Add item rarity management and random item generation logic

Repositories/ItemRepository.cs

@@ -7,9 +7,15 @@ namespace Pet.Companion.Repositories
     public class ItemRepository
     {
         private readonly Dictionary<string, Item> _itemTemplates = new();
+        private readonly Dictionary<ItemRarity, List<string>> _itemsByRarity = new();
+        private readonly Random _random = new();
 
         public ItemRepository()
         {
+            foreach (ItemRarity rarity in Enum.GetValues(typeof(ItemRarity)))
+            {
+                _itemsByRarity[rarity] = new List<string>();
+            }
             LoadItemsFromCsv();
         }
 
@@ -33,6 +39,7 @@ namespace Pet.Companion.Repositories
                 };
 
                 _itemTemplates.Add(name, item);
+                _itemsByRarity[rarity].Add(name);
             }
         }
 
@@ -117,5 +124,53 @@ namespace Pet.Companion.Repositories
 
             throw new KeyNotFoundException($"Item template not found: {itemName}");
         }
+
+        /// Usage:
+        /*  var rarityProbabilities = new Dictionary<ItemRarity, int>
+            {
+                { ItemRarity.Common, 50 },     // 50% chance
+                { ItemRarity.Uncommon, 30 },   // 30% chance
+                { ItemRarity.Rare, 15 },       // 15% chance
+                { ItemRarity.Legendary, 5 }    // 5% chance
+            };
+
+            var itemRepo = new ItemRepository();
+            var randomItem = itemRepo.GenerateRandomItem(rarityProbabilities);
+        */
+        public Item GenerateRandomItem(Dictionary<ItemRarity, int> rarityProbabilities)
+        {
+            // Validate probabilities
+            if (rarityProbabilities.Values.Sum() != 100)
+            {
+                throw new ArgumentException("Rarity probabilities must sum to 100");
+            }
+
+            // Generate random number between 0 and 100
+            var roll = _random.Next(1, 101);
+            var currentThreshold = 0;
+
+            // Determine which rarity we hit
+            ItemRarity selectedRarity = ItemRarity.Common;
+            foreach (var probability in rarityProbabilities)
+            {
+                currentThreshold += probability.Value;
+                if (roll <= currentThreshold)
+                {
+                    selectedRarity = probability.Key;
+                    break;
+                }
+            }
+
+            // Get random item from selected rarity
+            var possibleItems = _itemsByRarity[selectedRarity];
+            if (possibleItems.Count == 0)
+            {
+                // Fallback to common if no items of selected rarity
+                possibleItems = _itemsByRarity[ItemRarity.Common];
+            }
+
+            var randomItemName = possibleItems[_random.Next(possibleItems.Count)];
+            return CreateItem(randomItemName);
+        }
     }
 }