// Author: fruit.com.cn

import 'package:flutter/material.dart';

import '../theme/app_colors.dart';
import '../theme/app_dimens.dart';

const double _iconSize = 72;
const double _maxContentWidth = 260;
const double _regularHorizontal = 24;
const double _regularVertical = 28;
const double _compactHorizontal = 16;
const double _compactVertical = 4;
const double _regularGap = 20;
const double _compactGap = 12;
const double _actionMinHeight = 44;

/// 统一空列表占位：一枚图标、标题、可选说明与操作。
class EmptyState extends StatelessWidget {
  const EmptyState({
    super.key,
    required this.icon,
    required this.title,
    this.subtitle,
    this.actionLabel,
    this.actionKey,
    this.onAction,
    this.footer,
    this.compact = false,
    this.stretchContent = false,
  });

  final IconData icon;
  final String title;
  final String? subtitle;
  final String? actionLabel;
  final Key? actionKey;
  final VoidCallback? onAction;
  final Widget? footer;
  final bool compact;

  /// 让图标和文案占满内容宽度，适用于需要严格居中的宽版空状态。
  final bool stretchContent;

  @override
  Widget build(BuildContext context) {
    final hasAction = actionLabel != null && onAction != null;
    return Center(
      child: ConstrainedBox(
        key: const Key('empty-state-content'),
        constraints: const BoxConstraints(maxWidth: _maxContentWidth),
        child: Padding(
          key: const Key('empty-state-padding'),
          padding: EdgeInsets.symmetric(
            horizontal: compact ? _compactHorizontal : _regularHorizontal,
            vertical: compact ? _compactVertical : _regularVertical,
          ),
          child: SizedBox(
            width: stretchContent ? double.infinity : null,
            child: Semantics(
              container: true,
              label: title,
              child: Column(
                mainAxisSize: MainAxisSize.min,
                children: [
                  ExcludeSemantics(child: _EmptyMark(icon: icon)),
                  SizedBox(height: compact ? _compactGap : _regularGap),
                  SizedBox(
                    width: stretchContent ? double.infinity : null,
                    child: _EmptyCopy(
                      title: title,
                      subtitle: subtitle,
                      actionLabel: hasAction ? actionLabel : null,
                      actionKey: actionKey,
                      onAction: hasAction ? onAction : null,
                      footer: footer,
                      stretchContent: stretchContent,
                    ),
                  ),
                ],
              ),
            ),
          ),
        ),
      ),
    );
  }
}

/// 空列表只放一枚大图标，不画线框，也不铺底色。
class _EmptyMark extends StatelessWidget {
  const _EmptyMark({required this.icon});

  final IconData icon;

  @override
  Widget build(BuildContext context) {
    return Icon(
      icon,
      key: const Key('empty-state-icon'),
      size: _iconSize,
      color: AppColors.subtle,
    );
  }
}

class _EmptyCopy extends StatelessWidget {
  const _EmptyCopy({
    required this.title,
    required this.subtitle,
    required this.actionLabel,
    required this.actionKey,
    required this.onAction,
    required this.footer,
    required this.stretchContent,
  });

  final String title;
  final String? subtitle;
  final String? actionLabel;
  final Key? actionKey;
  final VoidCallback? onAction;
  final Widget? footer;
  final bool stretchContent;

  @override
  Widget build(BuildContext context) {
    return Column(
      mainAxisSize: MainAxisSize.min,
      crossAxisAlignment: stretchContent
          ? CrossAxisAlignment.stretch
          : CrossAxisAlignment.center,
      children: [
        ExcludeSemantics(
          child: Text(
            title,
            key: const Key('empty-state-title'),
            maxLines: 2,
            overflow: TextOverflow.ellipsis,
            textAlign: TextAlign.center,
            style: const TextStyle(
              color: AppColors.textTertiary,
              fontSize: 15,
              fontWeight: FontWeight.w400,
              height: 1.35,
            ),
          ),
        ),
        if (subtitle != null) ...[
          const SizedBox(height: 6),
          ExcludeSemantics(
            child: Text(
              subtitle!,
              maxLines: 2,
              overflow: TextOverflow.ellipsis,
              textAlign: TextAlign.center,
              style: const TextStyle(
                color: AppColors.muted,
                fontSize: AppDimens.emptyStateSubtitle,
                height: 1.45,
              ),
            ),
          ),
        ],
        if (actionLabel != null && onAction != null) ...[
          const SizedBox(height: 8),
          TextButton(
            key: actionKey ?? const Key('empty-state-action'),
            onPressed: onAction,
            style: TextButton.styleFrom(
              foregroundColor: AppColors.blueSoft,
              minimumSize: const Size(44, _actionMinHeight),
              padding: const EdgeInsets.symmetric(horizontal: 14),
            ),
            child: Text(
              actionLabel!,
              style: const TextStyle(fontSize: AppDimens.emptyStateAction),
            ),
          ),
        ],
        if (footer != null) ...[const SizedBox(height: 12), footer!],
      ],
    );
  }
}