Extract out conversation tree-building code

Tusker.xcodeproj/project.pbxproj

@@ -297,6 +297,7 @@
 		D6C1B2082545D1EC00DAAA66 /* StatusCardView.swift in Sources */ = {isa = PBXBuildFile; fileRef = D6C1B2072545D1EC00DAAA66 /* StatusCardView.swift */; };
 		D6C3F4F5298ED0890009FCFF /* LocalPredicateStatusesViewController.swift in Sources */ = {isa = PBXBuildFile; fileRef = D6C3F4F4298ED0890009FCFF /* LocalPredicateStatusesViewController.swift */; };
 		D6C3F4F7298ED7F70009FCFF /* FavoritesViewController.swift in Sources */ = {isa = PBXBuildFile; fileRef = D6C3F4F6298ED7F70009FCFF /* FavoritesViewController.swift */; };
+		D6C3F4F9298EDBF20009FCFF /* ConversationTree.swift in Sources */ = {isa = PBXBuildFile; fileRef = D6C3F4F8298EDBF20009FCFF /* ConversationTree.swift */; };
 		D6C693EF216192C2007D6A6D /* TuskerNavigationDelegate.swift in Sources */ = {isa = PBXBuildFile; fileRef = D6C693EE216192C2007D6A6D /* TuskerNavigationDelegate.swift */; };
 		D6C693FC2162FE6F007D6A6D /* LoadingViewController.swift in Sources */ = {isa = PBXBuildFile; fileRef = D6C693FB2162FE6F007D6A6D /* LoadingViewController.swift */; };
 		D6C693FE2162FEEA007D6A6D /* UIViewController+Children.swift in Sources */ = {isa = PBXBuildFile; fileRef = D6C693FD2162FEEA007D6A6D /* UIViewController+Children.swift */; };
@@ -706,6 +707,7 @@
 		D6C1B2072545D1EC00DAAA66 /* StatusCardView.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = StatusCardView.swift; sourceTree = "<group>"; };
 		D6C3F4F4298ED0890009FCFF /* LocalPredicateStatusesViewController.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = LocalPredicateStatusesViewController.swift; sourceTree = "<group>"; };
 		D6C3F4F6298ED7F70009FCFF /* FavoritesViewController.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = FavoritesViewController.swift; sourceTree = "<group>"; };
+		D6C3F4F8298EDBF20009FCFF /* ConversationTree.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = ConversationTree.swift; sourceTree = "<group>"; };
 		D6C693EE216192C2007D6A6D /* TuskerNavigationDelegate.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = TuskerNavigationDelegate.swift; sourceTree = "<group>"; };
 		D6C693FB2162FE6F007D6A6D /* LoadingViewController.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = LoadingViewController.swift; sourceTree = "<group>"; };
 		D6C693FD2162FEEA007D6A6D /* UIViewController+Children.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = "UIViewController+Children.swift"; sourceTree = "<group>"; };
@@ -1088,6 +1090,7 @@
 				D65B4B6329771EFF00DABDFB /* ConversationViewController.swift */,
 				D601FA5C297B2E6F00A8E8B5 /* ConversationCollectionViewController.swift */,
 				D601FA5E297B339100A8E8B5 /* ExpandThreadCollectionViewCell.swift */,
+				D6C3F4F8298EDBF20009FCFF /* ConversationTree.swift */,
 			);
 			path = Conversation;
 			sourceTree = "<group>";
@@ -2025,6 +2028,7 @@
 				D6E77D0F286F773900D8B732 /* SplitNavigationController.swift in Sources */,
 				D6B30E09254BAF63009CAEE5 /* ImageGrayscalifier.swift in Sources */,
 				D6A6C10F25B62D2400298D0F /* DiskCache.swift in Sources */,
+				D6C3F4F9298EDBF20009FCFF /* ConversationTree.swift in Sources */,
 				D6B81F3C2560365300F6E31D /* RefreshableViewController.swift in Sources */,
 				D646C958213B367000269FB5 /* LargeImageShrinkAnimationController.swift in Sources */,
 				D6674AEA23341F7600E8DF94 /* AppShortcutItems.swift in Sources */,

Tusker/Screens/Conversation/ConversationCollectionViewController.swift

@@ -9,16 +9,6 @@
 import UIKit
 import Pachyderm
 
-class ConversationNode {
-    let status: StatusMO
-    var children: [ConversationNode]
-    
-    init(status: StatusMO) {
-        self.status = status
-        self.children = []
-    }
-}
-
 class ConversationCollectionViewController: UIViewController, CollectionViewController {
     
     private let mastodonController: MastodonController
@@ -136,32 +126,27 @@ class ConversationCollectionViewController: UIViewController, CollectionViewCont
     }
     
     func addContext(_ context: ConversationContext, for mainStatus: StatusMO) async {
-        let parentIDs = getDirectParents(inReplyTo: mainStatus.inReplyToID, from: context.ancestors)
+        await mastodonController.persistentContainer.addAll(statuses: context.ancestors + context.descendants)
-        let parentStatuses = context.ancestors.filter { parentIDs.contains($0.id) }
-        
-        await mastodonController.persistentContainer.addAll(statuses: parentStatuses + context.descendants)
-        
-        var snapshot = dataSource.snapshot()
-        snapshot.deleteItems([.loadingIndicator])
-        let mainStatusItem = Item.status(id: mainStatusID, state: mainStatusState, prevLink: mainStatus.inReplyToID != nil, nextLink: false)
-        let parentItems = parentIDs.enumerated().map { index, id in
-            Item.status(id: id, state: .unknown, prevLink: index > 0, nextLink: true)
-        }
-        snapshot.insertItems(parentItems, beforeItem: mainStatusItem)
-        snapshot.reloadItems([mainStatusItem])
         
         // fetch all descendant status managed objects
         let descendantIDs = context.descendants.map(\.id)
         let request = StatusMO.fetchRequest()
         request.predicate = NSPredicate(format: "id IN %@", descendantIDs)
+        let descendants = try? mastodonController.persistentContainer.viewContext.fetch(request)
         
-        if let descendants = try? mastodonController.persistentContainer.viewContext.fetch(request) {
+        let tree = ConversationTree.build(from: context, mainStatus: mainStatus, descendants: descendants ?? [])
-            // convert array of descendant statuses into tree of sub-threads
-            let childThreads = self.getDescendantThreads(mainStatus: mainStatus, descendants: descendants)
         
-            // convert sub-threads into items for section and add to snapshot
+        var snapshot = dataSource.snapshot()
-            self.addFlattenedChildThreadsToSnapshot(childThreads, mainStatus: mainStatus, snapshot: &snapshot)
+        snapshot.deleteItems([.loadingIndicator])
+        let mainStatusItem = Item.status(id: mainStatusID, state: mainStatusState, prevLink: mainStatus.inReplyToID != nil, nextLink: false)
+        let parentItems = tree.ancestors.enumerated().map { index, id in
+            Item.status(id: id, state: .unknown, prevLink: index > 0, nextLink: true)
         }
+        snapshot.insertItems(parentItems, beforeItem: mainStatusItem)
+        snapshot.reloadItems([mainStatusItem])
+
+        // convert sub-threads into items for section and add to snapshot
+        self.addFlattenedChildThreadsToSnapshot(tree.descendants, mainStatus: mainStatus, snapshot: &snapshot)
         
         self.dataSource.apply(snapshot, animatingDifferences: false) {
             let item: Item
@@ -187,54 +172,6 @@ class ConversationCollectionViewController: UIViewController, CollectionViewCont
         }
     }
     
-    private func getDirectParents(inReplyTo inReplyToID: String?, from statuses: [Status]) -> [String] {
-        var statuses = statuses
-        var parents = [String]()
-        
-        var parentID: String? = inReplyToID
-
-        while parentID != nil, let parentIndex = statuses.firstIndex(where: { $0.id == parentID }) {
-            let parentStatus = statuses.remove(at: parentIndex)
-            parents.insert(parentStatus.id, at: 0)
-            parentID = parentStatus.inReplyToID
-        }
-        
-        return parents
-    }
-    
-    private func getDescendantThreads(mainStatus: StatusMO, descendants: [StatusMO]) -> [ConversationNode] {
-        var descendants = descendants
-        
-        func removeAllInReplyTo(id: String) -> [StatusMO] {
-            let statuses = descendants.filter { $0.inReplyToID == id }
-            descendants.removeAll { $0.inReplyToID == id }
-            return statuses
-        }
-        
-        var nodes: [String: ConversationNode] = [
-            mainStatus.id: ConversationNode(status: mainStatus)
-        ]
-        
-        var idsToCheck = [mainStatusID]
-        
-        while !idsToCheck.isEmpty {
-            let inReplyToID = idsToCheck.removeFirst()
-            let nodeForID = nodes[inReplyToID]!
-            
-            let inReply = removeAllInReplyTo(id: inReplyToID)
-            for reply in inReply {
-                idsToCheck.append(reply.id)
-                
-                let replyNode = ConversationNode(status: reply)
-                nodes[reply.id] = replyNode
-                
-                nodeForID.children.append(replyNode)
-            }
-        }
-        
-        return nodes[mainStatusID]!.children
-    }
-    
     private func addFlattenedChildThreadsToSnapshot(_ childThreads: [ConversationNode], mainStatus: StatusMO, snapshot: inout NSDiffableDataSourceSnapshot<Section, Item>) {
         var childThreads = childThreads
         

Tusker/Screens/Conversation/ConversationTree.swift

@@ -0,0 +1,80 @@
+//
+//  ConversationTree.swift
+//  Tusker
+//
+//  Created by Shadowfacts on 2/4/23.
+//  Copyright © 2023 Shadowfacts. All rights reserved.
+//
+
+import Foundation
+import Pachyderm
+
+class ConversationNode {
+    let status: StatusMO
+    var children: [ConversationNode]
+    
+    init(status: StatusMO) {
+        self.status = status
+        self.children = []
+    }
+}
+struct ConversationTree {
+    let ancestors: [String]
+    let descendants: [ConversationNode]
+    
+    static func build(from context: ConversationContext, mainStatus: StatusMO, descendants: [StatusMO]) -> ConversationTree {
+        let ancestors = getDirectParents(inReplyTo: mainStatus.inReplyToID, from: context)
+        let childThreads = getDescendantThreads(mainStatus: mainStatus, descendants: descendants)
+        return ConversationTree(ancestors: ancestors, descendants: childThreads)
+    }
+    
+    private static func getDirectParents(inReplyTo inReplyToID: String?, from context: ConversationContext) -> [String] {
+        var statuses = context.ancestors
+        var parents = [String]()
+        
+        var parentID: String? = inReplyToID
+        
+        while let currentParentID = parentID,
+              let parentIndex = statuses.firstIndex(where: { $0.id == currentParentID }) {
+            let parentStatus = statuses.remove(at: parentIndex)
+            parents.insert(parentStatus.id, at: 0)
+            parentID = parentStatus.inReplyToID
+        }
+        
+        return parents
+    }
+    
+    private static func getDescendantThreads(mainStatus: StatusMO, descendants: [StatusMO]) -> [ConversationNode] {
+        var descendants = descendants
+        
+        func removeAllInReplyTo(id: String) -> [StatusMO] {
+            let statuses = descendants.filter { $0.inReplyToID == id }
+            descendants.removeAll { $0.inReplyToID == id }
+            return statuses
+        }
+        
+        let mainStatusNode = ConversationNode(status: mainStatus)
+        var nodes: [String: ConversationNode] = [
+            mainStatus.id: mainStatusNode
+        ]
+        
+        var idsToCheck = [mainStatus.id]
+        
+        while !idsToCheck.isEmpty {
+            let inReplyToID = idsToCheck.removeFirst()
+            let nodeForID = nodes[inReplyToID]!
+            
+            let inReply = removeAllInReplyTo(id: inReplyToID)
+            for reply in inReply {
+                idsToCheck.append(reply.id)
+                
+                let replyNode = ConversationNode(status: reply)
+                nodes[reply.id] = replyNode
+                
+                nodeForID.children.append(replyNode)
+            }
+        }
+        
+        return mainStatusNode.children
+    }
+}