From 1cb490f822ae36e6b920cddce2824ae6400e453d Mon Sep 17 00:00:00 2001
From: "Hedden, Kyle Matthew" <kyle.hedden@verizonwireless.com>
Date: Mon, 18 Sep 2023 19:20:26 -0400
Subject: [PATCH] Add will render event to avoid circumvent
 addRemoveListItemBehavior conflict. Page concurrent update sequentialization.

---
 MVMCoreUI/BaseControllers/ViewController.swift  | 17 ++++++++++-------
 .../Behaviors/AddRemoveMoleculeBehavior.swift   |  2 +-
 .../Protocols/PageBehaviorProtocol.swift        |  2 ++
 3 files changed, 13 insertions(+), 8 deletions(-)

diff --git a/MVMCoreUI/BaseControllers/ViewController.swift b/MVMCoreUI/BaseControllers/ViewController.swift
index 37051176..73bba7b9 100644
--- a/MVMCoreUI/BaseControllers/ViewController.swift
+++ b/MVMCoreUI/BaseControllers/ViewController.swift
@@ -38,7 +38,7 @@ import MVMCore
     public var behaviors: [PageBehaviorProtocol]?
     
     public var needsUpdateUI = false
-    private var observingForResponses = false
+    private var observingForResponses: NSObjectProtocol?
     private var initialLoadFinished = false
     public var previousScreenSize = CGSize.zero
     
@@ -54,18 +54,21 @@ import MVMCore
     //--------------------------------------------------
     
     open func observeForResponseJSONUpdates() {
-        guard !observingForResponses,
+        guard observingForResponses == nil,
               (pagesToListenFor()?.count ?? 0 > 0 || modulesToListenFor()?.count ?? 0 > 0)
         else { return }
         
-        observingForResponses = true
-        NotificationCenter.default.addObserver(self, selector: #selector(responseJSONUpdated(notification:)), name: NSNotification.Name(rawValue: NotificationResponseLoaded), object: nil)
+        let pageUpdateQueue = OperationQueue()
+        pageUpdateQueue.maxConcurrentOperationCount = 1
+        pageUpdateQueue.qualityOfService = .userInteractive
+        
+        observingForResponses = NotificationCenter.default.addObserver(forName: NSNotification.Name(rawValue: NotificationResponseLoaded), object: nil, queue: pageUpdateQueue, using: responseJSONUpdated(notification:))
     }
     
     open func stopObservingForResponseJSONUpdates() {
-        guard observingForResponses else { return }
-        NotificationCenter.default.removeObserver(self, name: NSNotification.Name(rawValue: NotificationResponseLoaded), object: nil)
-        observingForResponses = false
+        guard let observingForResponses = observingForResponses else { return }
+        NotificationCenter.default.removeObserver(observingForResponses)
+        self.observingForResponses = nil
     }
     
     open func pagesToListenFor() -> [String]? {
diff --git a/MVMCoreUI/Behaviors/AddRemoveMoleculeBehavior.swift b/MVMCoreUI/Behaviors/AddRemoveMoleculeBehavior.swift
index ed9b8196..6e11e074 100644
--- a/MVMCoreUI/Behaviors/AddRemoveMoleculeBehavior.swift
+++ b/MVMCoreUI/Behaviors/AddRemoveMoleculeBehavior.swift
@@ -76,7 +76,7 @@ public class AddRemoveMoleculesBehavior: PageCustomActionHandlerBehavior, PageMo
         self.delegate = delegateObject
     }
     
-    public func onPageNew(rootMolecules: [MoleculeModelProtocol], _ delegateObject: MVMCoreUIDelegateObject?) {
+    public func willRender(rootMolecules: [MoleculeModelProtocol], _ delegateObject: MVMCoreUIDelegateObject?) {
         guard let list = delegate?.moleculeListDelegate else { return }
         for case let model as (MoleculeModelProtocol & ListItemModelProtocol & AddMolecules) in rootMolecules {
             if let moleculesToAdd = model.getRecursiveMoleculesToAdd(),
diff --git a/MVMCoreUI/Behaviors/Protocols/PageBehaviorProtocol.swift b/MVMCoreUI/Behaviors/Protocols/PageBehaviorProtocol.swift
index 6d6fda04..7fb9dc1f 100644
--- a/MVMCoreUI/Behaviors/Protocols/PageBehaviorProtocol.swift
+++ b/MVMCoreUI/Behaviors/Protocols/PageBehaviorProtocol.swift
@@ -35,6 +35,7 @@ public protocol PageMoleculeTransformationBehavior: PageBehaviorProtocol {
     func didSetupMolecule(view: MoleculeViewProtocol, withModel: MoleculeModelProtocol)
     func willSetupNavigationBar(with model: NavigationItemModelProtocol, updating view: UINavigationBar)
     func didSetupNavigationBar(view: UINavigationBar, with model: NavigationItemModelProtocol)
+    func willRender(rootMolecules: [MoleculeModelProtocol], _ delegateObject: MVMCoreUIDelegateObject?)
     func shouldFinishProcessingLoad(_ loadObject: MVMCoreLoadObject) throws -> Bool
 }
 
@@ -45,6 +46,7 @@ public extension PageMoleculeTransformationBehavior {
     func didSetupMolecule(view: MoleculeViewProtocol, withModel: MoleculeModelProtocol) {}
     func willSetupNavigationBar(with model: NavigationItemModelProtocol, updating view: UINavigationBar) {}
     func didSetupNavigationBar(view: UINavigationBar, with model: NavigationItemModelProtocol) {}
+    func willRender(rootMolecules: [MoleculeModelProtocol], _ delegateObject: MVMCoreUIDelegateObject?) {}
     func shouldFinishProcessingLoad(_ loadObject: MVMCoreLoadObject) throws -> Bool { return true }
 }