SwiftUI timeline refactor + TimelineViewState decoupling (#1392)

* swiftUI conversion + scroll to bottom

* remove unused

* back pagination implemented, however when a lot of elements are in the scroll the perfomance diminishes not sure what may be causing it

* scroll adapter solution

* way better

* works but height animation in cells are broken

* code improvement

* everything implemented

* rebase fix

* fix

* doc

* fix test compilation

* code improvement and animation improvement

* code improvement

* code improvements

* tests updated.

* pr comments

* better identifiers

* fix

* some PR comments

* pr comments

ElementX/Sources/Services/Timeline/TimelineItems/RoomTimelineItemView.swift

@@ -16,17 +16,27 @@
 import SwiftUI
 
 struct RoomTimelineItemView: View {
-    @ObservedObject var viewModel: RoomTimelineItemViewModel
+    @EnvironmentObject private var context: RoomScreenViewModel.Context
+    let viewState: RoomTimelineItemViewState
 
     var body: some View {
         timelineView
-            .environment(\.timelineGroupStyle, viewModel.groupStyle)
-            .animation(.elementDefault, value: viewModel.type)
-            .animation(.elementDefault, value: viewModel.groupStyle)
+            .environmentObject(context)
+            .environment(\.timelineGroupStyle, viewState.groupStyle)
+            .onAppear {
+                context.send(viewAction: .itemAppeared(itemID: viewState.identifier))
+            }
+            .onDisappear {
+                context.send(viewAction: .itemDisappeared(itemID: viewState.identifier))
+            }
+            .environment(\.openURL, OpenURLAction { url in
+                context.send(viewAction: .linkClicked(url: url))
+                return .systemAction
+            })
     }
 
     @ViewBuilder private var timelineView: some View {
-        switch viewModel.type {
+        switch viewState.type {
         case .text(let item):
             TextRoomTimelineView(timelineItem: item)
         case .separator(let item):
@@ -69,6 +79,6 @@ struct RoomTimelineItemView: View {
     }
 
     var timelineGroupStyle: TimelineGroupStyle {
-        viewModel.groupStyle
+        viewState.groupStyle
     }
 }

ElementX/Sources/Services/Timeline/TimelineItems/RoomTimelineItemViewState.swift

@@ -16,25 +16,18 @@
 
 import Foundation
 
-final class RoomTimelineItemViewModel: Identifiable, Equatable, ObservableObject {
-    static func == (lhs: RoomTimelineItemViewModel, rhs: RoomTimelineItemViewModel) -> Bool {
-        lhs.type == rhs.type && lhs.groupStyle == rhs.groupStyle
-    }
+struct RoomTimelineItemViewState: Identifiable, Equatable {
+    let type: RoomTimelineItemType
+    let groupStyle: TimelineGroupStyle
 
-    @Published var type: RoomTimelineItemType
-    @Published var groupStyle: TimelineGroupStyle
-
-    var id: TimelineItemIdentifier {
+    /// Contains all the identification info of the item, `timelineID`, `eventID` and `transactionID`
+    var identifier: TimelineItemIdentifier {
         type.id
     }
 
-    convenience init(item: RoomTimelineItemProtocol, groupStyle: TimelineGroupStyle) {
-        self.init(type: .init(item: item), groupStyle: groupStyle)
-    }
-
-    init(type: RoomTimelineItemType, groupStyle: TimelineGroupStyle) {
-        self.type = type
-        self.groupStyle = groupStyle
+    /// The `timelineID` of the item, used for the timeline view level identification, do not use for any business logic use `identifier` instead
+    var id: String {
+        identifier.timelineID
     }
 
     var isReactable: Bool {
@@ -42,6 +35,12 @@ final class RoomTimelineItemViewModel: Identifiable, Equatable, ObservableObject
     }
 }
 
+extension RoomTimelineItemViewState {
+    init(item: RoomTimelineItemProtocol, groupStyle: TimelineGroupStyle) {
+        self.init(type: .init(item: item), groupStyle: groupStyle)
+    }
+}
+
 enum RoomTimelineItemType: Equatable {
     case text(TextRoomTimelineItem)
     case separator(SeparatorRoomTimelineItem)