import "package:provider/provider.dart";
import "package:shadcn_flutter/shadcn_flutter.dart";

import "../providers/chat_provider.dart";
import "message_bubble.dart";

class ChatView extends StatefulWidget {
  const ChatView();

  @override
  State<ChatView> createState() => _ChatViewState();
}

class _ChatViewState extends State<ChatView> {
  late ScrollController _scrollController;
  List<String> _previousMessageContents = [];
  bool _isUserScrolling = false;
  DateTime? _lastScrollTime;
  bool _showJumpToBottom = false;
  bool _hasNewMessagesWhileScrolledAway = false;

  @override
  void initState() {
    super.initState();
    _scrollController = ScrollController();
    _scrollController.addListener(_handleScroll);
  }

  @override
  void dispose() {
    _scrollController.removeListener(_handleScroll);
    _scrollController.dispose();
    super.dispose();
  }

  void _handleScroll() {
    _lastScrollTime = DateTime.now();
    _isUserScrolling = true;
    
    // Update whether to show jump-to-bottom button
    if (_scrollController.hasClients) {
      final position = _scrollController.position;
      final isFarFromBottom = position.pixels < position.maxScrollExtent - 200;
      if (isFarFromBottom != _showJumpToBottom) {
        setState(() {
          _showJumpToBottom = isFarFromBottom;
        });
      }
      
      // If user scrolls to bottom manually, clear the new messages flag
      if (!isFarFromBottom) {
        setState(() {
          _hasNewMessagesWhileScrolledAway = false;
        });
      }
    }
    
    // Check if scrolling has stopped (no scroll events for 150ms)
    Future.delayed(const Duration(milliseconds: 150), () {
      if (_lastScrollTime != null && 
          DateTime.now().difference(_lastScrollTime!) >= const Duration(milliseconds: 150)) {
        if (mounted) {
          setState(() {
            _isUserScrolling = false;
          });
        }
      }
    });
  }

  bool _isNearBottom() {
    if (!_scrollController.hasClients) return false;
    
    final position = _scrollController.position;
    // Consider user to be "near bottom" if they're within 150 pixels of the bottom
    // Add a small buffer so we don't trigger on exact bottom
    return position.pixels >= position.maxScrollExtent - 150;
  }

  void _jumpToBottom() {
    if (_scrollController.hasClients) {
      _scrollController.animateTo(
        _scrollController.position.maxScrollExtent,
        duration: const Duration(milliseconds: 300),
        curve: Curves.easeOut,
      );
      setState(() {
        _showJumpToBottom = false;
        _hasNewMessagesWhileScrolledAway = false;
      });
    }
  }

  @override
  Widget build(BuildContext context) {
    return Consumer<ChatProvider>(
      builder: (context, chatProvider, _) {
        // Get current messages
        final currentMessages = chatProvider.messages;
        
        // Check if messages have actually changed (not just re-renders)
        bool messagesChanged = false;
        
        if (currentMessages.length != _previousMessageContents.length) {
          messagesChanged = true;
        } else {
          for (int i = 0; i < currentMessages.length; i++) {
            if (i >= _previousMessageContents.length || 
                currentMessages[i].content != _previousMessageContents[i]) {
              messagesChanged = true;
              break;
            }
          }
        }
        
        if (messagesChanged && currentMessages.isNotEmpty) {
          // Check if we're near the bottom
          final nearBottom = _isNearBottom();
          
          if (nearBottom && !_isUserScrolling) {
            // Auto-scroll to bottom if user is near bottom and not scrolling
            WidgetsBinding.instance.addPostFrameCallback((_) {
              if (_scrollController.hasClients) {
                _scrollController.animateTo(
                  _scrollController.position.maxScrollExtent,
                  duration: const Duration(milliseconds: 300),
                  curve: Curves.easeOut,
                );
              }
            });
            _hasNewMessagesWhileScrolledAway = false;
          } else if (!nearBottom) {
            // User is scrolled away from bottom when new messages arrive
            _hasNewMessagesWhileScrolledAway = true;
          }
        }

        // Update previous message state for next build
        WidgetsBinding.instance.addPostFrameCallback((_) {
          _previousMessageContents = currentMessages.map((m) => m.content).toList();
        });

        return Stack(
          children: [
            ListView.builder(
              controller: _scrollController,
              itemCount: currentMessages.length,
              itemBuilder: (context, index) {
                final message = currentMessages[index];
                return Padding(
                  padding: EdgeInsetsGeometry.only(
                    top: index != 0 ? 12 : 0
                  ),
                  child: MessageBubble(message: message)
                );
              },
            ),
            if (_showJumpToBottom && _hasNewMessagesWhileScrolledAway)
              Positioned(
                bottom: 16,
                right: 16,
                child: GestureDetector(
                  onTap: _jumpToBottom,
                  child: AnimatedContainer(
                    duration: const Duration(milliseconds: 200),
                    padding: const EdgeInsets.all(12),
                    decoration: BoxDecoration(
                      color: Theme.of(context).colorScheme.background.withOpacity(0.9),
                      borderRadius: BorderRadius.circular(24),
                      boxShadow: [
                        BoxShadow(
                          color: const Color(0xFF000000).withOpacity(0.1),
                          blurRadius: 8,
                          offset: const Offset(0, 2),
                        ),
                      ],
                    ),
                    child: Row(
                      mainAxisSize: MainAxisSize.min,
                      children: [
                        Icon(
                          LucideIcons.arrowDown,
                          size: 16,
                          color: Theme.of(context).colorScheme.foreground,
                        ),
                        const SizedBox(width: 6),
                        Text(
                          "New messages",
                          style: TextStyle(
                            fontSize: 12,
                            fontWeight: FontWeight.w500,
                            color: Theme.of(context).colorScheme.foreground,
                          ),
                        ),
                      ],
                    ),
                  ),
                ),
              ),
          ],
        );
      },
    );
  }
}