bentopdf/src/js/logic/add-blank-page.ts

import { showLoader, hideLoader, showAlert } from '../ui.js';
import { downloadFile } from '../utils/helpers.js';
import { state } from '../state.js';
import { PDFDocument as PDFLibDocument } from 'pdf-lib';

export async function addBlankPage() {
    // @ts-expect-error TS(2339) FIXME: Property 'value' does not exist on type 'HTMLEleme... Remove this comment to see the full error message
    const pageNumberInput = document.getElementById('page-number').value;
    if (pageNumberInput.trim() === '') {
        showAlert('Invalid Input', 'Please enter a page number.');
        return;
    }

    const position = parseInt(pageNumberInput);
    const totalPages = state.pdfDoc.getPageCount();
    if (isNaN(position) || position < 0 || position > totalPages) {
        showAlert('Invalid Input', `Please enter a number between 0 and ${totalPages}.`);
        return;
    }

    showLoader('Adding page...');
    try {
        const newPdf = await PDFLibDocument.create();
        const { width, height } = state.pdfDoc.getPage(0).getSize();
        const allIndices = Array.from({ length: totalPages }, (_, i) => i);
        
        const indicesBefore = allIndices.slice(0, position);
        const indicesAfter = allIndices.slice(position);

        if (indicesBefore.length > 0) {
            const copied = await newPdf.copyPages(state.pdfDoc, indicesBefore);
            copied.forEach((p: any) => newPdf.addPage(p));
        }

        newPdf.addPage([width, height]);

        if (indicesAfter.length > 0) {
            const copied = await newPdf.copyPages(state.pdfDoc, indicesAfter);
            copied.forEach((p: any) => newPdf.addPage(p));
        }

        const newPdfBytes = await newPdf.save();
        downloadFile(new Blob([newPdfBytes], { type: 'application/pdf' }), 'page-added.pdf');
    } catch (e) {
        console.error(e);
        showAlert('Error', 'Could not add a blank page.');
    } finally {
        hideLoader();
    }
}