import 'package:flutter/cupertino.dart';
import 'package:flutter/material.dart';

import 'package:collection/collection.dart';
import 'package:scroll_to_index/scroll_to_index.dart';

import 'package:fluffychat/config/themes.dart';
import 'package:fluffychat/l10n/l10n.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(
      threadId: controller.activeThreadId,
    );
    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.canRequestFuture) {
                return Center(
                  child: TextButton.icon(
                    onPressed: timeline.isRequestingFuture
                        ? null
                        : controller.requestFuture,
                    icon: timeline.isRequestingFuture
                        ? CircularProgressIndicator.adaptive(strokeWidth: 2)
                        : const Icon(Icons.arrow_downward_outlined),
                    label: Text(L10n.of(context).loadMore),
                  ),
                );
              }
              return Column(
                mainAxisSize: .min,
                children: [SeenByRow(controller), TypingIndicators(controller)],
              );
            }

            // Request history button or progress indicator:
            if (i == events.length + 1) {
              if (controller.activeThreadId != null ||
                  !timeline.canRequestHistory) {
                return const SizedBox.shrink();
              }
              return Builder(
                builder: (context) {
                  final visibleIndex = timeline.events.lastIndexWhere(
                    (event) => !event.isCollapsedState && event.isVisibleInGui,
                  );
                  if (visibleIndex > timeline.events.length - 50) {
                    WidgetsBinding.instance.addPostFrameCallback(
                      controller.requestHistory,
                    );
                  }
                  return Center(
                    child: TextButton.icon(
                      onPressed: timeline.isRequestingHistory
                          ? null
                          : controller.requestHistory,
                      icon: timeline.isRequestingHistory
                          ? CircularProgressIndicator.adaptive(strokeWidth: 2)
                          : const Icon(Icons.arrow_upward_outlined),
                      label: Text(L10n.of(context).loadMore),
                    ),
                  );
                },
              );
            }
            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,
                enterThread: controller.activeThreadId == null
                    ? controller.enterThread
                    : null,
                onExpand: canExpand
                    ? () => controller.expandEventsFrom(
                        event,
                        !controller.expandedEventIds.contains(event.eventId),
                      )
                    : null,
              ),
            );
          },
          childCount: events.length + 2,
          findChildIndexCallback: (key) =>
              controller.findChildIndexCallback(key, thisEventsKeyMap),
        ),
      ),
    );
  }
}