Stirling-PDF/src/main/java/stirling/software/SPDF/controller/SplitPDFController.java

package stirling.software.SPDF.controller;

import java.io.ByteArrayOutputStream;
import java.io.File;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.net.URI;
import java.nio.file.FileSystem;
import java.nio.file.FileSystems;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.stream.Collectors;

import org.apache.pdfbox.pdmodel.PDDocument;
import org.apache.pdfbox.pdmodel.PDPage;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.core.io.ByteArrayResource;
import org.springframework.core.io.Resource;
import org.springframework.http.HttpHeaders;
import org.springframework.http.MediaType;
import org.springframework.http.ResponseEntity;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.multipart.MultipartFile;

@Controller
public class SplitPDFController {

	private static final Logger logger = LoggerFactory.getLogger(SplitPDFController.class);

	@GetMapping("/split-pdfs")
	public String splitPdfForm() {
		return "split-pdfs";
	}

	@PostMapping("/split-pages")
	public ResponseEntity<Resource> splitPdf(@RequestParam("fileInput") MultipartFile file,
			@RequestParam("pages") String pages) throws IOException {
		// parse user input

		// open the pdf document
		InputStream inputStream = file.getInputStream();
		PDDocument document = PDDocument.load(inputStream);

		List<Integer> pageNumbers = new ArrayList<>();
		pages = pages.replaceAll("\\s+", ""); // remove whitespaces
		if (pages.toLowerCase().equals("all")) {
			for (int i = 0; i < document.getNumberOfPages(); i++) {
				pageNumbers.add(i);
			}
		} else {
			List<String> pageNumbersStr = new ArrayList<>(Arrays.asList(pages.split(",")));
			if (!pageNumbersStr.contains(String.valueOf(document.getNumberOfPages()))) {
				String lastpage = String.valueOf(document.getNumberOfPages());
				pageNumbersStr.add(lastpage);
			}
			for (String page : pageNumbersStr) {
				if (page.contains("-")) {
					String[] range = page.split("-");
					int start = Integer.parseInt(range[0]);
					int end = Integer.parseInt(range[1]);
					for (int i = start; i <= end; i++) {
						pageNumbers.add(i);
					}
				} else {
					pageNumbers.add(Integer.parseInt(page));
				}
			}
		}

		logger.info("Splitting PDF into pages: {}",
				pageNumbers.stream().map(String::valueOf).collect(Collectors.joining(",")));

		// split the document
		List<ByteArrayOutputStream> splitDocumentsBoas = new ArrayList<>();
		int currentPage = 0;
		for (int pageNumber : pageNumbers) {
			try (PDDocument splitDocument = new PDDocument()) {
				for (int i = currentPage; i < pageNumber; i++) {
					PDPage page = document.getPage(i);
					splitDocument.addPage(page);
					logger.debug("Adding page {} to split document", i);
				}
				currentPage = pageNumber;
				logger.debug("Setting current page to {}", currentPage);

				ByteArrayOutputStream baos = new ByteArrayOutputStream();
				splitDocument.save(baos);

				splitDocumentsBoas.add(baos);
			} catch (Exception e) {
				logger.error("Failed splitting documents and saving them", e);
				throw e;
			}
		}

		// closing the original document
		document.close();

		// create the zip file
		Path zipFile = Paths.get("split_documents.zip");
		URI uri = URI.create("jar:file:" + zipFile.toUri().getPath());
		Map<String, String> env = new HashMap<>();
		env.put("create", "true");
		FileSystem zipfs = FileSystems.newFileSystem(uri, env);

		// loop through the split documents and write them to the zip file
		for (int i = 0; i < splitDocumentsBoas.size(); i++) {
			String fileName = "split_document_" + (i + 1) + ".pdf";
			ByteArrayOutputStream baos = splitDocumentsBoas.get(i);
			byte[] pdf = baos.toByteArray();
			Path pathInZipfile = zipfs.getPath(fileName);
			try (OutputStream os = Files.newOutputStream(pathInZipfile)) {
				os.write(pdf);
				logger.info("Wrote split document {} to zip file", fileName);
			} catch (Exception e) {
				logger.error("Failed writing to zip", e);
				throw e;
			}
		}
		zipfs.close();
		logger.info("Successfully created zip file with split documents: {}", zipFile.toString());
		byte[] data = Files.readAllBytes(zipFile);
		ByteArrayResource resource = new ByteArrayResource(data);
		new File("split_documents.zip").delete();
		// return the Resource in the response
		return ResponseEntity.ok().header(HttpHeaders.CONTENT_DISPOSITION, "attachment; filename=split_documents.zip")
				.contentType(MediaType.APPLICATION_OCTET_STREAM).contentLength(resource.contentLength()).body(resource);
	}
}