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

import '../../core/exceptions.dart';
import '../../data/models/message.dart';
import '../../providers/briefing_provider.dart';
import '../../widgets/briefing_digest_card.dart';
import '../../widgets/chat_message_bubble.dart';
import 'briefing_history_screen.dart';

class BriefingScreen extends ConsumerStatefulWidget {
  const BriefingScreen({super.key});

  @override
  ConsumerState<BriefingScreen> createState() => _BriefingScreenState();
}

class _BriefingScreenState extends ConsumerState<BriefingScreen> {
  final _controller = TextEditingController();
  final _scrollController = ScrollController();
  bool _refreshing = false;

  @override
  void dispose() {
    _controller.dispose();
    _scrollController.dispose();
    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> _sendReply() async {
    final text = _controller.text.trim();
    if (text.isEmpty) return;
    _controller.clear();
    try {
      await ref.read(briefingProvider.notifier).sendReply(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 reply.')),
        );
      }
    }
  }

  Future<void> _refresh() async {
    setState(() => _refreshing = true);
    try {
      await ref.read(briefingProvider.notifier).refresh('compilation');
    } catch (_) {
      if (mounted) {
        ScaffoldMessenger.of(context).showSnackBar(
          const SnackBar(content: Text('Could not generate briefing.')),
        );
      }
    } finally {
      if (mounted) setState(() => _refreshing = false);
    }
  }

  @override
  Widget build(BuildContext context) {
    final briefingAsync = ref.watch(briefingProvider);
    final isStreaming = ref.watch(isBriefingStreamingProvider);
    final scheme = Theme.of(context).colorScheme;

    // Scroll to bottom when messages change
    ref.listen(briefingProvider, (_, _) => _scrollToBottom());

    return Scaffold(
      appBar: AppBar(
        title: Column(
          crossAxisAlignment: CrossAxisAlignment.start,
          children: [
            Text('Briefing', style: Theme.of(context).textTheme.titleLarge),
            Text(
              _todayLabel(),
              style: Theme.of(context).textTheme.labelSmall?.copyWith(
                    color: scheme.onSurfaceVariant,
                  ),
            ),
          ],
        ),
        actions: [
          if (_refreshing)
            const Padding(
              padding: EdgeInsets.symmetric(horizontal: 12),
              child: SizedBox(
                width: 20,
                height: 20,
                child: CircularProgressIndicator(strokeWidth: 2),
              ),
            )
          else
            IconButton(
              icon: const Icon(Icons.refresh_outlined),
              tooltip: 'Generate briefing',
              onPressed: _refresh,
            ),
          PopupMenuButton<String>(
            onSelected: (value) {
              if (value == 'history') {
                Navigator.of(context).push(MaterialPageRoute(
                  builder: (_) => const BriefingHistoryScreen(),
                ));
              }
            },
            itemBuilder: (_) => const [
              PopupMenuItem(
                value: 'history',
                child: Text('View past briefings'),
              ),
            ],
          ),
        ],
      ),
      body: briefingAsync.when(
        loading: () => const Center(child: CircularProgressIndicator()),
        error: (_, _) => Center(
          child: Column(
            mainAxisSize: MainAxisSize.min,
            children: [
              const Text("Could not load today's briefing."),
              const SizedBox(height: 12),
              FilledButton.tonal(
                onPressed: () => ref.invalidate(briefingProvider),
                child: const Text('Retry'),
              ),
            ],
          ),
        ),
        data: (conv) {
          // First assistant message for the digest card (null if none yet)
          final Message? firstAssistant = conv.messages
              .where((m) => m.role == MessageRole.assistant)
              .toList()
              .firstOrNull;

          return Column(
            children: [
              // Digest card header
              BriefingDigestCard(
                message: firstAssistant,
                onGenerateNow: _refresh,
              ),

              // Divider + label
              if (conv.messages.isNotEmpty) ...[
                const SizedBox(height: 4),
                Row(children: [
                  const Expanded(child: Divider()),
                  Padding(
                    padding: const EdgeInsets.symmetric(horizontal: 10),
                    child: Text(
                      'Conversation',
                      style: Theme.of(context).textTheme.labelSmall?.copyWith(
                            color: scheme.onSurfaceVariant,
                          ),
                    ),
                  ),
                  const Expanded(child: Divider()),
                ]),
              ],

              // Message list
              Expanded(
                child: ListView.builder(
                  controller: _scrollController,
                  padding: const EdgeInsets.symmetric(
                      horizontal: 8, vertical: 8),
                  itemCount: conv.messages.length,
                  itemBuilder: (_, i) =>
                      ChatMessageBubble(message: conv.messages[i]),
                ),
              ),

              // Progress bar while streaming
              if (isStreaming)
                LinearProgressIndicator(
                  minHeight: 2,
                  color: scheme.primary,
                ),

              // Reply bar
              const Divider(height: 1),
              SafeArea(
                child: Padding(
                  padding: const EdgeInsets.fromLTRB(8, 6, 8, 6),
                  child: Row(
                    children: [
                      Expanded(
                        child: TextField(
                          controller: _controller,
                          decoration: const InputDecoration(
                            hintText: 'Reply to your briefing…',
                            border: OutlineInputBorder(),
                            isDense: true,
                            contentPadding: EdgeInsets.symmetric(
                                horizontal: 12, vertical: 10),
                          ),
                          minLines: 1,
                          maxLines: 4,
                          textInputAction: TextInputAction.newline,
                          enabled: !isStreaming,
                        ),
                      ),
                      const SizedBox(width: 8),
                      _GradientSendButton(
                        onPressed: isStreaming ? null : _sendReply,
                        isStreaming: isStreaming,
                      ),
                    ],
                  ),
                ),
              ),
            ],
          );
        },
      ),
    );
  }

  String _todayLabel() {
    final now = DateTime.now();
    const days = [
      'Monday', 'Tuesday', 'Wednesday', 'Thursday',
      'Friday', 'Saturday', 'Sunday'
    ];
    const months = [
      'January', 'February', 'March', 'April', 'May', 'June',
      'July', 'August', 'September', 'October', 'November', 'December'
    ];
    return '${days[now.weekday - 1]}, ${months[now.month - 1]} ${now.day}';
  }
}

class _GradientSendButton extends StatelessWidget {
  final VoidCallback? onPressed;
  final bool isStreaming;

  const _GradientSendButton({
    required this.onPressed,
    required this.isStreaming,
  });

  @override
  Widget build(BuildContext context) {
    final scheme = Theme.of(context).colorScheme;
    final disabled = onPressed == null;

    return DecoratedBox(
      decoration: BoxDecoration(
        gradient: disabled
            ? null
            : const LinearGradient(
                begin: Alignment.topLeft,
                end: Alignment.bottomRight,
                colors: [Color(0xFF6366F1), Color(0xFF4F46E5)],
              ),
        color: disabled ? scheme.onSurface.withValues(alpha: 0.12) : null,
        borderRadius: BorderRadius.circular(10),
      ),
      child: IconButton(
        icon: isStreaming
            ? const SizedBox(
                width: 20,
                height: 20,
                child: CircularProgressIndicator(
                  strokeWidth: 2,
                  color: Colors.white,
                ),
              )
            : Icon(
                Icons.send,
                color: disabled
                    ? scheme.onSurface.withValues(alpha: 0.38)
                    : Colors.white,
              ),
        onPressed: onPressed,
      ),
    );
  }
}