package com.ruoyi.warehouse.util;

import java.io.InputStream;
import java.util.Iterator;
import java.util.Locale;
import java.util.Set;
import javax.imageio.ImageIO;
import javax.imageio.ImageReader;
import javax.imageio.stream.ImageInputStream;
import org.apache.commons.io.FilenameUtils;
import org.springframework.web.multipart.MultipartFile;
import com.ruoyi.common.exception.ServiceException;
import com.ruoyi.common.utils.StringUtils;

public final class WarehouseFileUtils
{
    private static final long MAX_IMAGE_PIXELS = 40_000_000L;

    private WarehouseFileUtils()
    {
    }

    public static String validateUpload(MultipartFile file, long maxFileSize, Set<String> allowedExtensions)
    {
        if (file == null || file.isEmpty())
        {
            throw new ServiceException("请选择要上传的文件");
        }
        if (file.getSize() > maxFileSize)
        {
            throw new ServiceException("文件不能超过" + (maxFileSize / 1024 / 1024) + "MB");
        }
        String extension = StringUtils.defaultString(FilenameUtils.getExtension(file.getOriginalFilename()))
                .toLowerCase(Locale.ROOT);
        if (!allowedExtensions.contains(extension))
        {
            throw new ServiceException("不支持的文件类型");
        }
        try
        {
            byte[] header;
            try (InputStream input = file.getInputStream())
            {
                header = input.readNBytes(12);
            }
            if ("xls".equals(extension) && !startsWith(header, 0xD0, 0xCF, 0x11, 0xE0))
            {
                throw new ServiceException("文件内容不是有效的Excel文件");
            }
            if ("xlsx".equals(extension) && !startsWith(header, 0x50, 0x4B))
            {
                throw new ServiceException("文件内容不是有效的Excel文件");
            }
            if (isImage(extension))
            {
                validateImage(file, extension, header);
            }
            return extension;
        }
        catch (ServiceException e)
        {
            throw e;
        }
        catch (Exception e)
        {
            throw new ServiceException("无法读取上传文件，请确认文件未损坏");
        }
    }

    private static void validateImage(MultipartFile file, String extension, byte[] header) throws Exception
    {
        if ("webp".equals(extension))
        {
            if (!matchesAscii(header, 0, "RIFF") || !matchesAscii(header, 8, "WEBP"))
            {
                throw new ServiceException("文件内容不是有效的WebP图片");
            }
            return;
        }
        try (ImageInputStream input = ImageIO.createImageInputStream(file.getInputStream()))
        {
            if (input == null)
            {
                throw new ServiceException("文件内容不是有效图片");
            }
            Iterator<ImageReader> readers = ImageIO.getImageReaders(input);
            if (!readers.hasNext())
            {
                throw new ServiceException("文件内容不是有效图片");
            }
            ImageReader reader = readers.next();
            try
            {
                reader.setInput(input, true, true);
                long pixels = (long) reader.getWidth(0) * reader.getHeight(0);
                if (pixels <= 0 || pixels > MAX_IMAGE_PIXELS)
                {
                    throw new ServiceException("图片尺寸过大，最大支持4000万像素");
                }
            }
            finally
            {
                reader.dispose();
            }
        }
    }

    private static boolean isImage(String extension)
    {
        return Set.of("jpg", "jpeg", "png", "bmp", "webp").contains(extension);
    }

    private static boolean startsWith(byte[] source, int... prefix)
    {
        if (source.length < prefix.length)
        {
            return false;
        }
        for (int i = 0; i < prefix.length; i++)
        {
            if ((source[i] & 0xFF) != prefix[i])
            {
                return false;
            }
        }
        return true;
    }

    private static boolean matchesAscii(byte[] source, int offset, String expected)
    {
        if (source.length < offset + expected.length())
        {
            return false;
        }
        for (int i = 0; i < expected.length(); i++)
        {
            if (source[offset + i] != (byte) expected.charAt(i))
            {
                return false;
            }
        }
        return true;
    }
}