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

/// 通用底部弹窗选择器
/// Example:
/// ```dart
/// final choice = await BottomPicker.show<String>(
///   context,
///   items: ['选项1', '选项2', '选项3'],
///   itemBuilder: (item) => Text(item, textAlign: TextAlign.center),
///   initialIndex: 1,
/// );
/// if (choice != null) {
///   // 用户点击确定并选择了 choice
/// }
/// ```
class BottomPicker {
  /// 显示底部选择器弹窗
  ///
  /// [items]: 选项列表
  /// [itemBuilder]: 每个选项的展示 Widget
  /// [initialIndex]: 初始选中索引
  /// [itemExtent]: 列表行高
  /// [height]: 弹窗总高度
  static Future<T?> show<T>(
      BuildContext context, {
        required List<T> items,
        required Widget Function(T item) itemBuilder,
        int initialIndex = 0,
        double itemExtent = 40.0,
        double height = 250,
      }) {
    // 当前选中项
    T selected = items[initialIndex];

    return showModalBottomSheet<T>(
      context: context,
      backgroundColor: Colors.white,
      shape: const RoundedRectangleBorder(
        borderRadius: BorderRadius.vertical(top: Radius.circular(12)),
      ),
      builder: (ctx) {
        return SizedBox(
          height: height,
          child: Column(
            children: [
              // 按钮行
              Padding(
                padding: const EdgeInsets.symmetric(horizontal: 16, vertical: 8),
                child: Row(
                  mainAxisAlignment: MainAxisAlignment.spaceBetween,
                  children: [
                    TextButton(
                      onPressed: () => Navigator.of(ctx).pop(),
                      child: const Text('取消'),
                    ),
                    TextButton(
                      onPressed: () => Navigator.of(ctx).pop(selected),
                      child: const Text('确定'),
                    ),
                  ],
                ),
              ),
              const Divider(height: 1),
              // 滚动选择器
              Expanded(
                child: CupertinoPicker(
                  scrollController:
                  FixedExtentScrollController(initialItem: initialIndex),
                  itemExtent: 30,
                  onSelectedItemChanged: (index) {
                    selected = items[index];
                  },
                  children: items.map(itemBuilder).toList(),
                ),
              ),
            ],
          ),
        );
      },
    );
  }
}