content: import 'package:flutter/cupertino.dart';
  import 'package:flutter/material.dart';
  
  import 'package:scroll_to_index/scroll_to_index.dart';
  
  import 'package:fluffychat/config/themes.dart';
  import 'package:fluffychat/pages/chat/chat.dart';
  import 'package:fluffychat/pages/chat/events/message.dart';
  import 'package:fluffychat/pages/chat/seen_by_row.dart';
  import 'package:fluffychat/pages/chat/typing_indicators.dart';
  import 'package:fluffychat/utils/account_config.dart';
  import 'package:fluffychat/utils/matrix_sdk_extensions/filtered_timeline_extension.dart';
  import 'package:fluffychat/utils/platform_infos.dart';
  
  class ChatEventList extends StatelessWidget {
    final ChatController controller;
  
    const ChatEventList({
      super.key,
      required this.controller,
    });
  
    @override
    Widget build(BuildContext context) {
      final timeline = controller.timeline;
  
      if (timeline == null) {
        return const Center(child: CupertinoActivityIndicator());
      }
      final theme = Theme.of(context);
  
      final colors = [
        theme.secondaryBubbleColor,
        theme.bubbleColor,
      ];
  
      final horizontalPadding = FluffyThemes.isColumnMode(context) ? 8.0 : 0.0;
  
      final events = timeline.events.filterByVisibleInGui();
      final animateInEventIndex = controller.animateInEventIndex;
  
      // create a map of eventId --> index to greatly improve performance of
      // ListView's findChildIndexCallback
      final thisEventsKeyMap = <String, int>{};
      for (var i = 0; i < events.length; i++) {
        thisEventsKeyMap[events[i].eventId] = i;
      }
  
      final hasWallpaper =
          controller.room.client.applicationAccountConfig.wallpaperUrl != null;
  
      return SelectionArea(
        child: ListView.custom(
          padding: EdgeInsets.only(
            top: 16,
            bottom: 8,
            left: horizontalPadding,
            right: horizontalPadding,
          ),
          reverse: true,
          controller: controller.scrollController,
          keyboardDismissBehavior: PlatformInfos.isIOS
              ? ScrollViewKeyboardDismissBehavior.onDrag
              : ScrollViewKeyboardDismissBehavior.manual,
          childrenDelegate: SliverChildBuilderDelegate(
            (BuildContext context, int i) {
              // Footer to display typing indicator and read receipts:
              if (i == 0) {
                if (timeline.isRequestingFuture) {
                  return const Center(
                    child: CircularProgressIndicator.adaptive(strokeWidth: 2),
                  );
                }
                if (timeline.canRequestFuture) {
                  return Center(
                    child: IconButton(
                      onPressed: controller.requestFuture,
                      icon: const Icon(Icons.refresh_outlined),
                    ),
                  );
                }
                return Column(
                  mainAxisSize: MainAxisSize.min,
                  children: [
                    SeenByRow(controller),
                    TypingIndicators(controller),
                  ],
                );
              }
  
              // Request history button or progress indicator:
              if (i == events.length + 1) {
                if (timeline.isRequestingHistory) {
                  return const Center(
                    child: CircularProgressIndicator.adaptive(strokeWidth: 2),
                  );
                }
                if (timeline.canRequestHistory) {
                  return Builder(
                    builder: (context) {
                      WidgetsBinding.instance
                          .addPostFrameCallback(controller.requestHistory);
                      return Center(
                        child: IconButton(
                          onPressed: controller.requestHistory,
                          icon: const Icon(Icons.refresh_outlined),
                        ),
                      );
                    },
                  );
                }
                return const SizedBox.shrink();
              }
              i--;
  
              // The message at this index:
              final event = events[i];
              final animateIn = animateInEventIndex != null &&
                  timeline.events.length > animateInEventIndex &&
                  event == timeline.events[animateInEventIndex];
  
              final nextEvent = i + 1 < events.length ? events[i + 1] : null;
              final previousEvent = i > 0 ? events[i - 1] : null;
  
              // Collapsed state event
              final canExpand = event.isCollapsedState &&
                  nextEvent?.isCollapsedState == true &&
                  previousEvent?.isCollapsedState != true;
              final isCollapsed = event.isCollapsedState &&
                  previousEvent?.isCollapsedState == true &&
                  !controller.expandedEventIds.contains(event.eventId);
  
              return AutoScrollTag(
                key: ValueKey(event.eventId),
                index: i,
                controller: controller.scrollController,
                child: Message(
                  event,
                  animateIn: animateIn,
                  resetAnimateIn: () {
                    controller.animateInEventIndex = null;
                  },
                  onSwipe: () => controller.replyAction(replyTo: event),
                  onInfoTab: controller.showEventInfo,
                  onMention: () => controller.sendController.text +=
                      '${event.senderFromMemoryOrFallback.mention} ',
                  highlightMarker:
                      controller.scrollToEventIdMarker == event.eventId,
                  onSelect: controller.onSelectMessage,
                  scrollToEventId: (String eventId) =>
                      controller.scrollToEventId(eventId),
                  longPressSelect: controller.selectedEvents.isNotEmpty,
                  selected: controller.selectedEvents
                      .any((e) => e.eventId == event.eventId),
                  singleSelected:
                      controller.selectedEvents.singleOrNull?.eventId ==
                          event.eventId,
                  onEdit: () => controller.editSelectedEventAction(),
                  timeline: timeline,
                  displayReadMarker:
                      i > 0 && controller.readMarkerEventId == event.eventId,
                  nextEvent: nextEvent,
                  previousEvent: previousEvent,
                  wallpaperMode: hasWallpaper,
                  scrollController: controller.scrollController,
                  colors: colors,
                  isCollapsed: isCollapsed,
                  onExpand: canExpand
                      ? () => controller.expandEventsFrom(
                            event,
                            !controller.expandedEventIds.contains(event.eventId),
                          )
                      : null,
                ),
              );
            },
            childCount: events.length + 2,
            findChildIndexCallback: (key) =>
                controller.findChildIndexCallback(key, thisEventsKeyMap),
          ),
        ),
      );
    }
  }
  