From 4cbf15a3a75e250c033e7abcd7150da276f8fa86 Mon Sep 17 00:00:00 2001
From: "Hedden, Kyle Matthew" <kyle.hedden@verizonwireless.com>
Date: Wed, 3 Jul 2024 15:42:12 -0400
Subject: [PATCH] Digital PCT265 defect CXTDT-579050: Change batching to the
 UI.

---
 .../BaseControllers/ViewController.swift      | 63 ++++++++++++-------
 1 file changed, 39 insertions(+), 24 deletions(-)

diff --git a/MVMCoreUI/BaseControllers/ViewController.swift b/MVMCoreUI/BaseControllers/ViewController.swift
index e67188a0..950b330e 100644
--- a/MVMCoreUI/BaseControllers/ViewController.swift
+++ b/MVMCoreUI/BaseControllers/ViewController.swift
@@ -70,41 +70,34 @@ import Combine
         observingForResponses = NotificationCenter.default.publisher(for: NSNotification.Name(rawValue: NotificationResponseLoaded))
             .receive(on: self.pageUpdateQueue) // Background serial queue.
             .map { [weak self] notification in
-                guard let self = self else { return (nil, nil, nil) }
-                // Get the page data.
-                let pageUpdates = self.extractInterestedPageType(from: notification.userInfo?.optionalDictionaryForKey(KeyPageMap) ?? [:])
-                // Convert the page data into a new model.
-                var pageModel: PageModelProtocol? = nil
-                if let pageUpdates {
-                    do {
-                        // TODO: Rewiring to parse from plain JSON rather than this protocol indirection.
-                        pageModel = try (self as? any TemplateProtocol & PageBehaviorHandlerProtocol & MVMCoreViewControllerProtocol)?.parseTemplate(pageJSON: pageUpdates)
-                    } catch {
-                        if let coreError = MVMCoreErrorObject.createErrorObject(for: error, location: "updateJSON for pageType: \(String(describing: self.pageType))") {
-                            MVMCoreLoggingHandler.shared()?.addError(toLog: coreError)
-                        }
-                    }
-                }
-                // Get the module data.
-                let moduleUpdates = self.extractInterestedModules(from: notification.userInfo?.optionalDictionaryForKey(KeyModuleMap) ?? [:])
-                // Bundle the transformations.
-                return (pageUpdates, pageModel, moduleUpdates)
+                self?.pullUpdates(from: notification) ?? (nil, nil, nil)
             }
             .filter { (pageUpdates: [String : Any]?, pageModel: PageModelProtocol?, moduleUpdates: [String : Any]?) in
                 // Skip any non-updates.
                 (pageUpdates != nil && pageModel != nil) || (moduleUpdates != nil && moduleUpdates!.count > 0)
             }
-            // Opportunity: Merge all module only updates into one event.
+            // Merge all page and module updates into one update event.
+            //.print("[Update pipe] merging")
+            .scan((nil, nil, nil)) { accumulator, next in
+                // Always take the latest page and the latest modules with same key.
+                return (next.0, next.1, next.2?.mergingRight(accumulator.2 ?? [:]))
+            }
+            //.print("[Update pipe] into buffer")
+            // Hold onto the latest merged state until UI is ready for an update. Keep only the latest from scan.
+            .buffer(size: 1, prefetch: .byRequest, whenFull: .dropOldest)
+            //.print("[Update pipe] out of buffer")
             // Delay allowing the previous model update to settle before triggering a re-render.
-            .buffer(size: 100, prefetch: .byRequest, whenFull: .dropOldest)
-            .flatMap(maxPublishers: .max(1)) { Just($0).delay(for: .seconds(0.1), scheduler: RunLoop.main) }
+            .flatMap(maxPublishers: .max(1)) { buffer in
+                Just(buffer).delay(for: .seconds(0.1), scheduler: RunLoop.main)
+            }
             .sink { [weak self] (pageUpdates: [String : Any]?, pageModel: PageModelProtocol?, moduleUpdates: [String : Any]?) in
                 guard let self = self else { return }
-                if let pageUpdates, let pageModel {
+                if let pageUpdates, pageModel != nil {
                     self.loadObject?.pageJSON = pageUpdates
                 }
-                var mergedModuleUpdates = (loadObject?.modulesJSON ?? [:]).mergingLeft(moduleUpdates ?? [:])
+                let mergedModuleUpdates = (loadObject?.modulesJSON ?? [:]).mergingLeft(moduleUpdates ?? [:])
                 self.loadObject?.modulesJSON = mergedModuleUpdates
+                self.debugLog("Applying async update page model \(pageModel.debugDescription) and modules \(mergedModuleUpdates.keys) to page.")
                 self.handleNewData(pageModel)
             }
     }
@@ -115,6 +108,28 @@ import Combine
         self.observingForResponses = nil
     }
     
+    func pullUpdates(from notification: Notification) -> (pageUpdates: [String : Any]?, pageModel: PageModelProtocol?, moduleUpdates: [String : Any]?) {
+       // Get the page data.
+       let pageUpdates = extractInterestedPageType(from: notification.userInfo?.optionalDictionaryForKey(KeyPageMap) ?? [:])
+       // Convert the page data into a new model.
+       var pageModel: PageModelProtocol? = nil
+       if let pageUpdates {
+           do {
+               // TODO: Rewiring to parse from plain JSON rather than this protocol indirection.
+               pageModel = try (self as? any TemplateProtocol & PageBehaviorHandlerProtocol & MVMCoreViewControllerProtocol)?.parseTemplate(pageJSON: pageUpdates)
+           } catch {
+               if let coreError = MVMCoreErrorObject.createErrorObject(for: error, location: "updateJSON for pageType: \(String(describing: self.pageType))") {
+                   MVMCoreLoggingHandler.shared()?.addError(toLog: coreError)
+               }
+           }
+       }
+       // Get the module data.
+       let moduleUpdates = extractInterestedModules(from: notification.userInfo?.optionalDictionaryForKey(KeyModuleMap) ?? [:])
+        debugLog("Receiving page \(pageModel?.pageType ?? "none") & \(moduleUpdates?.keys.description ?? "none") modules from  \((notification.userInfo?["MVMCoreLoadObject"] as? MVMCoreLoadObject)?.requestParameters?.url?.absoluteString ?? "")")
+       // Bundle the transformations.
+       return (pageUpdates, pageModel, moduleUpdates)
+    }
+    
     open func pagesToListenFor() -> [String]? {
         guard let pageType = loadObject?.pageType else { return nil }
         return [pageType]