<!--

SPDX-License-Identifier: MIT

This shortcut was originally taken from: https://github.com/anvithks/hugo-embed-pdf-shortcode,
where it is available under the MIT License, where it was originally created by https://github.com/anvithks

Since the project seems discontinued, it has been re-created here
-->

<!-- Load the PDF-JS from the local folder (should be updated over time) -->
<script src= '/js/pdf-js/build/pdf.js'></script>

<!-- Set the navigation menu -->
<div id="paginator">
    <button id="prev">Previous</button>
    <button id="next">Next</button>
    &nbsp; &nbsp;
    <span>Page: <span id="page_num"></span> / <span id="page_count"></span></span>
</div>

<!-- And the canvas where the PDF will load -->
<div id="embed-pdf-container">
    <div id="loadingWrapper">
      <div id="loading"></div>
    </div>
    <canvas id="the-canvas"></canvas>
</div>

<!-- This script gets the PDF, sets it and passes it on to the already-loaded pdf-js -->
<script type="text/javascript">
window.onload = function() {
// If absolute URL from the remote server is provided, configure the CORS
// header on that server.
var url = "{{.Site.BaseURL}}" + '{{ .Get "src" }}';

var hidePaginator = "{{ .Get "hidePaginator" }}" === "true";
var hideLoader = "{{ .Get "hideLoader" }}" === "true";
var selectedPageNum = parseInt("{{ .Get "renderPageNum" }}") || 1;

// Loaded via <script> tag, create shortcut to access PDF.js exports.
var pdfjsLib = window['pdfjs-dist/build/pdf'];

// The workerSrc property shall be specified.
pdfjsLib.GlobalWorkerOptions.workerSrc = "{{.Site.BaseURL}}" + '/js/pdf-js/build/pdf.worker.js';

// Change the Scale value for lower or higher resolution.
var pdfDoc = null,
    pageNum = selectedPageNum,
    pageRendering = false,
    pageNumPending = null,
    scale = 3,
    canvas = document.getElementById('the-canvas'),
    ctx = canvas.getContext('2d'),
    paginator = document.getElementById("paginator"),
    loadingWrapper = document.getElementById('loadingWrapper');


// Attempt to show paginator and loader if enabled
showPaginator();
showLoader();

/**
 * Get page info from document, resize canvas accordingly, and render page.
 * @param num Page number.
 */
function renderPage(num) {
  pageRendering = true;
  // Using promise to fetch the page
  pdfDoc.getPage(num).then(function(page) {
    var viewport = page.getViewport({scale: scale});
    canvas.height = viewport.height;
    canvas.width = viewport.width;

    // Render PDF page into canvas context
    var renderContext = {
      canvasContext: ctx,
      viewport: viewport
    };
    var renderTask = page.render(renderContext);

    // Wait for rendering to finish
    renderTask.promise.then(function() {
      pageRendering = false;
      showContent();

      if (pageNumPending !== null) {
        // New page rendering is pending
        renderPage(pageNumPending);
        pageNumPending = null;
      }
    });
  });

  // Update page counters
  document.getElementById('page_num').textContent = num;
}

/**
 * Hides loader and shows canvas
 */
function showContent() {
  loadingWrapper.style.display = 'none';
  canvas.style.display = 'block';
}

/**
 * If we haven't disabled the loader, show loader and hide canvas
 */
function showLoader() {
  if(hideLoader) return
  loadingWrapper.style.display = 'flex';
  canvas.style.display = 'none';
}

/**
 * If we haven't disabled the paginator, show paginator
 */
function showPaginator() {
  if(hidePaginator) return
  paginator.style.display = 'block';
}

/**
 * If another page rendering in progress, waits until the rendering is
 * finished. Otherwise, executes rendering immediately.
 */
function queueRenderPage(num) {
  if (pageRendering) {
    pageNumPending = num;
  } else {
    renderPage(num);
  }
}

/**
 * Displays previous page.
 */
function onPrevPage() {
  if (pageNum <= 1) {
    return;
  }
  pageNum--;
  queueRenderPage(pageNum);
}
document.getElementById('prev').addEventListener('click', onPrevPage);

/**
 * Displays next page.
 */
function onNextPage() {
  if (pageNum >= pdfDoc.numPages) {
    return;
  }
  pageNum++;
  queueRenderPage(pageNum);
}
document.getElementById('next').addEventListener('click', onNextPage);

/**
 * Asynchronously downloads PDF.
 */
pdfjsLib.getDocument(url).promise.then(function(pdfDoc_) {
  pdfDoc = pdfDoc_;
  var numPages = pdfDoc.numPages;
  document.getElementById('page_count').textContent = numPages;

  // If the user passed in a number that is out of range, render the last page.
  if(pageNum > numPages) {
    pageNum = numPages
  }

  // Initial/first page rendering
  renderPage(pageNum);
});
}

</script>

<!-- Finally, make the canvas more beautiful -->
<style>
#the-canvas {
  border: 1px solid black;
  direction: ltr;
  width: 100%;
  height: auto;
  display: none;
}

#paginator {
  display: none;
  text-align: center;
  margin-bottom: 10px;
}

#loadingWrapper {
  display: none;
  justify-content: center;
  align-items: center;
  width: 100%;
  height: 350px;
}

#loading {
  display: inline-block;
  width: 50px;
  height: 50px;
  border: 3px solid #d2d0d0;;
  border-radius: 50%;
  border-top-color: #383838;
  animation: spin 1s ease-in-out infinite;
  -webkit-animation: spin 1s ease-in-out infinite;
}

@keyframes spin {
  to { -webkit-transform: rotate(360deg); }
}
@-webkit-keyframes spin {
  to { -webkit-transform: rotate(360deg); }
}
</style>
