package com.imyeyu.api.util;

import org.bytedeco.javacv.FFmpegFrameGrabber;
import org.bytedeco.javacv.Frame;
import org.bytedeco.javacv.Java2DFrameConverter;

import javax.imageio.ImageIO;
import java.awt.image.BufferedImage;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.InputStream;

/// JavaCV 工具类
///
/// @author 夜雨
/// @since 2025-10-23 17:05
public class JavaCV {

	/// 从视频流顺序解码并提取指定时间附近的一帧 PNG 图片
	///
	/// 不执行时间定位，避免为了取实时缩略图而把整个视频复制到临时文件
	///
	/// @param stream        视频输入流
	/// @param targetSeconds 目标时间，单位为秒
	/// @return PNG 图片字节流
	/// @throws Exception 视频解析或取帧失败
	public static ByteArrayOutputStream captureThumbnail(InputStream stream, double targetSeconds) throws Exception {
		long targetMicros = toMicros(targetSeconds);
		ByteArrayOutputStream firstFrame = new ByteArrayOutputStream();
		try (FFmpegFrameGrabber grabber = new FFmpegFrameGrabber(stream)) {
			grabber.start();
			try (Java2DFrameConverter converter = new Java2DFrameConverter()) {
				Frame frame;
				while ((frame = grabber.grabImage()) != null) {
					BufferedImage image = converter.getBufferedImage(frame);
					if (image == null) {
						continue;
					}
					if (!(0 < firstFrame.size())) {
						firstFrame = toPng(image);
					}
					if (grabber.getTimestamp() >= targetMicros) {
						return targetMicros == 0 ? firstFrame : toPng(image);
					}
				}
			}
		}
		// 短视频提前结束时退回首个有效帧
		return firstFrame;
	}

	private static long toMicros(double targetSeconds) {
		double seconds = Double.isFinite(targetSeconds) ? Math.max(0, targetSeconds) : 0;
		return Math.round(seconds * 1_000_000D);
	}

	private static ByteArrayOutputStream toPng(BufferedImage image) throws IOException {
		ByteArrayOutputStream output = new ByteArrayOutputStream();
		if (ImageIO.write(image, "png", output)) {
			return output;
		}
		return new ByteArrayOutputStream();
	}
}