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

import '../../ai/tools/tool_envelope.dart';
import '../../state/chat_providers.dart';

/// AI chat surface (#260). Multi-turn tool calling powered by Gemma 4 +
/// in-process tool runtime. ConfirmGate modals appear on destructive
/// tool calls (add_habit, log_tracker_entry).
class ChatScreen extends ConsumerStatefulWidget {
  const ChatScreen({super.key});

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

class _ChatScreenState extends ConsumerState<ChatScreen> {
  final _textCtrl = TextEditingController();
  final _scrollCtrl = ScrollController();

  @override
  void dispose() {
    _textCtrl.dispose();
    _scrollCtrl.dispose();
    super.dispose();
  }

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

  Future<void> _send() async {
    final text = _textCtrl.text.trim();
    if (text.isEmpty) return;
    _textCtrl.clear();
    await ref
        .read(chatSessionControllerProvider.notifier)
        .userTurn(text, context);
    _scrollToBottom();
  }

  @override
  Widget build(BuildContext context) {
    final depsAsync = ref.watch(toolDepsProvider);
    return Scaffold(
      appBar: AppBar(
        title: const Text('AI 코치'),
        actions: [
          IconButton(
            icon: const Icon(Icons.refresh),
            tooltip: '새 대화',
            onPressed: () {
              ref.read(chatSessionControllerProvider.notifier).clear();
            },
          ),
        ],
      ),
      body: depsAsync.when(
        loading: () => const Center(child: CircularProgressIndicator()),
        error: (e, _) => Center(child: Text('초기화 실패: $e')),
        data: (_) => _buildBody(context),
      ),
    );
  }

  Widget _buildBody(BuildContext context) {
    final state = ref.watch(chatSessionControllerProvider);
    _scrollToBottom();
    return Column(
      children: [
        if (state.error != null)
          Container(
            width: double.infinity,
            color: Theme.of(context).colorScheme.errorContainer,
            padding: const EdgeInsets.all(12),
            child: Text(
              state.error!,
              style: TextStyle(
                color: Theme.of(context).colorScheme.onErrorContainer,
              ),
            ),
          ),
        Expanded(
          child: ListView.builder(
            controller: _scrollCtrl,
            padding: const EdgeInsets.all(12),
            itemCount: state.messages.length +
                (state.streamingText != null &&
                        state.streamingText!.isNotEmpty
                    ? 1
                    : 0),
            itemBuilder: (context, i) {
              if (i < state.messages.length) {
                return _MessageBubble(message: state.messages[i]);
              }
              return _MessageBubble(
                message: ModelChatMessage(state.streamingText ?? ''),
                streaming: true,
              );
            },
          ),
        ),
        const Divider(height: 1),
        Padding(
          padding: const EdgeInsets.all(8),
          child: Row(
            crossAxisAlignment: CrossAxisAlignment.end,
            children: [
              Expanded(
                child: TextField(
                  controller: _textCtrl,
                  enabled: !state.isStreaming,
                  decoration: const InputDecoration(
                    hintText: '습관 추가, 기록, 카탈로그 질문…',
                    border: OutlineInputBorder(),
                    isDense: true,
                  ),
                  maxLines: 4,
                  minLines: 1,
                  textInputAction: TextInputAction.send,
                  onSubmitted: (_) => _send(),
                ),
              ),
              const SizedBox(width: 8),
              state.isStreaming
                  ? const Padding(
                      padding: EdgeInsets.all(8),
                      child: SizedBox(
                        width: 24,
                        height: 24,
                        child: CircularProgressIndicator(strokeWidth: 2),
                      ),
                    )
                  : IconButton.filled(
                      onPressed: _send,
                      icon: const Icon(Icons.send),
                    ),
            ],
          ),
        ),
      ],
    );
  }
}

class _MessageBubble extends StatelessWidget {
  final ChatMessage message;
  final bool streaming;
  const _MessageBubble({required this.message, this.streaming = false});

  @override
  Widget build(BuildContext context) {
    final theme = Theme.of(context);
    switch (message) {
      case UserChatMessage m:
        return _bubble(
          context,
          align: Alignment.centerRight,
          color: theme.colorScheme.primaryContainer,
          textColor: theme.colorScheme.onPrimaryContainer,
          text: m.text,
        );
      case ModelChatMessage m:
        return _bubble(
          context,
          align: Alignment.centerLeft,
          color: theme.colorScheme.surfaceContainerHighest,
          textColor: theme.colorScheme.onSurface,
          text: m.text + (streaming ? '▍' : ''),
        );
      case ToolCallChatMessage m:
        return Align(
          alignment: Alignment.center,
          child: Container(
            margin: const EdgeInsets.symmetric(vertical: 4),
            padding: const EdgeInsets.symmetric(horizontal: 10, vertical: 6),
            decoration: BoxDecoration(
              color: theme.colorScheme.surfaceContainerLow,
              borderRadius: BorderRadius.circular(12),
              border: Border.all(color: theme.colorScheme.outlineVariant),
            ),
            child: Text(
              '🛠 ${m.name} → ${_toolResultLabel(m.result)}',
              style: theme.textTheme.bodySmall,
            ),
          ),
        );
      case SystemChatMessage m:
        return Padding(
          padding: const EdgeInsets.symmetric(vertical: 4),
          child: Text(
            m.text,
            textAlign: TextAlign.center,
            style: theme.textTheme.bodySmall?.copyWith(
              color: theme.colorScheme.outline,
            ),
          ),
        );
    }
  }

  Widget _bubble(
    BuildContext context, {
    required Alignment align,
    required Color color,
    required Color textColor,
    required String text,
  }) {
    return Align(
      alignment: align,
      child: Container(
        margin: const EdgeInsets.symmetric(vertical: 4),
        padding: const EdgeInsets.symmetric(horizontal: 12, vertical: 8),
        constraints: BoxConstraints(
          maxWidth: MediaQuery.of(context).size.width * 0.75,
        ),
        decoration: BoxDecoration(
          color: color,
          borderRadius: BorderRadius.circular(12),
        ),
        child: Text(text, style: TextStyle(color: textColor)),
      ),
    );
  }

  String _toolResultLabel(ToolResult r) {
    switch (r) {
      case ToolOk _:
        return 'OK';
      case ToolErr e:
        return '오류: ${e.code}';
      case ToolCancelled _:
        return '취소됨';
    }
  }
}