xls magic because why not

XlsStyleHelper.java

import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.nio.charset.StandardCharsets;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

import org.apache.commons.compress.archivers.zip.ZipArchiveEntry;
import org.apache.commons.compress.archivers.zip.ZipArchiveInputStream;
import org.apache.commons.compress.archivers.zip.ZipArchiveOutputStream;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

public class XlsStyleHelper {

	static Logger logger = LoggerFactory.getLogger(XlsStyleHelper.class);

	private XlsStyleHelper() {
	}

	public static ByteArrayOutputStream forceTextStyleInXls(ByteArrayOutputStream originalZip) throws IOException {
		ByteArrayOutputStream modifiedXLS = new ByteArrayOutputStream();

		try (ZipArchiveInputStream zis = new ZipArchiveInputStream(new ByteArrayInputStream(originalZip.toByteArray())); ZipArchiveOutputStream zos = new ZipArchiveOutputStream(modifiedXLS)) {
			ZipArchiveEntry entry;
			while ((entry = zis.getNextEntry()) != null) {
				if ("xl/styles.xml".equals(entry.getName())) {
					copyEntryAndReplace(entry.getName(), zis, zos, false);
				} else if ("xl/worksheets/sheet1.xml".equals(entry.getName())) {
					copyEntryAndReplace(entry.getName(), zis, zos, true);
				} else {
					copyEntry(zis, zos, entry);
				}
			}
		}

		return modifiedXLS;
	}

	public static void copyEntry(ZipArchiveInputStream zis, ZipArchiveOutputStream zos, ZipArchiveEntry entry) throws IOException {
		zos.putArchiveEntry(new ZipArchiveEntry(entry.getName()));
		byte[] buffer = new byte[1024];
		int len;
		while ((len = zis.read(buffer)) > 0) {
			zos.write(buffer, 0, len);
		}
		zos.closeArchiveEntry();
	}

	public static void copyEntryAndReplace(String entryName, ZipArchiveInputStream zis, ZipArchiveOutputStream zos, boolean isSheet) throws IOException {

		ByteArrayOutputStream entryOutputStream = new ByteArrayOutputStream();
		byte[] buffer = new byte[1024];
		int len;

		while ((len = zis.read(buffer)) > 0) {
			entryOutputStream.write(buffer, 0, len);
		}

		// Replace the content in styles.xml
		String content = entryOutputStream.toString(StandardCharsets.UTF_8);

		if (isSheet) {
			content = enforceTextType(content);
			content = enforceTextStyle(content);
		} else {
			content = addTextCellStyle(content);
		}
		ZipArchiveEntry newEntry = new ZipArchiveEntry(entryName);
		newEntry.setSize(content.getBytes(StandardCharsets.UTF_8).length);
		newEntry.setUnixMode(0);
		newEntry.setTime(System.currentTimeMillis());

		zos.putArchiveEntry(newEntry);
		zos.write(content.getBytes(StandardCharsets.UTF_8));
		zos.closeArchiveEntry();
	}

	private static String addTextCellStyle(String content) {
		String[] from = { "<cellXfs count=\"1\"><xf numFmtId=\"0\" fontId=\"0\" fillId=\"0\" borderId=\"0\" xfId=\"0\"/></cellXfs>" };
		String[] to = {
				"<cellXfs count=\"2\"><xf numFmtId=\"0\" fontId=\"0\" fillId=\"0\" borderId=\"0\" xfId=\"0\"/><xf numFmtId=\"49\" fontId=\"0\" fillId=\"0\" borderId=\"0\" xfId=\"0\" applyNumberFormat=\"1\"/></cellXfs>" };
		for (int i = 0; i < from.length; i++) {
			content = content.replace(from[i], to[i]);
		}
		return content;
	}

	
	private static String enforceTextType(String content) {
		String regex = "<c r=\"([^\"]+)\" t=\"n\"><v>(\\d+\\.\\d+)<\\/v><\\/c>";
		Pattern pattern = Pattern.compile(regex);
		Matcher matcher = pattern.matcher(content);
        return  matcher.replaceAll("<c r=\"$1\" t=\"inlineStr\" s=\"1\"><is><t>$2</t></is></c>");
	}
	
	private static String enforceTextStyle(String content) {
		// enforce text style everywhere
		String regex = "<([^<>]+)(?<!s=\"1\") t=\"s\">"; // Match tag string tags that don't have styling 1 (TEXT) yet
		Pattern pattern = Pattern.compile(regex);
		Matcher matcher = pattern.matcher(content);
		StringBuilder modifiedInput = new StringBuilder();
		int lastEnd = 0;
		while (matcher.find()) {
			modifiedInput.append(content, lastEnd, matcher.start());
			String modifiedTag = matcher.group(0).replace(" t=\"s\"", " s=\"1\" t=\"s\"");
			modifiedInput.append(modifiedTag);
			lastEnd = matcher.end();
		}
		modifiedInput.append(content.substring(lastEnd));
		content = modifiedInput.toString();
		return content;
	}

	public static String cleanStringForXls(String input) {
		String regex = "(\\!)*\\[[^\\]]*]\\(([^\\)]+)\\)";
		Pattern pattern = Pattern.compile(regex);
		Matcher matcher = pattern.matcher(input);

		StringBuilder sb = new StringBuilder();
		while (matcher.find()) {
			String replacemenet = "error";
			try {
				replacemenet = matcher.group(2).startsWith("api/1") ? "" : matcher.group(2);
			} catch (Exception e) {
				logger.warn("Error while cleaning string for xls", e);
			}
			matcher.appendReplacement(sb, replacemenet);
		}
		matcher.appendTail(sb);

		return sb.toString().replace("\\", "\\\\");
	}
}