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

import '../../api/note_api.dart';
import '../../core/network/api_exception.dart';
import '../../utils/toast.dart';
import '../../widgets/state_views.dart';

/// 笔记编辑页
///
/// [noteId] 为 null 时是新建，否则是编辑已有笔记。
/// 保存成功会 pop(true)，上一页据此刷新数据。
///
/// 这里用 StatefulWidget + TextEditingController 管理表单，
/// 而不是像账单编辑页那样走 Notifier —— 后者需要额外的 revision
/// 字段来同步受控输入框，对纯文本编辑没有必要。
class NoteEditPage extends ConsumerStatefulWidget {
  const NoteEditPage({super.key, this.noteId});

  final int? noteId;

  bool get isCreate => noteId == null;

  @override
  ConsumerState<NoteEditPage> createState() => _NoteEditPageState();
}

class _NoteEditPageState extends ConsumerState<NoteEditPage> {
  final _titleController = TextEditingController();
  final _tagsController = TextEditingController();
  final _contentController = TextEditingController();

  bool _loading = false;
  bool _saving = false;
  bool _preview = false;
  String? _loadError;

  /// 是否已经成功保存过——用于「返回时提示未保存」的判断
  bool _saved = false;

  @override
  void initState() {
    super.initState();
    if (!widget.isCreate) _load();
  }

  @override
  void dispose() {
    _titleController.dispose();
    _tagsController.dispose();
    _contentController.dispose();
    super.dispose();
  }

  Future<void> _load() async {
    setState(() {
      _loading = true;
      _loadError = null;
    });
    try {
      final note = await ref.read(noteApiProvider).detail(widget.noteId!);
      if (!mounted) return;
      _titleController.text = note.title;
      _tagsController.text = note.tags.join(',');
      _contentController.text = note.content;
      setState(() => _loading = false);
    } on ApiException catch (e) {
      if (!mounted) return;
      setState(() {
        _loading = false;
        _loadError = e.message;
      });
    } catch (_) {
      if (!mounted) return;
      setState(() {
        _loading = false;
        _loadError = '笔记加载失败';
      });
    }
  }

  bool get _dirty =>
      !_saved &&
      (_titleController.text.isNotEmpty ||
          _tagsController.text.isNotEmpty ||
          _contentController.text.isNotEmpty);

  Future<void> _save() async {
    final title = _titleController.text.trim();
    final tags = _tagsController.text.trim();
    final content = _contentController.text;

    if (title.isEmpty && content.trim().isEmpty) {
      showToast(context, '标题和内容不能同时为空', error: true);
      return;
    }

    setState(() => _saving = true);
    try {
      final api = ref.read(noteApiProvider);
      if (widget.isCreate) {
        await api.create(title: title, content: content, tags: tags);
      } else {
        await api.update(widget.noteId!, title: title, content: content, tags: tags);
      }
      if (!mounted) return;
      _saved = true;
      showToast(context, '✅ 已保存');
      Navigator.of(context).pop(true);
    } on ApiException catch (e) {
      if (mounted) showToast(context, e.message, error: true);
    } catch (_) {
      if (mounted) showToast(context, '保存失败，请重试', error: true);
    } finally {
      if (mounted) setState(() => _saving = false);
    }
  }

  Future<void> _confirmDiscard() async {
    final leave = await showDialog<bool>(
      context: context,
      builder: (dialogContext) => AlertDialog(
        title: const Text('放弃编辑？'),
        content: const Text('当前改动还没有保存，返回将丢失。'),
        shape: RoundedRectangleBorder(borderRadius: BorderRadius.circular(16)),
        actions: [
          TextButton(
            onPressed: () => Navigator.pop(dialogContext, false),
            child: const Text('继续编辑', style: TextStyle(color: Color(0xFF8D6E63))),
          ),
          TextButton(
            onPressed: () => Navigator.pop(dialogContext, true),
            child: const Text('放弃', style: TextStyle(color: Color(0xFFD32F2F))),
          ),
        ],
      ),
    );
    if (leave == true && mounted) Navigator.of(context).pop(false);
  }

  @override
  Widget build(BuildContext context) {
    return PopScope(
      canPop: !_dirty,
      onPopInvokedWithResult: (didPop, _) {
        if (!didPop) _confirmDiscard();
      },
      child: Scaffold(
        appBar: AppBar(
          title: Text(widget.isCreate ? '新建笔记' : '编辑笔记'),
          actions: [
            IconButton(
              tooltip: _preview ? '继续编辑' : '预览',
              icon: Icon(_preview ? Icons.edit_outlined : Icons.visibility_outlined),
              onPressed: _loading ? null : () => setState(() => _preview = !_preview),
            ),
            Padding(
              padding: const EdgeInsets.only(right: 8),
              child: TextButton(
                onPressed: (_saving || _loading) ? null : _save,
                child: _saving
                    ? const SizedBox(
                        width: 16,
                        height: 16,
                        child: CircularProgressIndicator(
                          strokeWidth: 2,
                          color: Color(0xFFC8956E),
                        ),
                      )
                    : const Text(
                        '保存',
                        style: TextStyle(
                          fontSize: 15,
                          fontWeight: FontWeight.w600,
                          color: Color(0xFFC8956E),
                        ),
                      ),
              ),
            ),
          ],
        ),
        body: _body(),
      ),
    );
  }

  Widget _body() {
    if (_loading) return const Center(child: LoadingView(tip: '笔记加载中...'));

    if (_loadError != null) {
      return Center(
        child: ErrorView(message: _loadError!, onRetry: _load),
      );
    }

    if (_preview) return _previewBody();

    return ListView(
      padding: const EdgeInsets.fromLTRB(20, 16, 20, 40),
      children: [
        TextField(
          controller: _titleController,
          style: const TextStyle(
            fontSize: 19,
            fontWeight: FontWeight.bold,
            color: Color(0xFF3E2723),
          ),
          decoration: const InputDecoration(
            hintText: '标题（留空则自动取正文首行）',
            hintStyle: TextStyle(fontSize: 17, color: Color(0xFFD7CCC8)),
            border: InputBorder.none,
          ),
        ),
        const Divider(height: 20, color: Color(0xFFF0E6D8)),
        TextField(
          controller: _tagsController,
          style: const TextStyle(fontSize: 14, color: Color(0xFF5D4037)),
          decoration: const InputDecoration(
            hintText: '标签，用逗号分隔，例如：工作,服务器',
            hintStyle: TextStyle(fontSize: 13.5, color: Color(0xFFD7CCC8)),
            prefixIcon: Icon(Icons.label_outline, size: 18, color: Color(0xFFBCAAA4)),
            prefixIconConstraints: BoxConstraints(minWidth: 34),
            border: InputBorder.none,
          ),
        ),
        const Divider(height: 20, color: Color(0xFFF0E6D8)),
        TextField(
          controller: _contentController,
          maxLines: null,
          minLines: 16,
          keyboardType: TextInputType.multiline,
          textAlignVertical: TextAlignVertical.top,
          style: const TextStyle(fontSize: 15, height: 1.7, color: Color(0xFF3E2723)),
          decoration: const InputDecoration(
            hintText: '正文，支持 Markdown…',
            hintStyle: TextStyle(fontSize: 15, color: Color(0xFFD7CCC8)),
            border: InputBorder.none,
          ),
        ),
      ],
    );
  }

  Widget _previewBody() {
    final content = _contentController.text;
    if (content.trim().isEmpty) {
      return const Center(
        child: EmptyView(icon: '📄', title: '还没有内容', tip: '切回编辑模式写点什么吧'),
      );
    }

    final base = MarkdownStyleSheet.fromTheme(Theme.of(context));
    return SingleChildScrollView(
      padding: const EdgeInsets.fromLTRB(20, 18, 20, 40),
      child: MarkdownBody(
        data: content,
        selectable: true,
        styleSheet: base.copyWith(
          p: const TextStyle(fontSize: 15, height: 1.75, color: Color(0xFF3E2723)),
          h1: const TextStyle(fontSize: 21, fontWeight: FontWeight.bold, color: Color(0xFF3E2723)),
          h2: const TextStyle(fontSize: 18, fontWeight: FontWeight.bold, color: Color(0xFF3E2723)),
          h3: const TextStyle(fontSize: 16, fontWeight: FontWeight.w600, color: Color(0xFF3E2723)),
          code: const TextStyle(
            fontSize: 13.5,
            fontFamily: 'monospace',
            backgroundColor: Color(0xFFF5EFE8),
            color: Color(0xFFB4654A),
          ),
          codeblockDecoration: BoxDecoration(
            color: const Color(0xFFF7F3EE),
            borderRadius: BorderRadius.circular(10),
            border: Border.all(color: const Color(0xFFEDE3D8)),
          ),
        ),
      ),
    );
  }
}