1 files changed, 38 insertions, 14 deletions
diff --git a/internal/validate/checks.go b/internal/validate/checks.go
index b35a3de..cdeee44 100644
--- a/internal/validate/checks.go
+++ b/internal/validate/checks.go
@@ -377,6 +377,44 @@ func validateMobs(s Source) []Issue {
 					id, def.FinishingBlow),
 			})
 		}
+
+		if def.Shop != nil {
+			if def.Shop.BuyPercentage < 0 || def.Shop.ChangePercentage < 0 {
+				issues = append(issues, Issue{
+					Level:   "ERROR",
+					Type:    "reference",
+					Message: fmt.Sprintf("Mob %q: shop buy_percentage/change_percentage must not be negative", id),
+				})
+			}
+			seenShop := map[string]bool{}
+			for _, si := range def.Shop.Items {
+				if si.ItemID == "" {
+					continue
+				}
+				if !itemIDs[si.ItemID] {
+					issues = append(issues, Issue{
+						Level:   "ERROR",
+						Type:    "reference",
+						Message: fmt.Sprintf("Mob %q: shop item %q does not exist", id, si.ItemID),
+					})
+				}
+				if seenShop[si.ItemID] {
+					issues = append(issues, Issue{
+						Level:   "WARN",
+						Type:    "reference",
+						Message: fmt.Sprintf("Mob %q: shop lists item %q more than once", id, si.ItemID),
+					})
+				}
+				seenShop[si.ItemID] = true
+				if si.Stock < 0 {
+					issues = append(issues, Issue{
+						Level:   "ERROR",
+						Type:    "reference",
+						Message: fmt.Sprintf("Mob %q: shop item %q has negative stock", id, si.ItemID),
+					})
+				}
+			}
+		}
 	}
 
 	return issues
@@ -865,7 +903,6 @@ func validateRoomWiring(s Source) []Issue {
 	return issues
 }
 
-
 // validateRoomGrid embeds the entire reachable world on a single 3D grid
 // starting from the configured root rooms and reports when the exit layout
 // cannot be embedded without conflict:
@@ -1170,18 +1207,5 @@ func validateNodeAction(prefix string, na *behavior.NodeAction, itemIDs map[stri
 		}
 	}
 
-	if na.Shop != nil {
-		for _, si := range na.Shop.Items {
-			if si.ItemID != "" && !itemIDs[si.ItemID] {
-				issues = append(issues, Issue{
-					Level: "ERROR",
-					Type:  "reference",
-					Message: fmt.Sprintf("%s: shop item %q does not exist",
-						prefix, si.ItemID),
-				})
-			}
-		}
-	}
-
 	return issues
 }