From e74daa4df068ff458323ae8b804df85ff7f6d604 Mon Sep 17 00:00:00 2001
From: Justin Mazzocchi <2831158+jzzocc@users.noreply.github.com>
Date: Wed, 26 Aug 2020 01:25:34 -0700
Subject: [PATCH] Refactoring

---
 Shared/View Models/StatusesViewModel.swift    | 19 +++++--
 .../StatusListViewController.swift            | 55 ++++++++-----------
 iOS/Views/StatusTableViewCell.swift           | 10 ++--
 3 files changed, 41 insertions(+), 43 deletions(-)

diff --git a/Shared/View Models/StatusesViewModel.swift b/Shared/View Models/StatusesViewModel.swift
index 83074c6..dc7466b 100644
--- a/Shared/View Models/StatusesViewModel.swift	
+++ b/Shared/View Models/StatusesViewModel.swift	
@@ -4,10 +4,11 @@ import Foundation
 import Combine
 
 class StatusesViewModel: ObservableObject {
-    @Published private(set) var statusSections = [[Status]]()
+    @Published private(set) var statusIDs = [[String]]()
     @Published var alertItem: AlertItem?
     @Published private(set) var loading = false
     private(set) var maintainScrollPositionOfStatusID: String?
+    private var statuses = [String: Status]()
     private let statusListService: StatusListService
     private var statusViewModelCache = [Status: (StatusViewModel, AnyCancellable)]()
     private var cancellables = Set<AnyCancellable>()
@@ -19,9 +20,11 @@ class StatusesViewModel: ObservableObject {
             .handleEvents(receiveOutput: { [weak self] in
                 self?.determineIfScrollPositionShouldBeMaintained(newStatusSections: $0)
                 self?.cleanViewModelCache(newStatusSections: $0)
+                self?.statuses = Dictionary(uniqueKeysWithValues: $0.reduce([], +).map { ($0.id, $0) })
             })
             .assignErrorsToAlertItem(to: \.alertItem, on: self)
-            .assign(to: &$statusSections)
+            .map { $0.map { section in section.map(\.id) } }
+            .assign(to: &$statusIDs)
     }
 }
 
@@ -38,7 +41,9 @@ extension StatusesViewModel {
             .store(in: &cancellables)
     }
 
-    func statusViewModel(status: Status) -> StatusViewModel {
+    func statusViewModel(id: String) -> StatusViewModel? {
+        guard let status = statuses[id] else { return nil }
+
         var statusViewModel: StatusViewModel
 
         if let cachedViewModel = statusViewModelCache[status]?.0 {
@@ -59,8 +64,10 @@ extension StatusesViewModel {
         return statusViewModel
     }
 
-    func contextViewModel(status: Status) -> StatusesViewModel {
-        StatusesViewModel(statusListService: statusListService.contextService(status: status))
+    func contextViewModel(id: String) -> StatusesViewModel? {
+        guard let status = statuses[id] else { return nil }
+
+        return StatusesViewModel(statusListService: statusListService.contextService(status: status))
     }
 }
 
@@ -69,7 +76,7 @@ private extension StatusesViewModel {
         maintainScrollPositionOfStatusID = nil // clear old value
 
         // Maintain scroll position of parent after initial load of context
-        if let contextParentID = contextParentID, statusSections.reduce([], +).map(\.id) == [contextParentID] {
+        if let contextParentID = contextParentID, statusIDs.reduce([], +) == [contextParentID] {
             maintainScrollPositionOfStatusID = contextParentID
         }
     }
diff --git a/iOS/View Controllers/StatusListViewController.swift b/iOS/View Controllers/StatusListViewController.swift
index 486b72f..7a9e20d 100644
--- a/iOS/View Controllers/StatusListViewController.swift	
+++ b/iOS/View Controllers/StatusListViewController.swift	
@@ -6,10 +6,10 @@ import Combine
 class StatusListViewController: UITableViewController {
     private let viewModel: StatusesViewModel
     private var cancellables = Set<AnyCancellable>()
-    private var cellHeightCaches = [CGFloat: [Status: CGFloat]]()
+    private var cellHeightCaches = [CGFloat: [String: CGFloat]]()
 
-    private lazy var dataSource: UITableViewDiffableDataSource<Int, Status> = {
-        UITableViewDiffableDataSource(tableView: tableView) { [weak self] tableView, indexPath, status in
+    private lazy var dataSource: UITableViewDiffableDataSource<Int, String> = {
+        UITableViewDiffableDataSource(tableView: tableView) { [weak self] tableView, indexPath, statusID in
             guard
                 let self = self,
                 let cell = tableView.dequeueReusableCell(
@@ -17,9 +17,7 @@ class StatusListViewController: UITableViewController {
                     for: indexPath) as? StatusTableViewCell
             else { return nil }
 
-            let statusViewModel = self.viewModel.statusViewModel(status: status)
-
-            cell.viewModel = statusViewModel
+            cell.viewModel = self.viewModel.statusViewModel(id: statusID)
             cell.delegate = self
 
             return cell
@@ -50,7 +48,7 @@ class StatusListViewController: UITableViewController {
         tableView.cellLayoutMarginsFollowReadableWidth = true
         tableView.separatorInset = .zero
 
-        viewModel.$statusSections.map { $0.snapshot() }
+        viewModel.$statusIDs
             .sink { [weak self] in
                 guard let self = self else { return }
 
@@ -58,16 +56,16 @@ class StatusListViewController: UITableViewController {
 
                 if
                     let id = self.viewModel.maintainScrollPositionOfStatusID,
-                    let indexPath = self.indexPath(statusID: id),
+                    let indexPath = self.dataSource.indexPath(for: id),
                     let navigationBar = self.navigationController?.navigationBar {
                     let navigationBarMaxY = self.tableView.convert(navigationBar.bounds, from: navigationBar).maxY
                     offsetFromNavigationBar = self.tableView.rectForRow(at: indexPath).origin.y - navigationBarMaxY
                 }
 
-                self.dataSource.apply($0, animatingDifferences: false) {
+                self.dataSource.apply($0.snapshot(), animatingDifferences: false) {
                     if
                         let id = self.viewModel.maintainScrollPositionOfStatusID,
-                        let indexPath = self.indexPath(statusID: id),
+                        let indexPath = self.dataSource.indexPath(for: id),
                         let offsetFromNavigationBar = offsetFromNavigationBar {
                         self.tableView.scrollToRow(at: indexPath, at: .top, animated: false)
                         self.tableView.contentOffset.y -= offsetFromNavigationBar
@@ -88,7 +86,7 @@ class StatusListViewController: UITableViewController {
                             forRowAt indexPath: IndexPath) {
         guard let item = dataSource.itemIdentifier(for: indexPath) else { return }
 
-        var heightCache = cellHeightCaches[tableView.frame.width] ?? [Status: CGFloat]()
+        var heightCache = cellHeightCaches[tableView.frame.width] ?? [String: CGFloat]()
 
         heightCache[item] = cell.frame.height
         cellHeightCaches[tableView.frame.width] = heightCache
@@ -101,41 +99,32 @@ class StatusListViewController: UITableViewController {
     }
 
     override func tableView(_ tableView: UITableView, shouldHighlightRowAt indexPath: IndexPath) -> Bool {
-        viewModel.statusSections[indexPath.section][indexPath.row].id != viewModel.contextParentID
+        guard let id = dataSource.itemIdentifier(for: indexPath) else { return true }
+
+        return id != viewModel.contextParentID
     }
 
     override func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {
-        let status = viewModel.statusSections[indexPath.section][indexPath.row]
+        guard
+            let id = dataSource.itemIdentifier(for: indexPath),
+            let contextViewModel = viewModel.contextViewModel(id: id)
+        else { return }
 
         navigationController?.pushViewController(
-            StatusListViewController(viewModel: viewModel.contextViewModel(status: status)),
+            StatusListViewController(viewModel: contextViewModel),
             animated: true)
     }
 }
 
 extension StatusListViewController: StatusTableViewCellDelegate {
     func statusTableViewCellDidHaveShareButtonTapped(_ cell: StatusTableViewCell) {
-        guard let url = cell.viewModel.sharingURL else { return }
+        guard let url = cell.viewModel?.sharingURL else { return }
 
         share(url: url)
     }
 }
 
 private extension StatusListViewController {
-    func indexPath(statusID: String) -> IndexPath? {
-        for section in 0..<dataSource.numberOfSections(in: tableView) {
-            for row in 0..<dataSource.tableView(tableView, numberOfRowsInSection: section) {
-                let indexPath = IndexPath(row: row, section: section)
-
-                if dataSource.itemIdentifier(for: indexPath)?.id == statusID {
-                    return indexPath
-                }
-            }
-        }
-
-        return nil
-    }
-
     func share(url: URL) {
         let activityViewController = UIActivityViewController(activityItems: [url], applicationActivities: nil)
 
@@ -143,16 +132,16 @@ private extension StatusListViewController {
     }
 }
 
-private extension Array where Element == [Status] {
-    func snapshot() -> NSDiffableDataSourceSnapshot<Int, Status> {
-        var snapshot = NSDiffableDataSourceSnapshot<Int, Status>()
+private extension Array where Element: Sequence, Element.Element: Hashable {
+    func snapshot() -> NSDiffableDataSourceSnapshot<Int, Element.Element> {
+        var snapshot = NSDiffableDataSourceSnapshot<Int, Element.Element>()
 
         let sections = [Int](0..<count)
 
         snapshot.appendSections(sections)
 
         for section in sections {
-            snapshot.appendItems(self[section], toSection: section)
+            snapshot.appendItems(self[section].map { $0 }, toSection: section)
         }
 
         return snapshot
diff --git a/iOS/Views/StatusTableViewCell.swift b/iOS/Views/StatusTableViewCell.swift
index f0e742c..098d9bc 100644
--- a/iOS/Views/StatusTableViewCell.swift
+++ b/iOS/Views/StatusTableViewCell.swift
@@ -58,8 +58,10 @@ class StatusTableViewCell: UITableViewCell {
 
     @IBOutlet private var separatorConstraints: [NSLayoutConstraint]!
 
-    var viewModel: StatusViewModel! {
+    var viewModel: StatusViewModel? {
         didSet {
+            guard let viewModel = viewModel else { return }
+
             let mutableContent = NSMutableAttributedString(attributedString: viewModel.content)
             let mutableDisplayName = NSMutableAttributedString(string: viewModel.displayName)
             let mutableSpoilerText = NSMutableAttributedString(string: viewModel.spoilerText)
@@ -274,7 +276,7 @@ extension StatusTableViewCell {
     }
 
     @IBAction func favoriteButtonTapped(_ sender: UIButton) {
-        viewModel.toggleFavorited()
+        viewModel?.toggleFavorited()
     }
 
     @IBAction func actionsButtonTapped(_ sender: Any) {
@@ -325,7 +327,7 @@ private extension StatusTableViewCell {
         let reblogColor: UIColor = reblogged ? .systemGreen : .secondaryLabel
         let reblogButton: UIButton
 
-        if viewModel.isContextParent {
+        if viewModel?.isContextParent ?? false {
             reblogButton = contextParentReblogButton
         } else {
             reblogButton = self.reblogButton
@@ -340,7 +342,7 @@ private extension StatusTableViewCell {
         let favoriteButton: UIButton
         let scale: UIImage.SymbolScale
 
-        if viewModel.isContextParent {
+        if viewModel?.isContextParent ?? false {
             favoriteButton = contextParentFavoriteButton
             scale = .medium
         } else {