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

import '../../api/ai_api.dart';
import '../../core/network/api_env.dart';
import '../../models/ai.dart';
import '../../providers/ai_provider.dart';
import '../../utils/toast.dart';
import '../../widgets/state_views.dart';
import '../../widgets/cute_icon.dart';

/// 助手：和 AI 对话，问账单、问笔记。
///
/// 既是底部 Tab，也能从首页那个输入框 push 进来 —— 所以顶部自己画了
/// 返回箭头（canPop 时才画）。
class AssistantPage extends ConsumerStatefulWidget {
  const AssistantPage({super.key});

  @override
  ConsumerState<AssistantPage> createState() => _AssistantPageState();
}

class _AssistantPageState extends ConsumerState<AssistantPage> {
  final _input = TextEditingController();
  final _scroll = ScrollController();

  /// 空状态下的引导问题 —— 让用户知道能问什么，比一句「你好」有用
  static const _suggestions = [
    '这个月花了多少钱？',
    '上个月的支出分类排行',
    '我的笔记里有哪些关于 MySQL 的？',
  ];

  @override
  void initState() {
    super.initState();
    // 打开就把上一次的对话展开，而不是每次都从空白开始。
    // 放进 postFrameCallback：initState 里改 provider 状态会撞上「构建期间改状态」。
    WidgetsBinding.instance.addPostFrameCallback((_) {
      if (!mounted) return;
      ref.read(assistantProvider.notifier).restoreLastSessionIfNeeded();
    });
  }

  @override
  void dispose() {
    _input.dispose();
    _scroll.dispose();
    super.dispose();
  }

  @override
  Widget build(BuildContext context) {
    final state = ref.watch(assistantProvider);
    _scheduleScroll();

    return Scaffold(
      body: Container(
        width: double.infinity,
        height: double.infinity,
        decoration: const BoxDecoration(
          gradient: LinearGradient(
            begin: Alignment.topLeft,
            end: Alignment.bottomRight,
            colors: [Color(0xFFFFE5CC), Color(0xFFFFD4A8), Color(0xFFFFC08A)],
          ),
        ),
        child: SafeArea(
          child: Column(
            children: [
              _header(context),
              Expanded(child: _body(context, state)),
              if (state.error != null) _errorBar(state.error!),
              _inputBar(state),
            ],
          ),
        ),
      ),
    );
  }

  // ---------------------------------------------------------------- 顶部

  Widget _header(BuildContext context) {
    return Padding(
      padding: const EdgeInsets.fromLTRB(10, 6, 8, 6),
      child: Row(
        children: [
          if (Navigator.of(context).canPop())
            _iconButton(
              icon: Icons.arrow_back,
              tooltip: '返回',
              onTap: () => Navigator.of(context).pop(),
            ),
          const Padding(
            padding: EdgeInsets.only(left: 6),
            child: Text(
              '助手',
              style: TextStyle(
                fontSize: 20,
                fontWeight: FontWeight.bold,
                color: Color(0xFF5D4037),
              ),
            ),
          ),
          const Spacer(),
          _iconButton(
            icon: Icons.history,
            tooltip: '历史对话',
            onTap: () => _showSessions(context),
          ),
          _iconButton(
            icon: Icons.add_comment_outlined,
            tooltip: '新对话',
            onTap: () => ref.read(assistantProvider.notifier).newChat(),
          ),
        ],
      ),
    );
  }

  Widget _iconButton({
    required IconData icon,
    required String tooltip,
    required VoidCallback onTap,
  }) {
    return Tooltip(
      message: tooltip,
      child: InkWell(
        onTap: onTap,
        borderRadius: BorderRadius.circular(20),
        child: Padding(
          padding: const EdgeInsets.all(7),
          child: Icon(icon, size: 21, color: const Color(0xFF5D4037)),
        ),
      ),
    );
  }

  // ---------------------------------------------------------------- 主体

  Widget _body(BuildContext context, AssistantState state) {
    if (state.loadingHistory) {
      return const LoadingView(tip: '正在加载对话…');
    }
    if (state.isEmpty) {
      return _welcome(context);
    }

    final showTool = state.streaming && state.bubbles.isNotEmpty;
    return ListView.builder(
      controller: _scroll,
      physics: const AlwaysScrollableScrollPhysics(),
      padding: const EdgeInsets.fromLTRB(14, 8, 14, 12),
      itemCount: state.bubbles.length + (showTool ? 1 : 0),
      itemBuilder: (context, index) {
        if (index >= state.bubbles.length) {
          return _toolIndicator(state.activeTool);
        }
        return _bubble(context, state.bubbles[index]);
      },
    );
  }

  Widget _welcome(BuildContext context) {
    return ListView(
      padding: const EdgeInsets.fromLTRB(24, 40, 24, 0),
      children: [
        const Center(child: CuteIcon('assistant', size: 48)),
        const SizedBox(height: 14),
        const Center(
          child: Text(
            '问我点什么',
            style: TextStyle(
              fontSize: 17,
              fontWeight: FontWeight.w600,
              color: Color(0xFF5D4037),
            ),
          ),
        ),
        const SizedBox(height: 6),
        const Center(
          child: Text(
            '我能查你的账单统计和笔记',
            style: TextStyle(fontSize: 12.5, color: Color(0xFF8D6E63)),
          ),
        ),
        const SizedBox(height: 26),
        for (final s in _suggestions) ...[
          _suggestionChip(s),
          const SizedBox(height: 10),
        ],
      ],
    );
  }

  Widget _suggestionChip(String text) {
    return GestureDetector(
      onTap: () => _send(text),
      child: Container(
        padding: const EdgeInsets.symmetric(horizontal: 16, vertical: 13),
        decoration: BoxDecoration(
          color: Colors.white.withValues(alpha: 0.9),
          borderRadius: BorderRadius.circular(14),
          border: Border.all(color: const Color(0xFFE8D9C5)),
        ),
        child: Row(
          children: [
            Expanded(
              child: Text(
                text,
                style: const TextStyle(fontSize: 13.5, color: Color(0xFF5D4037)),
              ),
            ),
            const Icon(Icons.north_east, size: 15, color: Color(0xFFBCAAA4)),
          ],
        ),
      ),
    );
  }

  // ---------------------------------------------------------------- 气泡

  Widget _bubble(BuildContext context, ChatBubble bubble) {
    if (bubble.isUser) {
      return Align(
        alignment: Alignment.centerRight,
        child: Container(
          margin: const EdgeInsets.only(top: 10, left: 48),
          padding: const EdgeInsets.symmetric(horizontal: 14, vertical: 10),
          decoration: BoxDecoration(
            gradient: const LinearGradient(colors: [Color(0xFFC8956E), Color(0xFFD9A87C)]),
            borderRadius: const BorderRadius.only(
              topLeft: Radius.circular(16),
              topRight: Radius.circular(16),
              bottomLeft: Radius.circular(16),
              bottomRight: Radius.circular(4),
            ),
          ),
          child: SelectableText(
            bubble.content,
            style: const TextStyle(fontSize: 14.5, height: 1.5, color: Colors.white),
          ),
        ),
      );
    }

    return Align(
      alignment: Alignment.centerLeft,
      child: Container(
        margin: const EdgeInsets.only(top: 10, right: 24),
        padding: const EdgeInsets.fromLTRB(14, 10, 14, 10),
        decoration: BoxDecoration(
          color: Colors.white,
          borderRadius: const BorderRadius.only(
            topLeft: Radius.circular(16),
            topRight: Radius.circular(16),
            bottomLeft: Radius.circular(4),
            bottomRight: Radius.circular(16),
          ),
          boxShadow: [
            BoxShadow(
              color: const Color(0xFF5D4037).withValues(alpha: 0.06),
              blurRadius: 8,
              offset: const Offset(0, 2),
            ),
          ],
        ),
        child: Column(
          crossAxisAlignment: CrossAxisAlignment.start,
          children: [
            if (bubble.content.isEmpty)
              const _TypingDots()
            else
              MarkdownBody(
                data: bubble.content,
                selectable: true,
                styleSheet: _markdownStyle(context),
                onTapLink: (text, href, title) {
                  if (href == null || href.isEmpty) return;
                  Clipboard.setData(ClipboardData(text: href));
                  showToast(context, '链接已复制');
                },
                imageBuilder: (uri, title, alt) => Padding(
                  padding: const EdgeInsets.symmetric(vertical: 6),
                  child: ClipRRect(
                    borderRadius: BorderRadius.circular(8),
                    child: Image.network(resolveAssetUrl(uri.toString())),
                  ),
                ),
              ),
            if (bubble.streaming && bubble.content.isNotEmpty) ...[
              const SizedBox(height: 6),
              const _TypingDots(),
            ],
          ],
        ),
      ),
    );
  }

  MarkdownStyleSheet _markdownStyle(BuildContext context) {
    final base = MarkdownStyleSheet.fromTheme(Theme.of(context));
    return base.copyWith(
      p: const TextStyle(fontSize: 14.5, height: 1.6, color: Color(0xFF3E2723)),
      h1: const TextStyle(fontSize: 18, fontWeight: FontWeight.bold, height: 1.4, color: Color(0xFF3E2723)),
      h2: const TextStyle(fontSize: 16.5, fontWeight: FontWeight.bold, height: 1.4, color: Color(0xFF3E2723)),
      h3: const TextStyle(fontSize: 15.5, fontWeight: FontWeight.w600, height: 1.4, color: Color(0xFF3E2723)),
      listBullet: const TextStyle(fontSize: 14.5, height: 1.6, color: Color(0xFF3E2723)),
      code: const TextStyle(
        fontSize: 13,
        backgroundColor: Color(0xFFF5EFE6),
        color: Color(0xFF8D4B2A),
      ),
      codeblockDecoration: BoxDecoration(
        color: const Color(0xFFF5EFE6),
        borderRadius: BorderRadius.circular(8),
      ),
      blockquoteDecoration: BoxDecoration(
        color: const Color(0xFFFBF6EF),
        borderRadius: BorderRadius.circular(6),
        border: const Border(left: BorderSide(color: Color(0xFFC8956E), width: 3)),
      ),
      tableBorder: TableBorder.all(color: const Color(0xFFE8D9C5)),
      tableCellsPadding: const EdgeInsets.symmetric(horizontal: 8, vertical: 5),
    );
  }

  /// 工具调用提示：「正在查账单…」
  Widget _toolIndicator(String? tool) {
    return Padding(
      padding: const EdgeInsets.only(top: 10, left: 4),
      child: Row(
        children: [
          const SizedBox(
            width: 12,
            height: 12,
            child: CircularProgressIndicator(strokeWidth: 1.6, color: Color(0xFFC8956E)),
          ),
          const SizedBox(width: 8),
          Text(
            _toolLabel(tool),
            style: const TextStyle(fontSize: 12.5, color: Color(0xFF8D6E63)),
          ),
        ],
      ),
    );
  }

  String _toolLabel(String? name) => switch (name) {
        'query_bills' => '正在查账单…',
        'query_notes' => '正在搜笔记…',
        'get_note' => '正在读笔记…',
        _ => '正在查询…',
      };

  // ---------------------------------------------------------------- 错误与输入

  Widget _errorBar(String message) {
    return Container(
      width: double.infinity,
      margin: const EdgeInsets.fromLTRB(14, 0, 14, 6),
      padding: const EdgeInsets.symmetric(horizontal: 12, vertical: 9),
      decoration: BoxDecoration(
        color: const Color(0xFFFFEBEE),
        borderRadius: BorderRadius.circular(10),
      ),
      child: Row(
        children: [
          const Icon(Icons.error_outline, size: 16, color: Color(0xFFD32F2F)),
          const SizedBox(width: 8),
          Expanded(
            child: Text(
              message,
              style: const TextStyle(fontSize: 12.5, color: Color(0xFFB71C1C)),
            ),
          ),
          GestureDetector(
            onTap: () => ref.read(assistantProvider.notifier).clearError(),
            child: const Icon(Icons.close, size: 15, color: Color(0xFFB71C1C)),
          ),
        ],
      ),
    );
  }

  Widget _inputBar(AssistantState state) {
    return Container(
      padding: const EdgeInsets.fromLTRB(14, 8, 14, 10),
      child: Row(
        crossAxisAlignment: CrossAxisAlignment.end,
        children: [
          Expanded(
            child: Container(
              decoration: BoxDecoration(
                color: Colors.white,
                borderRadius: BorderRadius.circular(22),
                border: Border.all(color: const Color(0xFFE8D9C5)),
              ),
              padding: const EdgeInsets.symmetric(horizontal: 16, vertical: 2),
              child: TextField(
                controller: _input,
                enabled: !state.streaming,
                minLines: 1,
                maxLines: 4,
                textInputAction: TextInputAction.send,
                onSubmitted: _send,
                decoration: const InputDecoration(
                  border: InputBorder.none,
                  isDense: true,
                  contentPadding: EdgeInsets.symmetric(vertical: 12),
                  hintText: '问点什么…',
                  hintStyle: TextStyle(fontSize: 14, color: Color(0xFFBCAAA4)),
                ),
                style: const TextStyle(fontSize: 14.5, color: Color(0xFF5D4037)),
              ),
            ),
          ),
          const SizedBox(width: 8),
          _sendButton(state),
        ],
      ),
    );
  }

  Widget _sendButton(AssistantState state) {
    final disabled = state.streaming;
    return GestureDetector(
      onTap: disabled ? null : () => _send(_input.text),
      child: Container(
        width: 42,
        height: 42,
        decoration: BoxDecoration(
          shape: BoxShape.circle,
          gradient: disabled
              ? null
              : const LinearGradient(colors: [Color(0xFFC8956E), Color(0xFFF5D59E)]),
          color: disabled ? const Color(0xFFE8D9C5) : null,
        ),
        child: Icon(
          disabled ? Icons.hourglass_empty : Icons.arrow_upward,
          size: 20,
          color: disabled ? const Color(0xFFBCAAA4) : const Color(0xFF5D4037),
        ),
      ),
    );
  }

  void _send(String text) {
    final trimmed = text.trim();
    if (trimmed.isEmpty) return;
    _input.clear();
    ref.read(assistantProvider.notifier).send(trimmed);
  }

  // ---------------------------------------------------------------- 历史会话

  Future<void> _showSessions(BuildContext context) async {
    final selected = await showModalBottomSheet<int>(
      context: context,
      backgroundColor: Colors.white,
      isScrollControlled: true,
      shape: const RoundedRectangleBorder(
        borderRadius: BorderRadius.vertical(top: Radius.circular(20)),
      ),
      builder: (_) => const _SessionSheet(),
    );
    if (selected == null || !mounted) return;
    ref.read(assistantProvider.notifier).openSession(selected);
  }

  // ---------------------------------------------------------------- 滚动

  /// 只在用户本来就贴着底部时才自动滚动 —— 生成过程中用户往上翻看历史时别抢
  void _scheduleScroll() {
    WidgetsBinding.instance.addPostFrameCallback((_) {
      if (!mounted || !_scroll.hasClients) return;
      final pos = _scroll.position;
      if (pos.maxScrollExtent - pos.pixels > 140) return;
      _scroll.jumpTo(pos.maxScrollExtent);
    });
  }
}

/// 生成中的三个点
class _TypingDots extends StatelessWidget {
  const _TypingDots();

  @override
  Widget build(BuildContext context) {
    return const Text(
      '●●●',
      style: TextStyle(fontSize: 7, letterSpacing: 2, color: Color(0xFFC8956E)),
    );
  }
}

/// 历史会话面板
class _SessionSheet extends ConsumerWidget {
  const _SessionSheet();

  @override
  Widget build(BuildContext context, WidgetRef ref) {
    final sessionsAsync = ref.watch(chatSessionsProvider);

    return SafeArea(
      child: Padding(
        padding: const EdgeInsets.fromLTRB(16, 16, 16, 12),
        child: Column(
          mainAxisSize: MainAxisSize.min,
          children: [
            const Text(
              '历史对话',
              style: TextStyle(
                fontSize: 15,
                fontWeight: FontWeight.w600,
                color: Color(0xFF5D4037),
              ),
            ),
            const SizedBox(height: 12),
            Flexible(
              child: sessionsAsync.when(
                loading: () => const LoadingView(tip: '加载中…'),
                error: (e, _) => ErrorView(
                  message: '会话列表加载失败',
                  onRetry: () => ref.invalidate(chatSessionsProvider),
                ),
                data: (sessions) {
                  if (sessions.isEmpty) {
                    return const EmptyView(title: '还没有对话', tip: '问一句就有了');
                  }
                  return ListView.builder(
                    shrinkWrap: true,
                    itemCount: sessions.length,
                    itemBuilder: (context, index) {
                      final s = sessions[index];
                      return ListTile(
                        contentPadding: const EdgeInsets.symmetric(horizontal: 4),
                        title: Text(
                          s.title,
                          maxLines: 1,
                          overflow: TextOverflow.ellipsis,
                          style: const TextStyle(fontSize: 14.5, color: Color(0xFF5D4037)),
                        ),
                        subtitle: Text(
                          s.updateTime,
                          style: const TextStyle(fontSize: 11.5, color: Color(0xFFBCAAA4)),
                        ),
                        trailing: IconButton(
                          tooltip: '删除',
                          icon: const Icon(Icons.delete_outline, size: 19),
                          color: const Color(0xFFBCAAA4),
                          onPressed: () => _confirmDelete(context, ref, s),
                        ),
                        onTap: () => Navigator.pop(context, s.id),
                      );
                    },
                  );
                },
              ),
            ),
          ],
        ),
      ),
    );
  }

  Future<void> _confirmDelete(BuildContext context, WidgetRef ref, ChatSessionItem session) async {
    final ok = await showDialog<bool>(
      context: context,
      builder: (dialogContext) => AlertDialog(
        title: const Text('删除对话'),
        content: Text('「${session.title}」将被删除，不能再恢复。'),
        actions: [
          TextButton(
            onPressed: () => Navigator.pop(dialogContext, false),
            child: const Text('取消'),
          ),
          TextButton(
            onPressed: () => Navigator.pop(dialogContext, true),
            child: const Text('删除', style: TextStyle(color: Color(0xFFD32F2F))),
          ),
        ],
      ),
    );
    if (ok != true) return;

    try {
      await ref.read(aiApiProvider).deleteSession(session.id);
      ref.invalidate(chatSessionsProvider);
      // 删掉的正好是当前打开的会话，就退回新对话
      final current = ref.read(assistantProvider).sessionId;
      if (current == session.id) {
        ref.read(assistantProvider.notifier).newChat();
      }
    } catch (e) {
      if (context.mounted) showToast(context, '删除失败', error: true);
    }
  }
}