script.js

// PDF.js Configuration
pdfjsLib.GlobalWorkerOptions.workerSrc = 'https://cdnjs.cloudflare.com/ajax/libs/pdf.js/3.11.174/pdf.worker.min.js';

// Theme Management
const themeToggle = document.getElementById('themeToggle');
const sunIcon = document.getElementById('sunIcon');
const moonIcon = document.getElementById('moonIcon');

// Initialize theme from localStorage or default to dark
const currentTheme = localStorage.getItem('theme') || 'dark';
if (currentTheme === 'light') {
    document.documentElement.setAttribute('data-theme', 'light');
    sunIcon.style.display = 'none';
    moonIcon.style.display = 'block';
}

// Toggle theme function
function toggleTheme() {
    const currentTheme = document.documentElement.getAttribute('data-theme');
    const newTheme = currentTheme === 'light' ? 'dark' : 'light';

    document.documentElement.setAttribute('data-theme', newTheme);
    localStorage.setItem('theme', newTheme);

    // Toggle icons
    if (newTheme === 'light') {
        sunIcon.style.display = 'none';
        moonIcon.style.display = 'block';
    } else {
        sunIcon.style.display = 'block';
        moonIcon.style.display = 'none';
    }
}

// State Management
const state = {
    pdfDoc: null,
    pageNum: 1,
    pageRendering: false,
    pageNumPending: null,
    scale: 1.5,
    canvas: document.getElementById('pdfCanvas'),
    ctx: null
};

// Initialize
state.ctx = state.canvas.getContext('2d');

// DOM Elements
const elements = {
    loadingOverlay: document.getElementById('loadingOverlay'),
    pageNum: document.getElementById('pageNum'),
    pageCount: document.getElementById('pageCount'),
    currentPageDisplay: document.getElementById('currentPageDisplay'),
    totalPagesDisplay: document.getElementById('totalPagesDisplay'),
    zoomLevel: document.getElementById('zoomLevel'),
    prevPageBtn: document.getElementById('prevPageBtn'),
    nextPageBtn: document.getElementById('nextPageBtn'),
    zoomInBtn: document.getElementById('zoomInBtn'),
    zoomOutBtn: document.getElementById('zoomOutBtn'),
    fitWidthBtn: document.getElementById('fitWidthBtn'),
    pageInput: document.getElementById('pageInput'),
    goToPageBtn: document.getElementById('goToPageBtn'),
    sidebar: document.getElementById('sidebar'),
    sidebarToggle: document.getElementById('sidebarToggle'),
    closeSidebarBtn: document.getElementById('closeSidebarBtn'),
    searchBtn: document.getElementById('searchBtn'),
    searchPanel: document.getElementById('searchPanel'),
    closeSearchBtn: document.getElementById('closeSearchBtn'),
    fullscreenBtn: document.getElementById('fullscreenBtn'),
    canvasContainer: document.getElementById('canvasContainer')
};

// Render Page
function renderPage(num) {
    state.pageRendering = true;

    state.pdfDoc.getPage(num).then(page => {
        const viewport = page.getViewport({ scale: state.scale });
        state.canvas.height = viewport.height;
        state.canvas.width = viewport.width;

        const renderContext = {
            canvasContext: state.ctx,
            viewport: viewport
        };

        const renderTask = page.render(renderContext);

        renderTask.promise.then(() => {
            state.pageRendering = false;

            if (state.pageNumPending !== null) {
                renderPage(state.pageNumPending);
                state.pageNumPending = null;
            }

            // Update UI
            updatePageDisplay();

            // Hide loading overlay on first render
            if (num === 1) {
                elements.loadingOverlay.classList.add('hidden');
            }
        });
    });

    // Update page display immediately
    elements.pageNum.textContent = num;
    elements.currentPageDisplay.textContent = num;
}

// Queue Page Render
function queueRenderPage(num) {
    if (state.pageRendering) {
        state.pageNumPending = num;
    } else {
        renderPage(num);
    }
}

// Update Page Display
function updatePageDisplay() {
    elements.zoomLevel.textContent = Math.round(state.scale * 100) + '%';
    updateThumbnailSelection();
}

// Navigate to Previous Page
function onPrevPage() {
    if (state.pageNum <= 1) {
        return;
    }
    state.pageNum--;
    queueRenderPage(state.pageNum);
}

// Navigate to Next Page
function onNextPage() {
    if (state.pageNum >= state.pdfDoc.numPages) {
        return;
    }
    state.pageNum++;
    queueRenderPage(state.pageNum);
}

// Zoom In
function zoomIn() {
    if (state.scale < 3) {
        state.scale += 0.25;
        queueRenderPage(state.pageNum);
    }
}

// Zoom Out
function zoomOut() {
    if (state.scale > 0.5) {
        state.scale -= 0.25;
        queueRenderPage(state.pageNum);
    }
}

// Fit to Width
function fitToWidth() {
    const containerWidth = elements.canvasContainer.clientWidth - 40;
    state.pdfDoc.getPage(state.pageNum).then(page => {
        const viewport = page.getViewport({ scale: 1 });
        state.scale = containerWidth / viewport.width;
        queueRenderPage(state.pageNum);
    });
}

// Go to Page
function goToPage() {
    const pageNumber = parseInt(elements.pageInput.value);
    if (pageNumber >= 1 && pageNumber <= state.pdfDoc.numPages) {
        state.pageNum = pageNumber;
        queueRenderPage(state.pageNum);
        elements.pageInput.value = '';
    }
}

// Toggle Sidebar
function toggleSidebar() {
    elements.sidebar.classList.toggle('hidden');
}

// Toggle Search
function toggleSearch() {
    elements.searchPanel.classList.toggle('active');
    if (elements.searchPanel.classList.contains('active')) {
        document.getElementById('searchInput').focus();
    }
}

// Toggle Fullscreen
function toggleFullscreen() {
    if (!document.fullscreenElement) {
        document.documentElement.requestFullscreen();
    } else {
        if (document.exitFullscreen) {
            document.exitFullscreen();
        }
    }
}

// Event Listeners
themeToggle.addEventListener('click', toggleTheme);
elements.prevPageBtn.addEventListener('click', onPrevPage);
elements.nextPageBtn.addEventListener('click', onNextPage);
elements.zoomInBtn.addEventListener('click', zoomIn);
elements.zoomOutBtn.addEventListener('click', zoomOut);
elements.fitWidthBtn.addEventListener('click', fitToWidth);
elements.goToPageBtn.addEventListener('click', goToPage);
elements.sidebarToggle.addEventListener('click', toggleSidebar);
elements.closeSidebarBtn.addEventListener('click', toggleSidebar);
elements.searchBtn.addEventListener('click', toggleSearch);
elements.closeSearchBtn.addEventListener('click', toggleSearch);
elements.fullscreenBtn.addEventListener('click', toggleFullscreen);

// Enter key for page input
elements.pageInput.addEventListener('keypress', (e) => {
    if (e.key === 'Enter') {
        goToPage();
    }
});

// Keyboard Shortcuts
document.addEventListener('keydown', (e) => {
    // Arrow keys for navigation
    if (e.key === 'ArrowLeft' || e.key === 'ArrowUp') {
        e.preventDefault();
        onPrevPage();
    } else if (e.key === 'ArrowRight' || e.key === 'ArrowDown') {
        e.preventDefault();
        onNextPage();
    }

    // Zoom shortcuts
    if (e.key === '+' || e.key === '=') {
        e.preventDefault();
        zoomIn();
    } else if (e.key === '-') {
        e.preventDefault();
        zoomOut();
    }

    // Search shortcut
    if ((e.ctrlKey || e.metaKey) && e.key === 'f') {
        e.preventDefault();
        toggleSearch();
    }

    // Fullscreen shortcut
    if (e.key === 'f' && !e.ctrlKey && !e.metaKey) {
        const activeElement = document.activeElement;
        if (activeElement.tagName !== 'INPUT') {
            toggleFullscreen();
        }
    }
});

// Search Functionality
let searchMatches = [];
let currentMatch = 0;

document.getElementById('searchInput').addEventListener('input', async (e) => {
    const query = e.target.value.toLowerCase();
    const results = document.getElementById('searchResults');

    if (query.length < 2) {
        results.textContent = '';
        searchMatches = [];
        return;
    }

    searchMatches = [];

    // Search through all pages
    for (let i = 1; i <= state.pdfDoc.numPages; i++) {
        const page = await state.pdfDoc.getPage(i);
        const textContent = await page.getTextContent();
        const text = textContent.items.map(item => item.str).join(' ').toLowerCase();

        if (text.includes(query)) {
            searchMatches.push(i);
        }
    }

    if (searchMatches.length > 0) {
        results.textContent = `Found ${searchMatches.length} matches`;
        currentMatch = 0;
    } else {
        results.textContent = 'No matches found';
    }
});

document.getElementById('searchNextBtn').addEventListener('click', () => {
    if (searchMatches.length > 0) {
        currentMatch = (currentMatch + 1) % searchMatches.length;
        state.pageNum = searchMatches[currentMatch];
        queueRenderPage(state.pageNum);
        document.getElementById('searchResults').textContent =
            `Match ${currentMatch + 1} of ${searchMatches.length} (Page ${searchMatches[currentMatch]})`;
    }
});

document.getElementById('searchPrevBtn').addEventListener('click', () => {
    if (searchMatches.length > 0) {
        currentMatch = (currentMatch - 1 + searchMatches.length) % searchMatches.length;
        state.pageNum = searchMatches[currentMatch];
        queueRenderPage(state.pageNum);
        document.getElementById('searchResults').textContent =
            `Match ${currentMatch + 1} of ${searchMatches.length} (Page ${searchMatches[currentMatch]})`;
    }
});

// Mouse Wheel Zoom
elements.canvasContainer.addEventListener('wheel', (e) => {
    if (e.ctrlKey) {
        e.preventDefault();
        if (e.deltaY < 0) {
            zoomIn();
        } else {
            zoomOut();
        }
    }
});

// Load PDF
const url = 'Machine-Learning-Systems.pdf';

pdfjsLib.getDocument(url).promise.then(pdfDoc => {
    state.pdfDoc = pdfDoc;
    elements.pageCount.textContent = pdfDoc.numPages;
    elements.totalPagesDisplay.textContent = pdfDoc.numPages;
    elements.pageInput.max = pdfDoc.numPages;

    // Render the first page
    renderPage(state.pageNum);

    // Generate thumbnails
    generateThumbnails();
}).catch(error => {
    console.error('Error loading PDF:', error);
    elements.loadingOverlay.innerHTML = `

        <div style="text-align: center;">

            <h2 style="color: var(--color-accent-primary); margin-bottom: 1rem;">Error Loading PDF</h2>

            <p style="color: var(--color-text-secondary);">Please make sure the PDF file is in the same directory as this HTML file.</p>

            <p style="color: var(--color-text-muted); margin-top: 1rem; font-size: 0.875rem;">Looking for: ${url}</p>

        </div>

    `;
});

// Generate Thumbnails
let currentThumbnailCount = 20;
const thumbnailsPerLoad = 20;

async function generateThumbnails(startFrom = 1, count = 20) {
    const thumbnailsContainer = document.getElementById('thumbnails');

    if (startFrom === 1) {
        thumbnailsContainer.innerHTML = '<h3 style="font-size: 0.875rem; font-weight: 600; margin-bottom: 0.5rem; color: var(--color-text-secondary);">Pages</h3>';
    }

    const endAt = Math.min(startFrom + count - 1, state.pdfDoc.numPages);

    for (let i = startFrom; i <= endAt; i++) {
        const page = await state.pdfDoc.getPage(i);
        const viewport = page.getViewport({ scale: 0.2 });

        const canvas = document.createElement('canvas');
        const ctx = canvas.getContext('2d');
        canvas.height = viewport.height;
        canvas.width = viewport.width;

        await page.render({
            canvasContext: ctx,
            viewport: viewport
        }).promise;

        const thumbnailDiv = document.createElement('div');
        thumbnailDiv.className = 'thumbnail-item';
        thumbnailDiv.dataset.page = i;

        // Create wrapper and label
        const wrapper = document.createElement('div');
        wrapper.className = 'thumbnail-canvas-wrapper';
        wrapper.appendChild(canvas); // Append the actual canvas object with drawing

        const label = document.createElement('div');
        label.className = 'thumbnail-label';
        label.textContent = `Page ${i}`;

        thumbnailDiv.appendChild(wrapper);
        thumbnailDiv.appendChild(label);

        thumbnailDiv.addEventListener('click', () => {
            state.pageNum = i;
            queueRenderPage(i);
            // Highlight selected thumbnail
            updateThumbnailSelection(); // Modified this line
        });

        thumbnailsContainer.appendChild(thumbnailDiv);
    }

    // Remove existing "Show More" button if present
    const existingShowMore = thumbnailsContainer.querySelector('.show-more-btn');
    if (existingShowMore) {
        existingShowMore.remove();
    }

    // Add "Show More" button if there are more pages
    if (endAt < state.pdfDoc.numPages) {
        const showMoreDiv = document.createElement('div');
        showMoreDiv.className = 'show-more-btn';
        showMoreDiv.innerHTML = `

            <button onclick="loadMoreThumbnails()">

                <svg viewBox="0 0 24 24" fill="none" xmlns="http://www.w3.org/2000/svg">

                    <path d="M12 5V19M5 12L12 19L19 12" stroke="currentColor" stroke-width="2" stroke-linecap="round" stroke-linejoin="round"/>

                </svg>

                Show More (${state.pdfDoc.numPages - endAt} remaining)

            </button>

        `;
        thumbnailsContainer.appendChild(showMoreDiv);
    }

    // Highlight the current page
    updateThumbnailSelection();
}

function loadMoreThumbnails() {
    const nextStart = currentThumbnailCount + 1;
    currentThumbnailCount += thumbnailsPerLoad;
    generateThumbnails(nextStart, thumbnailsPerLoad);
}

function updateThumbnailSelection() {
    document.querySelectorAll('.thumbnail-item').forEach(t => {
        if (parseInt(t.dataset.page) === state.pageNum) {
            t.classList.add('active');
            // Scroll to the active thumbnail if it's not in view
            t.scrollIntoView({ behavior: 'smooth', block: 'nearest' });
        } else {
            t.classList.remove('active');
        }
    });
}

// Responsive adjustments
window.addEventListener('resize', () => {
    if (window.innerWidth <= 768 && !elements.sidebar.classList.contains('hidden')) {
        elements.sidebar.classList.add('hidden');
    }
});

console.log('PDF Viewer initialized successfully!');