chore: use rust based cms signing

packages/signing/helpers/update-signing-placeholder.ts

@@ -0,0 +1,39 @@
+export type UpdateSigningPlaceholderOptions = {
+  pdf: Buffer;
+};
+
+export const updateSigningPlaceholder = ({ pdf }: UpdateSigningPlaceholderOptions) => {
+  const length = pdf.length;
+
+  const byteRangePos = pdf.lastIndexOf('/ByteRange');
+  const byteRangeStart = pdf.indexOf('[', byteRangePos);
+  const byteRangeEnd = pdf.indexOf(']', byteRangePos);
+
+  const byteRangeSlice = pdf.subarray(byteRangeStart, byteRangeEnd + 1);
+
+  const signaturePos = pdf.indexOf('/Contents', byteRangeEnd);
+  const signatureStart = pdf.indexOf('<', signaturePos);
+  const signatureEnd = pdf.indexOf('>', signaturePos);
+
+  const signatureSlice = pdf.subarray(signatureStart, signatureEnd + 1);
+
+  const byteRange = [0, 0, 0, 0];
+
+  byteRange[1] = signatureStart;
+  byteRange[2] = byteRange[1] + signatureSlice.length;
+  byteRange[3] = length - byteRange[2];
+
+  const newByteRange = `[${byteRange.join(' ')}]`.padEnd(byteRangeSlice.length, ' ');
+
+  const updatedPdf = Buffer.concat([
+    pdf.subarray(0, byteRangeStart),
+    Buffer.from(newByteRange),
+    pdf.subarray(byteRangeEnd + 1),
+  ]);
+
+  if (updatedPdf.length !== length) {
+    throw new Error('Updated PDF length does not match original length');
+  }
+
+  return { pdf: updatedPdf, byteRange };
+};