Implement basic tap-to-collapse

Packages/StatusKit/Sources/StatusKit/Detail/StatusDetailView.swift

@@ -113,12 +113,15 @@ public struct StatusDetailView: View {
     .navigationBarTitleDisplayMode(.inline)
   }
 
+  @ViewBuilder
   private func makeStatusesListView(statuses: [Status]) -> some View {
-    ForEach(statuses) { status in
+    let collapsedIds = viewModel.hierarchyCollapseState.implicitlyCollapsedStatusIds(for: statuses)
+    ForEach(statuses.filter { !collapsedIds.contains($0.id) }) { status in
       let (indentationLevel, extraInsets) = viewModel.getIndentationLevel(id: status.id, maxIndent: userPreferences.getRealMaxIndent())
       let viewModel: StatusRowViewModel = .init(status: status,
                                                 client: client,
                                                 routerPath: routerPath,
+                                                hierarchyCollapseState: viewModel.hierarchyCollapseState,
                                                 scrollToId: $viewModel.scrollToId)
       let isFocused = self.viewModel.statusId == status.id
 

Packages/StatusKit/Sources/StatusKit/Detail/StatusDetailViewModel.swift

@@ -11,6 +11,8 @@ import SwiftUI
 
   var client: Client?
   var routerPath: RouterPath?
+    
+  let hierarchyCollapseState = StatusHierarchyCollapseState()
 
   enum State {
     case loading, display(statuses: [Status]), error(error: Error)

Packages/StatusKit/Sources/StatusKit/Hierarchy/StatusHierarchyCollapseStatus.swift

@@ -0,0 +1,24 @@
+import Observation
+import Models
+
+@MainActor
+@Observable public class StatusHierarchyCollapseState {
+    public var explicitlyCollapsedStatusIds: Set<String>
+    
+    public init(explicitlyCollapsedStatusIds: Set<String> = []) {
+        self.explicitlyCollapsedStatusIds = explicitlyCollapsedStatusIds
+    }
+    
+    public func implicitlyCollapsedStatusIds(for statuses: [Status]) -> Set<String> {
+        let childs: [String: [String]] = Dictionary(
+            grouping: statuses.filter { $0.inReplyToId != nil },
+            by: { $0.inReplyToId! }
+        ).mapValues { $0.map(\.id) }
+        
+        func descendants(for id: String) -> [String] {
+            (childs[id] ?? []).flatMap { [$0] + descendants(for: $0) }
+        }
+        
+        return Set(explicitlyCollapsedStatusIds.flatMap(descendants(for:)))
+    }
+}

Packages/StatusKit/Sources/StatusKit/List/StatusesListView.swift

@@ -29,7 +29,9 @@ public struct StatusesListView<Fetcher>: View where Fetcher: StatusesFetcher {
     switch fetcher.statusesState {
     case .loading:
       ForEach(Status.placeholders()) { status in
-        StatusRowView(viewModel: .init(status: status, client: client, routerPath: routerPath),
+        StatusRowView(viewModel: .init(status: status,
+                                       client: client,
+                                       routerPath: routerPath),
                       context: .timeline)
           .redacted(reason: .placeholder)
           .allowsHitTesting(false)

Packages/StatusKit/Sources/StatusKit/Row/StatusRowView.swift

@@ -348,7 +348,11 @@ public struct StatusRowView: View {
     
   private func handleTap() {
     guard !isFocused else { return }
-    viewModel.navigateToDetail()
+    if indentationLevel > 0, viewModel.hierarchyCollapseState != nil {
+      viewModel.isHierarchyExplicitlyCollapsed.toggle()
+    } else {
+      viewModel.navigateToDetail()
+    }
   }
 }
 

Packages/StatusKit/Sources/StatusKit/Row/StatusRowViewModel.swift

@@ -18,6 +18,8 @@ import SwiftUI
 
   let client: Client
   let routerPath: RouterPath
+  
+  let hierarchyCollapseState: StatusHierarchyCollapseState?
 
   let userFollowedTag: HTMLString.Link?
 
@@ -67,6 +69,20 @@ import SwiftUI
       }
     }
   }
+  
+  // toggled on tap, collapses the post with its hierarchy of replies
+  var isHierarchyExplicitlyCollapsed: Bool {
+    get {
+      hierarchyCollapseState?.explicitlyCollapsedStatusIds.contains(status.id) ?? false
+    }
+    set {
+      if newValue {
+        hierarchyCollapseState?.explicitlyCollapsedStatusIds.insert(status.id)
+      } else {
+        hierarchyCollapseState?.explicitlyCollapsedStatusIds.remove(status.id)
+      }
+    }
+  }
 
   // used by the button to expand a collapsed post
   var isCollapsed: Bool = true {
@@ -162,6 +178,7 @@ import SwiftUI
   public init(status: Status,
               client: Client,
               routerPath: RouterPath,
+              hierarchyCollapseState: StatusHierarchyCollapseState? = nil,
               isRemote: Bool = false,
               showActions: Bool = true,
               textDisabled: Bool = false,
@@ -171,6 +188,7 @@ import SwiftUI
     finalStatus = status.reblog ?? status
     self.client = client
     self.routerPath = routerPath
+    self.hierarchyCollapseState = hierarchyCollapseState
     self.isRemote = isRemote
     self.showActions = showActions
     self.textDisabled = textDisabled