import 'package:flutter/material.dart';

/// 数据转换函数签名
/// 将原始数据转换为SelectOption类型的函数
typedef SelectOptionConverter<T> = SelectOption Function(T data);

/// 选择器选项数据模型
class SelectOption {
  final String label;
  final String value;
  final dynamic extra;

  SelectOption({required this.label, required this.value, this.extra});
}

/// 通用选择器组件
/// 支持静态数据源和动态API数据源
class VberSelect<T> extends StatefulWidget {
  /// 静态数据列表
  final List<T>? items;

  /// API获取数据的方法
  final Future<List<T>> Function()? fetchData;

  /// 数据转换方法，将原始数据转换为SelectOption
  final SelectOptionConverter<T> converter;

  /// 当前选中的值
  final String? value;

  /// 值改变回调
  final Function(String?)? onChanged;

  /// 提示文字
  final String? hint;

  /// 是否启用
  final bool enabled;

  /// 是否显示"全部"选项
  final bool showAll;

  /// 是否隐藏下划线
  final bool hideUnderline;

  /// 是否显示清空按钮
  final bool showClearButton;

  const VberSelect({
    super.key,
    this.items,
    this.fetchData,
    required this.converter,
    this.value,
    this.onChanged,
    this.hint,
    this.enabled = true,
    this.showAll = false,
    this.hideUnderline = false,
    this.showClearButton = false,
  });

  @override
  State<VberSelect<T>> createState() => _VberSelectState<T>();
}

class _VberSelectState<T> extends State<VberSelect<T>> {
  List<T>? _items;
  bool _loading = false;
  String? _selectedValue;

  @override
  void initState() {
    super.initState();
    _selectedValue = widget.value;
    // 使用WidgetsBinding.instance.addPostFrameCallback确保在widget构建完成后再加载数据
    WidgetsBinding.instance.addPostFrameCallback((_) {
      _loadData();
    });
  }

  @override
  void didUpdateWidget(covariant VberSelect<T> oldWidget) {
    super.didUpdateWidget(oldWidget);
    // 当外部传入的value发生变化时，同步更新内部状态
    if (oldWidget.value != widget.value) {
      setState(() {
        _selectedValue = widget.value;
      });
    }
  }

  Future<void> _loadData() async {
    // 如果提供了fetchData方法，则优先使用它获取数据
    if (widget.fetchData != null) {
      // 使用Future.microtask确保在下一个微任务中加载数据，避免在构建过程中修改状态
      Future.microtask(() async {
        setState(() {
          _loading = true;
        });

        try {
          final data = await widget.fetchData!();
          setState(() {
            _items = data;
            _loading = false;
          });
        } catch (e) {
          setState(() {
            _loading = false;
          });
        }
      });
    } else {
      // 否则使用传入的静态数据
      setState(() {
        _items = widget.items;
      });
    }
  }

  @override
  Widget build(BuildContext context) {
    if (_loading) {
      Widget dropdownWidget = DropdownButton<String>(
        items: [],
        hint: SizedBox(
          width: 16,
          height: 16,
          child: CircularProgressIndicator(strokeWidth: 2),
        ),
        onChanged: (String? value) {},
      );

      Widget selectWidget = widget.hideUnderline
          ? DropdownButtonHideUnderline(child: dropdownWidget)
          : dropdownWidget;

      if (widget.showClearButton) {
        return Row(
          children: [
            Expanded(child: selectWidget),
            IconButton(
              icon: const Icon(Icons.clear, size: 20),
              onPressed: widget.enabled
                  ? () {
                      setState(() {
                        _selectedValue = null;
                      });
                      widget.onChanged?.call(null);
                    }
                  : null,
            ),
          ],
        );
      }

      return selectWidget;
    }

    // 构建最终的下拉选项列表
    List<DropdownMenuItem<String>> dropdownItems = [];

    // 如果showAll为true，添加"全部"选项
    if (widget.showAll) {
      dropdownItems.add(DropdownMenuItem<String>(value: '', child: Text('全部')));
    }

    // 只有当_items不为null且不为空时才添加实际选项
    if (_items != null && _items!.isNotEmpty) {
      final options = _items!.map((item) => widget.converter(item)).toList();
      // 添加转换后的选项
      dropdownItems.addAll(
        options.map((option) {
          return DropdownMenuItem<String>(
            value: option.value,
            child: Text(option.label),
          );
        }).toList(),
      );
    }

    Widget dropdownWidget = DropdownButton<String>(
      value: _selectedValue,
      hint: Text(widget.hint ?? '请选择'),
      items: dropdownItems,
      onChanged: widget.enabled
          ? (String? newValue) {
              setState(() {
                _selectedValue = newValue;
              });
              widget.onChanged?.call(newValue);
            }
          : null,
      isExpanded: true,
    );

    Widget selectWidget = widget.hideUnderline
        ? DropdownButtonHideUnderline(child: dropdownWidget)
        : dropdownWidget;

    if (widget.showClearButton) {
      return Row(
        children: [
          Expanded(child: selectWidget),
          IconButton(
            icon: const Icon(Icons.clear, size: 20),
            onPressed: widget.enabled
                ? () {
                    setState(() {
                      _selectedValue = null;
                    });
                    widget.onChanged?.call(null);
                  }
                : null,
          ),
        ],
      );
    }

    return selectWidget;
  }
}