import 'dart:convert';
import 'dart:typed_data';

import 'package:image/image.dart';

/// PNG data URL 解析与像素层转换（Windows PavoApi 直打用）。
///
/// 卡面为 CR-80 @300dpi：横向 1014×642 / 纵向 642×1014，按源图纵横比自动选择；
/// 透明区域铺白，避免黑底（对齐 C# 版 Hiti/CardImage.cs）。
class CardImage {
  CardImage._(this._canvas, this.width, this.height);

  static const int landscapeWidth = 1014;
  static const int landscapeHeight = 642;

  final Image _canvas;
  final int width;
  final int height;

  /// 宽 ≥ 高 = 横向卡面
  bool get isLandscape => width >= height;

  /// 解析 data:image/png;base64,…（或其他 data URL 形式），缩放到卡面画布并铺白底。
  static CardImage fromDataUrl(String dataUrl) {
    if (dataUrl.trim().isEmpty) {
      throw ArgumentError('卡面图为空');
    }
    final comma = dataUrl.indexOf(',');
    final base64Part = comma >= 0 ? dataUrl.substring(comma + 1) : dataUrl;
    final bytes = base64.decode(base64Part.replaceAll(RegExp(r'\s'), ''));
    final raw = decodeImage(bytes);
    if (raw == null) {
      throw ArgumentError('卡面图解码失败（不支持的图片格式）');
    }

    final landscape = raw.width >= raw.height;
    final width = landscape ? landscapeWidth : landscapeHeight;
    final height = landscape ? landscapeHeight : landscapeWidth;

    final resized = copyResize(raw, width: width, height: height);
    final canvas = Image(width: width, height: height);
    // 手动 alpha 混合铺白底（与 C# 版逐像素语义一致）：
    // image 包的 compositeImage 对全透明 src 像素不是 src-over 语义，透明处会漏黑
    for (var y = 0; y < height; y++) {
      for (var x = 0; x < width; x++) {
        final p = resized.getPixel(x, y);
        final a = p.a.toInt() / 255.0;
        canvas.setPixelRgba(
          x,
          y,
          (255 * (1 - a) + p.r * a).round().clamp(0, 255),
          (255 * (1 - a) + p.g * a).round().clamp(0, 255),
          (255 * (1 - a) + p.b * a).round().clamp(0, 255),
          255,
        );
      }
    }
    return CardImage._(canvas, width, height);
  }

  /// 转 BGR 24bit 紧凑像素（无行对齐填充，PavoApi BITMAP 用）。
  Uint8List toBgr24() {
    final packed = Uint8List(width * 3 * height);
    for (var y = 0; y < height; y++) {
      var offset = y * width * 3;
      for (var x = 0; x < width; x++) {
        final p = _canvas.getPixel(x, y);
        packed[offset] = p.b.toInt() & 0xff;
        packed[offset + 1] = p.g.toInt() & 0xff;
        packed[offset + 2] = p.r.toInt() & 0xff;
        offset += 3;
      }
    }
    return packed;
  }

  /// 转 8bit 灰度（无行对齐）。树脂 K 层像素语义：0x00 = 转印黑色，
  /// 因此前端 K 层 PNG 为白底黑字，灰度值可直接使用。
  Uint8List toGray8() {
    final gray = Uint8List(width * height);
    for (var y = 0; y < height; y++) {
      var offset = y * width;
      for (var x = 0; x < width; x++) {
        final p = _canvas.getPixel(x, y);
        gray[offset + x] = (p.r.toInt() * 299 + p.g.toInt() * 587 + p.b.toInt() * 114) ~/ 1000 & 0xff;
      }
    }
    return gray;
  }
}