extract, rotate, split

public/functions/extractPages.js

@@ -0,0 +1,25 @@
+const { PDFDocument, ParseSpeeds } = PDFLib;
+
+export const extractPages = async (snapshot, pagesToExtractArray) => {
+    const pdfDoc = await PDFDocument.load(snapshot)
+
+    // TODO: invent a better format for pagesToExtractArray and convert it.
+    return createSubDocument(pdfDoc, pagesToExtractArray);
+};
+
+export async function createSubDocument(pdfDoc, pagesToExtractArray) {
+    const subDocument = await PDFDocument.create();
+
+    // Check that array max number is not larger pdf pages number
+    if(Math.max(...pagesToExtractArray) >= pdfDoc.getPageCount()) {
+        throw new Error(`The PDF document only has ${pdfDoc.getPageCount()} pages and you tried to extract page ${Math.max(...pagesToExtractArray)}`);
+    }
+
+    const copiedPages = await subDocument.copyPages(pdfDoc, pagesToExtractArray);
+
+    for (let i = 0; i < copiedPages.length; i++) {
+        subDocument.addPage(copiedPages[i]);
+    }
+
+    return subDocument.save();
+}