renderers.ts

/*-----------------------------------------------------------------------------
| Copyright (c) Jupyter Development Team.
| Distributed under the terms of the Modified BSD License.
|----------------------------------------------------------------------------*/
import {
  ansi_to_html, escape_for_html
} from 'ansi_up';

import * as marked
  from 'marked';

import {
  ISanitizer
} from '@jupyterlab/apputils';

import {
  Mode, CodeMirrorEditor
} from '@jupyterlab/codemirror';

import {
  URLExt
} from '@jupyterlab/coreutils';

import {
  IRenderMime
} from '@jupyterlab/rendermime-interfaces';

import {
  typeset, removeMath, replaceMath
} from './latex';


/**
 * Render HTML into a host node.
 *
 * @params options - The options for rendering.
 *
 * @returns A promise which resolves when rendering is complete.
 */
export
function renderHTML(options: renderHTML.IOptions): Promise<void> {
  // Unpack the options.
  let {
    host, source, trusted, sanitizer, resolver, linkHandler, shouldTypeset
  } = options;

  // Bail early if the source is empty.
  if (!source) {
    host.textContent = '';
    return Promise.resolve(undefined);
  }

  // Sanitize the source if it is not trusted. This removes all
  // `<script>` tags as well as other potentially harmful HTML.
  if (!trusted) {
    source = sanitizer.sanitize(source);
  }

  // Set the inner HTML of the host.
  host.innerHTML = source;

  // TODO - arbitrary script execution is disabled for now.
  // Eval any script tags contained in the HTML. This is not done
  // automatically by the browser when script tags are created by
  // setting `innerHTML`. The santizer should have removed all of
  // the script tags for untrusted source, but this extra trusted
  // check is just extra insurance.
  // if (trusted) {
  //   // TODO do we really want to run scripts? Because if so, there
  //   // is really no difference between this and a JS mime renderer.
  //   Private.evalInnerHTMLScriptTags(host);
  // }

  // Patch the urls if a resolver is available.
  let promise: Promise<void>;
  if (resolver) {
    promise = Private.handleUrls(host, resolver, linkHandler);
  } else {
    promise = Promise.resolve(undefined);
  }

  // Return the final rendered promise.
  return promise.then(() => { if (shouldTypeset) { typeset(host); } });
}


/**
 * The namespace for the `renderHTML` function statics.
 */
export
namespace renderHTML {
  /**
   * The options for the `renderHTML` function.
   */
  export
  interface IOptions {
    /**
     * The host node for the rendered HTML.
     */
    host: HTMLElement;

    /**
     * The HTML source to render.
     */
    source: string;

    /**
     * Whether the source is trusted.
     */
    trusted: boolean;

    /**
     * The html sanitizer for untrusted source.
     */
    sanitizer: ISanitizer;

    /**
     * An optional url resolver.
     */
    resolver: IRenderMime.IResolver | null;

    /**
     * An optional link handler.
     */
    linkHandler: IRenderMime.ILinkHandler | null;

    /**
     * Whether the node should be typeset.
     */
    shouldTypeset: boolean;
  }
}


/**
 * Render an image into a host node.
 *
 * @params options - The options for rendering.
 *
 * @returns A promise which resolves when rendering is complete.
 */
export
function renderImage(options: renderImage.IRenderOptions): Promise<void> {
  // Unpack the options.
  let { host, mimeType, source, width, height } = options;

  // Clear the content in the host.
  host.textContent = '';

  // Create the image element.
  let img = document.createElement('img');

  // Set the source of the image.
  img.src = `data:${mimeType};base64,${source}`;

  // Set the size of the image if provided.
  if (typeof height === 'number') {
    img.height = height;
  }
  if (typeof width === 'number') {
    img.width = width;
  }

  // Add the image to the host.
  host.appendChild(img);

  // Return the rendered promise.
  return Promise.resolve(undefined);
}


/**
 * The namespace for the `renderImage` function statics.
 */
export
namespace renderImage {
  /**
   * The options for the `renderImage` function.
   */
  export
  interface IRenderOptions {
    /**
     * The image node to update with the content.
     */
    host: HTMLElement;

    /**
     * The mime type for the image.
     */
    mimeType: string;

    /**
     * The base64 encoded source for the image.
     */
    source: string;

    /**
     * The optional width for the image.
     */
    width?: number;

    /**
     * The optional height for the image.
     */
    height?: number;
  }
}


/**
 * Render LaTeX into a host node.
 *
 * @params options - The options for rendering.
 *
 * @returns A promise which resolves when rendering is complete.
 */
export
function renderLatex(options: renderLatex.IRenderOptions): Promise<void> {
  // Unpack the options.
  let { host, source, shouldTypeset } = options;

  // Set the source on the node.
  host.textContent = source;

  // Typeset the node if needed.
  if (shouldTypeset) {
    typeset(host);
  }

  // Return the rendered promise.
  return Promise.resolve(undefined);
}


/**
 * The namespace for the `renderLatex` function statics.
 */
export
namespace renderLatex {
  /**
   * The options for the `renderLatex` function.
   */
  export
  interface IRenderOptions {
    /**
     * The host node for the rendered LaTeX.
     */
    host: HTMLElement;

    /**
     * The LaTeX source to render.
     */
    source: string;

    /**
     * Whether the node should be typeset.
     */
    shouldTypeset: boolean;
  }
}


/**
 * Render Markdown into a host node.
 *
 * @params options - The options for rendering.
 *
 * @returns A promise which resolves when rendering is complete.
 */
export
function renderMarkdown(options: renderMarkdown.IRenderOptions): Promise<void> {
  // Unpack the options.
  let {
    host, source, trusted, sanitizer, resolver, linkHandler, shouldTypeset
  } = options;

  // Clear the content if there is no source.
  if (!source) {
    host.textContent = '';
    return Promise.resolve(undefined);
  }

  // Separate math from normal markdown text.
  let parts = removeMath(source);

  // Render the markdown and handle sanitization.
  return Private.renderMarked(parts['text']).then(content => {
    // Restore the math content in the rendered markdown.
    content = replaceMath(content, parts['math']);

    // Santize the content it is not trusted.
    if (!trusted) {
      content = sanitizer.sanitize(content);
    }

    // Set the inner HTML of the host.
    host.innerHTML = content;

    // TODO arbitrary script execution is disabled for now.
    // Eval any script tags contained in the HTML. This is not done
    // automatically by the browser when script tags are created by
    // setting `innerHTML`. The santizer should have removed all of
    // the script tags for untrusted source, but this extra trusted
    // check is just extra insurance.
    // if (trusted) {
    //   // TODO really want to run scripts?
    //   Private.evalInnerHTMLScriptTags(host);
    // }

    // Apply ids to the header nodes.
    Private.headerAnchors(host);

    // Patch the urls if a resolver is available.
    let promise: Promise<void>;
    if (resolver) {
      promise = Private.handleUrls(host, resolver, linkHandler);
    } else {
      promise = Promise.resolve(undefined);
    }

    // Return the rendered promise.
    return promise;
  }).then(() => { if (shouldTypeset) { typeset(host) } });
}


/**
 * The namespace for the `renderMarkdown` function statics.
 */
export
namespace renderMarkdown {
  /**
   * The options for the `renderMarkdown` function.
   */
  export
  interface IRenderOptions {
    /**
     * The host node for the rendered Markdown.
     */
    host: HTMLElement;

    /**
     * The Markdown source to render.
     */
    source: string;

    /**
     * Whether the source is trusted.
     */
    trusted: boolean;

    /**
     * The html sanitizer for untrusted source.
     */
    sanitizer: ISanitizer;

    /**
     * An optional url resolver.
     */
    resolver: IRenderMime.IResolver | null;

    /**
     * An optional link handler.
     */
    linkHandler: IRenderMime.ILinkHandler | null;

    /**
     * Whether the node should be typeset.
     */
    shouldTypeset: boolean;
  }
}


/**
 * Render a PDF into a host node.
 *
 * @params options - The options for rendering.
 *
 * @returns A promise which resolves when rendering is complete.
 */
export
function renderPDF(options: renderPDF.IRenderOptions): Promise<void> {
  // Unpack the options.
  let { host, source, trusted } = options;

  // Clear the content if there is no source.
  if (!source) {
    host.textContent = '';
    return Promise.resolve(undefined);
  }

  // Display a message if the source is not trusted.
  if (!trusted) {
    host.textContent = 'Cannot display an untrusted PDF. Maybe you need to run the cell?';
    return Promise.resolve(undefined);
  }

  // Update the host with the display content.
  let href = `data:application/pdf;base64,${source}`;
  host.innerHTML = `<a target="_blank" href="${href}">View PDF</a>`;

  // Return the final rendered promise.
  return Promise.resolve(undefined);
}


/**
 * The namespace for the `renderPDF` function statics.
 */
export
namespace renderPDF {
  /**
   * The options for the `renderPDF` function.
   */
  export
  interface IRenderOptions {
    /**
     * The host node for the rendered PDF.
     */
    host: HTMLElement;

    /**
     * The base64 encoded source for the PDF.
     */
    source: string;

    /**
     * Whether the source is trusted.
     */
    trusted: boolean;
  }
}


/**
 * Render SVG into a host node.
 *
 * @params options - The options for rendering.
 *
 * @returns A promise which resolves when rendering is complete.
 */
export
function renderSVG(options: renderSVG.IRenderOptions): Promise<void> {
  // Unpack the options.
  let {
    host, source, trusted, resolver, linkHandler, shouldTypeset
  } = options;

  // Clear the content if there is no source.
  if (!source) {
    host.textContent = '';
    return Promise.resolve(undefined);
  }

  // Display a message if the source is not trusted.
  if (!trusted) {
    host.textContent = 'Cannot display an untrusted SVG. Maybe you need to run the cell?';
    return Promise.resolve(undefined);
  }

  // Set the inner HTML of the host.
  host.innerHTML = source;

  // TODO
  // what about script tags inside the svg?

  // Patch the urls if a resolver is available.
  let promise: Promise<void>;
  if (resolver) {
    promise = Private.handleUrls(host, resolver, linkHandler);
  } else {
    promise = Promise.resolve(undefined);
  }

  // Return the final rendered promise.
  return promise.then(() => { if (shouldTypeset) { typeset(host); } });
}


/**
 * The namespace for the `renderSVG` function statics.
 */
export
namespace renderSVG {
  /**
   * The options for the `renderSVG` function.
   */
  export
  interface IRenderOptions {
    /**
     * The host node for the rendered SVG.
     */
    host: HTMLElement;

    /**
     * The SVG source.
     */
    source: string;

    /**
     * Whether the source is trusted.
     */
    trusted: boolean;

    /**
     * An optional url resolver.
     */
    resolver: IRenderMime.IResolver | null;

    /**
     * An optional link handler.
     */
    linkHandler: IRenderMime.ILinkHandler | null;

    /**
     * Whether the node should be typeset.
     */
    shouldTypeset: boolean;
  }
}


/**
 * Render text into a host node.
 *
 * @params options - The options for rendering.
 *
 * @returns A promise which resolves when rendering is complete.
 */
export
function renderText(options: renderText.IRenderOptions): Promise<void> {
  // Unpack the options.
  let { host, source } = options;

  // Escape the terminal codes and HTML tags.
  let data = escape_for_html(source);

  // Create the HTML content.
  let content = ansi_to_html(data, { use_classes: true });

  // Set the inner HTML for the host node.
  host.innerHTML = `<pre>${content}</pre>`;

  // Return the rendered promise.
  return Promise.resolve(undefined);
}


/**
 * The namespace for the `renderText` function statics.
 */
export
namespace renderText {
  /**
   * The options for the `renderText` function.
   */
  export
  interface IRenderOptions {
    /**
     * The host node for the text content.
     */
    host: HTMLElement;

    /**
     * The source text to render.
     */
    source: string;
  }
}


/**
 * The namespace for module implementation details.
 */
namespace Private {
  // This is disabled for now until we decide we actually really
  // truly want to allow arbitrary script execution.
  /**
   * Eval the script tags contained in a host populated by `innerHTML`.
   *
   * When script tags are created via `innerHTML`, the browser does not
   * evaluate them when they are added to the page. This function works
   * around that by creating new equivalent script nodes manually, and
   * replacing the originals.
   */
  // export
  // function evalInnerHTMLScriptTags(host: HTMLElement): void {
  //   // Create a snapshot of the current script nodes.
  //   let scripts = toArray(host.getElementsByTagName('script'));

  //   // Loop over each script node.
  //   for (let script of scripts) {
  //     // Skip any scripts which no longer have a parent.
  //     if (!script.parentNode) {
  //       continue;
  //     }

  //     // Create a new script node which will be clone.
  //     let clone = document.createElement('script');

  //     // Copy the attributes into the clone.
  //     let attrs = script.attributes;
  //     for (let i = 0, n = attrs.length; i < n; ++i) {
  //       let { name, value } = attrs[i];
  //       clone.setAttribute(name, value);
  //     }

  //     // Copy the text content into the clone.
  //     clone.textContent = script.textContent;

  //     // Replace the old script in the parent.
  //     script.parentNode.replaceChild(clone, script);
  //   }
  // }

  /**
   * Render markdown for the specified content.
   *
   * @param content - The string of markdown to render.
   *
   * @return A promise which resolves with the rendered content.
   */
  export
  function renderMarked(content: string): Promise<string> {
    initializeMarked();
    return new Promise<string>((resolve, reject) => {
      marked(content, (err: any, content: string) => {
        if (err) {
          reject(err);
        } else {
          resolve(content);
        }
      });
    });
  }

  /**
   * Resolve the relative urls in element `src` and `href` attributes.
   *
   * @param node - The head html element.
   *
   * @param resolver - A url resolver.
   *
   * @param linkHandler - An optional link handler for nodes.
   *
   * @returns a promise fulfilled when the relative urls have been resolved.
   */
  export
  function handleUrls(node: HTMLElement, resolver: IRenderMime.IResolver, linkHandler: IRenderMime.ILinkHandler | null): Promise<void> {
    // Set up an array to collect promises.
    let promises: Promise<void>[] = [];

    // Handle HTML Elements with src attributes.
    let nodes = node.querySelectorAll('*[src]');
    for (let i = 0; i < nodes.length; i++) {
      promises.push(handleAttr(nodes[i] as HTMLElement, 'src', resolver));
    }

    // Handle achor elements.
    let anchors = node.getElementsByTagName('a');
    for (let i = 0; i < anchors.length; i++) {
      promises.push(handleAnchor(anchors[i], resolver, linkHandler));
    }

    // Handle link elements.
    let links = node.getElementsByTagName('link');
    for (let i = 0; i < links.length; i++) {
      promises.push(handleAttr(links[i], 'href', resolver));
    }

    // Wait on all promises.
    return Promise.all(promises).then(() => undefined);
  }

  /**
   * Apply ids to headers.
   */
  export
  function headerAnchors(node: HTMLElement): void {
    let headerNames = ['h1', 'h2', 'h3', 'h4', 'h5', 'h6'];
    for (let headerType of headerNames){
      let headers = node.getElementsByTagName(headerType);
      for (let i=0; i < headers.length; i++) {
        let header = headers[i];
        header.id = header.innerHTML.replace(/ /g, '-');
        let anchor = document.createElement('a');
        anchor.target = '_self';
        anchor.textContent = '¶';
        anchor.href = '#' + header.id;
        anchor.classList.add('jp-InternalAnchorLink');
        header.appendChild(anchor);
      }
    }
  }

  /**
   * Handle a node with a `src` or `href` attribute.
   */
  function handleAttr(node: HTMLElement, name: 'src' | 'href', resolver: IRenderMime.IResolver): Promise<void> {
    let source = node.getAttribute(name);
    if (!source) {
      return Promise.resolve(undefined);
    }
    node.setAttribute(name, '');
    return resolver.resolveUrl(source).then(path => {
      return resolver.getDownloadUrl(path);
    }).then(url => {
      node.setAttribute(name, url);
    });
  }

  /**
   * Handle an anchor node.
   */
  function handleAnchor(anchor: HTMLAnchorElement, resolver: IRenderMime.IResolver, linkHandler: IRenderMime.ILinkHandler | null): Promise<void> {
    anchor.target = '_blank';
    // Get the link path without the location prepended.
    // (e.g. "./foo.md#Header 1" vs "http://localhost:8888/foo.md#Header 1")
    let href = anchor.getAttribute('href');
    // Bail if it is not a file-like url.
    if (!href || href.indexOf('://') !== -1 && href.indexOf('//') === 0) {
      return Promise.resolve(undefined);
    }
    // Remove the hash until we can handle it.
    let hash = anchor.hash;
    if (hash) {
      // Handle internal link in the file.
      if (hash === href) {
        anchor.target = '_self';
        return Promise.resolve(undefined);
      }
      // For external links, remove the hash until we have hash handling.
      href = href.replace(hash, '');
    }
    // Get the appropriate file path.
    return resolver.resolveUrl(href).then(path => {
      // Handle the click override.
      if (linkHandler && URLExt.isLocal(path)) {
        linkHandler.handleLink(anchor, path);
      }
      // Get the appropriate file download path.
      return resolver.getDownloadUrl(path);
    }).then(url => {
      // Set the visible anchor.
      anchor.href = url + hash;
    });
  }

  let markedInitialized = false;

  /**
   * Support GitHub flavored Markdown, leave sanitizing to external library.
   */
  function initializeMarked(): void {
    if (markedInitialized) {
      return;
    }
    markedInitialized = true;
    marked.setOptions({
      gfm: true,
      sanitize: false,
      tables: true,
      // breaks: true; We can't use GFM breaks as it causes problems with tables
      langPrefix: `cm-s-${CodeMirrorEditor.defaultConfig.theme} language-`,
      highlight: (code, lang, callback) => {
        if (!lang) {
            // no language, no highlight
            if (callback) {
                callback(null, code);
                return;
            } else {
                return code;
            }
        }
        Mode.ensure(lang).then(spec => {
          let el = document.createElement('div');
          if (!spec) {
              console.log(`No CodeMirror mode: ${lang}`);
              callback(null, code);
              return;
          }
          try {
            Mode.run(code, spec.mime, el);
            callback(null, el.innerHTML);
          } catch (err) {
            console.log(`Failed to highlight ${lang} code`, err);
            callback(err, code);
          }
        }).catch(err => {
          console.log(`No CodeMirror mode: ${lang}`);
          console.log(`Require CodeMirror mode error: ${err}`);
          callback(null, code);
        });
      }
    });
  }
}