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

import '../../core/exceptions.dart';
import '../../data/models/message.dart';
import '../../providers/chat_provider.dart';
import '../../providers/voice_provider.dart';
import '../../widgets/chat_message_bubble.dart';
import '../../widgets/voice_mic_button.dart';

class ChatScreen extends ConsumerStatefulWidget {
  final int conversationId;
  const ChatScreen({super.key, required this.conversationId});

  @override
  ConsumerState<ChatScreen> createState() => _ChatScreenState();
}

class _ChatScreenState extends ConsumerState<ChatScreen>
    with WidgetsBindingObserver {
  final _controller = TextEditingController();
  final _scrollController = ScrollController();
  bool _refreshing = false;

  Future<void> _refreshMessages() async {
    if (_refreshing) return;
    setState(() => _refreshing = true);
    try {
      await ref
          .read(messagesProvider(widget.conversationId).notifier)
          .refresh();
    } catch (_) {
      if (mounted) {
        ScaffoldMessenger.of(context).showSnackBar(
          const SnackBar(content: Text('Could not refresh messages.')),
        );
      }
    } finally {
      if (mounted) setState(() => _refreshing = false);
    }
  }

  @override
  void initState() {
    super.initState();
    WidgetsBinding.instance.addObserver(this);
  }

  @override
  void didChangeAppLifecycleState(AppLifecycleState state) {
    if (state == AppLifecycleState.resumed) {
      ref.read(messagesProvider(widget.conversationId).notifier).refresh();
    }
  }

  @override
  void dispose() {
    WidgetsBinding.instance.removeObserver(this);
    _controller.dispose();
    _scrollController.dispose();
    // Exit voice mode if the user navigates away mid-session.
    ref.read(voiceProvider.notifier).exitVoiceMode();
    super.dispose();
  }

  void _scrollToBottom() {
    WidgetsBinding.instance.addPostFrameCallback((_) {
      if (_scrollController.hasClients) {
        _scrollController.animateTo(
          _scrollController.position.maxScrollExtent,
          duration: const Duration(milliseconds: 200),
          curve: Curves.easeOut,
        );
      }
    });
  }

  Future<void> _send() async {
    final text = _controller.text.trim();
    if (text.isEmpty) return;
    _controller.clear();
    try {
      await ref
          .read(messagesProvider(widget.conversationId).notifier)
          .sendMessage(text);
    } on AppException catch (e) {
      if (mounted) {
        ScaffoldMessenger.of(context)
            .showSnackBar(SnackBar(content: Text(e.message)));
      }
    } catch (_) {
      if (mounted) {
        ScaffoldMessenger.of(context).showSnackBar(
          const SnackBar(content: Text('Failed to send message.')),
        );
      }
    }
  }

  Future<void> _toggleVoiceMode() async {
    final voice = ref.read(voiceProvider);
    if (voice.voiceModeActive) {
      ref.read(voiceProvider.notifier).exitVoiceMode();
      return;
    }
    await ref.read(voiceProvider.notifier).enterVoiceMode(
      onTranscript: (transcript) async {
        await ref
            .read(messagesProvider(widget.conversationId).notifier)
            .sendMessage(transcript);
      },
      enableTts: true,
      onError: (msg) {
        if (mounted) {
          ScaffoldMessenger.of(context)
              .showSnackBar(SnackBar(content: Text(msg)));
        }
      },
    );
  }

  @override
  Widget build(BuildContext context) {
    final messagesAsync = ref.watch(messagesProvider(widget.conversationId));
    final isStreaming = ref.watch(isStreamingProvider(widget.conversationId));
    final streamingStatus =
        ref.watch(streamingStatusProvider(widget.conversationId));
    final voiceState = ref.watch(voiceProvider);

    // Scroll when messages change.
    ref.listen(messagesProvider(widget.conversationId), (prev, next) {
      _scrollToBottom();
    });

    // Feed streaming content to VoiceNotifier for TTS.
    ref.listen(messagesProvider(widget.conversationId), (prev, next) {
      if (!voiceState.voiceModeActive) return;
      final messages = next.value;
      if (messages == null || messages.isEmpty) return;
      final last = messages.last;
      if (last.role != MessageRole.assistant) return;
      final isComplete = last.status != 'generating';
      ref
          .read(voiceProvider.notifier)
          .feedContent(last.content, isComplete: isComplete);
    });

    final convTitle = ref
        .watch(conversationsProvider)
        .value
        ?.where((c) => c.id == widget.conversationId)
        .firstOrNull
        ?.title;

    return Scaffold(
      appBar: AppBar(
        title: Text(convTitle?.isNotEmpty == true ? convTitle! : 'Chat'),
        actions: [
          IconButton(
            tooltip: 'Refresh',
            onPressed: _refreshing ? null : _refreshMessages,
            icon: _refreshing
                ? const SizedBox(
                    width: 18,
                    height: 18,
                    child: CircularProgressIndicator(strokeWidth: 2),
                  )
                : const Icon(Icons.refresh),
          ),
        ],
      ),
      body: Column(
        children: [
          Expanded(
            child: messagesAsync.when(
              loading: () =>
                  const Center(child: CircularProgressIndicator()),
              error: (err, stack) => const Center(
                child: Text('Could not load messages.'),
              ),
              data: (messages) {
                return RefreshIndicator(
                  onRefresh: _refreshMessages,
                  child: messages.isEmpty
                      ? ListView(
                          // Needs to be scrollable for RefreshIndicator to
                          // fire on empty state — plain Center won't work.
                          physics: const AlwaysScrollableScrollPhysics(),
                          children: const [
                            SizedBox(height: 240),
                            Center(child: Text('Send a message to start.')),
                          ],
                        )
                      : ListView.builder(
                          controller: _scrollController,
                          physics: const AlwaysScrollableScrollPhysics(),
                          padding: const EdgeInsets.symmetric(
                              horizontal: 8, vertical: 12),
                          itemCount: messages.length,
                          itemBuilder: (context, i) => ChatMessageBubble(
                            message: messages[i],
                            streamingStatus: (i == messages.length - 1 &&
                                    messages[i].status == 'generating')
                                ? streamingStatus
                                : '',
                          ),
                        ),
                );
              },
            ),
          ),
          // Voice mode banner
          if (voiceState.voiceModeActive)
            Container(
              width: double.infinity,
              color: const Color(0xFFEF4444).withValues(alpha: 0.12),
              padding:
                  const EdgeInsets.symmetric(horizontal: 16, vertical: 6),
              child: const Text(
                '🎤 Listening… tap mic to exit voice mode',
                style: TextStyle(
                  fontSize: 12,
                  color: Color(0xFFF87171),
                ),
              ),
            ),
          const Divider(height: 1),
          SafeArea(
            child: Padding(
              padding:
                  const EdgeInsets.symmetric(horizontal: 8, vertical: 6),
              child: Row(
                children: [
                  Expanded(
                    child: TextField(
                      controller: _controller,
                      decoration: InputDecoration(
                        hintText: voiceState.voiceModeActive
                            ? 'Listening…'
                            : 'Message…',
                        hintStyle: voiceState.voiceModeActive
                            ? const TextStyle(fontStyle: FontStyle.italic)
                            : null,
                        border: const OutlineInputBorder(),
                        isDense: true,
                        contentPadding: const EdgeInsets.symmetric(
                            horizontal: 12, vertical: 10),
                      ),
                      maxLines:
                          MediaQuery.of(context).size.width >= 600 ? 2 : 4,
                      minLines: 1,
                      textInputAction: TextInputAction.newline,
                      enabled: !isStreaming && !voiceState.voiceModeActive,
                    ),
                  ),
                  const SizedBox(width: 8),
                  VoiceMicButton(
                    mode: voiceState.mode,
                    voiceModeActive: voiceState.voiceModeActive,
                    onTap: _toggleVoiceMode,
                  ),
                  const SizedBox(width: 6),
                  IconButton.filled(
                    onPressed: (isStreaming || voiceState.voiceModeActive)
                        ? null
                        : _send,
                    icon: isStreaming
                        ? const SizedBox(
                            width: 20,
                            height: 20,
                            child:
                                CircularProgressIndicator(strokeWidth: 2),
                          )
                        : const Icon(Icons.send),
                  ),
                ],
              ),
            ),
          ),
        ],
      ),
    );
  }
}