chore(auto-place): factor out deconflict position into method

lib/features/auto-place/AutoPlaceUtil.js

@@ -34,21 +34,14 @@ function getFlowNodePosition(source, element) {
     y: sourceMid.y
   };
 
-  var existingTarget;
+  var escapeDirection = {
+    y: {
+      margin: 30,
+      rowSize: 80
+    }
+  };
 
-  // make sure we don't place targets a
-  while ((existingTarget = getConnectedAtPosition(source, position, element))) {
-
-    position = {
-      x: position.x,
-      y: Math.max(
-        existingTarget.y + existingTarget.height + 30 + element.height / 2,
-        position.y + 80
-      )
-    };
-  }
-
-  return position;
+  return deconflictPosition(source, element, position, escapeDirection);
 }
 
 module.exports.getFlowNodePosition = getFlowNodePosition;
@@ -153,27 +146,19 @@ function getTextAnnotationPosition(source, element) {
 
   var sourceTrbl = asTRBL(source);
 
-  // todo: adaptive
   var position = {
     x: sourceTrbl.right + 30 + element.width / 2,
     y: sourceTrbl.top - 50 - element.height / 2
   };
 
-  var existingTarget;
+  var escapeDirection = {
+    y: {
+      margin: -30,
+      rowSize: 30
+    }
+  };
 
-  while ((existingTarget = getConnectedAtPosition(source, position, element))) {
-
-    // escape to top
-    position = {
-      x: position.x,
-      y: Math.min(
-        existingTarget.y - 30 - element.height / 2,
-        position.y - 30
-      )
-    };
-  }
-
-  return position;
+  return deconflictPosition(source, element, position, escapeDirection);
 }
 
 module.exports.getTextAnnotationPosition = getTextAnnotationPosition;
@@ -191,21 +176,14 @@ function getDataElementPosition(source, element) {
     y: sourceTrbl.bottom + 40 + element.width / 2
   };
 
-  var existingTarget;
+  var escapeDirection = {
+    x: {
+      margin: 30,
+      rowSize: 80
+    }
+  };
 
-  while ((existingTarget = getConnectedAtPosition(source, position, element))) {
-
-    // escape to right
-    position = {
-      x: Math.min(
-        existingTarget.x + existingTarget.width + 30 + element.width / 2,
-        position.x + 80
-      ),
-      y: position.y
-    };
-  }
-
-  return position;
+  return deconflictPosition(source, element, position, escapeDirection);
 }
 
 module.exports.getDataElementPosition = getDataElementPosition;
@@ -260,3 +238,70 @@ function getConnectedAtPosition(source, position, element) {
 }
 
 module.exports.getConnectedAtPosition = getConnectedAtPosition;
+
+
+/**
+ * Returns a new, position for the given element
+ * based on the given element that is not occupied
+ * by any element connected to source.
+ *
+ * Take into account the escapeDirection (where to move
+ * on positining clashes) in the computation.
+ *
+ * @param {djs.model.Shape} source
+ * @param {djs.model.Shape} element
+ * @param {Point} position
+ * @param {Object} escapeDelta
+ *
+ * @return {Point}
+ */
+function deconflictPosition(source, element, position, escapeDelta) {
+
+  function nextPosition(existingElement) {
+
+    var newPosition = {
+      x: position.x,
+      y: position.y
+    };
+
+    [ 'x', 'y' ].forEach(function(axis) {
+
+      var axisDelta = escapeDelta[axis];
+
+      if (!axisDelta) {
+        return;
+      }
+
+      var dimension = axis === 'x' ? 'width' : 'height';
+
+      var margin = axisDelta.margin,
+          rowSize = axisDelta.rowSize;
+
+      if (margin < 0) {
+        newPosition[axis] = Math.min(
+          existingElement[axis] + margin - element[dimension] / 2,
+          position[axis] - rowSize + margin
+        );
+      } else {
+        newPosition[axis] = Math.max(
+          existingTarget[axis] + existingTarget[dimension] + margin + element[dimension] / 2,
+          position[axis] + rowSize + margin
+        );
+      }
+    });
+
+    return newPosition;
+  }
+
+  var existingTarget;
+
+
+  // deconflict position until free slot is found
+  while ((existingTarget = getConnectedAtPosition(source, position, element))) {
+    position = nextPosition(existingTarget);
+  }
+
+  return position;
+}
+
+module.exports.deconflictPosition = deconflictPosition;