add logic to resize AST divs and iframes (prebid#3206)

* add logic to resize AST divs and iframes

* fix import package

* replace AST lookup with new API function

src/secureCreatives.js

@@ -6,7 +6,7 @@
 import events from './events';
 import { fireNativeTrackers } from './native';
 import { EVENTS } from './constants';
-import { isSlotMatchingAdUnitCode } from './utils';
+import { isSlotMatchingAdUnitCode, logWarn } from './utils';
 import { auctionManager } from './auctionManager';
 import find from 'core-js/library/fn/array/find';
 import { isRendererRequired, executeRenderer } from './Renderer';
@@ -84,21 +84,38 @@ function sendAdToCreative(adObject, remoteDomain, source) {
 function resizeRemoteCreative({ adUnitCode, width, height }) {
   // resize both container div + iframe
   ['div', 'iframe'].forEach(elmType => {
-    let elementStyle = getElementByAdUnit(elmType).style;
-    elementStyle.width = `${width}px`;
-    elementStyle.height = `${height}px`;
+    let element = getElementByAdUnit(elmType);
+    if (element) {
+      let elementStyle = element.style;
+      elementStyle.width = width + 'px';
+      elementStyle.height = height + 'px';
+    } else {
+      logWarn(`Unable to locate matching page element for adUnitCode ${adUnitCode}.  Can't resize it to ad's dimensions.  Please review setup.`);
+    }
   });
+
   function getElementByAdUnit(elmType) {
-    return document
-      .getElementById(
-        find(
-          window.googletag
-            .pubads()
-            .getSlots()
-            .filter(isSlotMatchingAdUnitCode(adUnitCode)),
-          slot => slot
-        ).getSlotElementId()
-      )
-      .querySelector(elmType);
+    let id = getElementIdBasedOnAdServer(adUnitCode);
+    let parentDivEle = document.getElementById(id);
+    return parentDivEle && parentDivEle.querySelector(elmType);
+  }
+
+  function getElementIdBasedOnAdServer(adUnitCode) {
+    if (window.googletag) {
+      return getDfpElementId(adUnitCode)
+    } else if (window.apntag) {
+      return getAstElementId(adUnitCode)
+    } else {
+      return adUnitCode;
+    }
+  }
+
+  function getDfpElementId(adUnitCode) {
+    return find(window.googletag.pubads().getSlots().filter(isSlotMatchingAdUnitCode(adUnitCode)), slot => slot).getSlotElementId()
+  }
+
+  function getAstElementId(adUnitCode) {
+    let astTag = window.apntag.getTag(adUnitCode);
+    return astTag && astTag.targetId;
   }
 }