import 'package:auto_route/auto_route.dart';
import 'package:flutter/material.dart';
import 'package:flutter_riverpod/flutter_riverpod.dart';
import 'package:google_fonts/google_fonts.dart';
import 'package:trainhub_flutter/core/constants/ui_constants.dart';
import 'package:trainhub_flutter/core/theme/app_colors.dart';
import 'package:trainhub_flutter/data/services/ai_process_manager.dart';
import 'package:trainhub_flutter/domain/entities/chat_session.dart';
import 'package:trainhub_flutter/presentation/chat/chat_controller.dart';
import 'package:trainhub_flutter/presentation/chat/chat_state.dart';
import 'package:trainhub_flutter/presentation/chat/widgets/message_bubble.dart';
import 'package:trainhub_flutter/presentation/chat/widgets/missing_models_state.dart';
import 'package:trainhub_flutter/presentation/chat/widgets/new_chat_button.dart';
import 'package:trainhub_flutter/presentation/chat/widgets/typing_bubble.dart';
import 'package:trainhub_flutter/presentation/chat/widgets/typing_indicator.dart';
import 'package:trainhub_flutter/presentation/settings/ai_model_settings_controller.dart';

@RoutePage()
class ChatPage extends ConsumerStatefulWidget {
  const ChatPage({super.key});

  @override
  ConsumerState<ChatPage> createState() => _ChatPageState();
}

class _ChatPageState extends ConsumerState<ChatPage> {
  final TextEditingController _inputController = TextEditingController();
  final ScrollController _scrollController = ScrollController();
  final FocusNode _inputFocusNode = FocusNode();
  String? _hoveredSessionId;

  @override
  void dispose() {
    _inputController.dispose();
    _scrollController.dispose();
    _inputFocusNode.dispose();
    super.dispose();
  }

  void _scrollToBottom() {
    WidgetsBinding.instance.addPostFrameCallback((_) {
      if (_scrollController.hasClients) {
        _scrollController.animateTo(
          _scrollController.position.maxScrollExtent,
          duration: const Duration(milliseconds: 300),
          curve: Curves.easeOut,
        );
      }
    });
  }

  void _sendMessage(ChatController controller) {
    final text = _inputController.text.trim();
    if (text.isEmpty) return;
    controller.sendMessage(text);
    _inputController.clear();
    _inputFocusNode.requestFocus();
  }

  String _formatTimestamp(String timestamp) {
    try {
      final dt = DateTime.parse(timestamp);
      final now = DateTime.now();
      final hour = dt.hour.toString().padLeft(2, '0');
      final minute = dt.minute.toString().padLeft(2, '0');
      if (dt.year == now.year &&
          dt.month == now.month &&
          dt.day == now.day) {
        return '$hour:$minute';
      }
      return '${dt.day}/${dt.month} $hour:$minute';
    } catch (_) {
      return '';
    }
  }

  @override
  Widget build(BuildContext context) {
    final modelsValidated =
        ref.watch(aiModelSettingsControllerProvider).areModelsValidated;
    final state = ref.watch(chatControllerProvider);
    final controller = ref.read(chatControllerProvider.notifier);
    ref.listen(chatControllerProvider, (prev, next) {
      if (next.hasValue &&
          (prev?.value?.messages.length ?? 0) <
              next.value!.messages.length) {
        _scrollToBottom();
      }
      if (next.hasValue &&
          next.value!.isTyping &&
          !(prev?.value?.isTyping ?? false)) {
        _scrollToBottom();
      }
    });
    if (!modelsValidated) {
      return const Scaffold(
        backgroundColor: AppColors.surface,
        body: MissingModelsState(),
      );
    }
    return Scaffold(
      backgroundColor: AppColors.surface,
      body: Row(
        children: [
          _buildSidePanel(state, controller),
          Expanded(child: _buildChatArea(state, controller)),
        ],
      ),
    );
  }

  Widget _buildSidePanel(
    AsyncValue<ChatState> asyncState,
    ChatController controller,
  ) {
    return Container(
      width: 250,
      decoration: const BoxDecoration(
        color: AppColors.surfaceContainer,
        border: Border(right: BorderSide(color: AppColors.border, width: 1)),
      ),
      child: Column(
        children: [
          Padding(
            padding: const EdgeInsets.all(UIConstants.spacing12),
            child: SizedBox(
              width: double.infinity,
              child: NewChatButton(onPressed: controller.createSession),
            ),
          ),
          const Divider(height: 1, color: AppColors.border),
          Expanded(
            child: asyncState.when(
              data: (data) {
                if (data.sessions.isEmpty) {
                  return const Center(
                    child: Padding(
                      padding: EdgeInsets.all(UIConstants.spacing24),
                      child: Text(
                        'No conversations yet',
                        style: TextStyle(
                          color: AppColors.textMuted,
                          fontSize: 13,
                        ),
                      ),
                    ),
                  );
                }
                return ListView.builder(
                  padding: const EdgeInsets.symmetric(
                    vertical: UIConstants.spacing8,
                  ),
                  itemCount: data.sessions.length,
                  itemBuilder: (context, index) {
                    final session = data.sessions[index];
                    return _buildSessionTile(
                      session: session,
                      isActive: session.id == data.activeSession?.id,
                      controller: controller,
                    );
                  },
                );
              },
              error: (_, __) => const Center(
                child: Text(
                  'Error loading sessions',
                  style: TextStyle(color: AppColors.textMuted, fontSize: 13),
                ),
              ),
              loading: () => const Center(
                child: SizedBox(
                  width: 20,
                  height: 20,
                  child: CircularProgressIndicator(
                    strokeWidth: 2,
                    color: AppColors.textMuted,
                  ),
                ),
              ),
            ),
          ),
        ],
      ),
    );
  }

  Widget _buildSessionTile({
    required ChatSessionEntity session,
    required bool isActive,
    required ChatController controller,
  }) {
    final isHovered = _hoveredSessionId == session.id;
    return MouseRegion(
      onEnter: (_) => setState(() => _hoveredSessionId = session.id),
      onExit: (_) => setState(() {
        if (_hoveredSessionId == session.id) _hoveredSessionId = null;
      }),
      child: GestureDetector(
        onTap: () => controller.loadSession(session.id),
        child: AnimatedContainer(
          duration: const Duration(milliseconds: 150),
          margin: const EdgeInsets.symmetric(
            horizontal: UIConstants.spacing8,
            vertical: 2,
          ),
          padding: const EdgeInsets.symmetric(
            horizontal: UIConstants.spacing12,
            vertical: UIConstants.spacing8,
          ),
          decoration: BoxDecoration(
            color: isActive
                ? AppColors.zinc700.withValues(alpha: 0.7)
                : isHovered
                    ? AppColors.zinc800.withValues(alpha: 0.6)
                    : Colors.transparent,
            borderRadius:
                BorderRadius.circular(UIConstants.smallBorderRadius),
            border: isActive
                ? Border.all(
                    color: AppColors.accent.withValues(alpha: 0.3),
                  )
                : null,
          ),
          child: Row(
            children: [
              Icon(
                Icons.chat_bubble_outline_rounded,
                size: 14,
                color: isActive ? AppColors.accent : AppColors.textMuted,
              ),
              const SizedBox(width: UIConstants.spacing8),
              Expanded(
                child: Text(
                  session.title ?? 'New Chat',
                  maxLines: 1,
                  overflow: TextOverflow.ellipsis,
                  style: TextStyle(
                    color: isActive
                        ? AppColors.textPrimary
                        : AppColors.textSecondary,
                    fontSize: 13,
                    fontWeight:
                        isActive ? FontWeight.w500 : FontWeight.normal,
                  ),
                ),
              ),
              AnimatedOpacity(
                duration: const Duration(milliseconds: 150),
                opacity: isHovered ? 1.0 : 0.0,
                child: IgnorePointer(
                  ignoring: !isHovered,
                  child: SizedBox(
                    width: 24,
                    height: 24,
                    child: IconButton(
                      padding: EdgeInsets.zero,
                      iconSize: 14,
                      splashRadius: 14,
                      icon: const Icon(
                        Icons.delete_outline_rounded,
                        color: AppColors.textMuted,
                      ),
                      onPressed: () =>
                          controller.deleteSession(session.id),
                      tooltip: 'Delete',
                    ),
                  ),
                ),
              ),
            ],
          ),
        ),
      ),
    );
  }

  Widget _buildChatArea(
    AsyncValue<ChatState> asyncState,
    ChatController controller,
  ) {
    return Column(
      children: [
        Expanded(
          child: asyncState.when(
            data: (data) {
              if (data.messages.isEmpty) return _buildEmptyState();
              return ListView.builder(
                controller: _scrollController,
                padding: const EdgeInsets.symmetric(
                  horizontal: UIConstants.spacing24,
                  vertical: UIConstants.spacing16,
                ),
                itemCount:
                    data.messages.length + (data.isTyping ? 1 : 0),
                itemBuilder: (context, index) {
                  if (index == data.messages.length) {
                    if (data.thinkingSteps.isNotEmpty ||
                        (data.streamingContent != null &&
                            data.streamingContent!.isNotEmpty)) {
                      return TypingBubble(
                        thinkingSteps: data.thinkingSteps,
                        streamingContent: data.streamingContent,
                      );
                    }
                    return const TypingIndicator();
                  }
                  final msg = data.messages[index];
                  return MessageBubble(
                    message: msg,
                    formattedTime: _formatTimestamp(msg.createdAt),
                  );
                },
              );
            },
            error: (e, _) => const Center(
              child: Column(
                mainAxisAlignment: MainAxisAlignment.center,
                children: [
                  Icon(
                    Icons.error_outline_rounded,
                    color: AppColors.destructive,
                    size: 40,
                  ),
                  SizedBox(height: UIConstants.spacing12),
                  Text(
                    'Something went wrong',
                    style: TextStyle(
                      color: AppColors.textSecondary,
                      fontSize: 14,
                    ),
                  ),
                ],
              ),
            ),
            loading: () => const Center(
              child: SizedBox(
                width: 24,
                height: 24,
                child: CircularProgressIndicator(
                  strokeWidth: 2,
                  color: AppColors.textMuted,
                ),
              ),
            ),
          ),
        ),
        _buildInputBar(asyncState, controller),
      ],
    );
  }

  Widget _buildEmptyState() {
    return Center(
      child: Column(
        mainAxisAlignment: MainAxisAlignment.center,
        children: [
          Container(
            width: 64,
            height: 64,
            decoration: BoxDecoration(
              color: AppColors.surfaceContainerHigh,
              borderRadius: BorderRadius.circular(16),
            ),
            child: const Icon(
              Icons.auto_awesome_outlined,
              size: 32,
              color: AppColors.textMuted,
            ),
          ),
          const SizedBox(height: UIConstants.spacing16),
          const Text(
            'Ask me anything about your training!',
            style: TextStyle(
              color: AppColors.textSecondary,
              fontSize: 15,
              fontWeight: FontWeight.w500,
            ),
          ),
          const SizedBox(height: UIConstants.spacing8),
          const Text(
            'Start a conversation to get personalized advice.',
            style: TextStyle(color: AppColors.textMuted, fontSize: 13),
          ),
        ],
      ),
    );
  }

  Widget _buildInputBar(
    AsyncValue<ChatState> asyncState,
    ChatController controller,
  ) {
    final aiManager = ref.watch(aiProcessManagerProvider);
    final isTyping = asyncState.valueOrNull?.isTyping ?? false;
    final isStarting = aiManager.status == AiServerStatus.starting;
    final isError = aiManager.status == AiServerStatus.error;
    final isReady = aiManager.status == AiServerStatus.ready;
    String? statusMessage;
    Color statusColor = AppColors.textMuted;
    if (isStarting) {
      statusMessage =
          'Starting AI inference server (this may take a moment)...';
      statusColor = AppColors.info;
    } else if (isError) {
      statusMessage =
          'AI Server Error: ${aiManager.errorMessage ?? "Unknown error"}';
      statusColor = AppColors.destructive;
    } else if (!isReady) {
      statusMessage = 'AI Server offline. Reconnecting...';
    }
    return Container(
      decoration: const BoxDecoration(
        color: AppColors.surface,
        border: Border(top: BorderSide(color: AppColors.border, width: 1)),
      ),
      padding: const EdgeInsets.symmetric(
        horizontal: UIConstants.spacing16,
        vertical: UIConstants.spacing12,
      ),
      child: Column(
        children: [
          if (statusMessage != null)
            Padding(
              padding: const EdgeInsets.only(bottom: UIConstants.spacing8),
              child: Row(
                children: [
                  if (isStarting)
                    Container(
                      margin: const EdgeInsets.only(right: 8),
                      width: 12,
                      height: 12,
                      child: const CircularProgressIndicator(
                        strokeWidth: 2,
                        color: AppColors.info,
                      ),
                    )
                  else if (isError)
                    const Padding(
                      padding: EdgeInsets.only(right: 8),
                      child: Icon(
                        Icons.error_outline,
                        size: 14,
                        color: AppColors.destructive,
                      ),
                    ),
                  Expanded(
                    child: Text(
                      statusMessage,
                      style: GoogleFonts.inter(
                        fontSize: 12,
                        color: statusColor,
                        fontWeight: FontWeight.w500,
                      ),
                    ),
                  ),
                  if (isError)
                    TextButton(
                      style: TextButton.styleFrom(
                        padding: const EdgeInsets.symmetric(horizontal: 8),
                        minimumSize: Size.zero,
                        tapTargetSize: MaterialTapTargetSize.shrinkWrap,
                      ),
                      onPressed: () => aiManager.startServers(),
                      child: Text(
                        'Retry',
                        style: GoogleFonts.inter(
                          fontSize: 12,
                          color: AppColors.accent,
                        ),
                      ),
                    ),
                ],
              ),
            ),
          Row(
            crossAxisAlignment: CrossAxisAlignment.end,
            children: [
              Expanded(
                child: Container(
                  decoration: BoxDecoration(
                    color: AppColors.surfaceContainer,
                    borderRadius:
                        BorderRadius.circular(UIConstants.borderRadius),
                    border:
                        Border.all(color: AppColors.border, width: 1),
                  ),
                  child: TextField(
                    controller: _inputController,
                    focusNode: _inputFocusNode,
                    enabled: isReady,
                    style: TextStyle(
                      color: isReady
                          ? AppColors.textPrimary
                          : AppColors.textMuted,
                      fontSize: 14,
                    ),
                    maxLines: 4,
                    minLines: 1,
                    decoration: InputDecoration(
                      hintText: isReady
                          ? 'Type a message...'
                          : 'Waiting for AI...',
                      hintStyle: const TextStyle(
                        color: AppColors.textMuted,
                        fontSize: 14,
                      ),
                      contentPadding: const EdgeInsets.symmetric(
                        horizontal: UIConstants.spacing16,
                        vertical: UIConstants.spacing12,
                      ),
                      border: InputBorder.none,
                      enabledBorder: InputBorder.none,
                      focusedBorder: InputBorder.none,
                      disabledBorder: InputBorder.none,
                    ),
                    onSubmitted: isReady
                        ? (_) => _sendMessage(controller)
                        : null,
                    textInputAction: TextInputAction.send,
                  ),
                ),
              ),
              const SizedBox(width: UIConstants.spacing8),
              SizedBox(
                width: 40,
                height: 40,
                child: Material(
                  color: (isTyping || !isReady)
                      ? AppColors.zinc700
                      : AppColors.accent,
                  borderRadius:
                      BorderRadius.circular(UIConstants.borderRadius),
                  child: InkWell(
                    borderRadius:
                        BorderRadius.circular(UIConstants.borderRadius),
                    onTap: (isTyping || !isReady)
                        ? null
                        : () => _sendMessage(controller),
                    child: Icon(
                      Icons.arrow_upward_rounded,
                      color: (isTyping || !isReady)
                          ? AppColors.textMuted
                          : AppColors.zinc950,
                      size: 20,
                    ),
                  ),
                ),
              ),
            ],
          ),
        ],
      ),
    );
  }
}