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import 'package:flutter/material.dart';
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import 'package:provider/provider.dart';
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import '../../constants/app_colors.dart';
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import '../../models/comment.dart';
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import '../../models/post.dart';
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import '../../providers/comments_provider.dart';
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import '../../utils/error_messages.dart';
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import '../../widgets/comment_thread.dart';
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import '../../widgets/comments_header.dart';
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import '../../widgets/loading_error_states.dart';
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import '../../widgets/post_card.dart';
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/// Post Detail Screen
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/// Displays a full post with its comments.
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/// Architecture: Standalone screen for route destination and PageView child.
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/// - Full post display (reuses PostCard widget)
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/// - Sort selector (Hot/Top/New) using dropdown
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/// - Comment list with ListView.builder for performance
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/// - Pull-to-refresh with RefreshIndicator
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/// - Loading, empty, and error states
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/// - Automatic comment loading on screen init
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class PostDetailScreen extends StatefulWidget {
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const PostDetailScreen({required this.post, super.key});
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/// Post to display (passed via route extras)
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final FeedViewPost post;
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State<PostDetailScreen> createState() => _PostDetailScreenState();
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class _PostDetailScreenState extends State<PostDetailScreen> {
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final ScrollController _scrollController = ScrollController();
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// Current sort option
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String _currentSort = 'hot';
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// Initialize scroll controller for pagination
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_scrollController.addListener(_onScroll);
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// Load comments after frame is built using provider from tree
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WidgetsBinding.instance.addPostFrameCallback((_) {
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_scrollController.dispose();
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/// Load comments for the current post
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void _loadComments() {
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context.read<CommentsProvider>().loadComments(
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postUri: widget.post.post.uri,
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/// Handle sort changes from dropdown
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Future<void> _onSortChanged(String newSort) async {
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final previousSort = _currentSort;
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_currentSort = newSort;
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final commentsProvider = context.read<CommentsProvider>();
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final success = await commentsProvider.setSortOption(newSort);
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// Show error snackbar and revert UI if sort change failed
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if (!success && mounted) {
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_currentSort = previousSort;
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ScaffoldMessenger.of(context).showSnackBar(
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content: const Text('Failed to change sort order. Please try again.'),
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backgroundColor: AppColors.primary,
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behavior: SnackBarBehavior.floating,
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duration: const Duration(seconds: 3),
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action: SnackBarAction(
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textColor: AppColors.textPrimary,
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_onSortChanged(newSort);
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/// Handle scroll for pagination
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if (_scrollController.position.pixels >=
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_scrollController.position.maxScrollExtent - 200) {
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context.read<CommentsProvider>().loadMoreComments();
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/// Handle pull-to-refresh
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Future<void> _onRefresh() async {
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final commentsProvider = context.read<CommentsProvider>();
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await commentsProvider.refreshComments();
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Widget build(BuildContext context) {
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backgroundColor: AppColors.background,
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backgroundColor: AppColors.background,
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foregroundColor: AppColors.textPrimary,
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title: Text(widget.post.post.title ?? 'Post'),
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// Explicitly set bottom to prevent iOS home indicator overlap
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child: _buildContent(),
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/// Build main content area
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Widget _buildContent() {
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// Use Consumer to rebuild when comments provider changes
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return Consumer<CommentsProvider>(
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builder: (context, commentsProvider, child) {
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final isLoading = commentsProvider.isLoading;
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final error = commentsProvider.error;
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final comments = commentsProvider.comments;
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final isLoadingMore = commentsProvider.isLoadingMore;
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// Loading state (only show full-screen loader for initial load)
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if (isLoading && comments.isEmpty) {
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return const FullScreenLoading();
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// Error state (only show full-screen error when no comments loaded yet)
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if (error != null && comments.isEmpty) {
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return FullScreenError(
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title: 'Failed to load comments',
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message: ErrorMessages.getUserFriendly(error),
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onRetry: commentsProvider.retry,
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// Content with RefreshIndicator
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return RefreshIndicator(
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onRefresh: _onRefresh,
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color: AppColors.primary,
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child: ListView.builder(
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controller: _scrollController,
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// Post + comments + loading indicator
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1 + comments.length + (isLoadingMore || error != null ? 1 : 0),
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itemBuilder: (context, index) {
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// Post card (index 0)
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// Reuse PostCard (hide comment button in detail view)
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// Use ValueListenableBuilder to only rebuild when time changes
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currentTimeNotifier: commentsProvider.currentTimeNotifier,
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// Comments header with sort dropdown
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commentCount: comments.length,
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currentSort: _currentSort,
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onSortChanged: _onSortChanged,
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// Loading indicator or error at the end
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if (index == comments.length + 1) {
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if (isLoadingMore) {
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return const InlineLoading();
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if (error != null) {
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return InlineError(
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message: ErrorMessages.getUserFriendly(error),
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..loadMoreComments();
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// Comment item - use existing CommentThread widget
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final comment = comments[index - 1];
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return _CommentItem(
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currentTimeNotifier: commentsProvider.currentTimeNotifier,
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/// Post header widget that only rebuilds when time changes
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/// Extracted to prevent unnecessary rebuilds when comment list changes.
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/// Uses ValueListenableBuilder to listen only to time updates.
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class _PostHeader extends StatelessWidget {
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const _PostHeader({
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required this.post,
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required this.currentTimeNotifier,
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final FeedViewPost post;
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final ValueNotifier<DateTime?> currentTimeNotifier;
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Widget build(BuildContext context) {
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return ValueListenableBuilder<DateTime?>(
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valueListenable: currentTimeNotifier,
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builder: (context, currentTime, child) {
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currentTime: currentTime,
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showCommentButton: false,
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disableNavigation: true,
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/// Comment item wrapper that only rebuilds when time changes
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/// Uses ValueListenableBuilder to prevent rebuilds when unrelated
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/// provider state changes (like loading state or error state).
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class _CommentItem extends StatelessWidget {
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const _CommentItem({
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required this.comment,
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required this.currentTimeNotifier,
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final ThreadViewComment comment;
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final ValueNotifier<DateTime?> currentTimeNotifier;
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Widget build(BuildContext context) {
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return ValueListenableBuilder<DateTime?>(
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valueListenable: currentTimeNotifier,
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builder: (context, currentTime, child) {
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return CommentThread(
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currentTime: currentTime,
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