package com.doumee.core.utils;

import lombok.extern.slf4j.Slf4j;
import org.apache.commons.lang3.StringUtils;

import java.io.BufferedReader;
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStreamReader;
import java.nio.charset.StandardCharsets;
import java.nio.file.Files;
import java.nio.file.StandardCopyOption;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
import java.util.concurrent.TimeUnit;

/**
 * 将海康等设备下载的媒体流转为浏览器 video 标签可播的 MP4（H.264 + AAC）。
 * 海康 MP4 常见损坏的 MP2 音频轨，默认丢弃异常音频仅保留视频。
 */
@Slf4j
public final class VideoTranscodeUtil {

    private static final long TRANSCODE_TIMEOUT_MINUTES = 30;

    private VideoTranscodeUtil() {
    }

    /**
     * 将 MP4 视频（含海康 .mp4 扩展名但内容为 MPEG-PS 的情况）转为浏览器可播 MP4。
     * 调用方需已通过文件名等条件确认是 MP4 视频，本方法不再因缺少 ftyp 头而跳过。
     */
    public static boolean transcodeToBrowserMp4(String ffmpegPath, File source, File target) {
        if (source == null || !source.exists() || source.length() <= 0) {
            return false;
        }
        String ffmpeg = resolveExecutable(ffmpegPath, "ffmpeg");
        String ffprobe = resolveFfprobe(ffmpegPath);
        boolean mpegPs = false;
        boolean mp4Container = false;
        try {
            mpegPs = isMpegPs(source);
            mp4Container = hasMp4Header(source);
        } catch (IOException e) {
            log.warn("视频文件头检测失败，继续尝试 FFmpeg 转码: {}", e.getMessage());
        }
        if (mpegPs) {
            log.info("检测到 MPEG-PS 流（扩展名可能为 .mp4），将转码为标准 MP4: size={}", source.length());
        } else if (!mp4Container) {
            log.info("文件无 MP4 容器头(无 ftyp)，尝试 FFmpeg 按视频流转码: size={}", source.length());
        }

        try {
            if (mp4Container && isBrowserPlayableMp4(ffmpeg, source)) {
                Files.copy(source.toPath(), target.toPath(), StandardCopyOption.REPLACE_EXISTING);
                log.info("视频已是浏览器可播 MP4，跳过转码 size={}", source.length());
                return target.exists() && target.length() > 0;
            }
        } catch (Exception e) {
            log.warn("检测视频编码失败，将尝试转码: {}", e.getMessage());
        }

        String inputPath = source.getAbsolutePath();
        String outputPath = target.getAbsolutePath();
        String videoCodec = probeStreamCodec(ffprobe, source, "v:0");

        // 1. MP4 容器 + H.264：重封装并丢弃损坏音频
        if (mp4Container && "h264".equalsIgnoreCase(videoCodec)) {
            if (runFfmpeg(buildRemuxCommand(ffmpeg, source, inputPath, outputPath), "重封装(H.264 copy, 无音频)")) {
                return isValidOutput(target);
            }
        }

        // 2. 转码视频轨（适用于 MPEG-PS、损坏 MP4 等）
        if (runFfmpeg(buildEncodeVideoNoAudioCommand(ffmpeg, source, inputPath, outputPath), "转码(仅视频)")) {
            return isValidOutput(target);
        }

        // 3. 音频轨正常时才尝试带上音频
        String audioCodec = probeStreamCodec(ffprobe, source, "a:0");
        if (isDecodableAudio(audioCodec)) {
            if (runFfmpeg(buildEncodeVideoWithAudioCommand(ffmpeg, source, inputPath, outputPath), "转码(视频+音频)")) {
                return isValidOutput(target);
            }
        }

        log.error("视频转码全部策略失败 source={}", source.getAbsolutePath());
        return false;
    }

    public static boolean isBrowserPlayableMp4(String ffmpegPath, File file) throws IOException {
        if (!hasMp4Header(file)) {
            return false;
        }
        if (isMpegPs(file)) {
            return false;
        }
        String ffprobe = resolveFfprobe(ffmpegPath);
        String videoCodec = probeStreamCodec(ffprobe, file, "v:0");
        if (!"h264".equalsIgnoreCase(videoCodec)) {
            return false;
        }
        String audioCodec = probeStreamCodec(ffprobe, file, "a:0");
        if (StringUtils.isBlank(audioCodec)) {
            return true;
        }
        return "aac".equalsIgnoreCase(audioCodec);
    }

    public static boolean hasMp4Header(File file) throws IOException {
        byte[] head = readHead(file, 12);
        return head.length >= 8 && head[4] == 'f' && head[5] == 't' && head[6] == 'y' && head[7] == 'p';
    }

    public static boolean isMpegPs(File file) throws IOException {
        byte[] head = readHead(file, 4);
        return head.length >= 4 && head[0] == 0 && head[1] == 0 && head[2] == 1 && (head[3] & 0xFF) == 0xBA;
    }

    private static boolean isDecodableAudio(String codec) {
        if (StringUtils.isBlank(codec)) {
            return false;
        }
        return "aac".equalsIgnoreCase(codec)
                || "mp3".equalsIgnoreCase(codec)
                || codec.toLowerCase().startsWith("pcm");
    }

    private static boolean isValidOutput(File target) {
        return target != null && target.exists() && target.length() > 0;
    }

    private static List<String> buildInputArgs(String ffmpeg, File source, String inputPath) {
        List<String> cmd = new ArrayList<>();
        cmd.add(ffmpeg);
        cmd.add("-y");
        cmd.add("-fflags");
        cmd.add("+discardcorrupt");
        cmd.add("-err_detect");
        cmd.add("ignore_err");
        try {
            if (isMpegPs(source)) {
                cmd.add("-f");
                cmd.add("mpeg");
            }
        } catch (IOException ignored) {
        }
        cmd.add("-i");
        cmd.add(inputPath);
        return cmd;
    }

    /** 重封装：复制 H.264 视频，丢弃损坏音频 */
    private static List<String> buildRemuxCommand(String ffmpeg, File source, String inputPath, String outputPath) {
        List<String> cmd = buildInputArgs(ffmpeg, source, inputPath);
        cmd.add("-map");
        cmd.add("0:v:0");
        cmd.add("-an");
        cmd.add("-c:v");
        cmd.add("copy");
        cmd.add("-movflags");
        cmd.add("+faststart");
        cmd.add(outputPath);
        return cmd;
    }

    /** 转码：仅视频轨，无音频 */
    private static List<String> buildEncodeVideoNoAudioCommand(String ffmpeg, File source, String inputPath, String outputPath) {
        List<String> cmd = buildInputArgs(ffmpeg, source, inputPath);
        cmd.add("-map");
        cmd.add("0:v:0");
        cmd.add("-an");
        cmd.add("-c:v");
        cmd.add("libx264");
        cmd.add("-preset");
        cmd.add("fast");
        cmd.add("-crf");
        cmd.add("23");
        cmd.add("-pix_fmt");
        cmd.add("yuv420p");
        cmd.add("-movflags");
        cmd.add("+faststart");
        cmd.add(outputPath);
        return cmd;
    }

    /** 转码：视频 + 可解码音频 */
    private static List<String> buildEncodeVideoWithAudioCommand(String ffmpeg, File source, String inputPath, String outputPath) {
        List<String> cmd = buildInputArgs(ffmpeg, source, inputPath);
        cmd.add("-map");
        cmd.add("0:v:0");
        cmd.add("-map");
        cmd.add("0:a:0?");
        cmd.add("-c:v");
        cmd.add("libx264");
        cmd.add("-preset");
        cmd.add("fast");
        cmd.add("-crf");
        cmd.add("23");
        cmd.add("-pix_fmt");
        cmd.add("yuv420p");
        cmd.add("-c:a");
        cmd.add("aac");
        cmd.add("-b:a");
        cmd.add("128k");
        cmd.add("-ac");
        cmd.add("2");
        cmd.add("-movflags");
        cmd.add("+faststart");
        cmd.add(outputPath);
        return cmd;
    }

    private static boolean runFfmpeg(List<String> command, String label) {
        try {
            int exitCode = runCommand(command, TRANSCODE_TIMEOUT_MINUTES);
            if (exitCode == 0) {
                log.info("FFmpeg {} 成功", label);
                return true;
            }
            log.warn("FFmpeg {} 失败 exitCode={}", label, exitCode);
        } catch (Exception e) {
            log.warn("FFmpeg {} 异常: {}", label, e.getMessage());
        }
        return false;
    }

    private static byte[] readHead(File file, int len) throws IOException {
        byte[] head = new byte[len];
        try (FileInputStream in = new FileInputStream(file)) {
            int n = in.read(head);
            if (n <= 0) {
                return new byte[0];
            }
            if (n < len) {
                byte[] actual = new byte[n];
                System.arraycopy(head, 0, actual, 0, n);
                return actual;
            }
        }
        return head;
    }

    private static String probeStreamCodec(String ffprobe, File file, String stream) {
        List<String> command = Arrays.asList(
                ffprobe,
                "-v", "error",
                "-select_streams", stream,
                "-show_entries", "stream=codec_name",
                "-of", "default=noprint_wrappers=1:nokey=1",
                file.getAbsolutePath()
        );
        try {
            ProcessBuilder builder = new ProcessBuilder(command);
            builder.redirectErrorStream(true);
            Process process = builder.start();
            String output = readStream(process.getInputStream());
            boolean finished = process.waitFor(2, TimeUnit.MINUTES);
            if (!finished) {
                process.destroyForcibly();
                return null;
            }
            if (process.exitValue() != 0) {
                return null;
            }
            return output.trim();
        } catch (Exception e) {
            log.warn("ffprobe 检测失败 stream={}: {}", stream, e.getMessage());
            return null;
        }
    }

    private static String resolveExecutable(String configuredPath, String defaultName) {
        if (StringUtils.isNotBlank(configuredPath)) {
            return configuredPath.trim();
        }
        return defaultName;
    }

    private static String resolveFfprobe(String ffmpegPath) {
        if (StringUtils.isNotBlank(ffmpegPath)) {
            String path = ffmpegPath.trim();
            if (path.toLowerCase().endsWith("ffmpeg.exe") || path.toLowerCase().endsWith("ffmpeg")) {
                int idx = path.lastIndexOf('/');
                if (idx < 0) {
                    idx = path.lastIndexOf('\\');
                }
                String dir = idx >= 0 ? path.substring(0, idx + 1) : "";
                String name = path.substring(idx + 1);
                if (name.toLowerCase().endsWith(".exe")) {
                    return dir + name.replaceAll("(?i)ffmpeg\\.exe$", "ffprobe.exe");
                }
                return dir + name.replaceAll("(?i)ffmpeg$", "ffprobe");
            }
            return path.replaceAll("(?i)ffmpeg", "ffprobe");
        }
        return "ffprobe";
    }

    private static int runCommand(List<String> command, long timeoutMinutes) throws IOException, InterruptedException {
        ProcessBuilder builder = new ProcessBuilder(command);
        builder.redirectErrorStream(true);
        Process process = builder.start();
        String output = readStream(process.getInputStream());
        boolean finished = process.waitFor(timeoutMinutes, TimeUnit.MINUTES);
        if (!finished) {
            process.destroyForcibly();
            log.error("FFmpeg 执行超时: {}", String.join(" ", command));
            return -1;
        }
        if (StringUtils.isNotBlank(output)) {
            if (process.exitValue() != 0) {
                log.warn("FFmpeg 输出: {}", output.length() > 2000 ? output.substring(0, 2000) + "..." : output);
            } else {
                log.debug("FFmpeg 输出: {}", output.length() > 2000 ? output.substring(0, 2000) + "..." : output);
            }
        }
        return process.exitValue();
    }

    private static String readStream(java.io.InputStream inputStream) throws IOException {
        StringBuilder sb = new StringBuilder();
        try (BufferedReader reader = new BufferedReader(new InputStreamReader(inputStream, StandardCharsets.UTF_8))) {
            String line;
            while ((line = reader.readLine()) != null) {
                sb.append(line).append('\n');
            }
        }
        return sb.toString().trim();
    }
}