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

import { showLoader, hideLoader, showAlert } from '../ui.js';
import { downloadFile, formatBytes } from '../utils/helpers.js';
import { createIcons, icons } from 'lucide';
import { PDFDocument as PDFLibDocument } from 'pdf-lib';
import { AddBlankPageState } from '@/types';


const pageState: AddBlankPageState = {
    file: null,
    pdfDoc: null,
};

function resetState() {
    pageState.file = null;
    pageState.pdfDoc = null;

    const fileDisplayArea = document.getElementById('file-display-area');
    if (fileDisplayArea) fileDisplayArea.innerHTML = '';

    const toolOptions = document.getElementById('tool-options');
    if (toolOptions) toolOptions.classList.add('hidden');

    const fileInput = document.getElementById('file-input') as HTMLInputElement;
    if (fileInput) fileInput.value = '';

    const pagePositionInput = document.getElementById('page-position') as HTMLInputElement;
    if (pagePositionInput) pagePositionInput.value = '0';

    const pageCountInput = document.getElementById('page-count') as HTMLInputElement;
    if (pageCountInput) pageCountInput.value = '1';
}

async function updateUI() {
    const fileDisplayArea = document.getElementById('file-display-area');
    const toolOptions = document.getElementById('tool-options');
    const pagePositionHint = document.getElementById('page-position-hint');
    const pagePositionInput = document.getElementById('page-position') as HTMLInputElement;

    if (!fileDisplayArea) return;

    fileDisplayArea.innerHTML = '';

    if (pageState.file) {
        const fileDiv = document.createElement('div');
        fileDiv.className = 'flex items-center justify-between bg-gray-700 p-3 rounded-lg text-sm';

        const infoContainer = document.createElement('div');
        infoContainer.className = 'flex flex-col overflow-hidden';

        const nameSpan = document.createElement('div');
        nameSpan.className = 'truncate font-medium text-gray-200 text-sm mb-1';
        nameSpan.textContent = pageState.file.name;

        const metaSpan = document.createElement('div');
        metaSpan.className = 'text-xs text-gray-400';
        metaSpan.textContent = `${formatBytes(pageState.file.size)} • Loading...`;

        infoContainer.append(nameSpan, metaSpan);

        const removeBtn = document.createElement('button');
        removeBtn.className = 'ml-4 text-red-400 hover:text-red-300 flex-shrink-0';
        removeBtn.innerHTML = '<i data-lucide="trash-2" class="w-4 h-4"></i>';
        removeBtn.onclick = function () {
            resetState();
        };

        fileDiv.append(infoContainer, removeBtn);
        fileDisplayArea.appendChild(fileDiv);
        createIcons({ icons });

        // Load PDF document
        try {
            showLoader('Loading PDF...');
            const arrayBuffer = await pageState.file.arrayBuffer();
            pageState.pdfDoc = await PDFLibDocument.load(arrayBuffer, {
                ignoreEncryption: true,
                throwOnInvalidObject: false
            });
            hideLoader();

            const pageCount = pageState.pdfDoc.getPageCount();
            metaSpan.textContent = `${formatBytes(pageState.file.size)} • ${pageCount} pages`;

            if (pagePositionHint) {
                pagePositionHint.textContent = `Enter 0 to insert at the beginning, or ${pageCount} to insert at the end.`;
            }
            if (pagePositionInput) {
                pagePositionInput.max = pageCount.toString();
            }

            if (toolOptions) toolOptions.classList.remove('hidden');
        } catch (error) {
            console.error('Error loading PDF:', error);
            hideLoader();
            showAlert('Error', 'Failed to load PDF file.');
            resetState();
        }
    } else {
        if (toolOptions) toolOptions.classList.add('hidden');
    }
}

async function addBlankPages() {
    if (!pageState.pdfDoc || !pageState.file) {
        showAlert('Error', 'Please upload a PDF first.');
        return;
    }

    const pagePositionInput = document.getElementById('page-position') as HTMLInputElement;
    const pageCountInput = document.getElementById('page-count') as HTMLInputElement;

    const position = parseInt(pagePositionInput.value);
    const insertCount = parseInt(pageCountInput.value);
    const totalPages = pageState.pdfDoc.getPageCount();

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

    if (isNaN(insertCount) || insertCount < 1) {
        showAlert('Invalid Input', 'Please enter a valid number of pages (1 or more).');
        return;
    }

    showLoader(`Adding ${insertCount} blank page${insertCount > 1 ? 's' : ''}...`);

    try {
        const newPdf = await PDFLibDocument.create();
        const { width, height } = pageState.pdfDoc.getPage(0).getSize();
        const allIndices = Array.from({ length: totalPages }, function (_, i) { return i; });

        const indicesBefore = allIndices.slice(0, position);
        const indicesAfter = allIndices.slice(position);

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

        // Add the specified number of blank pages
        for (let i = 0; i < insertCount; i++) {
            newPdf.addPage([width, height]);
        }

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

        const newPdfBytes = await newPdf.save();
        const originalName = pageState.file.name.replace(/\.pdf$/i, '');

        downloadFile(
            new Blob([new Uint8Array(newPdfBytes)], { type: 'application/pdf' }),
            `${originalName}_blank-pages-added.pdf`
        );

        showAlert('Success', `Added ${insertCount} blank page${insertCount > 1 ? 's' : ''} successfully!`, 'success', function () {
            resetState();
        });
    } catch (e) {
        console.error(e);
        showAlert('Error', `Could not add blank page${insertCount > 1 ? 's' : ''}.`);
    } finally {
        hideLoader();
    }
}

function handleFileSelect(files: FileList | null) {
    if (files && files.length > 0) {
        const file = files[0];
        if (file.type === 'application/pdf' || file.name.toLowerCase().endsWith('.pdf')) {
            pageState.file = file;
            updateUI();
        }
    }
}

document.addEventListener('DOMContentLoaded', function () {
    const fileInput = document.getElementById('file-input') as HTMLInputElement;
    const dropZone = document.getElementById('drop-zone');
    const processBtn = document.getElementById('process-btn');
    const backBtn = document.getElementById('back-to-tools');

    if (backBtn) {
        backBtn.addEventListener('click', function () {
            window.location.href = import.meta.env.BASE_URL;
        });
    }

    if (fileInput && dropZone) {
        fileInput.addEventListener('change', function (e) {
            handleFileSelect((e.target as HTMLInputElement).files);
        });

        dropZone.addEventListener('dragover', function (e) {
            e.preventDefault();
            dropZone.classList.add('bg-gray-700');
        });

        dropZone.addEventListener('dragleave', function (e) {
            e.preventDefault();
            dropZone.classList.remove('bg-gray-700');
        });

        dropZone.addEventListener('drop', function (e) {
            e.preventDefault();
            dropZone.classList.remove('bg-gray-700');
            const files = e.dataTransfer?.files;
            if (files && files.length > 0) {
                const pdfFiles = Array.from(files).filter(function (f) {
                    return f.type === 'application/pdf' || f.name.toLowerCase().endsWith('.pdf');
                });
                if (pdfFiles.length > 0) {
                    const dataTransfer = new DataTransfer();
                    dataTransfer.items.add(pdfFiles[0]);
                    handleFileSelect(dataTransfer.files);
                }
            }
        });

        fileInput.addEventListener('click', function () {
            fileInput.value = '';
        });
    }

    if (processBtn) {
        processBtn.addEventListener('click', addBlankPages);
    }
});