chore(space-tool): refactor participant minimum height function

lib/features/modeling/behavior/SpaceToolBehavior.js

@@ -1,7 +1,4 @@
-import {
-  forEach,
-  reduce
-} from 'min-dash';
+import { forEach } from 'min-dash';
 
 import { is } from '../../../util/ModelUtil';
 
@@ -59,6 +56,9 @@ SpaceToolBehavior.$inject = [ 'eventBus' ];
 
 
 // helpers //////////
+function isHorizontal(axis) {
+  return axis === 'x';
+}
 
 /**
  * Get minimum height for participant taking lanes into account.
@@ -69,39 +69,56 @@ SpaceToolBehavior.$inject = [ 'eventBus' ];
  * @returns {Object}
  */
 function getParticipantMinHeight(participant, start) {
-  var lanes = getChildLanes(participant);
+  var lanesMinHeight;
 
-  if (!lanes.length) {
+  if (!hasChildLanes(participant)) {
     return PARTICIPANT_MIN_DIMENSIONS.height;
   }
 
-  function getLanesMinHeight(element) {
-    return reduce(getChildLanes(element), function(minHeight, lane) {
-      if (start >= lane.y && start <= lane.y + lane.height) {
+  lanesMinHeight = getLanesMinHeight(participant, start);
 
-        // resizing lane
-        if (hasChildLanes(lane)) {
-          minHeight += getLanesMinHeight(lane);
-        } else {
-          minHeight += lane.y + LANE_MIN_DIMENSIONS.height - participant.y;
-        }
-      } else if (start <= lane.y) {
-
-        // lane after resizing lane
-        minHeight += lane.height;
-      }
-
-      return minHeight;
-    }, 0);
-  }
-
-  return max(PARTICIPANT_MIN_DIMENSIONS.height, getLanesMinHeight(participant));
+  return max(PARTICIPANT_MIN_DIMENSIONS.height, lanesMinHeight);
 }
 
 function hasChildLanes(element) {
   return !!getChildLanes(element).length;
 }
 
-function isHorizontal(axis) {
-  return axis === 'x';
-}
+function getLanesMinHeight(participant, resizeStart) {
+  var lanes = getChildLanes(participant),
+      resizedLane;
+
+  // find the nested lane which is currently resized
+  resizedLane = findResizedLane(lanes, resizeStart);
+
+  // resized lane cannot shrink below the minimum height
+  // but remaining lanes' dimensions are kept intact
+  return participant.height - resizedLane.height + LANE_MIN_DIMENSIONS.height;
+}
+
+/**
+ * Find nested lane which is currently resized.
+ *
+ * @param {Array<djs.model.Shape>} lanes
+ * @param {number} resizeStart
+ */
+function findResizedLane(lanes, resizeStart) {
+  var i, lane, childLanes;
+
+  for (i = 0; i < lanes.length; i++) {
+    lane = lanes[i];
+
+    // resizing current lane or a lane nested
+    if (resizeStart >= lane.y && resizeStart <= lane.y + lane.height) {
+      childLanes = getChildLanes(lane);
+
+      // a nested lane is resized
+      if (childLanes.length) {
+        return findResizedLane(childLanes, resizeStart);
+      }
+
+      // current lane is the resized one
+      return lane;
+    }
+  }
+}