/// ============================================================
/// 闲言APP — 带水印的版权证书图片组件
/// 创建时间: 2026-06-02
/// 更新时间: 2026-06-02
/// 作用: 展示软件著作权证书图片，带对角线"闲言"水印，点击全屏查看
/// 上次更新: 初始创建
/// ============================================================

import 'dart:math';

import 'package:flutter/cupertino.dart';

import '../../../core/theme/app_radius.dart';
import '../../../core/theme/app_spacing.dart';
import '../../../core/theme/app_theme.dart';
import '../../../core/theme/app_typography.dart';

class WatermarkedCopyrightImage extends StatelessWidget {
  const WatermarkedCopyrightImage({super.key});

  static const _assetPath = 'assets/images/empty/rz.png';
  static const _watermarkText = '闲言';

  @override
  Widget build(BuildContext context) {
    final ext = AppTheme.ext(context);

    return GestureDetector(
      onTap: () => _showFullScreen(context),
      child: Container(
        margin: const EdgeInsets.symmetric(vertical: AppSpacing.sm),
        decoration: BoxDecoration(
          borderRadius: AppRadius.lgBorder,
          border: Border.all(
            color: ext.textHint.withValues(alpha: 0.15),
            width: 0.5,
          ),
          boxShadow: [
            BoxShadow(
              color: ext.textPrimary.withValues(alpha: 0.06),
              blurRadius: 12,
              offset: const Offset(0, 4),
            ),
          ],
        ),
        clipBehavior: Clip.antiAlias,
        child: Stack(
          children: [
            ClipRRect(
              borderRadius: AppRadius.lgBorder,
              child: Image.asset(
                _assetPath,
                fit: BoxFit.fitWidth,
                width: double.infinity,
                errorBuilder: (_, __, ___) => _buildErrorPlaceholder(ext),
              ),
            ),
            Positioned.fill(
              child: IgnorePointer(
                child: CustomPaint(
                  painter: _DiagonalWatermarkPainter(
                    text: _watermarkText,
                    color: ext.textPrimary.withValues(alpha: 0.08),
                  ),
                ),
              ),
            ),
            Positioned(
              right: AppSpacing.sm,
              top: AppSpacing.sm,
              child: Container(
                padding: const EdgeInsets.symmetric(
                  horizontal: AppSpacing.xs,
                  vertical: 2,
                ),
                decoration: BoxDecoration(
                  color: ext.bgPrimary.withValues(alpha: 0.7),
                  borderRadius: AppRadius.smBorder,
                ),
                child: Row(
                  mainAxisSize: MainAxisSize.min,
                  children: [
                    Icon(
                      CupertinoIcons.fullscreen,
                      size: 12,
                      color: ext.textSecondary,
                    ),
                    const SizedBox(width: 3),
                    Text(
                      '🔍',
                      style: AppTypography.caption2.copyWith(
                        color: ext.textSecondary,
                        fontSize: 10,
                      ),
                    ),
                  ],
                ),
              ),
            ),
          ],
        ),
      ),
    );
  }

  Widget _buildErrorPlaceholder(AppThemeExtension ext) {
    return Container(
      height: 200,
      decoration: BoxDecoration(
        color: ext.bgSecondary,
        borderRadius: AppRadius.lgBorder,
      ),
      child: Center(
        child: Column(
          mainAxisSize: MainAxisSize.min,
          children: [
            Icon(CupertinoIcons.doc_text_search, size: 36, color: ext.textHint),
            const SizedBox(height: AppSpacing.xs),
            Text(
              '证书图片加载失败',
              style: AppTypography.caption1.copyWith(color: ext.textHint),
            ),
          ],
        ),
      ),
    );
  }

  void _showFullScreen(BuildContext context) {
    final ext = AppTheme.ext(context);
    showCupertinoDialog<void>(
      context: context,
      barrierDismissible: true,
      builder: (dialogContext) => CupertinoPageScaffold(
        backgroundColor: ext.bgPrimary.withValues(alpha: 0.95),
        child: SafeArea(
          child: Column(
            children: [
              CupertinoNavigationBar(
                backgroundColor: ext.bgPrimary.withValues(alpha: 0.8),
                border: null,
                leading: CupertinoButton(
                  padding: EdgeInsets.zero,
                  onPressed: () => Navigator.of(dialogContext).pop(),
                  child: Icon(
                    CupertinoIcons.xmark_circle_fill,
                    color: ext.textHint,
                    size: 28,
                  ),
                ),
                middle: Text(
                  '📜 软件著作权证书',
                  style: AppTypography.subhead.copyWith(
                    color: ext.textPrimary,
                    fontWeight: FontWeight.w600,
                  ),
                ),
              ),
              Expanded(
                child: InteractiveViewer(
                  minScale: 0.5,
                  maxScale: 4.0,
                  child: Center(
                    child: Stack(
                      children: [
                        Padding(
                          padding: const EdgeInsets.all(AppSpacing.md),
                          child: Image.asset(
                            _assetPath,
                            fit: BoxFit.contain,
                            errorBuilder: (_, __, ___) => Center(
                              child: Column(
                                mainAxisSize: MainAxisSize.min,
                                children: [
                                  Icon(
                                    CupertinoIcons.doc_text_search,
                                    size: 48,
                                    color: ext.textHint,
                                  ),
                                  const SizedBox(height: AppSpacing.sm),
                                  Text(
                                    '图片加载失败',
                                    style: AppTypography.subhead.copyWith(
                                      color: ext.textHint,
                                    ),
                                  ),
                                ],
                              ),
                            ),
                          ),
                        ),
                        Positioned.fill(
                          child: IgnorePointer(
                            child: CustomPaint(
                              painter: _DiagonalWatermarkPainter(
                                text: _watermarkText,
                                color: ext.textPrimary.withValues(alpha: 0.06),
                                fontSize: 20,
                              ),
                            ),
                          ),
                        ),
                      ],
                    ),
                  ),
                ),
              ),
            ],
          ),
        ),
      ),
    );
  }
}

class _DiagonalWatermarkPainter extends CustomPainter {
  _DiagonalWatermarkPainter({
    required this.text,
    required this.color,
    this.fontSize = 14,
  });

  final String text;
  final Color color;
  final double fontSize;

  @override
  void paint(Canvas canvas, Size size) {
    final textStyle = TextStyle(
      color: color,
      fontSize: fontSize,
      fontWeight: FontWeight.w600,
      letterSpacing: 4,
    );
    final textSpan = TextSpan(text: text, style: textStyle);
    final textPainter = TextPainter(
      text: textSpan,
      textDirection: TextDirection.ltr,
    );
    textPainter.layout();

    final stepX = textPainter.width + 60;
    final stepY = textPainter.height + 80;
    const angle = -pi / 6;

    canvas.save();
    canvas.translate(size.width / 2, size.height / 2);
    canvas.rotate(angle);
    canvas.translate(-size.width, -size.height);

    final cols = (size.width * 3 / stepX).ceil() + 1;
    final rows = (size.height * 3 / stepY).ceil() + 1;

    for (var row = 0; row < rows; row++) {
      for (var col = 0; col < cols; col++) {
        final x = col * stepX.toDouble();
        final y = row * stepY.toDouble();
        textPainter.paint(canvas, Offset(x, y));
      }
    }

    canvas.restore();
  }

  @override
  bool shouldRepaint(covariant _DiagonalWatermarkPainter oldDelegate) {
    return oldDelegate.text != text ||
        oldDelegate.color != color ||
        oldDelegate.fontSize != fontSize;
  }
}