refactor(inventory): propagate UserError for predictable failures

src/modules/inventory/inventory.service.ts

@@ -4,6 +4,7 @@ import { DrizzleClient } from "@/lib/DrizzleClient";
 import { economyService } from "@/modules/economy/economy.service";
 import { levelingService } from "@/modules/leveling/leveling.service";
 import { config } from "@/lib/config";
+import { UserError } from "@/lib/errors";
 import { withTransaction } from "@/lib/db";
 import type { Transaction, ItemUsageData } from "@/lib/types";
 
@@ -28,7 +29,7 @@ export const inventoryService = {
             if (existing) {
                 const newQuantity = (existing.quantity ?? 0n) + quantity;
                 if (newQuantity > config.inventory.maxStackSize) {
-                    throw new Error(`Cannot exceed max stack size of ${config.inventory.maxStackSize}`);
+                    throw new UserError(`Cannot exceed max stack size of ${config.inventory.maxStackSize}`);
                 }
 
                 const [entry] = await txFn.update(inventory)
@@ -49,11 +50,11 @@ export const inventoryService = {
                     .where(eq(inventory.userId, BigInt(userId)));
 
                 if (inventoryCount && inventoryCount.count >= config.inventory.maxSlots) {
-                    throw new Error(`Inventory full (Max ${config.inventory.maxSlots} slots)`);
+                    throw new UserError(`Inventory full (Max ${config.inventory.maxSlots} slots)`);
                 }
 
                 if (quantity > config.inventory.maxStackSize) {
-                    throw new Error(`Cannot exceed max stack size of ${config.inventory.maxStackSize}`);
+                    throw new UserError(`Cannot exceed max stack size of ${config.inventory.maxStackSize}`);
                 }
 
                 const [entry] = await txFn.insert(inventory)
@@ -78,7 +79,7 @@ export const inventoryService = {
             });
 
             if (!existing || (existing.quantity ?? 0n) < quantity) {
-                throw new Error("Insufficient item quantity");
+                throw new UserError("Insufficient item quantity");
             }
 
             if ((existing.quantity ?? 0n) === quantity) {
@@ -119,8 +120,8 @@ export const inventoryService = {
                 where: eq(items.id, itemId),
             });
 
-            if (!item) throw new Error("Item not found");
-            if (!item.price) throw new Error("Item is not for sale");
+            if (!item) throw new UserError("Item not found");
+            if (!item.price) throw new UserError("Item is not for sale");
 
             const totalPrice = item.price * quantity;
 
@@ -151,14 +152,14 @@ export const inventoryService = {
             });
 
             if (!entry || (entry.quantity ?? 0n) < 1n) {
-                throw new Error("You do not own this item.");
+                throw new UserError("You do not own this item.");
             }
 
             const item = entry.item;
             const usageData = item.usageData as ItemUsageData | null;
 
             if (!usageData || !usageData.effects || usageData.effects.length === 0) {
-                throw new Error("This item cannot be used.");
+                throw new UserError("This item cannot be used.");
             }
 
             const results: string[] = [];