1 files changed, 21 insertions, 1 deletions
diff --git a/src/containers/map/layers/HoverTileLayer.js b/src/containers/map/layers/HoverTileLayer.js
index b8868233..d8a1d983 100644
--- a/src/containers/map/layers/HoverTileLayer.js
+++ b/src/containers/map/layers/HoverTileLayer.js
@@ -1,11 +1,31 @@
 import {connect} from "react-redux";
 import {toggleTileAtLocation} from "../../../actions/topology";
 import HoverTileLayerComponent from "../../../components/map/layers/HoverTileLayerComponent";
+import {
+    deriveValidNextTilePositions,
+    findPositionInPositions,
+    findPositionInRooms
+} from "../../../util/tile-calculations";
 
 const mapStateToProps = state => {
     return {
         currentRoomInConstruction: state.currentRoomInConstruction,
-        isValid: (x, y) => true, // TODO implement proper validation
+        isValid: (x, y) => {
+            const newRoom = Object.assign({}, state.objects.room[state.currentRoomInConstruction]);
+            const oldRooms = Object.keys(state.objects.room)
+                .map(id => Object.assign({}, state.objects.room[id]))
+                .filter(room => room.id !== state.currentRoomInConstruction);
+
+            [...oldRooms, newRoom].forEach(room => {
+                room.tiles = room.tileIds.map(tileId => state.objects.tile[tileId]);
+            });
+            if (newRoom.tileIds.length === 0) {
+                return findPositionInRooms(oldRooms, x, y) === -1;
+            }
+
+            const validNextPositions = deriveValidNextTilePositions(oldRooms, newRoom.tiles);
+            return findPositionInPositions(validNextPositions, x, y) !== -1;
+        },
     };
 };