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

import '../../ai/tools/tool_envelope.dart';
import '../../state/chat_providers.dart';
import '../../state/chat_warmup_provider.dart';
import 'settings_screen.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 initState() {
    super.initState();
    // #311 AC1: ChatScreen mount → background warm-up. depsAsync.data 가
    // resolve 되기 전에는 toolDepsProvider 도 미준비라 send 자체가 막혀
    // 있으므로, 그 사이에 native init 만 먼저 끝낸다.
    WidgetsBinding.instance.addPostFrameCallback((_) {
      if (!mounted) return;
      ref.read(chatWarmupProvider.notifier).start();
    });
  }

  @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 (이전 기록 비우기)',
            onPressed: () {
              ref.read(chatSessionControllerProvider.notifier).clear();
            },
          ),
        ],
      ),
      // Android edge-to-edge: 시스템 nav bar (3-button / gesture handle) 가
      // 입력창을 가리지 않도록 SafeArea 로 감싼다. AppBar 가 이미 top inset
      // 을 처리하므로 top 만 false.
      body: SafeArea(
        top: false,
        child: 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);
    final warmup = ref.watch(chatWarmupProvider);
    _scrollToBottom();

    // #311 AC3 / UX R3: warmup 중에는 hintText 만 교체. 입력창 자체는
    // enabled (사용자가 미리 타이핑 가능 — AC9).
    final isWarming = warmup is ChatWarmupLoading;
    final hintText = isWarming
        ? 'AI 준비 중… 첫 시작은 몇 초 걸려요'
        : '습관 추가, 기록, 카탈로그 질문…';

    // AC10: warmup ready 이고 streaming 중이 아닐 때 send 활성. 빈 텍스트는
    // _send() 가 early-return 하므로 별도 gating 불필요 (rebuild race 회피).
    final canSend = !state.isStreaming && !isWarming;
    final theme = Theme.of(context);

    return Column(
      children: [
        if (warmup is ChatWarmupFailed) _WarmupErrorBanner(warmup: warmup),
        if (state.error != null)
          // #342 dev — 단말에서 원인 진단을 위해 stack 까지 노출되는 케이스를
          // 위해 multi-line + scrollable + selectable. 높이는 화면의 1/3 까지만.
          Container(
            width: double.infinity,
            color: theme.colorScheme.errorContainer,
            padding: const EdgeInsets.all(12),
            constraints: BoxConstraints(
              maxHeight: MediaQuery.of(context).size.height / 3,
            ),
            child: SingleChildScrollView(
              child: SelectableText(
                state.error!,
                style: TextStyle(
                  color: theme.colorScheme.onErrorContainer,
                  fontFamily: 'monospace',
                  fontSize: 12,
                ),
              ),
            ),
          ),
        Expanded(
          child: state.messages.isEmpty && state.streamingText == null
              ? _EmptyChatHint(onPickPrompt: (p) {
                  _textCtrl.text = p;
                  _textCtrl.selection = TextSelection.fromPosition(
                    TextPosition(offset: p.length),
                  );
                })
              : 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: InputDecoration(
                    hintText: hintText,
                    border: const OutlineInputBorder(),
                    isDense: true,
                  ),
                  maxLines: 4,
                  minLines: 1,
                  textInputAction: TextInputAction.send,
                  onSubmitted: (_) => canSend ? _send() : null,
                ),
              ),
              const SizedBox(width: 8),
              if (state.isStreaming || isWarming)
                const Padding(
                  padding: EdgeInsets.all(8),
                  child: SizedBox(
                    width: 24,
                    height: 24,
                    child: CircularProgressIndicator(strokeWidth: 2),
                  ),
                )
              else
                IconButton.filled(
                  onPressed: canSend ? _send : null,
                  icon: const Icon(Icons.send),
                ),
            ],
          ),
        ),
      ],
    );
  }
}

/// #311 AC5 / UX R5+R6: 실패 메시지는 상태만 기술, 행동은 버튼이 담당.
/// fileMissing 은 retry 로 회복 불가 — 설정 화면으로 유도해 재다운로드 경로를 연다.
/// runtime 은 일시적일 수 있으므로 [다시 시도] (in-place retry).
class _WarmupErrorBanner extends ConsumerWidget {
  final ChatWarmupFailed warmup;
  const _WarmupErrorBanner({required this.warmup});

  @override
  Widget build(BuildContext context, WidgetRef ref) {
    final theme = Theme.of(context);
    final isFileMissing =
        warmup.kind == ChatWarmupFailureKind.fileMissing;
    return Container(
      width: double.infinity,
      color: theme.colorScheme.errorContainer,
      padding: const EdgeInsets.symmetric(horizontal: 12, vertical: 10),
      child: Column(
        crossAxisAlignment: CrossAxisAlignment.stretch,
        children: [
          Text(
            warmup.message,
            style: TextStyle(color: theme.colorScheme.onErrorContainer),
          ),
          const SizedBox(height: 8),
          Align(
            alignment: Alignment.centerRight,
            child: OutlinedButton(
              onPressed: () {
                if (isFileMissing) {
                  // SettingsScreen pop 후 자동 retry — 사용자가 거기서 다시
                  // 다운로드를 완료했다면 ChatScreen 으로 돌아오자마자 회복.
                  // 다운로드 안 했으면 다시 Failed 로 떨어져 같은 배너 노출.
                  Navigator.of(context)
                      .push(MaterialPageRoute(
                        builder: (_) => const SettingsScreen(),
                      ))
                      .then((_) {
                    if (!context.mounted) return;
                    ref.read(chatWarmupProvider.notifier).retry();
                  });
                } else {
                  ref.read(chatWarmupProvider.notifier).retry();
                }
              },
              child: Text(isFileMissing ? '설정으로 가기' : '다시 시도'),
            ),
          ),
        ],
      ),
    );
  }
}

/// 첫 진입 시 빈 대화창 안내. 사용자가 무엇을 물어볼 수 있는지
/// 예시 prompt 4개 + tool 카테고리 짧은 안내. tap 하면 입력창에 채워지고
/// 사용자가 보내기만 누르면 됨 (자동 send X — 사용자가 문구 수정 여지).
class _EmptyChatHint extends StatelessWidget {
  final ValueChanged<String> onPickPrompt;
  const _EmptyChatHint({required this.onPickPrompt});

  static const _examples = [
    '아침 햇빛 받기 습관 추가해줘',
    '오늘 운동 했어',
    '내 스트릭 보여줘',
    '수면 프로토콜 알려줘',
  ];

  @override
  Widget build(BuildContext context) {
    final theme = Theme.of(context);
    return SingleChildScrollView(
      padding: const EdgeInsets.symmetric(horizontal: 24, vertical: 32),
      child: Column(
        crossAxisAlignment: CrossAxisAlignment.stretch,
        children: [
          Icon(
            Icons.smart_toy_outlined,
            size: 48,
            color: theme.colorScheme.primary,
          ),
          const SizedBox(height: 16),
          Text(
            'AI 코치',
            style: theme.textTheme.titleLarge,
            textAlign: TextAlign.center,
          ),
          const SizedBox(height: 8),
          Text(
            '습관 추가·기록 · 카탈로그 검색 · 스트릭 조회를 도와드려요.',
            style: theme.textTheme.bodyMedium?.copyWith(
              color: theme.colorScheme.onSurfaceVariant,
            ),
            textAlign: TextAlign.center,
          ),
          const SizedBox(height: 24),
          Text(
            '예시',
            style: theme.textTheme.labelLarge?.copyWith(
              color: theme.colorScheme.onSurfaceVariant,
            ),
          ),
          const SizedBox(height: 8),
          ..._examples.map((p) => Padding(
                padding: const EdgeInsets.symmetric(vertical: 4),
                child: OutlinedButton(
                  onPressed: () => onPickPrompt(p),
                  style: OutlinedButton.styleFrom(
                    alignment: Alignment.centerLeft,
                    padding: const EdgeInsets.symmetric(
                        horizontal: 16, vertical: 12),
                  ),
                  child: Text(p),
                ),
              )),
        ],
      ),
    );
  }
}

/// Human-friendly Korean labels for the 6 tools registered in
/// `ToolRegistry.defaults()`. Falls back to the raw tool name for any
/// future tool that hasn't been mapped yet — better to show the raw id
/// than to silently drop the message.
const Map<String, String> _kToolKoreanLabels = {
  'search_catalog': '카탈로그 검색',
  'query_protocol': '프로토콜 상세',
  'list_active_habits': '활성 습관 조회',
  'get_streak': '스트릭 조회',
  'add_habit': '습관 추가',
  'log_tracker_entry': '체크 기록',
};

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:
        // Streaming cursor uses primary so it stays discoverable in both
        // light and dark themes (default onSurface low-contrasted with the
        // surfaceContainerHighest bubble in dark mode).
        return _bubble(
          context,
          align: Alignment.centerLeft,
          color: theme.colorScheme.surfaceContainerHighest,
          textColor: theme.colorScheme.onSurface,
          richText: streaming
              ? TextSpan(
                  children: [
                    TextSpan(text: m.text),
                    TextSpan(
                      text: '▍',
                      style: TextStyle(color: theme.colorScheme.primary),
                    ),
                  ],
                )
              : null,
          text: m.text,
        );
      case ToolCallChatMessage m:
        final label = _kToolKoreanLabels[m.name] ?? m.name;
        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(
              '🛠 $label → ${_toolResultLabel(m.result)}',
              style: theme.textTheme.bodySmall,
              textAlign: TextAlign.center,
            ),
          ),
        );
      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,
    TextSpan? richText,
  }) {
    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: richText != null
            ? Text.rich(richText, style: TextStyle(color: textColor))
            : 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';
    }
  }
}