pdf.js/web/pdf_link_service.js

/* Copyright 2015 Mozilla Foundation
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

/** @typedef {import("./event_utils").EventBus} EventBus */
/** @typedef {import("./interfaces").IPDFLinkService} IPDFLinkService */

import { parseQueryString } from "./ui_utils.js";
import { removeNullCharacters } from "pdfjs-lib";

const DEFAULT_LINK_REL = "noopener noreferrer nofollow";

const LinkTarget = {
  NONE: 0, // Default value.
  SELF: 1,
  BLANK: 2,
  PARENT: 3,
  TOP: 4,
};

/**
 * @typedef ExternalLinkParameters
 * @typedef {Object} ExternalLinkParameters
 * @property {string} url - An absolute URL.
 * @property {LinkTarget} [target] - The link target. The default value is
 *   `LinkTarget.NONE`.
 * @property {string} [rel] - The link relationship. The default value is
 *   `DEFAULT_LINK_REL`.
 * @property {boolean} [enabled] - Whether the link should be enabled. The
 *   default value is true.
 */

/**
 * Adds various attributes (href, title, target, rel) to hyperlinks.
 * @param {HTMLAnchorElement} link - The link element.
 * @param {ExternalLinkParameters} params
 */
function addLinkAttributes(link, { url, target, rel, enabled = true } = {}) {
  if (!url || typeof url !== "string") {
    throw new Error('A valid "url" parameter must provided.');
  }

  const urlNullRemoved = removeNullCharacters(url);
  if (enabled) {
    link.href = link.title = urlNullRemoved;
  } else {
    link.href = "";
    link.title = `Disabled: ${urlNullRemoved}`;
    link.onclick = () => {
      return false;
    };
  }

  let targetStr = ""; // LinkTarget.NONE
  switch (target) {
    case LinkTarget.NONE:
      break;
    case LinkTarget.SELF:
      targetStr = "_self";
      break;
    case LinkTarget.BLANK:
      targetStr = "_blank";
      break;
    case LinkTarget.PARENT:
      targetStr = "_parent";
      break;
    case LinkTarget.TOP:
      targetStr = "_top";
      break;
  }
  link.target = targetStr;

  link.rel = typeof rel === "string" ? rel : DEFAULT_LINK_REL;
}

/**
 * @typedef {Object} PDFLinkServiceOptions
 * @property {EventBus} eventBus - The application event bus.
 * @property {number} [externalLinkTarget] - Specifies the `target` attribute
 *   for external links. Must use one of the values from {LinkTarget}.
 *   Defaults to using no target.
 * @property {string} [externalLinkRel] - Specifies the `rel` attribute for
 *   external links. Defaults to stripping the referrer.
 * @property {boolean} [ignoreDestinationZoom] - Ignores the zoom argument,
 *   thus preserving the current zoom level in the viewer, when navigating
 *   to internal destinations. The default value is `false`.
 */

/**
 * Performs navigation functions inside PDF, such as opening specified page,
 * or destination.
 * @implements {IPDFLinkService}
 */
class PDFLinkService {
  /**
   * @param {PDFLinkServiceOptions} options
   */
  constructor({
    eventBus,
    externalLinkTarget = null,
    externalLinkRel = null,
    ignoreDestinationZoom = false,
  } = {}) {
    this.eventBus = eventBus;
    this.externalLinkTarget = externalLinkTarget;
    this.externalLinkRel = externalLinkRel;
    this.externalLinkEnabled = true;
    this._ignoreDestinationZoom = ignoreDestinationZoom;

    this.baseUrl = null;
    this.pdfDocument = null;
    this.pdfViewer = null;
    this.pdfHistory = null;

    this._pagesRefCache = null;
  }

  setDocument(pdfDocument, baseUrl = null) {
    this.baseUrl = baseUrl;
    this.pdfDocument = pdfDocument;
    this._pagesRefCache = Object.create(null);
  }

  setViewer(pdfViewer) {
    this.pdfViewer = pdfViewer;
  }

  setHistory(pdfHistory) {
    this.pdfHistory = pdfHistory;
  }

  /**
   * @type {number}
   */
  get pagesCount() {
    return this.pdfDocument ? this.pdfDocument.numPages : 0;
  }

  /**
   * @type {number}
   */
  get page() {
    return this.pdfViewer.currentPageNumber;
  }

  /**
   * @param {number} value
   */
  set page(value) {
    this.pdfViewer.currentPageNumber = value;
  }

  /**
   * @type {number}
   */
  get rotation() {
    return this.pdfViewer.pagesRotation;
  }

  /**
   * @param {number} value
   */
  set rotation(value) {
    this.pdfViewer.pagesRotation = value;
  }

  /**
   * @private
   */
  _goToDestinationHelper(rawDest, namedDest = null, explicitDest) {
    // Dest array looks like that: <page-ref> </XYZ|/FitXXX> <args..>
    const destRef = explicitDest[0];
    let pageNumber;

    if (typeof destRef === "object" && destRef !== null) {
      pageNumber = this._cachedPageNumber(destRef);

      if (!pageNumber) {
        // Fetch the page reference if it's not yet available. This could
        // only occur during loading, before all pages have been resolved.
        this.pdfDocument
          .getPageIndex(destRef)
          .then(pageIndex => {
            this.cachePageRef(pageIndex + 1, destRef);
            this._goToDestinationHelper(rawDest, namedDest, explicitDest);
          })
          .catch(() => {
            console.error(
              `PDFLinkService._goToDestinationHelper: "${destRef}" is not ` +
                `a valid page reference, for dest="${rawDest}".`
            );
          });
        return;
      }
    } else if (Number.isInteger(destRef)) {
      pageNumber = destRef + 1;
    } else {
      console.error(
        `PDFLinkService._goToDestinationHelper: "${destRef}" is not ` +
          `a valid destination reference, for dest="${rawDest}".`
      );
      return;
    }
    if (!pageNumber || pageNumber < 1 || pageNumber > this.pagesCount) {
      console.error(
        `PDFLinkService._goToDestinationHelper: "${pageNumber}" is not ` +
          `a valid page number, for dest="${rawDest}".`
      );
      return;
    }

    if (this.pdfHistory) {
      // Update the browser history before scrolling the new destination into
      // view, to be able to accurately capture the current document position.
      this.pdfHistory.pushCurrentPosition();
      this.pdfHistory.push({ namedDest, explicitDest, pageNumber });
    }

    this.pdfViewer.scrollPageIntoView({
      pageNumber,
      destArray: explicitDest,
      ignoreDestinationZoom: this._ignoreDestinationZoom,
    });
  }

  /**
   * This method will, when available, also update the browser history.
   *
   * @param {string|Array} dest - The named, or explicit, PDF destination.
   */
  async goToDestination(dest) {
    if (!this.pdfDocument) {
      return;
    }
    let namedDest, explicitDest;
    if (typeof dest === "string") {
      namedDest = dest;
      explicitDest = await this.pdfDocument.getDestination(dest);
    } else {
      namedDest = null;
      explicitDest = await dest;
    }
    if (!Array.isArray(explicitDest)) {
      console.error(
        `PDFLinkService.goToDestination: "${explicitDest}" is not ` +
          `a valid destination array, for dest="${dest}".`
      );
      return;
    }
    this._goToDestinationHelper(dest, namedDest, explicitDest);
  }

  /**
   * This method will, when available, also update the browser history.
   *
   * @param {number|string} val - The page number, or page label.
   */
  goToPage(val) {
    if (!this.pdfDocument) {
      return;
    }
    const pageNumber =
      (typeof val === "string" && this.pdfViewer.pageLabelToPageNumber(val)) ||
      val | 0;
    if (
      !(
        Number.isInteger(pageNumber) &&
        pageNumber > 0 &&
        pageNumber <= this.pagesCount
      )
    ) {
      console.error(`PDFLinkService.goToPage: "${val}" is not a valid page.`);
      return;
    }

    if (this.pdfHistory) {
      // Update the browser history before scrolling the new page into view,
      // to be able to accurately capture the current document position.
      this.pdfHistory.pushCurrentPosition();
      this.pdfHistory.pushPage(pageNumber);
    }

    this.pdfViewer.scrollPageIntoView({ pageNumber });
  }

  /**
   * Wrapper around the `addLinkAttributes` helper function.
   * @param {HTMLAnchorElement} link
   * @param {string} url
   * @param {boolean} [newWindow]
   */
  addLinkAttributes(link, url, newWindow = false) {
    addLinkAttributes(link, {
      url,
      target: newWindow ? LinkTarget.BLANK : this.externalLinkTarget,
      rel: this.externalLinkRel,
      enabled: this.externalLinkEnabled,
    });
  }

  /**
   * @param {string|Array} dest - The PDF destination object.
   * @returns {string} The hyperlink to the PDF object.
   */
  getDestinationHash(dest) {
    if (typeof dest === "string") {
      if (dest.length > 0) {
        return this.getAnchorUrl("#" + escape(dest));
      }
    } else if (Array.isArray(dest)) {
      const str = JSON.stringify(dest);
      if (str.length > 0) {
        return this.getAnchorUrl("#" + escape(str));
      }
    }
    return this.getAnchorUrl("");
  }

  /**
   * Prefix the full url on anchor links to make sure that links are resolved
   * relative to the current URL instead of the one defined in <base href>.
   * @param {string} anchor - The anchor hash, including the #.
   * @returns {string} The hyperlink to the PDF object.
   */
  getAnchorUrl(anchor) {
    return (this.baseUrl || "") + anchor;
  }

  /**
   * @param {string} hash
   */
  setHash(hash) {
    if (!this.pdfDocument) {
      return;
    }
    let pageNumber, dest;
    if (hash.includes("=")) {
      const params = parseQueryString(hash);
      if (params.has("search")) {
        this.eventBus.dispatch("findfromurlhash", {
          source: this,
          query: params.get("search").replace(/"/g, ""),
          phraseSearch: params.get("phrase") === "true",
        });
      }
      // borrowing syntax from "Parameters for Opening PDF Files"
      if (params.has("page")) {
        pageNumber = params.get("page") | 0 || 1;
      }
      if (params.has("zoom")) {
        // Build the destination array.
        const zoomArgs = params.get("zoom").split(","); // scale,left,top
        const zoomArg = zoomArgs[0];
        const zoomArgNumber = parseFloat(zoomArg);

        if (!zoomArg.includes("Fit")) {
          // If the zoomArg is a number, it has to get divided by 100. If it's
          // a string, it should stay as it is.
          dest = [
            null,
            { name: "XYZ" },
            zoomArgs.length > 1 ? zoomArgs[1] | 0 : null,
            zoomArgs.length > 2 ? zoomArgs[2] | 0 : null,
            zoomArgNumber ? zoomArgNumber / 100 : zoomArg,
          ];
        } else {
          if (zoomArg === "Fit" || zoomArg === "FitB") {
            dest = [null, { name: zoomArg }];
          } else if (
            zoomArg === "FitH" ||
            zoomArg === "FitBH" ||
            zoomArg === "FitV" ||
            zoomArg === "FitBV"
          ) {
            dest = [
              null,
              { name: zoomArg },
              zoomArgs.length > 1 ? zoomArgs[1] | 0 : null,
            ];
          } else if (zoomArg === "FitR") {
            if (zoomArgs.length !== 5) {
              console.error(
                'PDFLinkService.setHash: Not enough parameters for "FitR".'
              );
            } else {
              dest = [
                null,
                { name: zoomArg },
                zoomArgs[1] | 0,
                zoomArgs[2] | 0,
                zoomArgs[3] | 0,
                zoomArgs[4] | 0,
              ];
            }
          } else {
            console.error(
              `PDFLinkService.setHash: "${zoomArg}" is not ` +
                "a valid zoom value."
            );
          }
        }
      }
      if (dest) {
        this.pdfViewer.scrollPageIntoView({
          pageNumber: pageNumber || this.page,
          destArray: dest,
          allowNegativeOffset: true,
        });
      } else if (pageNumber) {
        this.page = pageNumber; // simple page
      }
      if (params.has("pagemode")) {
        this.eventBus.dispatch("pagemode", {
          source: this,
          mode: params.get("pagemode"),
        });
      }
      // Ensure that this parameter is *always* handled last, in order to
      // guarantee that it won't be overridden (e.g. by the "page" parameter).
      if (params.has("nameddest")) {
        this.goToDestination(params.get("nameddest"));
      }
    } else {
      // Named (or explicit) destination.
      dest = unescape(hash);
      try {
        dest = JSON.parse(dest);

        if (!Array.isArray(dest)) {
          // Avoid incorrectly rejecting a valid named destination, such as
          // e.g. "4.3" or "true", because `JSON.parse` converted its type.
          dest = dest.toString();
        }
      } catch (ex) {}

      if (typeof dest === "string" || isValidExplicitDestination(dest)) {
        this.goToDestination(dest);
        return;
      }
      console.error(
        `PDFLinkService.setHash: "${unescape(hash)}" is not ` +
          "a valid destination."
      );
    }
  }

  /**
   * @param {string} action
   */
  executeNamedAction(action) {
    // See PDF reference, table 8.45 - Named action
    switch (action) {
      case "GoBack":
        this.pdfHistory?.back();
        break;

      case "GoForward":
        this.pdfHistory?.forward();
        break;

      case "NextPage":
        this.pdfViewer.nextPage();
        break;

      case "PrevPage":
        this.pdfViewer.previousPage();
        break;

      case "LastPage":
        this.page = this.pagesCount;
        break;

      case "FirstPage":
        this.page = 1;
        break;

      default:
        break; // No action according to spec
    }

    this.eventBus.dispatch("namedaction", {
      source: this,
      action,
    });
  }

  /**
   * @param {number} pageNum - page number.
   * @param {Object} pageRef - reference to the page.
   */
  cachePageRef(pageNum, pageRef) {
    if (!pageRef) {
      return;
    }
    const refStr =
      pageRef.gen === 0 ? `${pageRef.num}R` : `${pageRef.num}R${pageRef.gen}`;
    this._pagesRefCache[refStr] = pageNum;
  }

  /**
   * @private
   */
  _cachedPageNumber(pageRef) {
    if (!pageRef) {
      return null;
    }
    const refStr =
      pageRef.gen === 0 ? `${pageRef.num}R` : `${pageRef.num}R${pageRef.gen}`;
    return this._pagesRefCache?.[refStr] || null;
  }

  /**
   * @param {number} pageNumber
   */
  isPageVisible(pageNumber) {
    return this.pdfViewer.isPageVisible(pageNumber);
  }

  /**
   * @param {number} pageNumber
   */
  isPageCached(pageNumber) {
    return this.pdfViewer.isPageCached(pageNumber);
  }
}

function isValidExplicitDestination(dest) {
  if (!Array.isArray(dest)) {
    return false;
  }
  const destLength = dest.length;
  if (destLength < 2) {
    return false;
  }
  const page = dest[0];
  if (
    !(
      typeof page === "object" &&
      Number.isInteger(page.num) &&
      Number.isInteger(page.gen)
    ) &&
    !(Number.isInteger(page) && page >= 0)
  ) {
    return false;
  }
  const zoom = dest[1];
  if (!(typeof zoom === "object" && typeof zoom.name === "string")) {
    return false;
  }
  let allowNull = true;
  switch (zoom.name) {
    case "XYZ":
      if (destLength !== 5) {
        return false;
      }
      break;
    case "Fit":
    case "FitB":
      return destLength === 2;
    case "FitH":
    case "FitBH":
    case "FitV":
    case "FitBV":
      if (destLength !== 3) {
        return false;
      }
      break;
    case "FitR":
      if (destLength !== 6) {
        return false;
      }
      allowNull = false;
      break;
    default:
      return false;
  }
  for (let i = 2; i < destLength; i++) {
    const param = dest[i];
    if (!(typeof param === "number" || (allowNull && param === null))) {
      return false;
    }
  }
  return true;
}

/**
 * @implements {IPDFLinkService}
 */
class SimpleLinkService {
  constructor() {
    this.externalLinkEnabled = true;
  }

  /**
   * @type {number}
   */
  get pagesCount() {
    return 0;
  }

  /**
   * @type {number}
   */
  get page() {
    return 0;
  }

  /**
   * @param {number} value
   */
  set page(value) {}

  /**
   * @type {number}
   */
  get rotation() {
    return 0;
  }

  /**
   * @param {number} value
   */
  set rotation(value) {}

  /**
   * @param {string|Array} dest - The named, or explicit, PDF destination.
   */
  async goToDestination(dest) {}

  /**
   * @param {number|string} val - The page number, or page label.
   */
  goToPage(val) {}

  /**
   * @param {HTMLAnchorElement} link
   * @param {string} url
   * @param {boolean} [newWindow]
   */
  addLinkAttributes(link, url, newWindow = false) {
    addLinkAttributes(link, { url, enabled: this.externalLinkEnabled });
  }

  /**
   * @param dest - The PDF destination object.
   * @returns {string} The hyperlink to the PDF object.
   */
  getDestinationHash(dest) {
    return "#";
  }

  /**
   * @param hash - The PDF parameters/hash.
   * @returns {string} The hyperlink to the PDF object.
   */
  getAnchorUrl(hash) {
    return "#";
  }

  /**
   * @param {string} hash
   */
  setHash(hash) {}

  /**
   * @param {string} action
   */
  executeNamedAction(action) {}

  /**
   * @param {number} pageNum - page number.
   * @param {Object} pageRef - reference to the page.
   */
  cachePageRef(pageNum, pageRef) {}

  /**
   * @param {number} pageNumber
   */
  isPageVisible(pageNumber) {
    return true;
  }

  /**
   * @param {number} pageNumber
   */
  isPageCached(pageNumber) {
    return true;
  }
}

export { LinkTarget, PDFLinkService, SimpleLinkService };