1 files changed, 60 insertions, 0 deletions
diff --git a/internal/validate/checks.go b/internal/validate/checks.go
index 197b8d3..9cff717 100644
--- a/internal/validate/checks.go
+++ b/internal/validate/checks.go
@@ -521,6 +521,66 @@ func validateCourses(s Source) []Issue {
 	return issues
 }
 
+func validateRoomEnterSteps(s Source) []Issue {
+	var issues []Issue
+	roomIndex := s.World.RoomIndex()
+	itemIDs := s.Items.IDSet()
+	mobIDs := s.Mobs.AllDefIDs()
+
+	for id := range roomIndex {
+		room, err := s.World.LoadRoom(id)
+		if err != nil || len(room.OnEnter) == 0 {
+			continue
+		}
+		for si, step := range room.OnEnter {
+			stepPrefix := fmt.Sprintf("Room %d: on_enter[%d]", id, si)
+			if step.SpawnMob != nil && step.SpawnMob.ID != "" {
+				if _, ok := mobIDs[step.SpawnMob.ID]; !ok {
+					issues = append(issues, Issue{
+						Level:   "ERROR",
+						Type:    "reference",
+						Message: fmt.Sprintf("%s: spawn_mob %q does not exist", stepPrefix, step.SpawnMob.ID),
+					})
+				}
+				for _, wr := range step.SpawnMob.DespawnRooms {
+					if _, ok := roomIndex[wr]; !ok {
+						issues = append(issues, Issue{
+							Level:   "ERROR",
+							Type:    "reference",
+							Message: fmt.Sprintf("%s: spawn_mob despawn_rooms references nonexistent room %d", stepPrefix, wr),
+						})
+					}
+				}
+			}
+			if step.GiveItem != "" && !itemIDs[step.GiveItem] {
+				issues = append(issues, Issue{
+					Level:   "ERROR",
+					Type:    "reference",
+					Message: fmt.Sprintf("%s: give_item %q does not exist", stepPrefix, step.GiveItem),
+				})
+			}
+			if step.TakeItem != "" && !itemIDs[step.TakeItem] {
+				issues = append(issues, Issue{
+					Level:   "ERROR",
+					Type:    "reference",
+					Message: fmt.Sprintf("%s: take_item %q does not exist", stepPrefix, step.TakeItem),
+				})
+			}
+			if step.Teleport > 0 {
+				if _, ok := roomIndex[step.Teleport]; !ok {
+					issues = append(issues, Issue{
+						Level:   "ERROR",
+						Type:    "reference",
+						Message: fmt.Sprintf("%s: teleport to nonexistent room %d", stepPrefix, step.Teleport),
+					})
+				}
+			}
+		}
+	}
+
+	return issues
+}
+
 func validateRoomTriggers(s Source) []Issue {
 	var issues []Issue
 	roomIndex := s.World.RoomIndex()