IceCubesApp/Packages/Timeline/Sources/Timeline/TimelineView.swift

import Charts
import DesignSystem
import Env
import Models
import Network
import Shimmer
import Status
import SwiftData
import SwiftUI
import SwiftUIIntrospect

@MainActor
public struct TimelineView: View {
  @Environment(\.scenePhase) private var scenePhase
  @Environment(Theme.self) private var theme
  @Environment(CurrentAccount.self) private var account
  @Environment(StreamWatcher.self) private var watcher
  @Environment(Client.self) private var client
  @Environment(RouterPath.self) private var routerPath

  @State private var viewModel = TimelineViewModel()
  @State private var prefetcher = TimelinePrefetcher()

  @State private var wasBackgrounded: Bool = false
  @State private var collectionView: UICollectionView?

  @Binding var timeline: TimelineFilter
  @Binding var selectedTagGroup: TagGroup?
  @Binding var scrollToTopSignal: Int

  @Query(sort: \TagGroup.creationDate, order: .reverse) var tagGroups: [TagGroup]

  private let canFilterTimeline: Bool

  public init(timeline: Binding<TimelineFilter>,
              selectedTagGroup: Binding<TagGroup?>,
              scrollToTopSignal: Binding<Int>,
              canFilterTimeline: Bool)
  {
    _timeline = timeline
    _selectedTagGroup = selectedTagGroup
    _scrollToTopSignal = scrollToTopSignal
    self.canFilterTimeline = canFilterTimeline
  }

  public var body: some View {
    ScrollViewReader { proxy in
      ZStack(alignment: .top) {
        List {
          scrollToTopView
          tagGroupHeaderView
          tagHeaderView
          switch viewModel.timeline {
          case .remoteLocal:
            StatusesListView(fetcher: viewModel, client: client, routerPath: routerPath, isRemote: true)
          default:
            StatusesListView(fetcher: viewModel, client: client, routerPath: routerPath)
              .environment(\.isHomeTimeline, timeline == .home)
          }
        }
        .id(client.id)
        .environment(\.defaultMinListRowHeight, 1)
        .listStyle(.plain)
        #if !os(visionOS)
        .scrollContentBackground(.hidden)
        .background(theme.primaryBackgroundColor)
        #endif
        .introspect(.list, on: .iOS(.v17)) { (collectionView: UICollectionView) in
          DispatchQueue.main.async {
            self.collectionView = collectionView
          }
          prefetcher.viewModel = viewModel
          collectionView.isPrefetchingEnabled = true
          collectionView.prefetchDataSource = prefetcher
        }
        if viewModel.timeline.supportNewestPagination {
          PendingStatusesObserverView(observer: viewModel.pendingStatusesObserver)
        }
      }
      .onChange(of: viewModel.scrollToIndex) { _, newValue in
        if let collectionView,
           let newValue,
           let rows = collectionView.dataSource?.collectionView(collectionView, numberOfItemsInSection: 0),
           rows > newValue
        {
          collectionView.scrollToItem(at: .init(row: newValue, section: 0),
                                      at: .top,
                                      animated: viewModel.scrollToIndexAnimated)
          viewModel.scrollToIndexAnimated = false
          viewModel.scrollToIndex = nil
        }
      }
      .onChange(of: scrollToTopSignal) {
        withAnimation {
          proxy.scrollTo(ScrollToView.Constants.scrollToTop, anchor: .top)
        }
      }
    }
    .toolbar {
      toolbarTitleView
      toolbarTagGroupButton
    }
    .navigationBarTitleDisplayMode(.inline)
    .onAppear {
      viewModel.isTimelineVisible = true

      if viewModel.client == nil {
        viewModel.client = client
      }

      viewModel.timeline = timeline
    }
    .onDisappear {
      viewModel.isTimelineVisible = false
      viewModel.saveMarker()
    }
    .refreshable {
      SoundEffectManager.shared.playSound(.pull)
      HapticManager.shared.fireHaptic(.dataRefresh(intensity: 0.3))
      await viewModel.pullToRefresh()
      HapticManager.shared.fireHaptic(.dataRefresh(intensity: 0.7))
      SoundEffectManager.shared.playSound(.refresh)
    }
    .onChange(of: watcher.latestEvent?.id) {
      if let latestEvent = watcher.latestEvent {
        viewModel.handleEvent(event: latestEvent, currentAccount: account)
      }
    }
    .onChange(of: timeline) { _, newValue in
      switch newValue {
      case let .remoteLocal(server, _):
        viewModel.client = Client(server: server)
      default:
        viewModel.client = client
      }
      viewModel.timeline = newValue
    }
    .onChange(of: viewModel.timeline) { _, newValue in
      timeline = newValue
    }
    .onChange(of: scenePhase) { _, newValue in
      switch newValue {
      case .active:
        if wasBackgrounded {
          wasBackgrounded = false
          viewModel.refreshTimeline()
        }
      case .background:
        wasBackgrounded = true
        viewModel.saveMarker()
        
      default:
        break
      }
    }
  }

  @ViewBuilder
  private var tagHeaderView: some View {
    if let tag = viewModel.tag {
      headerView {
        HStack {
          TagChartView(tag: tag)
            .padding(.top, 12)

          VStack(alignment: .leading, spacing: 4) {
            Text("#\(tag.name)")
              .font(.scaledHeadline)
            Text("timeline.n-recent-from-n-participants \(tag.totalUses) \(tag.totalAccounts)")
              .font(.scaledFootnote)
              .foregroundStyle(.secondary)
          }
          .accessibilityElement(children: .combine)
          Spacer()
          Button {
            Task {
              if tag.following {
                viewModel.tag = await account.unfollowTag(id: tag.name)
              } else {
                viewModel.tag = await account.followTag(id: tag.name)
              }
            }
          } label: {
            Text(tag.following ? "account.follow.following" : "account.follow.follow")
          }.buttonStyle(.bordered)
        }
      }
    }
  }

  @ViewBuilder
  private var tagGroupHeaderView: some View {
    if let group = selectedTagGroup {
      headerView {
        HStack {
          ScrollView(.horizontal) {
            HStack(spacing: 4) {
              ForEach(group.tags, id: \.self) { tag in
                Button {
                  routerPath.navigate(to: .hashTag(tag: tag, account: nil))
                } label: {
                  Text("#\(tag)")
                    .font(.scaledHeadline)
                }
                .buttonStyle(.plain)
              }
            }
          }
          .scrollIndicators(.hidden)
          Button("status.action.edit") {
            routerPath.presentedSheet = .editTagGroup(tagGroup: group, onSaved: { group in
              viewModel.timeline = .tagGroup(title: group.title, tags: group.tags)
            })
          }
          .buttonStyle(.bordered)
        }
      }
    }
  }

  @ViewBuilder
  private func headerView(
    @ViewBuilder content: () -> some View
  ) -> some View {
    VStack(alignment: .leading) {
      Spacer()
      content()
      Spacer()
    }
    .listRowBackground(theme.secondaryBackgroundColor)
    .listRowSeparator(.hidden)
    .listRowInsets(.init(top: 8,
                         leading: .layoutPadding,
                         bottom: 8,
                         trailing: .layoutPadding))
  }

  @ToolbarContentBuilder
  private var toolbarTitleView: some ToolbarContent {
    ToolbarItem(placement: .principal) {
      VStack(alignment: .center) {
        switch timeline {
        case let .remoteLocal(_, filter):
          Text(filter.localizedTitle())
            .font(.headline)
          Text(timeline.localizedTitle())
            .font(.caption)
            .foregroundStyle(.secondary)
        case .home:
          Text(timeline.localizedTitle())
            .font(.headline)
        default:
          Text(timeline.localizedTitle())
            .font(.headline)
        }
      }
      .accessibilityRepresentation {
        switch timeline {
        case let .remoteLocal(_, filter):
          if canFilterTimeline {
            Menu(filter.localizedTitle()) {}
          } else {
            Text(filter.localizedTitle())
          }
        default:
          if canFilterTimeline {
            Menu(timeline.localizedTitle()) {}
          } else {
            Text(timeline.localizedTitle())
          }
        }
      }
      .accessibilityAddTraits(.isHeader)
      .accessibilityRemoveTraits(.isButton)
      .accessibilityRespondsToUserInteraction(canFilterTimeline)
    }
  }

  @ToolbarContentBuilder
  private var toolbarTagGroupButton: some ToolbarContent {
    ToolbarItem(placement: .topBarTrailing) {
      switch timeline {
      case let .hashtag(tag, _):
        if !tagGroups.isEmpty {
          Menu {
            Section("tag-groups.edit.section.title") {
              ForEach(tagGroups) { group in
                Button {
                  if group.tags.contains(tag) {
                    group.tags.removeAll(where: { $0 == tag })
                  } else {
                    group.tags.append(tag)
                  }
                } label: {
                  Label(group.title,
                        systemImage: group.tags.contains(tag) ? "checkmark.rectangle.fill" : "checkmark.rectangle")
                }
              }
            }
          } label: {
            Image(systemName: "ellipsis")
          }
        }
      default:
        EmptyView()
      }
    }
  }

  private var scrollToTopView: some View {
    ScrollToView()
      .frame(height: .layoutPadding)
      .onAppear {
        viewModel.scrollToTopVisible = true
      }
      .onDisappear {
        viewModel.scrollToTopVisible = false
      }
  }
}