Stats Traffic: Optimize table view updates by integrating diffable da…

…ta source (#22542)
wordpress-mobile · Feb 22, 2024 · 4e97126 · 4e97126
2 parents 3ddebf7 + d130c3a
commit 4e97126
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Showing 11 changed files with 392 additions and 158 deletions.
diff --git a/WordPress/Classes/Utility/ImmuTable.swift b/WordPress/Classes/Utility/ImmuTable.swift
@@ -483,3 +483,64 @@ extension UITableView: CellRegistrar {
 }
 
 extension UITableViewController: TableViewContainer {}
+
+// MARK: - Diffable
+
+typealias ImmuTableDiffableDataSourceSnapshot = NSDiffableDataSourceSnapshot<AnyHashable, AnyHashableImmuTableRow>
+typealias ImmuTableDiffableDataSource = UITableViewDiffableDataSource<AnyHashable, AnyHashableImmuTableRow>
+
+struct AnyHashableImmuTableRow: Hashable {
+    let immuTableRow: any (ImmuTableRow & Hashable)
+
+    static func == (lhs: AnyHashableImmuTableRow, rhs: AnyHashableImmuTableRow) -> Bool {
+        return AnyHashable(lhs.immuTableRow) == AnyHashable(rhs.immuTableRow)
+    }
+
+    func hash(into hasher: inout Hasher) {
+        hasher.combine(AnyHashable(immuTableRow))
+    }
+}
+
+class ImmuTableDiffableViewHandler: ImmuTableViewHandler {
+    lazy var diffableDataSource: ImmuTableDiffableDataSource = {
+        return ImmuTableDiffableDataSource(tableView: target.tableView) { tableView, indexPath, item in
+            let row = item.immuTableRow
+            let cell = tableView.dequeueReusableCell(withIdentifier: row.reusableIdentifier, for: indexPath)
+            row.configureCell(cell)
+            return cell
+        }
+    }()
+
+    override init(takeOver target: ImmuTableViewHandler.UIViewControllerWithTableView, with passthroughScrollViewDelegate: UIScrollViewDelegate? = nil) {
+        super.init(takeOver: target, with: passthroughScrollViewDelegate)
+
+        self.target.tableView.dataSource = diffableDataSource
+        self.automaticallyReloadTableView = false
+    }
+
+    func item(for indexPath: IndexPath) -> ImmuTableRow? {
+        guard let diffableDataSource = target.tableView.dataSource as? UITableViewDiffableDataSource<AnyHashable, AnyHashableImmuTableRow> else {
+            return nil
+        }
+
+        return diffableDataSource.itemIdentifier(for: indexPath)?.immuTableRow
+    }
+
+    open override func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {
+        if target.responds(to: #selector(UITableViewDelegate.tableView(_:didSelectRowAt:))) {
+            target.tableView?(tableView, didSelectRowAt: indexPath)
+        } else if let item = item(for: indexPath) {
+            item.action?(item)
+        }
+        if automaticallyDeselectCells {
+            tableView.deselectRow(at: indexPath, animated: true)
+        }
+    }
+
+    open override func tableView(_ tableView: UITableView, heightForRowAt indexPath: IndexPath) -> CGFloat {
+        if let item = item(for: indexPath), let customHeight = type(of: item).customHeight {
+            return CGFloat(customHeight)
+        }
+        return tableView.rowHeight
+    }
+}
diff --git a/WordPress/Classes/ViewRelated/Stats/Period Stats/Countries/CountriesMap.swift b/WordPress/Classes/ViewRelated/Stats/Period Stats/Countries/CountriesMap.swift
@@ -1,6 +1,6 @@
 import Foundation
 
-struct CountriesMap {
+struct CountriesMap: Hashable {
     let minViewsCount: Int
     let maxViewsCount: Int
     let data: [String: NSNumber]

diff --git a/WordPress/Classes/ViewRelated/Stats/Period Stats/Overview/OverviewCell.swift b/WordPress/Classes/ViewRelated/Stats/Period Stats/Overview/OverviewCell.swift
@@ -1,6 +1,6 @@
 import UIKit
 
-struct OverviewTabData: FilterTabBarItem {
+struct OverviewTabData: FilterTabBarItem, Hashable {
     var tabTitle: String
     var tabData: Int
     var tabDataStub: String?

diff --git a/WordPress/Classes/ViewRelated/Stats/Period Stats/SiteStatsPeriodTableViewController.swift b/WordPress/Classes/ViewRelated/Stats/Period Stats/SiteStatsPeriodTableViewController.swift
@@ -48,12 +48,12 @@ final class SiteStatsPeriodTableViewController: SiteStatsBaseTableViewController
     private var changeReceipt: Receipt?
 
     private var viewModel: SiteStatsPeriodViewModel?
-    private var tableHeaderView: SiteStatsTableHeaderView?
+    private weak var tableHeaderView: SiteStatsTableHeaderView?
 
     private let analyticsTracker = BottomScrollAnalyticsTracker()
 
-    private lazy var tableHandler: ImmuTableViewHandler = {
-        return ImmuTableViewHandler(takeOver: self, with: analyticsTracker)
+    private lazy var tableHandler: ImmuTableDiffableViewHandler = {
+        return ImmuTableDiffableViewHandler(takeOver: self, with: analyticsTracker)
     }()
 
     init() {
@@ -173,9 +173,10 @@ private extension SiteStatsPeriodTableViewController {
             return
         }
 
-        tableHandler.viewModel = viewModel.tableViewModel()
+        tableHandler.diffableDataSource.apply(viewModel.tableViewSnapshot(), animatingDifferences: false)
 
         refreshControl.endRefreshing()
+        tableHeaderView?.animateGhostLayers(viewModel.isFetchingChart() == true)
 
         if viewModel.fetchingFailed() {
             displayFailureViewIfNecessary()
@@ -217,7 +218,7 @@ private extension SiteStatsPeriodTableViewController {
 
 extension SiteStatsPeriodTableViewController: NoResultsViewHost {
     private func displayFailureViewIfNecessary() {
-        guard tableHandler.viewModel.sections.isEmpty else {
+        guard tableHandler.diffableDataSource.snapshot().numberOfSections == 0 else {
             return
         }