Card) => {
-    setCollection(prev => {
-      const existing = prev.find(c => c.card.id === card.id);
-      if (existing) {
-        return prev.map(c => 
-          c.card.id === card.id 
-            ? { ...c, quantity: c.quantity + 1 }
-            : c
-        );
+    loadCollection();
+  }, [user]);
+
+  // Filter collection based on search query
+  useEffect(() => {
+    if (!searchQuery.trim()) {
+      setFilteredCollection(collection);
+      return;
     }
-      return [...prev, { card, quantity: 1 }];
+
+    const query = searchQuery.toLowerCase();
+    const filtered = collection.filter(({ card }) => {
+      return (
+        card.name.toLowerCase().includes(query) ||
+        card.type_line?.toLowerCase().includes(query) ||
+        card.oracle_text?.toLowerCase().includes(query) ||
+        card.colors?.some(color => color.toLowerCase().includes(query))
+      );
     });
+
+    setFilteredCollection(filtered);
+  }, [searchQuery, collection]);
+
+  // Update card quantity in collection
+  const updateCardQuantity = async (cardId: string, newQuantity: number) => {
+    if (!user || newQuantity < 0) return;
+
+    try {
+      setIsUpdating(true);
+
+      if (newQuantity === 0) {
+        // Remove card from collection
+        const { error } = await supabase
+          .from('collections')
+          .delete()
+          .eq('user_id', user.id)
+          .eq('card_id', cardId);
+
+        if (error) throw error;
+
+        // Update local state
+        setCollection(prev => prev.filter(item => item.card.id !== cardId));
+        setSelectedCard(null);
+        setSnackbar({ message: 'Card removed from collection', type: 'success' });
+      } else {
+        // Update quantity
+        const { error } = await supabase
+          .from('collections')
+          .update({ quantity: newQuantity, updated_at: new Date().toISOString() })
+          .eq('user_id', user.id)
+          .eq('card_id', cardId);
+
+        if (error) throw error;
+
+        // Update local state
+        setCollection(prev =>
+          prev.map(item =>
+            item.card.id === cardId ? { ...item, quantity: newQuantity } : item
+          )
+        );
+
+        if (selectedCard && selectedCard.card.id === cardId) {
+          setSelectedCard({ ...selectedCard, quantity: newQuantity });
+        }
+
+        setSnackbar({ message: 'Quantity updated', type: 'success' });
+      }
+    } catch (error) {
+      console.error('Error updating card quantity:', error);
+      setSnackbar({ message: 'Failed to update quantity', type: 'error' });
+    } finally {
+      setIsUpdating(false);
+      setTimeout(() => setSnackbar(null), 3000);
+    }
+  };
+
+  // Add one to quantity
+  const incrementQuantity = async (cardId: string, currentQuantity: number) => {
+    await updateCardQuantity(cardId, currentQuantity + 1);
+  };
+
+  // Remove one from quantity
+  const decrementQuantity = async (cardId: string, currentQuantity: number) => {
+    if (currentQuantity > 0) {
+      await updateCardQuantity(cardId, currentQuantity - 1);
+    }
   };
 
   return (
@@ -39,83 +193,306 @@ export default function Collection() {
       <div className="max-w-7xl mx-auto">
         <h1 className="text-3xl font-bold mb-6">My Collection</h1>
 
-        {/* Search */}
-        <form onSubmit={handleSearch} className="flex gap-2 mb-8">
-          <div className="relative flex-1">
+        {/* Search within collection */}
+        <div className="mb-8">
+          <div className="relative">
             <Search className="absolute left-3 top-1/2 transform -translate-y-1/2 text-gray-400" size={20} />
             <input
               type="text"
               value={searchQuery}
               onChange={(e) => setSearchQuery(e.target.value)}
               className="w-full pl-10 pr-4 py-2 bg-gray-800 border border-gray-700 rounded-lg focus:ring-2 focus:ring-blue-500 focus:border-transparent"
-              placeholder="Search cards to add..."
+              placeholder="Search your collection by name, type, or text..."
             />
           </div>
-          <button
-            type="submit"
-            className="px-4 py-2 bg-blue-600 hover:bg-blue-700 rounded-lg flex items-center gap-2"
-          >
-            <Search size={20} />
-            Search
-          </button>
-        </form>
-
-        {/* Search Results */}
-        {searchResults.length > 0 && (
-          <div className="mb-8">
-            <h2 className="text-xl font-semibold mb-4">Search Results</h2>
-            <div className="grid grid-cols-1 md:grid-cols-2 lg:grid-cols-3 xl:grid-cols-4 gap-4">
-              {searchResults.map(card => (
-                <div key={card.id} className="bg-gray-800 rounded-lg overflow-hidden">
-                  {card.image_uris?.normal && (
-                    <img
-                      src={card.image_uris.normal}
-                      alt={card.name}
-                      className="w-full h-auto"
-                    />
-                  )}
-                  <div className="p-4">
-                    <h3 className="font-bold mb-2">{card.name}</h3>
-                    <button
-                      onClick={() => addToCollection(card)}
-                      className="w-full px-4 py-2 bg-blue-600 hover:bg-blue-700 rounded-lg flex items-center justify-center gap-2"
-                    >
-                      <Plus size={20} />
-                      Add to Collection
-                    </button>
         </div>
-                </div>
-              ))}
-            </div>
-          </div>
-        )}
 
         {/* Collection */}
         <div>
-          <h2 className="text-xl font-semibold mb-4">My Cards</h2>
-          <div className="grid grid-cols-1 md:grid-cols-2 lg:grid-cols-3 xl:grid-cols-4 gap-4">
-            {collection.map(({ card, quantity }) => (
-              <div key={card.id} className="bg-gray-800 rounded-lg overflow-hidden">
-                {card.image_uris?.normal && (
+          <h2 className="text-xl font-semibold mb-4">
+            {searchQuery ? `Found ${filteredCollection.length} card(s)` : `My Cards (${collection.length} unique, ${collection.reduce((acc, c) => acc + c.quantity, 0)} total)`}
+          </h2>
+
+          {isLoadingCollection ? (
+            <div className="flex items-center justify-center py-12">
+              <Loader2 className="animate-spin text-blue-500" size={48} />
+            </div>
+          ) : collection.length === 0 ? (
+            <div className="text-center py-12 text-gray-400">
+              <p className="text-lg mb-2">Your collection is empty</p>
+              <p className="text-sm">Add cards from the Deck Manager to build your collection</p>
+            </div>
+          ) : filteredCollection.length === 0 ? (
+            <div className="text-center py-12 text-gray-400">
+              <p className="text-lg mb-2">No cards found</p>
+              <p className="text-sm">Try a different search term</p>
+            </div>
+          ) : (
+            <div className="grid grid-cols-3 sm:grid-cols-4 md:grid-cols-6 lg:grid-cols-8 xl:grid-cols-10 gap-3">
+              {filteredCollection.map(({ card, quantity }) => {
+                const currentFaceIndex = getCurrentFaceIndex(card.id);
+                const isMultiFaced = isDoubleFaced(card);
+                const displayName = isMultiFaced && card.card_faces
+                  ? card.card_faces[currentFaceIndex]?.name || card.name
+                  : card.name;
+
+                return (
+                  <div
+                    key={card.id}
+                    className="relative group cursor-pointer"
+                    onMouseEnter={() => setHoveredCard(card)}
+                    onMouseLeave={() => setHoveredCard(null)}
+                    onClick={() => setSelectedCard({ card, quantity })}
+                  >
+                    {/* Small card thumbnail */}
+                    <div className="relative rounded-lg overflow-hidden shadow-lg transition-all group-hover:ring-2 group-hover:ring-blue-500">
                       <img
-                    src={card.image_uris.normal}
-                    alt={card.name}
+                        src={getCardImageUri(card, currentFaceIndex)}
+                        alt={displayName}
                         className="w-full h-auto"
                       />
-                )}
-                <div className="p-4">
-                  <div className="flex justify-between items-center mb-2">
-                    <h3 className="font-bold">{card.name}</h3>
-                    <span className="text-sm bg-blue-600 px-2 py-1 rounded">
+                      {/* Quantity badge */}
+                      <div className="absolute top-1 right-1 bg-blue-600 text-white text-xs font-bold px-2 py-1 rounded-full shadow-lg">
                         x{quantity}
-                    </span>
+                      </div>
+                      {/* Flip button for double-faced cards */}
+                      {isMultiFaced && (
+                        <button
+                          onClick={(e) => {
+                            e.stopPropagation();
+                            toggleCardFace(card.id, card.card_faces!.length);
+                          }}
+                          className="absolute bottom-1 right-1 bg-purple-600 hover:bg-purple-700 text-white p-1 rounded-full shadow-lg transition-all"
+                          title="Flip card"
+                        >
+                          <RefreshCw size={12} />
+                        </button>
+                      )}
+                    </div>
+
+                    {/* Card name below thumbnail */}
+                    <div className="mt-1 text-xs text-center truncate px-1">
+                      {displayName}
                     </div>
                   </div>
+                );
+              })}
             </div>
-            ))}
+          )}
         </div>
       </div>
+
+      {/* Hover Card Preview - only show if no card is selected */}
+      {hoveredCard && !selectedCard && (() => {
+        const currentFaceIndex = getCurrentFaceIndex(hoveredCard.id);
+        const isMultiFaced = isDoubleFaced(hoveredCard);
+        const currentFace = isMultiFaced && hoveredCard.card_faces
+          ? hoveredCard.card_faces[currentFaceIndex]
+          : null;
+
+        const displayName = currentFace?.name || hoveredCard.name;
+        const displayTypeLine = currentFace?.type_line || hoveredCard.type_line;
+        const displayOracleText = currentFace?.oracle_text || hoveredCard.oracle_text;
+
+        return (
+          <div className="fixed top-1/2 right-8 transform -translate-y-1/2 z-40 pointer-events-none">
+            <div className="bg-gray-800 rounded-lg shadow-2xl p-4 max-w-md">
+              <div className="relative">
+                <img
+                  src={getCardLargeImageUri(hoveredCard, currentFaceIndex)}
+                  alt={displayName}
+                  className="w-full h-auto rounded-lg shadow-lg"
+                />
+                {isMultiFaced && (
+                  <div className="absolute top-2 right-2 bg-purple-600 text-white text-xs font-bold px-2 py-1 rounded-full shadow-lg">
+                    Face {currentFaceIndex + 1}/{hoveredCard.card_faces!.length}
+                  </div>
+                )}
+              </div>
+              <div className="mt-3 space-y-2">
+                <h3 className="text-xl font-bold">{displayName}</h3>
+                <p className="text-sm text-gray-400">{displayTypeLine}</p>
+                {displayOracleText && (
+                  <p className="text-sm text-gray-300 border-t border-gray-700 pt-2">
+                    {displayOracleText}
+                  </p>
+                )}
+                {hoveredCard.prices?.usd && (
+                  <div className="text-sm text-green-400 font-semibold border-t border-gray-700 pt-2">
+                    ${hoveredCard.prices.usd}
+                  </div>
+                )}
+              </div>
             </div>
           </div>
         );
+      })()}
+
+      {/* Card Detail Panel - slides in from right */}
+      {selectedCard && (() => {
+        const currentFaceIndex = getCurrentFaceIndex(selectedCard.card.id);
+        const isMultiFaced = isDoubleFaced(selectedCard.card);
+        const currentFace = isMultiFaced && selectedCard.card.card_faces
+          ? selectedCard.card.card_faces[currentFaceIndex]
+          : null;
+
+        const displayName = currentFace?.name || selectedCard.card.name;
+        const displayTypeLine = currentFace?.type_line || selectedCard.card.type_line;
+        const displayOracleText = currentFace?.oracle_text || selectedCard.card.oracle_text;
+
+        return (
+          <>
+            {/* Backdrop */}
+            <div
+              className="fixed inset-0 bg-black bg-opacity-50 z-40 transition-opacity duration-300"
+              onClick={() => setSelectedCard(null)}
+            />
+
+            {/* Sliding Panel */}
+            <div className="fixed top-0 right-0 h-full w-full md:w-96 bg-gray-800 shadow-2xl z-50 overflow-y-auto animate-slide-in-right">
+              <div className="p-6">
+                {/* Close button */}
+                <button
+                  onClick={() => setSelectedCard(null)}
+                  className="absolute top-4 right-4 text-gray-400 hover:text-white transition-colors"
+                >
+                  <X size={24} />
+                </button>
+
+                {/* Card Image */}
+                <div className="relative mb-4">
+                  <img
+                    src={getCardLargeImageUri(selectedCard.card, currentFaceIndex)}
+                    alt={displayName}
+                    className="w-full h-auto rounded-lg shadow-lg"
+                  />
+                  {isMultiFaced && (
+                    <>
+                      <div className="absolute top-2 right-2 bg-purple-600 text-white text-xs font-bold px-2 py-1 rounded-full shadow-lg">
+                        Face {currentFaceIndex + 1}/{selectedCard.card.card_faces!.length}
+                      </div>
+                      <button
+                        onClick={() => toggleCardFace(selectedCard.card.id, selectedCard.card.card_faces!.length)}
+                        className="absolute bottom-2 right-2 bg-purple-600 hover:bg-purple-700 text-white p-2 rounded-full shadow-lg transition-all"
+                        title="Flip card"
+                      >
+                        <RefreshCw size={20} />
+                      </button>
+                    </>
+                  )}
+                </div>
+
+                {/* Card Info */}
+                <div className="space-y-4">
+                  <div>
+                    <h2 className="text-2xl font-bold text-white mb-2">{displayName}</h2>
+                    <p className="text-sm text-gray-400">{displayTypeLine}</p>
+                  </div>
+
+                  {displayOracleText && (
+                    <div className="border-t border-gray-700 pt-3">
+                      <p className="text-sm text-gray-300">{displayOracleText}</p>
+                    </div>
+                  )}
+
+                  {selectedCard.card.prices?.usd && (
+                    <div className="border-t border-gray-700 pt-3">
+                      <div className="text-lg text-green-400 font-semibold">
+                        ${selectedCard.card.prices.usd} each
+                      </div>
+                      <div className="text-sm text-gray-400">
+                        Total value: ${(parseFloat(selectedCard.card.prices.usd) * selectedCard.quantity).toFixed(2)}
+                      </div>
+                    </div>
+                  )}
+
+                  {/* Quantity Management */}
+                  <div className="border-t border-gray-700 pt-3">
+                    <h3 className="text-lg font-semibold mb-3">Quantity in Collection</h3>
+                    <div className="flex items-center justify-between bg-gray-900 rounded-lg p-4">
+                      <button
+                        onClick={() => decrementQuantity(selectedCard.card.id, selectedCard.quantity)}
+                        disabled={isUpdating || selectedCard.quantity === 0}
+                        className="bg-red-600 hover:bg-red-700 disabled:bg-gray-600 disabled:cursor-not-allowed text-white p-2 rounded-lg transition-colors"
+                      >
+                        <Minus size={20} />
+                      </button>
+
+                      <div className="text-center">
+                        <div className="text-3xl font-bold">{selectedCard.quantity}</div>
+                        <div className="text-xs text-gray-400">copies</div>
+                      </div>
+
+                      <button
+                        onClick={() => incrementQuantity(selectedCard.card.id, selectedCard.quantity)}
+                        disabled={isUpdating}
+                        className="bg-green-600 hover:bg-green-700 disabled:bg-gray-600 disabled:cursor-not-allowed text-white p-2 rounded-lg transition-colors"
+                      >
+                        <Plus size={20} />
+                      </button>
+                    </div>
+
+                    {/* Remove from collection button */}
+                    <button
+                      onClick={() => {
+                        setConfirmModal({
+                          isOpen: true,
+                          cardId: selectedCard.card.id,
+                          cardName: displayName,
+                        });
+                      }}
+                      disabled={isUpdating}
+                      className="w-full mt-3 px-4 py-2 bg-red-600 hover:bg-red-700 disabled:bg-gray-600 disabled:cursor-not-allowed text-white rounded-lg flex items-center justify-center gap-2 transition-colors"
+                    >
+                      <Trash2 size={20} />
+                      Remove from Collection
+                    </button>
+                  </div>
+                </div>
+              </div>
+            </div>
+          </>
+        );
+      })()}
+
+      {/* Confirm Modal */}
+      <ConfirmModal
+        isOpen={confirmModal.isOpen}
+        onClose={() => setConfirmModal({ isOpen: false, cardId: '', cardName: '' })}
+        onConfirm={() => {
+          updateCardQuantity(confirmModal.cardId, 0);
+          setConfirmModal({ isOpen: false, cardId: '', cardName: '' });
+        }}
+        title="Remove from Collection"
+        message={`Are you sure you want to remove "${confirmModal.cardName}" from your collection? This action cannot be undone.`}
+        confirmText="Remove"
+        cancelText="Cancel"
+        variant="danger"
+        isLoading={isUpdating}
+      />
+
+      {/* Snackbar */}
+      {snackbar && (
+        <div
+          className={`fixed bottom-4 right-4 p-4 rounded-lg shadow-lg transition-all duration-300 ${
+            snackbar.type === 'success' ? 'bg-green-500' : 'bg-red-500'
+          } text-white z-50`}
+        >
+          <div className="flex items-center justify-between">
+            <div className="flex items-center">
+              {snackbar.type === 'success' ? (
+                <CheckCircle className="mr-2" size={20} />
+              ) : (
+                <XCircle className="mr-2" size={20} />
+              )}
+              <span>{snackbar.message}</span>
+            </div>
+            <button onClick={() => setSnackbar(null)} className="ml-4 text-gray-200 hover:text-white focus:outline-none">
+              <Trash2 size={16} />
+            </button>
+          </div>
+        </div>
+      )}
+    </div>
+  );
 }

src/components/ConfirmModal.tsx

@@ -0,0 +1,105 @@
+import React from 'react';
+import { AlertCircle, CheckCircle, Trash2, AlertTriangle } from 'lucide-react';
+import Modal from './Modal';
+
+interface ConfirmModalProps {
+  isOpen: boolean;
+  onClose: () => void;
+  onConfirm: () => void;
+  title: string;
+  message: string;
+  confirmText?: string;
+  cancelText?: string;
+  variant?: 'danger' | 'warning' | 'info' | 'success';
+  isLoading?: boolean;
+}
+
+export default function ConfirmModal({
+  isOpen,
+  onClose,
+  onConfirm,
+  title,
+  message,
+  confirmText = 'Confirm',
+  cancelText = 'Cancel',
+  variant = 'danger',
+  isLoading = false,
+}: ConfirmModalProps) {
+  const handleConfirm = () => {
+    onConfirm();
+    if (!isLoading) {
+      onClose();
+    }
+  };
+
+  const variantConfig = {
+    danger: {
+      icon: Trash2,
+      iconColor: 'text-red-500',
+      iconBg: 'bg-red-500/10',
+      buttonColor: 'bg-red-600 hover:bg-red-700',
+    },
+    warning: {
+      icon: AlertTriangle,
+      iconColor: 'text-yellow-500',
+      iconBg: 'bg-yellow-500/10',
+      buttonColor: 'bg-yellow-600 hover:bg-yellow-700',
+    },
+    info: {
+      icon: AlertCircle,
+      iconColor: 'text-blue-500',
+      iconBg: 'bg-blue-500/10',
+      buttonColor: 'bg-blue-600 hover:bg-blue-700',
+    },
+    success: {
+      icon: CheckCircle,
+      iconColor: 'text-green-500',
+      iconBg: 'bg-green-500/10',
+      buttonColor: 'bg-green-600 hover:bg-green-700',
+    },
+  };
+
+  const config = variantConfig[variant];
+  const Icon = config.icon;
+
+  return (
+    <Modal isOpen={isOpen} onClose={onClose} size="sm" showCloseButton={false}>
+      <div className="p-6">
+        {/* Icon */}
+        <div className="flex items-center justify-center mb-4">
+          <div className={`${config.iconBg} p-3 rounded-full`}>
+            <Icon className={config.iconColor} size={32} />
+          </div>
+        </div>
+
+        {/* Title */}
+        <h2 className="text-xl font-bold text-white text-center mb-2">
+          {title}
+        </h2>
+
+        {/* Message */}
+        <p className="text-gray-400 text-center mb-6">
+          {message}
+        </p>
+
+        {/* Buttons */}
+        <div className="flex gap-3">
+          <button
+            onClick={onClose}
+            disabled={isLoading}
+            className="flex-1 px-4 py-2 bg-gray-700 hover:bg-gray-600 disabled:bg-gray-600 disabled:cursor-not-allowed text-white rounded-lg transition-colors"
+          >
+            {cancelText}
+          </button>
+          <button
+            onClick={handleConfirm}
+            disabled={isLoading}
+            className={`flex-1 px-4 py-2 ${config.buttonColor} disabled:bg-gray-600 disabled:cursor-not-allowed text-white rounded-lg transition-colors`}
+          >
+            {isLoading ? 'Loading...' : confirmText}
+          </button>
+        </div>
+      </div>
+    </Modal>
+  );
+}

src/components/DeckManager.tsx

@@ -1,7 +1,7 @@
 import React, { useState, useEffect } from 'react';
-import { Plus, Search, Save, Trash2, Upload, Loader2, CheckCircle, XCircle } from 'lucide-react';
+import { Plus, Search, Save, Trash2, Loader2, CheckCircle, XCircle, AlertCircle, PackagePlus, RefreshCw } from 'lucide-react';
 import { Card, Deck } from '../types';
-import { searchCards } from '../services/api';
+import { searchCards, getUserCollection, addCardToCollection, addMultipleCardsToCollection } from '../services/api';
 import { useAuth } from '../contexts/AuthContext';
 import { supabase } from '../lib/supabase';
 import { validateDeck } from '../utils/deckValidation';
@@ -12,38 +12,33 @@ interface DeckManagerProps {
   onSave?: () => void;
 }
 
-const calculateManaCurve = (cards: { card; quantity: number }[]) => {
-  const manaValues = cards.map(({ card }) => {
-    if (!card.mana_cost) return 0;
-    // Basic heuristic: count mana symbols
-    return (card.mana_cost.match(/\{WUBRG0-9]\}/g) || []).length;
-  });
+// const calculateManaCurve = (cards: { card; quantity: number }[]) => {
+//   const manaValues = cards.map(({ card }) => {
+//     if (!card.mana_cost) return 0;
+//     // Basic heuristic: count mana symbols
+//     return (card.mana_cost.match(/\{WUBRG0-9]\}/g) || []).length;
+//   });
 
-  const averageManaValue = manaValues.reduce((a, b) => a + b, 0) / manaValues.length;
-  return averageManaValue;
-};
+//   const averageManaValue = manaValues.reduce((a, b) => a + b, 0) / manaValues.length;
+//   return averageManaValue;
+// };
 
 const suggestLandCountAndDistribution = (
   cards: { card; quantity: number }[],
   format: string
 ) => {
   const formatRules = {
-    standard: { minCards: 60, targetLands: 24.5 },
-    modern: { minCards: 60, targetLands: 24.5 },
-    commander: { minCards: 100, targetLands: 36.5 },
-    legacy: { minCards: 60, targetLands: 24.5 },
-    vintage: { minCards: 60, targetLands: 24.5 },
-    pauper: { minCards: 60, targetLands: 24.5 },
+    standard: { minCards: 60 },
+    modern: { minCards: 60 },
+    commander: { minCards: 100 },
+    legacy: { minCards: 60 },
+    vintage: { minCards: 60 },
+    pauper: { minCards: 60 },
   };
 
-  const { minCards, targetLands } =
+  const { minCards } =
     formatRules[format as keyof typeof formatRules] || formatRules.standard;
   const deckSize = cards.reduce((acc, { quantity }) => acc + quantity, 0);
-  const nonLandCards = cards.reduce(
-    (acc, { card, quantity }) =>
-      card.type_line?.toLowerCase().includes('land') ? acc : acc + quantity,
-    0
-  );
   const landsToAdd = Math.max(0, minCards - deckSize);
 
   const colorCounts = { W: 0, U: 0, B: 0, R: 0, G: 0 };
@@ -77,7 +72,7 @@ const suggestLandCountAndDistribution = (
     landDistribution[color] = Math.round(landsToAdd * proportion);
   }
 
-  let totalDistributed = Object.values(landDistribution).reduce(
+  const totalDistributed = Object.values(landDistribution).reduce(
     (acc, count) => acc + count,
     0
   );
@@ -120,6 +115,147 @@ export default function DeckManager({ initialDeck, onSave }: DeckManagerProps) {
   const [isSaving, setIsSaving] = useState(false);
   const [snackbar, setSnackbar] = useState<{ message: string; type: 'success' | 'error' } | null>(null);
 
+  // Collection management state
+  const [userCollection, setUserCollection] = useState<Map<string, number>>(new Map());
+  const [isLoadingCollection, setIsLoadingCollection] = useState(true);
+  const [addingCardId, setAddingCardId] = useState<string | null>(null);
+  const [isAddingAll, setIsAddingAll] = useState(false);
+  const [cardFaceIndex, setCardFaceIndex] = useState<Map<string, number>>(new Map());
+
+  // Load user collection on component mount
+  useEffect(() => {
+    const loadUserCollection = async () => {
+      if (!user) return;
+
+      try {
+        setIsLoadingCollection(true);
+        const collection = await getUserCollection(user.id);
+        setUserCollection(collection);
+      } catch (error) {
+        console.error('Error loading user collection:', error);
+        setSnackbar({ message: 'Failed to load collection', type: 'error' });
+      } finally {
+        setIsLoadingCollection(false);
+      }
+    };
+
+    loadUserCollection();
+  }, [user]);
+
+  // Helper functions for double-faced cards
+  const isDoubleFaced = (card: Card) => {
+    const backFaceLayouts = ['transform', 'modal_dfc', 'double_faced_token', 'reversible_card'];
+    return card.card_faces && card.card_faces.length > 1 && backFaceLayouts.includes(card.layout);
+  };
+
+  const getCurrentFaceIndex = (cardId: string) => {
+    return cardFaceIndex.get(cardId) || 0;
+  };
+
+  const toggleCardFace = (cardId: string, totalFaces: number) => {
+    setCardFaceIndex(prev => {
+      const newMap = new Map(prev);
+      const currentIndex = prev.get(cardId) || 0;
+      const nextIndex = (currentIndex + 1) % totalFaces;
+      newMap.set(cardId, nextIndex);
+      return newMap;
+    });
+  };
+
+  const getCardImageUri = (card: Card, faceIndex: number = 0) => {
+    if (isDoubleFaced(card) && card.card_faces) {
+      return card.card_faces[faceIndex]?.image_uris?.normal || card.card_faces[faceIndex]?.image_uris?.small;
+    }
+    return card.image_uris?.normal || card.image_uris?.small || card.card_faces?.[0]?.image_uris?.normal;
+  };
+
+  // Helper function to check if a card is in the collection
+  const isCardInCollection = (cardId: string, requiredQuantity: number = 1): boolean => {
+    const ownedQuantity = userCollection.get(cardId) || 0;
+    return ownedQuantity >= requiredQuantity;
+  };
+
+  // Helper function to get missing cards
+  const getMissingCards = () => {
+    return selectedCards.filter(({ card, quantity }) => {
+      return !isCardInCollection(card.id, quantity);
+    });
+  };
+
+  // Add single card to collection
+  const handleAddCardToCollection = async (cardId: string, quantity: number) => {
+    if (!user) return;
+
+    try {
+      setAddingCardId(cardId);
+      await addCardToCollection(user.id, cardId, quantity);
+
+      // Update local collection state
+      setUserCollection(prev => {
+        const newMap = new Map(prev);
+        const currentQty = newMap.get(cardId) || 0;
+        newMap.set(cardId, currentQty + quantity);
+        return newMap;
+      });
+
+      setSnackbar({ message: 'Card added to collection!', type: 'success' });
+    } catch (error) {
+      console.error('Error adding card to collection:', error);
+      setSnackbar({ message: 'Failed to add card to collection', type: 'error' });
+    } finally {
+      setAddingCardId(null);
+      setTimeout(() => setSnackbar(null), 3000);
+    }
+  };
+
+  // Add all missing cards to collection
+  const handleAddAllMissingCards = async () => {
+    if (!user) return;
+
+    const missingCards = getMissingCards();
+    if (missingCards.length === 0) {
+      setSnackbar({ message: 'All cards are already in your collection!', type: 'success' });
+      setTimeout(() => setSnackbar(null), 3000);
+      return;
+    }
+
+    try {
+      setIsAddingAll(true);
+
+      const cardsToAdd = missingCards.map(({ card, quantity }) => {
+        const ownedQuantity = userCollection.get(card.id) || 0;
+        const neededQuantity = Math.max(0, quantity - ownedQuantity);
+        return {
+          cardId: card.id,
+          quantity: neededQuantity,
+        };
+      }).filter(c => c.quantity > 0);
+
+      await addMultipleCardsToCollection(user.id, cardsToAdd);
+
+      // Update local collection state
+      setUserCollection(prev => {
+        const newMap = new Map(prev);
+        cardsToAdd.forEach(({ cardId, quantity }) => {
+          const currentQty = newMap.get(cardId) || 0;
+          newMap.set(cardId, currentQty + quantity);
+        });
+        return newMap;
+      });
+
+      setSnackbar({
+        message: `Successfully added ${cardsToAdd.length} card(s) to collection!`,
+        type: 'success'
+      });
+    } catch (error) {
+      console.error('Error adding cards to collection:', error);
+      setSnackbar({ message: 'Failed to add cards to collection', type: 'error' });
+    } finally {
+      setIsAddingAll(false);
+      setTimeout(() => setSnackbar(null), 3000);
+    }
+  };
+
   const handleSearch = async (e: React.FormEvent) => {
     e.preventDefault();
     if (!searchQuery.trim()) return;
@@ -162,12 +298,6 @@ export default function DeckManager({ initialDeck, onSave }: DeckManagerProps) {
     setSelectedCards(prev => {
       return prev.map(c => {
         if (c.card.id === cardId) {
-          const isBasicLand =
-            c.card.name === 'Plains' ||
-            c.card.name === 'Island' ||
-            c.card.name === 'Swamp' ||
-            c.card.name === 'Mountain' ||
-            c.card.name === 'Forest';
           return { ...c, quantity: quantity };
         }
         return c;
@@ -190,8 +320,6 @@ export default function DeckManager({ initialDeck, onSave }: DeckManagerProps) {
         updatedAt: new Date(),
       };
 
-      const validation = validateDeck(deckToSave);
-
       const deckData = {
         id: deckToSave.id,
         name: deckToSave.name,
@@ -328,11 +456,11 @@ export default function DeckManager({ initialDeck, onSave }: DeckManagerProps) {
               cardsToAdd.push({ card, quantity });
             } else {
               console.warn(`Card not found: ${cardName}`);
-              alert(`Card not found: ${cardName}`);
+              setSnackbar({ message: `Card not found: ${cardName}`, type: 'error' });
             }
           } catch (error) {
             console.error(`Failed to search card ${cardName}:`, error);
-            alert(`Failed to search card ${cardName}: ${error}`);
+            setSnackbar({ message: `Failed to import card: ${cardName}`, type: 'error' });
           }
         }
 
@@ -391,24 +519,82 @@ export default function DeckManager({ initialDeck, onSave }: DeckManagerProps) {
             </form>
 
             <div className="grid grid-cols-1 md:grid-cols-2 xl:grid-cols-3 gap-4">
-              {searchResults.map(card => (
+              {searchResults.map(card => {
+                const currentFaceIndex = getCurrentFaceIndex(card.id);
+                const isMultiFaced = isDoubleFaced(card);
+                const inCollection = userCollection.get(card.id) || 0;
+                const isAddingThisCard = addingCardId === card.id;
+
+                const displayName = isMultiFaced && card.card_faces
+                  ? card.card_faces[currentFaceIndex]?.name || card.name
+                  : card.name;
+
+                return (
                   <div
                     key={card.id}
                     className="bg-gray-800 rounded-lg overflow-hidden hover:ring-2 hover:ring-blue-500 transition-all"
                   >
+                    <div className="relative">
+                      {getCardImageUri(card, currentFaceIndex) ? (
+                        <img
+                          src={getCardImageUri(card, currentFaceIndex)}
+                          alt={displayName}
+                          className="w-full h-auto"
+                        />
+                      ) : (
                         <MagicCard card={card} />
+                      )}
+                      {isMultiFaced && (
+                        <button
+                          onClick={(e) => {
+                            e.stopPropagation();
+                            toggleCardFace(card.id, card.card_faces!.length);
+                          }}
+                          className="absolute bottom-2 right-2 bg-purple-600 hover:bg-purple-700 text-white p-2 rounded-full shadow-lg transition-all"
+                          title="Flip card"
+                        >
+                          <RefreshCw size={16} />
+                        </button>
+                      )}
+                    </div>
                     <div className="p-4">
-                    <h3 className="font-bold mb-2">{card.name}</h3>
+                      <div className="flex items-center justify-between mb-2">
+                        <h3 className="font-bold">{displayName}</h3>
+                        {inCollection > 0 && (
+                          <span className="text-xs bg-green-600 px-2 py-0.5 rounded-full flex items-center gap-1">
+                            <CheckCircle size={12} />
+                            x{inCollection}
+                          </span>
+                        )}
+                      </div>
+                      {card.prices?.usd && (
+                        <div className="text-sm text-gray-400 mb-2">${card.prices.usd}</div>
+                      )}
+                      <div className="flex gap-2">
                         <button
                           onClick={() => addCardToDeck(card)}
-                      className="w-full px-4 py-2 bg-blue-600 hover:bg-blue-700 rounded-lg flex items-center justify-center gap-2"
+                          className="flex-1 px-4 py-2 bg-blue-600 hover:bg-blue-700 rounded-lg flex items-center justify-center gap-2"
                         >
                           <Plus size={20} />
                           Add to Deck
                         </button>
+                        <button
+                          onClick={() => handleAddCardToCollection(card.id, 1)}
+                          disabled={isAddingThisCard}
+                          className="px-4 py-2 bg-green-600 hover:bg-green-700 disabled:bg-gray-600 disabled:cursor-not-allowed rounded-lg flex items-center justify-center gap-2"
+                          title="Add to collection"
+                        >
+                          {isAddingThisCard ? (
+                            <Loader2 className="animate-spin" size={20} />
+                          ) : (
+                            <PackagePlus size={20} />
+                          )}
+                        </button>
                       </div>
                     </div>
-              ))}
+                  </div>
+                );
+              })}
             </div>
           </div>
 
@@ -492,13 +678,51 @@ export default function DeckManager({ initialDeck, onSave }: DeckManagerProps) {
               )}
 
               <div className="space-y-2">
-                <h3 className="font-bold text-xl mb-4">
+                <div className="flex items-center justify-between mb-4">
+                  <h3 className="font-bold text-xl">
                     Cards ({selectedCards.reduce((acc, curr) => acc + curr.quantity, 0)})
                   </h3>
-                {selectedCards.map(({ card, quantity }) => (
+                  {!isLoadingCollection && getMissingCards().length > 0 && (
+                    <div className="flex items-center gap-2 text-sm text-yellow-500">
+                      <AlertCircle size={16} />
+                      <span>{getMissingCards().length} missing</span>
+                    </div>
+                  )}
+                </div>
+
+                {!isLoadingCollection && getMissingCards().length > 0 && (
+                  <button
+                    onClick={handleAddAllMissingCards}
+                    disabled={isAddingAll}
+                    className="w-full px-4 py-2 bg-yellow-600 hover:bg-yellow-700 disabled:bg-gray-600 disabled:cursor-not-allowed rounded-lg flex items-center justify-center gap-2 mb-3 relative"
+                  >
+                    {isAddingAll ? (
+                      <>
+                        <Loader2 className="animate-spin" size={20} />
+                        <span>Adding to collection...</span>
+                      </>
+                    ) : (
+                      <>
+                        <PackagePlus size={20} />
+                        <span>Add All Missing Cards to Collection</span>
+                      </>
+                    )}
+                  </button>
+                )}
+
+                {selectedCards.map(({ card, quantity }) => {
+                  const ownedQuantity = userCollection.get(card.id) || 0;
+                  const isMissing = !isCardInCollection(card.id, quantity);
+                  const neededQuantity = Math.max(0, quantity - ownedQuantity);
+
+                  return (
                     <div
                       key={card.id}
-                    className="flex items-center gap-4 bg-gray-700 p-2 rounded-lg"
+                      className={`flex items-center gap-4 p-2 rounded-lg ${
+                        isMissing
+                          ? 'bg-yellow-900/20 border border-yellow-700/50'
+                          : 'bg-gray-700'
+                      }`}
                     >
                       <img
                         src={card.image_uris?.art_crop}
@@ -506,11 +730,43 @@ export default function DeckManager({ initialDeck, onSave }: DeckManagerProps) {
                         className="w-12 h-12 rounded"
                       />
                       <div className="flex-1">
-                      <h4 className="font-medium">{card.name}</h4>
+                        <h4 className="font-medium flex items-center gap-2">
+                          {card.name}
+                          {isMissing && (
+                            <span className="text-xs bg-yellow-600 px-2 py-0.5 rounded-full flex items-center gap-1">
+                              <AlertCircle size={12} />
+                              Missing {neededQuantity}
+                            </span>
+                          )}
+                          {!isMissing && ownedQuantity > 0 && (
+                            <span className="text-xs bg-green-600 px-2 py-0.5 rounded-full flex items-center gap-1">
+                              <CheckCircle size={12} />
+                              Owned ({ownedQuantity})
+                            </span>
+                          )}
+                        </h4>
                         {card.prices?.usd && (
                           <div className="text-sm text-gray-400">${card.prices.usd}</div>
                         )}
                       </div>
+                      <div className="flex items-center gap-2">
+                        {isMissing && (
+                          <button
+                            onClick={() => handleAddCardToCollection(card.id, neededQuantity)}
+                            disabled={addingCardId === card.id}
+                            className="px-3 py-1 bg-yellow-600 hover:bg-yellow-700 disabled:bg-gray-600 disabled:cursor-not-allowed rounded text-sm flex items-center gap-1"
+                            title={`Add ${neededQuantity} to collection`}
+                          >
+                            {addingCardId === card.id ? (
+                              <Loader2 className="animate-spin" size={16} />
+                            ) : (
+                              <>
+                                <Plus size={16} />
+                                <span className="hidden sm:inline">Add</span>
+                              </>
+                            )}
+                          </button>
+                        )}
                         <input
                           type="number"
                           value={quantity}
@@ -527,7 +783,9 @@ export default function DeckManager({ initialDeck, onSave }: DeckManagerProps) {
                           <Trash2 size={20} />
                         </button>
                       </div>
-                ))}
+                    </div>
+                  );
+                })}
               </div>
 
               <div className="font-bold text-xl">

src/components/MagicCard.tsx

@@ -6,11 +6,14 @@ interface MagicCardProps {
 }
 
 const MagicCard = ({ card }: MagicCardProps) => {
+  // Handle both regular cards and double-faced cards (transform, modal_dfc, etc)
+  const imageUri = card.image_uris?.normal || card.card_faces?.[0]?.image_uris?.normal;
+
   return (
     <div className="relative card-hover animate-fade-in">
-      {card.image_uris?.normal ? (
+      {imageUri ? (
         <img
-          src={card.image_uris.normal}
+          src={imageUri}
           alt={card.name}
           className="w-full h-auto rounded-lg transition-smooth"
         />

src/components/Modal.tsx

@@ -0,0 +1,80 @@
+import React, { useEffect } from 'react';
+import { X } from 'lucide-react';
+
+interface ModalProps {
+  isOpen: boolean;
+  onClose: () => void;
+  children: React.ReactNode;
+  size?: 'sm' | 'md' | 'lg';
+  showCloseButton?: boolean;
+}
+
+export default function Modal({
+  isOpen,
+  onClose,
+  children,
+  size = 'md',
+  showCloseButton = true
+}: ModalProps) {
+  // Close modal on ESC key
+  useEffect(() => {
+    const handleEscape = (e: KeyboardEvent) => {
+      if (e.key === 'Escape' && isOpen) {
+        onClose();
+      }
+    };
+
+    document.addEventListener('keydown', handleEscape);
+    return () => document.removeEventListener('keydown', handleEscape);
+  }, [isOpen, onClose]);
+
+  // Prevent body scroll when modal is open
+  useEffect(() => {
+    if (isOpen) {
+      document.body.style.overflow = 'hidden';
+    } else {
+      document.body.style.overflow = 'unset';
+    }
+
+    return () => {
+      document.body.style.overflow = 'unset';
+    };
+  }, [isOpen]);
+
+  if (!isOpen) return null;
+
+  const sizeClasses = {
+    sm: 'max-w-md',
+    md: 'max-w-lg',
+    lg: 'max-w-2xl',
+  };
+
+  return (
+    <>
+      {/* Backdrop */}
+      <div
+        className="fixed inset-0 bg-black bg-opacity-50 z-50 transition-opacity duration-300 animate-fade-in"
+        onClick={onClose}
+      />
+
+      {/* Modal */}
+      <div className="fixed inset-0 z-50 flex items-center justify-center p-4 pointer-events-none">
+        <div
+          className={`${sizeClasses[size]} w-full bg-gray-800 rounded-lg shadow-2xl pointer-events-auto animate-scale-in`}
+          onClick={(e) => e.stopPropagation()}
+        >
+          {showCloseButton && (
+            <button
+              onClick={onClose}
+              className="absolute top-4 right-4 text-gray-400 hover:text-white transition-colors z-10"
+            >
+              <X size={24} />
+            </button>
+          )}
+
+          {children}
+        </div>
+      </div>
+    </>
+  );
+}

src/examples/CollectionIntegrationExample.tsx

@@ -0,0 +1,412 @@
+/**
+ * EXAMPLE FILE - Collection Integration Examples
+ *
+ * This file demonstrates how to integrate the collection service
+ * into your components. These are complete, working examples that
+ * can be used as templates for implementing the collection features.
+ *
+ * DO NOT DELETE - Reference for frontend integration
+ */
+
+import React, { useState, useEffect } from 'react';
+import { useCollection } from '../hooks/useCollection';
+import { CardOwnershipInfo, MissingCardInfo } from '../services/collectionService';
+import { Card } from '../types';
+import { Plus, CheckCircle, AlertCircle } from 'lucide-react';
+
+/**
+ * Example 1: Display Missing Cards Badge
+ * Shows a badge indicating how many cards are missing from collection
+ */
+export function MissingCardsBadge({ deckId }: { deckId: string }) {
+  const { getMissingCards, loading } = useCollection();
+  const [missingCount, setMissingCount] = useState(0);
+
+  useEffect(() => {
+    const fetchMissing = async () => {
+      const missing = await getMissingCards(deckId);
+      if (missing) {
+        setMissingCount(missing.length);
+      }
+    };
+    fetchMissing();
+  }, [deckId, getMissingCards]);
+
+  if (loading) return <span className="text-gray-400">...</span>;
+
+  return missingCount > 0 ? (
+    <span className="bg-red-500 text-white px-2 py-1 rounded text-sm">
+      {missingCount} cards missing
+    </span>
+  ) : (
+    <span className="bg-green-500 text-white px-2 py-1 rounded text-sm flex items-center gap-1">
+      <CheckCircle size={16} />
+      Complete
+    </span>
+  );
+}
+
+/**
+ * Example 2: Card Ownership Indicator
+ * Shows whether a specific card is owned and in what quantity
+ */
+interface CardOwnershipIndicatorProps {
+  cardId: string;
+  quantityNeeded: number;
+}
+
+export function CardOwnershipIndicator({ cardId, quantityNeeded }: CardOwnershipIndicatorProps) {
+  const { checkCardOwnership } = useCollection();
+  const [owned, setOwned] = useState(0);
+
+  useEffect(() => {
+    const check = async () => {
+      const card = await checkCardOwnership(cardId);
+      setOwned(card?.quantity || 0);
+    };
+    check();
+  }, [cardId, checkCardOwnership]);
+
+  const hasEnough = owned >= quantityNeeded;
+
+  return (
+    <div className={`flex items-center gap-2 ${hasEnough ? 'text-green-500' : 'text-red-500'}`}>
+      {hasEnough ? <CheckCircle size={16} /> : <AlertCircle size={16} />}
+      <span>
+        {owned} / {quantityNeeded} owned
+      </span>
+    </div>
+  );
+}
+
+/**
+ * Example 3: Add Single Card Button
+ * Button to add a specific card to collection
+ */
+interface AddCardButtonProps {
+  cardId: string;
+  cardName: string;
+  quantity?: number;
+  onSuccess?: () => void;
+}
+
+export function AddCardButton({ cardId, cardName, quantity = 1, onSuccess }: AddCardButtonProps) {
+  const { addCard, loading, error, clearError } = useCollection();
+
+  const handleAdd = async () => {
+    clearError();
+    const success = await addCard(cardId, quantity);
+    if (success) {
+      alert(`Added ${quantity}x ${cardName} to collection!`);
+      onSuccess?.();
+    }
+  };
+
+  return (
+    <div>
+      <button
+        onClick={handleAdd}
+        disabled={loading}
+        className="px-4 py-2 bg-blue-600 hover:bg-blue-700 disabled:bg-gray-600 disabled:cursor-not-allowed rounded-lg flex items-center gap-2"
+      >
+        <Plus size={16} />
+        {loading ? 'Adding...' : `Add ${quantity > 1 ? `${quantity}x ` : ''}to Collection`}
+      </button>
+      {error && <p className="text-red-500 text-sm mt-1">{error}</p>}
+    </div>
+  );
+}
+
+/**
+ * Example 4: Add All Missing Cards Button
+ * Button to add all missing cards from a deck to collection
+ */
+export function AddAllMissingCardsButton({ deckId, onSuccess }: { deckId: string; onSuccess?: () => void }) {
+  const { addMissingDeckCards, loading, error, clearError } = useCollection();
+  const [lastResult, setLastResult] = useState<string | null>(null);
+
+  const handleAddAll = async () => {
+    clearError();
+    setLastResult(null);
+
+    const results = await addMissingDeckCards(deckId);
+
+    if (results) {
+      const successCount = results.filter(r => r.success).length;
+      const failCount = results.filter(r => !r.success).length;
+
+      let message = `Added ${successCount} cards to collection`;
+      if (failCount > 0) {
+        message += `, ${failCount} failed`;
+      }
+
+      setLastResult(message);
+
+      if (successCount > 0) {
+        onSuccess?.();
+      }
+    }
+  };
+
+  return (
+    <div>
+      <button
+        onClick={handleAddAll}
+        disabled={loading}
+        className="px-6 py-3 bg-green-600 hover:bg-green-700 disabled:bg-gray-600 disabled:cursor-not-allowed rounded-lg flex items-center gap-2 font-semibold"
+      >
+        {loading ? 'Adding Cards...' : 'Add All Missing Cards to Collection'}
+      </button>
+      {lastResult && <p className="text-green-400 text-sm mt-2">{lastResult}</p>}
+      {error && <p className="text-red-500 text-sm mt-2">{error}</p>}
+    </div>
+  );
+}
+
+/**
+ * Example 5: Deck Card List with Collection Status
+ * Shows all cards in a deck with their collection status
+ */
+interface DeckCardWithStatusProps {
+  deckId: string;
+  cards: Array<{ card: Card; quantity: number }>;
+}
+
+export function DeckCardListWithStatus({ deckId, cards }: DeckCardWithStatusProps) {
+  const { getDeckOwnership, loading } = useCollection();
+  const [ownership, setOwnership] = useState<CardOwnershipInfo[]>([]);
+
+  useEffect(() => {
+    const fetchOwnership = async () => {
+      const data = await getDeckOwnership(deckId);
+      if (data) setOwnership(data);
+    };
+    fetchOwnership();
+  }, [deckId, getDeckOwnership]);
+
+  if (loading) {
+    return <div className="text-gray-400">Loading collection status...</div>;
+  }
+
+  const ownershipMap = new Map(ownership.map(o => [o.card_id, o]));
+
+  return (
+    <div className="space-y-2">
+      {cards.map(({ card, quantity }) => {
+        const status = ownershipMap.get(card.id);
+        const isOwned = status?.owned || false;
+        const quantityOwned = status?.quantity_in_collection || 0;
+        const quantityNeeded = status?.quantity_needed || 0;
+
+        return (
+          <div key={card.id} className="flex items-center gap-4 bg-gray-800 p-4 rounded-lg">
+            <img
+              src={card.image_uris?.art_crop}
+              alt={card.name}
+              className="w-16 h-16 rounded object-cover"
+            />
+
+            <div className="flex-1">
+              <h3 className="font-semibold">{card.name}</h3>
+              <p className="text-sm text-gray-400">
+                Need: {quantity} | Owned: {quantityOwned}
+              </p>
+            </div>
+
+            <div className="flex items-center gap-2">
+              {isOwned ? (
+                <span className="text-green-500 flex items-center gap-1">
+                  <CheckCircle size={20} />
+                  Complete
+                </span>
+              ) : (
+                <>
+                  <span className="text-red-500 flex items-center gap-1">
+                    <AlertCircle size={20} />
+                    Need {quantityNeeded} more
+                  </span>
+                  <AddCardButton
+                    cardId={card.id}
+                    cardName={card.name}
+                    quantity={quantityNeeded}
+                  />
+                </>
+              )}
+            </div>
+          </div>
+        );
+      })}
+    </div>
+  );
+}
+
+/**
+ * Example 6: Bulk Add with Preview
+ * Shows missing cards and allows bulk add with preview
+ */
+export function BulkAddWithPreview({ deckId }: { deckId: string }) {
+  const { getMissingCards, addCardsBulk, loading, error } = useCollection();
+  const [missingCards, setMissingCards] = useState<MissingCardInfo[]>([]);
+  const [showPreview, setShowPreview] = useState(false);
+
+  useEffect(() => {
+    const fetchMissing = async () => {
+      const missing = await getMissingCards(deckId);
+      if (missing) setMissingCards(missing);
+    };
+    fetchMissing();
+  }, [deckId, getMissingCards]);
+
+  const handleBulkAdd = async () => {
+    const cardsToAdd = missingCards.map(card => ({
+      card_id: card.card_id,
+      quantity: card.quantity_needed,
+    }));
+
+    const results = await addCardsBulk(cardsToAdd);
+
+    if (results) {
+      const successCount = results.filter(r => r.success).length;
+      alert(`Successfully added ${successCount} cards to collection!`);
+      setMissingCards([]);
+      setShowPreview(false);
+    }
+  };
+
+  if (missingCards.length === 0) {
+    return (
+      <div className="bg-green-500/10 border border-green-500 rounded-lg p-4 text-green-400">
+        All cards from this deck are in your collection!
+      </div>
+    );
+  }
+
+  return (
+    <div className="space-y-4">
+      <div className="flex items-center justify-between">
+        <h3 className="text-xl font-bold">Missing Cards: {missingCards.length}</h3>
+        <button
+          onClick={() => setShowPreview(!showPreview)}
+          className="text-blue-400 hover:text-blue-300"
+        >
+          {showPreview ? 'Hide' : 'Show'} Preview
+        </button>
+      </div>
+
+      {showPreview && (
+        <div className="bg-gray-800 rounded-lg p-4 space-y-2">
+          {missingCards.map(card => (
+            <div key={card.card_id} className="flex justify-between text-sm">
+              <span>{card.card_id}</span>
+              <span className="text-gray-400">
+                Need {card.quantity_needed} (have {card.quantity_in_collection})
+              </span>
+            </div>
+          ))}
+        </div>
+      )}
+
+      <button
+        onClick={handleBulkAdd}
+        disabled={loading}
+        className="w-full px-6 py-3 bg-green-600 hover:bg-green-700 disabled:bg-gray-600 disabled:cursor-not-allowed rounded-lg font-semibold"
+      >
+        {loading ? 'Adding...' : `Add All ${missingCards.length} Missing Cards`}
+      </button>
+
+      {error && (
+        <div className="bg-red-500/10 border border-red-500 rounded-lg p-4 text-red-400">
+          {error}
+        </div>
+      )}
+    </div>
+  );
+}
+
+/**
+ * Example 7: Complete Deck Editor Integration
+ * Full example of a deck editor with collection integration
+ */
+interface CompleteDeckEditorExampleProps {
+  deckId: string;
+  deckName: string;
+  cards: Array<{ card: Card; quantity: number }>;
+}
+
+export function CompleteDeckEditorExample({ deckId, deckName, cards }: CompleteDeckEditorExampleProps) {
+  const { getDeckOwnership, addMissingDeckCards, loading } = useCollection();
+  const [ownership, setOwnership] = useState<CardOwnershipInfo[]>([]);
+  const [refreshKey, setRefreshKey] = useState(0);
+
+  useEffect(() => {
+    const fetchOwnership = async () => {
+      const data = await getDeckOwnership(deckId);
+      if (data) setOwnership(data);
+    };
+    fetchOwnership();
+  }, [deckId, getDeckOwnership, refreshKey]);
+
+  const handleRefresh = () => setRefreshKey(prev => prev + 1);
+
+  const missingCount = ownership.filter(o => !o.owned).length;
+  const totalCards = cards.length;
+  const ownedCount = totalCards - missingCount;
+  const completionPercent = totalCards > 0 ? Math.round((ownedCount / totalCards) * 100) : 0;
+
+  return (
+    <div className="max-w-4xl mx-auto p-6 space-y-6">
+      {/* Header with stats */}
+      <div className="bg-gray-800 rounded-lg p-6">
+        <h1 className="text-3xl font-bold mb-4">{deckName}</h1>
+
+        <div className="grid grid-cols-3 gap-4 mb-4">
+          <div className="bg-gray-700 rounded p-3">
+            <div className="text-sm text-gray-400">Total Cards</div>
+            <div className="text-2xl font-bold">{totalCards}</div>
+          </div>
+          <div className="bg-gray-700 rounded p-3">
+            <div className="text-sm text-gray-400">Owned</div>
+            <div className="text-2xl font-bold text-green-500">{ownedCount}</div>
+          </div>
+          <div className="bg-gray-700 rounded p-3">
+            <div className="text-sm text-gray-400">Missing</div>
+            <div className="text-2xl font-bold text-red-500">{missingCount}</div>
+          </div>
+        </div>
+
+        {/* Progress bar */}
+        <div className="w-full bg-gray-700 rounded-full h-4 mb-4">
+          <div
+            className="bg-green-500 h-4 rounded-full transition-all"
+            style={{ width: `${completionPercent}%` }}
+          />
+        </div>
+
+        {/* Action buttons */}
+        <div className="flex gap-4">
+          {missingCount > 0 && (
+            <button
+              onClick={async () => {
+                await addMissingDeckCards(deckId);
+                handleRefresh();
+              }}
+              disabled={loading}
+              className="flex-1 px-6 py-3 bg-green-600 hover:bg-green-700 disabled:bg-gray-600 rounded-lg font-semibold"
+            >
+              {loading ? 'Adding...' : `Add All ${missingCount} Missing Cards`}
+            </button>
+          )}
+          <button
+            onClick={handleRefresh}
+            className="px-6 py-3 bg-gray-700 hover:bg-gray-600 rounded-lg"
+          >
+            Refresh
+          </button>
+        </div>
+      </div>
+
+      {/* Card list */}
+      <DeckCardListWithStatus deckId={deckId} cards={cards} />
+    </div>
+  );
+}

src/hooks/useCollection.ts

@@ -0,0 +1,233 @@
+import { useState, useCallback } from 'react';
+import {
+  getUserCollection,
+  getCardInCollection,
+  checkCardsOwnership,
+  getDeckCardOwnership,
+  getMissingCardsFromDeck,
+  addCardToCollection,
+  addCardsToCollectionBulk,
+  addMissingDeckCardsToCollection,
+  removeCardFromCollection,
+  CollectionCard,
+  CardOwnershipInfo,
+  MissingCardInfo,
+} from '../services/collectionService';
+
+/**
+ * Custom React hook for managing card collections
+ * Provides state management and loading/error handling for collection operations
+ */
+export const useCollection = () => {
+  const [loading, setLoading] = useState(false);
+  const [error, setError] = useState<string | null>(null);
+
+  /**
+   * Clear any existing error
+   */
+  const clearError = useCallback(() => {
+    setError(null);
+  }, []);
+
+  /**
+   * Get user's entire collection
+   */
+  const getCollection = useCallback(async (): Promise<CollectionCard[] | null> => {
+    setLoading(true);
+    setError(null);
+    try {
+      const collection = await getUserCollection();
+      return collection;
+    } catch (err) {
+      const errorMessage = err instanceof Error ? err.message : 'Failed to fetch collection';
+      setError(errorMessage);
+      return null;
+    } finally {
+      setLoading(false);
+    }
+  }, []);
+
+  /**
+   * Check if a single card is in the collection
+   */
+  const checkCardOwnership = useCallback(async (cardId: string): Promise<CollectionCard | null> => {
+    setLoading(true);
+    setError(null);
+    try {
+      const card = await getCardInCollection(cardId);
+      return card;
+    } catch (err) {
+      const errorMessage = err instanceof Error ? err.message : 'Failed to check card ownership';
+      setError(errorMessage);
+      return null;
+    } finally {
+      setLoading(false);
+    }
+  }, []);
+
+  /**
+   * Check ownership for multiple cards
+   */
+  const checkMultipleCardsOwnership = useCallback(
+    async (cardIds: string[]): Promise<Map<string, number> | null> => {
+      setLoading(true);
+      setError(null);
+      try {
+        const ownershipMap = await checkCardsOwnership(cardIds);
+        return ownershipMap;
+      } catch (err) {
+        const errorMessage = err instanceof Error ? err.message : 'Failed to check cards ownership';
+        setError(errorMessage);
+        return null;
+      } finally {
+        setLoading(false);
+      }
+    },
+    []
+  );
+
+  /**
+   * Get detailed ownership info for all cards in a deck
+   */
+  const getDeckOwnership = useCallback(
+    async (deckId: string): Promise<CardOwnershipInfo[] | null> => {
+      setLoading(true);
+      setError(null);
+      try {
+        const ownershipInfo = await getDeckCardOwnership(deckId);
+        return ownershipInfo;
+      } catch (err) {
+        const errorMessage = err instanceof Error ? err.message : 'Failed to get deck ownership info';
+        setError(errorMessage);
+        return null;
+      } finally {
+        setLoading(false);
+      }
+    },
+    []
+  );
+
+  /**
+   * Get list of missing cards from a deck
+   */
+  const getMissingCards = useCallback(
+    async (deckId: string): Promise<MissingCardInfo[] | null> => {
+      setLoading(true);
+      setError(null);
+      try {
+        const missingCards = await getMissingCardsFromDeck(deckId);
+        return missingCards;
+      } catch (err) {
+        const errorMessage = err instanceof Error ? err.message : 'Failed to get missing cards';
+        setError(errorMessage);
+        return null;
+      } finally {
+        setLoading(false);
+      }
+    },
+    []
+  );
+
+  /**
+   * Add a single card to collection
+   */
+  const addCard = useCallback(
+    async (cardId: string, quantity: number = 1): Promise<boolean> => {
+      setLoading(true);
+      setError(null);
+      try {
+        await addCardToCollection(cardId, quantity);
+        return true;
+      } catch (err) {
+        const errorMessage = err instanceof Error ? err.message : 'Failed to add card to collection';
+        setError(errorMessage);
+        return false;
+      } finally {
+        setLoading(false);
+      }
+    },
+    []
+  );
+
+  /**
+   * Add multiple cards to collection in bulk
+   */
+  const addCardsBulk = useCallback(
+    async (
+      cards: Array<{ card_id: string; quantity: number }>
+    ): Promise<Array<{ card_id: string; success: boolean; error?: string }> | null> => {
+      setLoading(true);
+      setError(null);
+      try {
+        const results = await addCardsToCollectionBulk(cards);
+        return results;
+      } catch (err) {
+        const errorMessage = err instanceof Error ? err.message : 'Failed to add cards to collection';
+        setError(errorMessage);
+        return null;
+      } finally {
+        setLoading(false);
+      }
+    },
+    []
+  );
+
+  /**
+   * Add all missing cards from a deck to collection
+   */
+  const addMissingDeckCards = useCallback(
+    async (
+      deckId: string
+    ): Promise<Array<{ card_id: string; success: boolean; error?: string }> | null> => {
+      setLoading(true);
+      setError(null);
+      try {
+        const results = await addMissingDeckCardsToCollection(deckId);
+        return results;
+      } catch (err) {
+        const errorMessage = err instanceof Error ? err.message : 'Failed to add missing cards';
+        setError(errorMessage);
+        return null;
+      } finally {
+        setLoading(false);
+      }
+    },
+    []
+  );
+
+  /**
+   * Remove a card from collection
+   */
+  const removeCard = useCallback(
+    async (cardId: string, quantity?: number): Promise<boolean> => {
+      setLoading(true);
+      setError(null);
+      try {
+        await removeCardFromCollection(cardId, quantity);
+        return true;
+      } catch (err) {
+        const errorMessage = err instanceof Error ? err.message : 'Failed to remove card from collection';
+        setError(errorMessage);
+        return false;
+      } finally {
+        setLoading(false);
+      }
+    },
+    []
+  );
+
+  return {
+    loading,
+    error,
+    clearError,
+    getCollection,
+    checkCardOwnership,
+    checkMultipleCardsOwnership,
+    getDeckOwnership,
+    getMissingCards,
+    addCard,
+    addCardsBulk,
+    addMissingDeckCards,
+    removeCard,
+  };
+};

src/services/api.ts

@@ -1,4 +1,5 @@
 import { Card } from '../types';
+import { supabase } from '../lib/supabase';
 
 const SCRYFALL_API = 'https://api.scryfall.com';
 
@@ -52,3 +53,127 @@ export const getCardsByIds = async (cardIds: string[]): Promise<Card[]> => {
 
   return allCards;
 };
+
+// Collection API functions
+export const getUserCollection = async (userId: string): Promise<Map<string, number>> => {
+  const { data, error } = await supabase
+    .from('collections')
+    .select('card_id, quantity')
+    .eq('user_id', userId);
+
+  if (error) {
+    console.error('Error fetching user collection:', error);
+    throw error;
+  }
+
+  // Create a map of card_id to quantity for easy lookup
+  const collectionMap = new Map<string, number>();
+  data?.forEach((item) => {
+    collectionMap.set(item.card_id, item.quantity);
+  });
+
+  return collectionMap;
+};
+
+export const addCardToCollection = async (
+  userId: string,
+  cardId: string,
+  quantity: number = 1
+): Promise<void> => {
+  // Check if card already exists in collection
+  const { data: existing, error: fetchError } = await supabase
+    .from('collections')
+    .select('id, quantity')
+    .eq('user_id', userId)
+    .eq('card_id', cardId)
+    .single();
+
+  if (fetchError && fetchError.code !== 'PGRST116') {
+    // PGRST116 is "not found" error, which is expected for new cards
+    throw fetchError;
+  }
+
+  if (existing) {
+    // Update existing card quantity
+    const { error: updateError } = await supabase
+      .from('collections')
+      .update({
+        quantity: existing.quantity + quantity,
+        updated_at: new Date().toISOString()
+      })
+      .eq('id', existing.id);
+
+    if (updateError) throw updateError;
+  } else {
+    // Insert new card
+    const { error: insertError } = await supabase
+      .from('collections')
+      .insert({
+        user_id: userId,
+        card_id: cardId,
+        quantity: quantity,
+      });
+
+    if (insertError) throw insertError;
+  }
+};
+
+export const addMultipleCardsToCollection = async (
+  userId: string,
+  cards: { cardId: string; quantity: number }[]
+): Promise<void> => {
+  // Fetch existing cards in collection
+  const cardIds = cards.map(c => c.cardId);
+  const { data: existingCards, error: fetchError } = await supabase
+    .from('collections')
+    .select('card_id, quantity, id')
+    .eq('user_id', userId)
+    .in('card_id', cardIds);
+
+  if (fetchError) throw fetchError;
+
+  const existingMap = new Map<string, { id: string; quantity: number }>();
+  existingCards?.forEach((item) => {
+    existingMap.set(item.card_id, { id: item.id, quantity: item.quantity });
+  });
+
+  const toInsert = [];
+  const toUpdate = [];
+
+  for (const card of cards) {
+    const existing = existingMap.get(card.cardId);
+    if (existing) {
+      toUpdate.push({
+        id: existing.id,
+        quantity: existing.quantity + card.quantity,
+        updated_at: new Date().toISOString(),
+      });
+    } else {
+      toInsert.push({
+        user_id: userId,
+        card_id: card.cardId,
+        quantity: card.quantity,
+      });
+    }
+  }
+
+  // Perform bulk operations
+  if (toInsert.length > 0) {
+    const { error: insertError } = await supabase
+      .from('collections')
+      .insert(toInsert);
+
+    if (insertError) throw insertError;
+  }
+
+  if (toUpdate.length > 0) {
+    for (const update of toUpdate) {
+      const { error: updateError } = await supabase
+        .from('collections')
+        .update({ quantity: update.quantity, updated_at: update.updated_at })
+        .eq('id', update.id);
+
+      if (updateError) throw updateError;
+    }
+  }
+};

src/services/collectionService.ts

@@ -0,0 +1,546 @@
+import { supabase } from '../lib/supabase';
+
+/**
+ * Collection Service
+ * Handles all backend operations related to user card collections
+ */
+
+export interface CollectionCard {
+  id: string;
+  user_id: string;
+  card_id: string;
+  quantity: number;
+  created_at: string;
+  updated_at: string;
+}
+
+export interface MissingCardInfo {
+  card_id: string;
+  quantity_needed: number;
+  quantity_in_collection: number;
+}
+
+export interface CardOwnershipInfo {
+  card_id: string;
+  owned: boolean;
+  quantity_in_collection: number;
+  quantity_in_deck: number;
+  quantity_needed: number;
+}
+
+/**
+ * Get the current authenticated user's ID
+ * @throws Error if user is not authenticated
+ */
+const getCurrentUserId = async (): Promise<string> => {
+  const { data: { user }, error } = await supabase.auth.getUser();
+
+  if (error || !user) {
+    throw new Error('User not authenticated');
+  }
+
+  return user.id;
+};
+
+/**
+ * Get all cards in the user's collection
+ * @returns Array of collection cards with user's ownership info
+ */
+export const getUserCollection = async (): Promise<CollectionCard[]> => {
+  try {
+    const userId = await getCurrentUserId();
+
+    const { data, error } = await supabase
+      .from('collections')
+      .select('*')
+      .eq('user_id', userId);
+
+    if (error) {
+      throw new Error(`Failed to fetch collection: ${error.message}`);
+    }
+
+    return data || [];
+  } catch (error) {
+    console.error('Error in getUserCollection:', error);
+    throw error;
+  }
+};
+
+/**
+ * Check if a single card exists in the user's collection
+ * @param cardId - The Scryfall card ID
+ * @returns CollectionCard or null if not found
+ */
+export const getCardInCollection = async (cardId: string): Promise<CollectionCard | null> => {
+  try {
+    const userId = await getCurrentUserId();
+
+    const { data, error } = await supabase
+      .from('collections')
+      .select('*')
+      .eq('user_id', userId)
+      .eq('card_id', cardId)
+      .maybeSingle();
+
+    if (error) {
+      throw new Error(`Failed to check card ownership: ${error.message}`);
+    }
+
+    return data;
+  } catch (error) {
+    console.error('Error in getCardInCollection:', error);
+    throw error;
+  }
+};
+
+/**
+ * Check ownership status for multiple cards
+ * @param cardIds - Array of Scryfall card IDs
+ * @returns Map of card_id to quantity owned
+ */
+export const checkCardsOwnership = async (
+  cardIds: string[]
+): Promise<Map<string, number>> => {
+  try {
+    const userId = await getCurrentUserId();
+
+    // Remove duplicates
+    const uniqueCardIds = [...new Set(cardIds)];
+
+    if (uniqueCardIds.length === 0) {
+      return new Map();
+    }
+
+    const { data, error } = await supabase
+      .from('collections')
+      .select('card_id, quantity')
+      .eq('user_id', userId)
+      .in('card_id', uniqueCardIds);
+
+    if (error) {
+      throw new Error(`Failed to check cards ownership: ${error.message}`);
+    }
+
+    const ownershipMap = new Map<string, number>();
+
+    if (data) {
+      data.forEach(item => {
+        ownershipMap.set(item.card_id, item.quantity || 0);
+      });
+    }
+
+    return ownershipMap;
+  } catch (error) {
+    console.error('Error in checkCardsOwnership:', error);
+    throw error;
+  }
+};
+
+/**
+ * Get detailed card ownership information for a deck
+ * @param deckId - The deck ID to check
+ * @returns Array of CardOwnershipInfo for each card in the deck
+ */
+export const getDeckCardOwnership = async (
+  deckId: string
+): Promise<CardOwnershipInfo[]> => {
+  try {
+    const userId = await getCurrentUserId();
+
+    // First verify the user owns this deck
+    const { data: deck, error: deckError } = await supabase
+      .from('decks')
+      .select('id, user_id')
+      .eq('id', deckId)
+      .eq('user_id', userId)
+      .single();
+
+    if (deckError || !deck) {
+      throw new Error('Deck not found or access denied');
+    }
+
+    // Get all cards in the deck
+    const { data: deckCards, error: deckCardsError } = await supabase
+      .from('deck_cards')
+      .select('card_id, quantity')
+      .eq('deck_id', deckId);
+
+    if (deckCardsError) {
+      throw new Error(`Failed to fetch deck cards: ${deckCardsError.message}`);
+    }
+
+    if (!deckCards || deckCards.length === 0) {
+      return [];
+    }
+
+    // Create a map of card quantities in deck
+    const deckCardMap = new Map<string, number>();
+    deckCards.forEach(card => {
+      const currentQty = deckCardMap.get(card.card_id) || 0;
+      deckCardMap.set(card.card_id, currentQty + (card.quantity || 1));
+    });
+
+    // Get ownership info for all cards
+    const cardIds = Array.from(deckCardMap.keys());
+    const ownershipMap = await checkCardsOwnership(cardIds);
+
+    // Build the result
+    const ownershipInfo: CardOwnershipInfo[] = [];
+
+    deckCardMap.forEach((quantityInDeck, cardId) => {
+      const quantityInCollection = ownershipMap.get(cardId) || 0;
+      const quantityNeeded = Math.max(0, quantityInDeck - quantityInCollection);
+
+      ownershipInfo.push({
+        card_id: cardId,
+        owned: quantityInCollection >= quantityInDeck,
+        quantity_in_collection: quantityInCollection,
+        quantity_in_deck: quantityInDeck,
+        quantity_needed: quantityNeeded,
+      });
+    });
+
+    return ownershipInfo;
+  } catch (error) {
+    console.error('Error in getDeckCardOwnership:', error);
+    throw error;
+  }
+};
+
+/**
+ * Get list of missing cards from a deck
+ * @param deckId - The deck ID to check
+ * @returns Array of missing cards with quantity needed
+ */
+export const getMissingCardsFromDeck = async (
+  deckId: string
+): Promise<MissingCardInfo[]> => {
+  try {
+    const ownershipInfo = await getDeckCardOwnership(deckId);
+
+    return ownershipInfo
+      .filter(info => !info.owned)
+      .map(info => ({
+        card_id: info.card_id,
+        quantity_needed: info.quantity_needed,
+        quantity_in_collection: info.quantity_in_collection,
+      }));
+  } catch (error) {
+    console.error('Error in getMissingCardsFromDeck:', error);
+    throw error;
+  }
+};
+
+/**
+ * Add a single card to the user's collection
+ * If the card already exists, increment its quantity
+ * @param cardId - The Scryfall card ID
+ * @param quantity - The quantity to add (default: 1)
+ * @returns The updated or created collection card
+ */
+export const addCardToCollection = async (
+  cardId: string,
+  quantity: number = 1
+): Promise<CollectionCard> => {
+  try {
+    if (!cardId || cardId.trim() === '') {
+      throw new Error('Invalid card ID');
+    }
+
+    if (quantity < 1) {
+      throw new Error('Quantity must be at least 1');
+    }
+
+    const userId = await getCurrentUserId();
+
+    // Check if card already exists in collection
+    const existingCard = await getCardInCollection(cardId);
+
+    if (existingCard) {
+      // Update existing card quantity
+      const newQuantity = existingCard.quantity + quantity;
+
+      const { data, error } = await supabase
+        .from('collections')
+        .update({
+          quantity: newQuantity,
+          updated_at: new Date().toISOString(),
+        })
+        .eq('id', existingCard.id)
+        .select()
+        .single();
+
+      if (error) {
+        throw new Error(`Failed to update card quantity: ${error.message}`);
+      }
+
+      return data;
+    } else {
+      // Insert new card
+      const { data, error } = await supabase
+        .from('collections')
+        .insert({
+          user_id: userId,
+          card_id: cardId,
+          quantity: quantity,
+        })
+        .select()
+        .single();
+
+      if (error) {
+        throw new Error(`Failed to add card to collection: ${error.message}`);
+      }
+
+      return data;
+    }
+  } catch (error) {
+    console.error('Error in addCardToCollection:', error);
+    throw error;
+  }
+};
+
+/**
+ * Add multiple cards to the user's collection in bulk
+ * @param cards - Array of {card_id, quantity} objects
+ * @returns Array of results with success/failure status for each card
+ */
+export const addCardsToCollectionBulk = async (
+  cards: Array<{ card_id: string; quantity: number }>
+): Promise<Array<{ card_id: string; success: boolean; error?: string }>> => {
+  try {
+    if (!cards || cards.length === 0) {
+      throw new Error('No cards provided');
+    }
+
+    // Validate all cards first
+    const validationErrors: string[] = [];
+    cards.forEach((card, index) => {
+      if (!card.card_id || card.card_id.trim() === '') {
+        validationErrors.push(`Card at index ${index} has invalid ID`);
+      }
+      if (card.quantity < 1) {
+        validationErrors.push(`Card at index ${index} has invalid quantity`);
+      }
+    });
+
+    if (validationErrors.length > 0) {
+      throw new Error(`Validation failed: ${validationErrors.join(', ')}`);
+    }
+
+    const userId = await getCurrentUserId();
+
+    // Get current collection state for all cards
+    const cardIds = cards.map(c => c.card_id);
+
+    // Prepare updates and inserts
+    const toUpdate: Array<{ id: string; card_id: string; quantity: number }> = [];
+    const toInsert: Array<{ user_id: string; card_id: string; quantity: number }> = [];
+
+    // First, get existing collection entries for update
+    const { data: existingCards, error: fetchError } = await supabase
+      .from('collections')
+      .select('id, card_id, quantity')
+      .eq('user_id', userId)
+      .in('card_id', cardIds);
+
+    if (fetchError) {
+      throw new Error(`Failed to fetch existing cards: ${fetchError.message}`);
+    }
+
+    const existingCardsMap = new Map(
+      (existingCards || []).map(card => [card.card_id, card])
+    );
+
+    // Categorize cards for update or insert
+    cards.forEach(card => {
+      const existing = existingCardsMap.get(card.card_id);
+
+      if (existing) {
+        toUpdate.push({
+          id: existing.id,
+          card_id: card.card_id,
+          quantity: existing.quantity + card.quantity,
+        });
+      } else {
+        toInsert.push({
+          user_id: userId,
+          card_id: card.card_id,
+          quantity: card.quantity,
+        });
+      }
+    });
+
+    const results: Array<{ card_id: string; success: boolean; error?: string }> = [];
+
+    // Process updates
+    for (const updateCard of toUpdate) {
+      try {
+        const { error } = await supabase
+          .from('collections')
+          .update({
+            quantity: updateCard.quantity,
+            updated_at: new Date().toISOString(),
+          })
+          .eq('id', updateCard.id);
+
+        if (error) {
+          results.push({
+            card_id: updateCard.card_id,
+            success: false,
+            error: error.message,
+          });
+        } else {
+          results.push({
+            card_id: updateCard.card_id,
+            success: true,
+          });
+        }
+      } catch (err) {
+        results.push({
+          card_id: updateCard.card_id,
+          success: false,
+          error: err instanceof Error ? err.message : 'Unknown error',
+        });
+      }
+    }
+
+    // Process inserts in batches (Supabase recommends batches of 1000)
+    const batchSize = 1000;
+    for (let i = 0; i < toInsert.length; i += batchSize) {
+      const batch = toInsert.slice(i, i + batchSize);
+
+      try {
+        const { error } = await supabase
+          .from('collections')
+          .insert(batch);
+
+        if (error) {
+          // If batch fails, mark all as failed
+          batch.forEach(card => {
+            results.push({
+              card_id: card.card_id,
+              success: false,
+              error: error.message,
+            });
+          });
+        } else {
+          // Mark all as success
+          batch.forEach(card => {
+            results.push({
+              card_id: card.card_id,
+              success: true,
+            });
+          });
+        }
+      } catch (err) {
+        // If batch fails with exception, mark all as failed
+        batch.forEach(card => {
+          results.push({
+            card_id: card.card_id,
+            success: false,
+            error: err instanceof Error ? err.message : 'Unknown error',
+          });
+        });
+      }
+    }
+
+    return results;
+  } catch (error) {
+    console.error('Error in addCardsToCollectionBulk:', error);
+    throw error;
+  }
+};
+
+/**
+ * Add all missing cards from a deck to the user's collection
+ * @param deckId - The deck ID
+ * @returns Array of results with success/failure status for each card
+ */
+export const addMissingDeckCardsToCollection = async (
+  deckId: string
+): Promise<Array<{ card_id: string; success: boolean; error?: string }>> => {
+  try {
+    const userId = await getCurrentUserId();
+
+    // Verify deck ownership
+    const { data: deck, error: deckError } = await supabase
+      .from('decks')
+      .select('id')
+      .eq('id', deckId)
+      .eq('user_id', userId)
+      .single();
+
+    if (deckError || !deck) {
+      throw new Error('Deck not found or access denied');
+    }
+
+    // Get missing cards
+    const missingCards = await getMissingCardsFromDeck(deckId);
+
+    if (missingCards.length === 0) {
+      return [];
+    }
+
+    // Convert to format for bulk add
+    const cardsToAdd = missingCards.map(card => ({
+      card_id: card.card_id,
+      quantity: card.quantity_needed,
+    }));
+
+    return await addCardsToCollectionBulk(cardsToAdd);
+  } catch (error) {
+    console.error('Error in addMissingDeckCardsToCollection:', error);
+    throw error;
+  }
+};
+
+/**
+ * Remove a card from the user's collection
+ * @param cardId - The Scryfall card ID
+ * @param quantity - The quantity to remove (default: all)
+ * @returns true if successful
+ */
+export const removeCardFromCollection = async (
+  cardId: string,
+  quantity?: number
+): Promise<boolean> => {
+  try {
+    const existingCard = await getCardInCollection(cardId);
+
+    if (!existingCard) {
+      throw new Error('Card not found in collection');
+    }
+
+    // If no quantity specified or quantity >= existing, delete the entry
+    if (!quantity || quantity >= existingCard.quantity) {
+      const { error } = await supabase
+        .from('collections')
+        .delete()
+        .eq('id', existingCard.id);
+
+      if (error) {
+        throw new Error(`Failed to remove card: ${error.message}`);
+      }
+    } else {
+      // Otherwise, decrease the quantity
+      const newQuantity = existingCard.quantity - quantity;
+
+      const { error } = await supabase
+        .from('collections')
+        .update({
+          quantity: newQuantity,
+          updated_at: new Date().toISOString(),
+        })
+        .eq('id', existingCard.id);
+
+      if (error) {
+        throw new Error(`Failed to update card quantity: ${error.message}`);
+      }
+    }
+
+    return true;
+  } catch (error) {
+    console.error('Error in removeCardFromCollection:', error);
+    throw error;
+  }
+};

src/types/index.ts

@@ -16,6 +16,20 @@ export interface Card {
   type_line?: string;
   oracle_text?: string;
   colors?: string[];
+  prices?: {
+    usd?: string;
+    usd_foil?: string;
+    eur?: string;
+  };
+}
+
+export interface Collection {
+  id: string;
+  user_id: string;
+  card_id: string;
+  quantity: number;
+  created_at: string;
+  updated_at: string;
 }
 
 export interface Deck {