import 'package:flutter/material.dart';
import 'package:flutter_riverpod/flutter_riverpod.dart';
import '../core/app_colors.dart';
import 'app_error_state.dart';

/// 基于 FutureBuilder 的四态封装：统一处理"加载中 / 失败"，
/// "空数据 / 有数据"交由 onData 自行判断（不同页面空态文案不同）。
///
/// onData 拿到非空数据后，自行判断 isEmpty 决定显示空态还是列表。
class AppFutureView<T> extends StatelessWidget {
  final Future<T>? future;
  final Widget Function(BuildContext context, T data) onData;
  final VoidCallback? onRetry;
  final Widget? loading;
  final String? errorTitle;

  const AppFutureView({
    super.key,
    required this.future,
    required this.onData,
    this.onRetry,
    this.loading,
    this.errorTitle,
  });

  @override
  Widget build(BuildContext context) {
    return FutureBuilder<T>(
      future: future,
      builder: (ctx, snap) {
        // 失败优先于其它判断，避免把错误显示成"暂无数据"
        if (snap.hasError) {
          return AppErrorState(title: errorTitle ?? '加载失败', onRetry: onRetry);
        }
        // 首次加载、尚无数据 → 转圈
        if (snap.connectionState == ConnectionState.waiting && !snap.hasData) {
          return loading ??
              const Center(
                child: CircularProgressIndicator(color: AppColors.primary),
              );
        }
        if (!snap.hasData) {
          return loading ??
              const Center(
                child: CircularProgressIndicator(color: AppColors.primary),
              );
        }
        return onData(ctx, snap.data as T);
      },
    );
  }
}

/// Riverpod 异步数据视图。Provider 会保留最近一次成功数据，刷新时不清空页面。
class AppAsyncValueView<T> extends StatelessWidget {
  final AsyncValue<T> value;
  final Widget Function(BuildContext context, T data) onData;
  final VoidCallback? onRetry;
  final Widget? loading;
  final String? errorTitle;

  const AppAsyncValueView({
    super.key,
    required this.value,
    required this.onData,
    this.onRetry,
    this.loading,
    this.errorTitle,
  });

  @override
  Widget build(BuildContext context) => value.when(
    skipLoadingOnRefresh: true,
    skipLoadingOnReload: true,
    data: (data) => onData(context, data),
    error: (_, _) =>
        AppErrorState(title: errorTitle ?? '加载失败', onRetry: onRetry),
    loading: () =>
        loading ??
        const Center(
          child: CircularProgressIndicator(color: AppColors.primary),
        ),
  );
}