package com.talentcard.server.upload;

import java.io.IOException;
import java.io.InputStream;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.StandardCopyOption;
import java.util.Locale;
import java.util.UUID;

import com.talentcard.server.common.BusinessException;
import com.talentcard.server.common.ErrorCode;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.stereotype.Service;
import org.springframework.web.multipart.MultipartFile;

@Service
public class ImageUploadService {

	private static final long MAX_IMAGE_SIZE = 10L * 1024 * 1024;
	private static final long MAX_PDF_SIZE = 20L * 1024 * 1024;

	private final Path uploadDirectory;

	@Autowired
	public ImageUploadService(@Value("${app.upload.directory:uploads}") String uploadDirectory) {
		this(Path.of(uploadDirectory));
	}

	ImageUploadService(Path uploadDirectory) {
		this.uploadDirectory = uploadDirectory.toAbsolutePath().normalize();
	}

	public ImageUploadResult upload(MultipartFile file) {
		if (file == null || file.isEmpty()) {
			throw new BusinessException(ErrorCode.BAD_REQUEST, "Please select an image");
		}
		if (file.getSize() > MAX_IMAGE_SIZE) {
			throw new BusinessException(ErrorCode.BAD_REQUEST, "Image size cannot exceed 10 MB");
		}

		String extension = detectImageExtension(file);
		String filename = UUID.randomUUID() + "." + extension;
		try {
			Files.createDirectories(uploadDirectory);
			Path destination = uploadDirectory.resolve(filename).normalize();
			if (!destination.startsWith(uploadDirectory)) {
				throw new BusinessException(ErrorCode.BAD_REQUEST, "Invalid image filename");
			}
			try (InputStream input = file.getInputStream()) {
				Files.copy(input, destination, StandardCopyOption.REPLACE_EXISTING);
			}
		} catch (IOException exception) {
			throw new BusinessException(ErrorCode.INTERNAL_ERROR, "Failed to save image");
		}
		return new ImageUploadResult("/uploads/" + filename);
	}

	public ImageUploadResult uploadPdf(MultipartFile file) {
		if (file == null || file.isEmpty()) {
			throw new BusinessException(ErrorCode.BAD_REQUEST, "请选择 PDF 文件");
		}
		if (file.getSize() > MAX_PDF_SIZE) {
			throw new BusinessException(ErrorCode.BAD_REQUEST, "PDF 文件大小不能超过 20 MB");
		}
		try (InputStream input = file.getInputStream()) {
			byte[] header = input.readNBytes(5);
			if (header.length < 5 || header[0] != '%' || header[1] != 'P' || header[2] != 'D' || header[3] != 'F' || header[4] != '-') {
				throw new BusinessException(ErrorCode.BAD_REQUEST, "仅支持 PDF 文件");
			}
		} catch (IOException exception) {
			throw new BusinessException(ErrorCode.BAD_REQUEST, "无法读取 PDF 文件");
		}
		String contentType = file.getContentType() == null ? "" : file.getContentType().toLowerCase(Locale.ROOT);
		if (!contentType.isBlank() && !"application/pdf".equals(contentType) && !"application/octet-stream".equals(contentType)) {
			throw new BusinessException(ErrorCode.BAD_REQUEST, "仅支持 PDF 文件");
		}
		String filename = UUID.randomUUID() + ".pdf";
		try {
			Files.createDirectories(uploadDirectory);
			Path destination = uploadDirectory.resolve(filename).normalize();
			if (!destination.startsWith(uploadDirectory)) throw new BusinessException(ErrorCode.BAD_REQUEST, "Invalid PDF filename");
			Files.copy(file.getInputStream(), destination, StandardCopyOption.REPLACE_EXISTING);
		} catch (IOException exception) {
			throw new BusinessException(ErrorCode.INTERNAL_ERROR, "保存 PDF 文件失败");
		}
		return new ImageUploadResult("/uploads/" + filename);
	}

	private String detectImageExtension(MultipartFile file) {
		byte[] header = new byte[12];
		try (InputStream input = file.getInputStream()) {
			int count = input.readNBytes(header, 0, header.length);
			if (count >= 3 && (header[0] & 0xff) == 0xff && (header[1] & 0xff) == 0xd8 && (header[2] & 0xff) == 0xff) {
				return "jpg";
			}
			if (count >= 8 && header[0] == (byte) 0x89 && header[1] == 0x50 && header[2] == 0x4e
					&& header[3] == 0x47 && header[4] == 0x0d && header[5] == 0x0a && header[6] == 0x1a && header[7] == 0x0a) {
				return "png";
			}
			if (count >= 12 && new String(header, 0, 4).equals("RIFF") && new String(header, 8, 4).equals("WEBP")) {
				return "webp";
			}
		} catch (IOException exception) {
			throw new BusinessException(ErrorCode.BAD_REQUEST, "Unable to read image");
		}

		String contentType = file.getContentType();
		String type = contentType == null ? "" : contentType.toLowerCase(Locale.ROOT);
		throw new BusinessException(ErrorCode.BAD_REQUEST,
				"Only JPG, PNG, and WEBP images are supported" + (type.isBlank() ? "" : " (received " + type + ")"));
	}
}