import 'package:flutter/material.dart';

class Category {
  final String id;
  final String title;
  final List<Category> children;

  Category({
    required this.id,
    required this.title,
    this.children = const [],
  });
}

class DepartmentPicker extends StatefulWidget {
  final List<Category> data;
  final String? initialSelectedId;
  final Set<String>? initialExpandedSet;
  final ValueChanged<String?> onSelected;

  const DepartmentPicker({
    Key? key,
    required this.data,
    this.initialSelectedId,
    this.initialExpandedSet,
    required this.onSelected,
  }) : super(key: key);

  @override
  _DepartmentPickerState createState() => _DepartmentPickerState();
}

class _DepartmentPickerState extends State<DepartmentPicker> {
  late String? selectedId;
  late Set<String> expandedSet;

  @override
  void initState() {
    super.initState();
    selectedId = widget.initialSelectedId;
    expandedSet = Set<String>.from(widget.initialExpandedSet ?? {});
  }

  Widget _buildRow(Category cat, int indent) {
    final bool hasChildren = cat.children.isNotEmpty;
    final bool isExpanded = expandedSet.contains(cat.id);
    final bool isSelected = cat.id == selectedId;

    return Column(
      children: [
        InkWell(
          onTap: () {
            setState(() {
              if (hasChildren) {
                if (isExpanded) {
                  expandedSet.remove(cat.id);
                } else {
                  expandedSet.add(cat.id);
                }
              }
              selectedId = cat.id;
            });
          },
          child: Container(
            color: Colors.white,
            child: Row(
              crossAxisAlignment: CrossAxisAlignment.center,
              children: [
                // 左侧缩进
                SizedBox(width: 16.0 * indent),
                // 展开/占位图标
                SizedBox(
                  width: 24,
                  child: hasChildren
                      ? Icon(
                    isExpanded ? Icons.expand_less : Icons.expand_more,
                    size: 20,
                    color: Colors.grey[600],
                  )
                      : const SizedBox.shrink(),
                ),
                const SizedBox(width: 8),
                // 标题
                Expanded(
                  child: Padding(
                    padding: const EdgeInsets.symmetric(vertical: 12),
                    child: Text(cat.title),
                  ),
                ),
                // 单选圈保持右侧对齐
                Padding(
                  padding: const EdgeInsets.symmetric(horizontal: 16),
                  child: Icon(
                    isSelected
                        ? Icons.radio_button_checked
                        : Icons.radio_button_unchecked,
                    color: Colors.green,
                  ),
                ),
              ],
            ),
          ),
        ),
        if (hasChildren && isExpanded)
          ...cat.children.map((c) => _buildRow(c, indent + 1)),
        // const Divider(height: 1),
      ],
    );
  }

  @override
  Widget build(BuildContext context) {
    return Container(
      width: MediaQuery.of(context).size.width,
      height: MediaQuery.of(context).size.height * 0.7,
      color: Colors.transparent,
      child: Column(
        children: [
          // 顶部操作栏
          Container(
            color: Colors.white,
            padding: const EdgeInsets.symmetric(horizontal: 16, vertical: 12),
            child: Row(
              mainAxisAlignment: MainAxisAlignment.spaceBetween,
              children: [
                GestureDetector(
                  onTap: () => Navigator.of(context).pop(),
                  child: const Text('取消', style: TextStyle(fontSize: 16)),
                ),
                GestureDetector(
                  onTap: () => Navigator.of(context).pop(selectedId),
                  child: const Text('确定', style: TextStyle(fontSize: 16, color: Colors.green),),
                ),
              ],
            ),
          ),
          const Divider(height: 1),
          // 列表区
          Expanded(
            child: Container(
              color: Colors.white,
              child: ListView.builder(
                itemCount: widget.data.length,
                itemBuilder: (ctx, idx) => _buildRow(widget.data[idx], 0),
              ),
            ),
          ),
        ],
      ),
    );
  }
}