extract, rotate, split

public/functions/extractPages.js

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+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();
+}

public/functions/rotatePDF.js

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+const { PDFDocument, ParseSpeeds, degrees } = PDFLib;
+
+export const rotatePages = async (snapshot, rotation) => {
+    // Load the original PDF file
+    const pdfDoc = await PDFDocument.load(snapshot, {
+        parseSpeed: ParseSpeeds.Fastest,
+    });
+
+    const pages = pdfDoc.getPages();
+
+    pages.forEach(page => {
+        // Change page size
+        page.setRotation(degrees(rotation))
+    });
+
+    // Serialize the modified document
+    return pdfDoc.save();
+};

public/functions/splitPDF.js

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+import { createSubDocument } from "./extractPages.js";
+
+const { PDFDocument, ParseSpeeds } = PDFLib;
+
+export const splitPDF = async (snapshot, splitAfterPageArray) => {
+    const pdfDoc = await PDFDocument.load(snapshot)
+
+    const numberOfPages = pdfDoc.getPages().length;
+
+    let pagesArray = [];
+    let splitAfter = splitAfterPageArray.shift();
+    const subDocuments = [];
+
+    for (let i = 0; i < numberOfPages; i++) {
+        if(i > splitAfter && pagesArray.length > 0) {
+            subDocuments.push(await createSubDocument(pdfDoc, pagesArray));
+            splitAfter = splitAfterPageArray.shift();
+            pagesArray = [];
+        }
+        pagesArray.push(i);        
+    }
+    subDocuments.push(await createSubDocument(pdfDoc, pagesArray));
+    pagesArray = [];
+
+    return subDocuments;
+};