/* Copyright 2014 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.
 */

import {
  CSS_UNITS,
  DEFAULT_SCALE,
  DEFAULT_SCALE_VALUE,
  getGlobalEventBus,
  getVisibleElements,
  isPortraitOrientation,
  isValidRotation,
  isValidScrollMode,
  isValidSpreadMode,
  MAX_AUTO_SCALE,
  moveToEndOfArray,
  NullL10n,
  PresentationModeState,
  RendererType,
  SCROLLBAR_PADDING,
  scrollIntoView,
  ScrollMode,
  SpreadMode,
  TextLayerMode,
  UNKNOWN_SCALE,
  VERTICAL_PADDING,
  watchScroll,
} from "./ui_utils";
import { PDFRenderingQueue, RenderingStates } from "./pdf_rendering_queue";
import { AnnotationLayerBuilder } from "./annotation_layer_builder";
import { createPromiseCapability } from "pdfjs-lib";
import { PDFPageView } from "./pdf_page_view";
import { SimpleLinkService } from "./pdf_link_service";
import { TextLayerBuilder } from "./text_layer_builder";

const DEFAULT_CACHE_SIZE = 10;

/**
 * @typedef {Object} PDFViewerOptions
 * @property {HTMLDivElement} container - The container for the viewer element.
 * @property {HTMLDivElement} [viewer] - The viewer element.
 * @property {EventBus} eventBus - The application event bus.
 * @property {IPDFLinkService} linkService - The navigation/linking service.
 * @property {DownloadManager} [downloadManager] - The download manager
 *   component.
 * @property {PDFFindController} [findController] - The find controller
 *   component.
 * @property {PDFRenderingQueue} [renderingQueue] - The rendering queue object.
 * @property {boolean} [removePageBorders] - Removes the border shadow around
 *   the pages. The default value is `false`.
 * @property {number} [textLayerMode] - Controls if the text layer used for
 *   selection and searching is created, and if the improved text selection
 *   behaviour is enabled. The constants from {TextLayerMode} should be used.
 *   The default value is `TextLayerMode.ENABLE`.
 * @property {string} [imageResourcesPath] - Path for image resources, mainly
 *   mainly for annotation icons. Include trailing slash.
 * @property {boolean} [renderInteractiveForms] - Enables rendering of
 *   interactive form elements. The default is `false`.
 * @property {boolean} [enablePrintAutoRotate] - Enables automatic rotation of
 *   pages whose orientation differ from the first page upon printing. The
 *   default is `false`.
 * @property {string} renderer - 'canvas' or 'svg'. The default is 'canvas'.
 * @property {boolean} [enableWebGL] - Enables WebGL accelerated rendering for
 *   some operations. The default value is `false`.
 * @property {boolean} [useOnlyCssZoom] - Enables CSS only zooming. The default
 *   value is `false`.
 * @property {number} [maxCanvasPixels] - The maximum supported canvas size in
 *   total pixels, i.e. width * height. Use -1 for no limit. The default value
 *   is 4096 * 4096 (16 mega-pixels).
 * @property {IL10n} l10n - Localization service.
 */

function PDFPageViewBuffer(size) {
  const data = [];
  this.push = function(view) {
    const i = data.indexOf(view);
    if (i >= 0) {
      data.splice(i, 1);
    }
    data.push(view);
    if (data.length > size) {
      data.shift().destroy();
    }
  };
  /**
   * After calling resize, the size of the buffer will be newSize. The optional
   * parameter pagesToKeep is, if present, an array of pages to push to the back
   * of the buffer, delaying their destruction. The size of pagesToKeep has no
   * impact on the final size of the buffer; if pagesToKeep has length larger
   * than newSize, some of those pages will be destroyed anyway.
   */
  this.resize = function(newSize, pagesToKeep) {
    size = newSize;
    if (pagesToKeep) {
      const pageIdsToKeep = new Set();
      for (let i = 0, iMax = pagesToKeep.length; i < iMax; ++i) {
        pageIdsToKeep.add(pagesToKeep[i].id);
      }
      moveToEndOfArray(data, function(page) {
        return pageIdsToKeep.has(page.id);
      });
    }
    while (data.length > size) {
      data.shift().destroy();
    }
  };
}

function isSameScale(oldScale, newScale) {
  if (newScale === oldScale) {
    return true;
  }
  if (Math.abs(newScale - oldScale) < 1e-15) {
    // Prevent unnecessary re-rendering of all pages when the scale
    // changes only because of limited numerical precision.
    return true;
  }
  return false;
}

/**
 * Simple viewer control to display PDF content/pages.
 * @implements {IRenderableView}
 */
class BaseViewer {
  /**
   * @param {PDFViewerOptions} options
   */
  constructor(options) {
    if (this.constructor === BaseViewer) {
      throw new Error("Cannot initialize BaseViewer.");
    }
    this._name = this.constructor.name;

    this.container = options.container;
    this.viewer = options.viewer || options.container.firstElementChild;
    this.eventBus = options.eventBus || getGlobalEventBus();
    this.linkService = options.linkService || new SimpleLinkService();
    this.downloadManager = options.downloadManager || null;
    this.findController = options.findController || null;
    this.removePageBorders = options.removePageBorders || false;
    this.textLayerMode = Number.isInteger(options.textLayerMode)
      ? options.textLayerMode
      : TextLayerMode.ENABLE;
    this.imageResourcesPath = options.imageResourcesPath || "";
    this.renderInteractiveForms = options.renderInteractiveForms || false;
    this.enablePrintAutoRotate = options.enablePrintAutoRotate || false;
    this.renderer = options.renderer || RendererType.CANVAS;
    this.enableWebGL = options.enableWebGL || false;
    this.useOnlyCssZoom = options.useOnlyCssZoom || false;
    this.maxCanvasPixels = options.maxCanvasPixels;
    this.l10n = options.l10n || NullL10n;

    this.defaultRenderingQueue = !options.renderingQueue;
    if (this.defaultRenderingQueue) {
      // Custom rendering queue is not specified, using default one
      this.renderingQueue = new PDFRenderingQueue();
      this.renderingQueue.setViewer(this);
    } else {
      this.renderingQueue = options.renderingQueue;
    }

    this.scroll = watchScroll(this.container, this._scrollUpdate.bind(this));
    this.presentationModeState = PresentationModeState.UNKNOWN;
    this._onBeforeDraw = this._onAfterDraw = null;
    this._resetView();

    if (this.removePageBorders) {
      this.viewer.classList.add("removePageBorders");
    }
    // Defer the dispatching of this event, to give other viewer components
    // time to initialize *and* register 'baseviewerinit' event listeners.
    Promise.resolve().then(() => {
      this.eventBus.dispatch("baseviewerinit", { source: this });
    });
  }

  get pagesCount() {
    return this._pages.length;
  }

  getPageView(index) {
    return this._pages[index];
  }

  /**
   * @type {boolean} - True if all {PDFPageView} objects are initialized.
   */
  get pageViewsReady() {
    if (!this._pageViewsReady) {
      return false;
    }
    // Prevent printing errors when 'disableAutoFetch' is set, by ensuring
    // that *all* pages have in fact been completely loaded.
    return this._pages.every(function(pageView) {
      return !!(pageView && pageView.pdfPage);
    });
  }

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

  /**
   * @param {number} val - The page number.
   */
  set currentPageNumber(val) {
    if (!Number.isInteger(val)) {
      throw new Error("Invalid page number.");
    }
    if (!this.pdfDocument) {
      return;
    }
    // The intent can be to just reset a scroll position and/or scale.
    if (!this._setCurrentPageNumber(val, /* resetCurrentPageView = */ true)) {
      console.error(
        `${this._name}.currentPageNumber: "${val}" is not a valid page.`
      );
    }
  }

  /**
   * @returns {boolean} Whether the pageNumber is valid (within bounds).
   * @private
   */
  _setCurrentPageNumber(val, resetCurrentPageView = false) {
    if (this._currentPageNumber === val) {
      if (resetCurrentPageView) {
        this._resetCurrentPageView();
      }
      return true;
    }

    if (!(0 < val && val <= this.pagesCount)) {
      return false;
    }
    this._currentPageNumber = val;

    this.eventBus.dispatch("pagechanging", {
      source: this,
      pageNumber: val,
      pageLabel: this._pageLabels && this._pageLabels[val - 1],
    });

    if (resetCurrentPageView) {
      this._resetCurrentPageView();
    }
    return true;
  }

  /**
   * @type {string|null} Returns the current page label, or `null` if no page
   *   labels exist.
   */
  get currentPageLabel() {
    return this._pageLabels && this._pageLabels[this._currentPageNumber - 1];
  }

  /**
   * @param {string} val - The page label.
   */
  set currentPageLabel(val) {
    if (!this.pdfDocument) {
      return;
    }
    let page = val | 0; // Fallback page number.
    if (this._pageLabels) {
      const i = this._pageLabels.indexOf(val);
      if (i >= 0) {
        page = i + 1;
      }
    }
    // The intent can be to just reset a scroll position and/or scale.
    if (!this._setCurrentPageNumber(page, /* resetCurrentPageView = */ true)) {
      console.error(
        `${this._name}.currentPageLabel: "${val}" is not a valid page.`
      );
    }
  }

  /**
   * @type {number}
   */
  get currentScale() {
    return this._currentScale !== UNKNOWN_SCALE
      ? this._currentScale
      : DEFAULT_SCALE;
  }

  /**
   * @param {number} val - Scale of the pages in percents.
   */
  set currentScale(val) {
    if (isNaN(val)) {
      throw new Error("Invalid numeric scale.");
    }
    if (!this.pdfDocument) {
      return;
    }
    this._setScale(val, false);
  }

  /**
   * @type {string}
   */
  get currentScaleValue() {
    return this._currentScaleValue;
  }

  /**
   * @param val - The scale of the pages (in percent or predefined value).
   */
  set currentScaleValue(val) {
    if (!this.pdfDocument) {
      return;
    }
    this._setScale(val, false);
  }

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

  /**
   * @param {number} rotation - The rotation of the pages (0, 90, 180, 270).
   */
  set pagesRotation(rotation) {
    if (!isValidRotation(rotation)) {
      throw new Error("Invalid pages rotation angle.");
    }
    if (!this.pdfDocument) {
      return;
    }
    if (this._pagesRotation === rotation) {
      return; // The rotation didn't change.
    }
    this._pagesRotation = rotation;

    const pageNumber = this._currentPageNumber;

    for (let i = 0, ii = this._pages.length; i < ii; i++) {
      const pageView = this._pages[i];
      pageView.update(pageView.scale, rotation);
    }
    // Prevent errors in case the rotation changes *before* the scale has been
    // set to a non-default value.
    if (this._currentScaleValue) {
      this._setScale(this._currentScaleValue, true);
    }

    this.eventBus.dispatch("rotationchanging", {
      source: this,
      pagesRotation: rotation,
      pageNumber,
    });

    if (this.defaultRenderingQueue) {
      this.update();
    }
  }

  get _setDocumentViewerElement() {
    // In most viewers, e.g. `PDFViewer`, this should return `this.viewer`.
    throw new Error("Not implemented: _setDocumentViewerElement");
  }

  /**
   * @param pdfDocument {PDFDocument}
   */
  setDocument(pdfDocument) {
    if (this.pdfDocument) {
      this._cancelRendering();
      this._resetView();

      if (this.findController) {
        this.findController.setDocument(null);
      }
    }

    this.pdfDocument = pdfDocument;
    if (!pdfDocument) {
      return;
    }
    const pagesCount = pdfDocument.numPages;

    const pagesCapability = createPromiseCapability();
    this.pagesPromise = pagesCapability.promise;

    pagesCapability.promise.then(() => {
      this._pageViewsReady = true;
      this.eventBus.dispatch("pagesloaded", {
        source: this,
        pagesCount,
      });
    });

    const onePageRenderedCapability = createPromiseCapability();
    this.onePageRendered = onePageRenderedCapability.promise;

    const firstPagePromise = pdfDocument.getPage(1);
    this.firstPagePromise = firstPagePromise;

    this._onBeforeDraw = evt => {
      const pageView = this._pages[evt.pageNumber - 1];
      if (!pageView) {
        return;
      }
      // Add the page to the buffer at the start of drawing. That way it can be
      // evicted from the buffer and destroyed even if we pause its rendering.
      this._buffer.push(pageView);
    };
    this.eventBus.on("pagerender", this._onBeforeDraw);

    this._onAfterDraw = evt => {
      if (evt.cssTransform || onePageRenderedCapability.settled) {
        return;
      }
      onePageRenderedCapability.resolve();

      this.eventBus.off("pagerendered", this._onAfterDraw);
      this._onAfterDraw = null;
    };
    this.eventBus.on("pagerendered", this._onAfterDraw);

    // Fetch a single page so we can get a viewport that will be the default
    // viewport for all pages
    firstPagePromise
      .then(firstPdfPage => {
        const scale = this.currentScale;
        const viewport = firstPdfPage.getViewport({ scale: scale * CSS_UNITS });
        for (let pageNum = 1; pageNum <= pagesCount; ++pageNum) {
          let textLayerFactory = null;
          if (this.textLayerMode !== TextLayerMode.DISABLE) {
            textLayerFactory = this;
          }
          const pageView = new PDFPageView({
            container: this._setDocumentViewerElement,
            eventBus: this.eventBus,
            id: pageNum,
            scale,
            defaultViewport: viewport.clone(),
            renderingQueue: this.renderingQueue,
            textLayerFactory,
            textLayerMode: this.textLayerMode,
            annotationLayerFactory: this,
            imageResourcesPath: this.imageResourcesPath,
            renderInteractiveForms: this.renderInteractiveForms,
            renderer: this.renderer,
            enableWebGL: this.enableWebGL,
            useOnlyCssZoom: this.useOnlyCssZoom,
            maxCanvasPixels: this.maxCanvasPixels,
            l10n: this.l10n,
          });
          this._pages.push(pageView);
        }
        // Set the first `pdfPage` immediately, since it's already loaded,
        // rather than having to repeat the `PDFDocumentProxy.getPage` call in
        // the `this._ensurePdfPageLoaded` method before rendering can start.
        const firstPageView = this._pages[0];
        if (firstPageView) {
          firstPageView.setPdfPage(firstPdfPage);
          this.linkService.cachePageRef(1, firstPdfPage.ref);
        }
        if (this._spreadMode !== SpreadMode.NONE) {
          this._updateSpreadMode();
        }

        // Fetch all the pages since the viewport is needed before printing
        // starts to create the correct size canvas. Wait until one page is
        // rendered so we don't tie up too many resources early on.
        onePageRenderedCapability.promise.then(() => {
          if (this.findController) {
            this.findController.setDocument(pdfDocument); // Enable searching.
          }

          // In addition to 'disableAutoFetch' being set, also attempt to reduce
          // resource usage when loading *very* long/large documents.
          if (
            pdfDocument.loadingParams["disableAutoFetch"] ||
            pagesCount > 7500
          ) {
            // XXX: Printing is semi-broken with auto fetch disabled.
            pagesCapability.resolve();
            return;
          }
          let getPagesLeft = pagesCount - 1; // The first page was already loaded.

          if (getPagesLeft <= 0) {
            pagesCapability.resolve();
            return;
          }
          for (let pageNum = 2; pageNum <= pagesCount; ++pageNum) {
            pdfDocument.getPage(pageNum).then(
              pdfPage => {
                const pageView = this._pages[pageNum - 1];
                if (!pageView.pdfPage) {
                  pageView.setPdfPage(pdfPage);
                }
                this.linkService.cachePageRef(pageNum, pdfPage.ref);
                if (--getPagesLeft === 0) {
                  pagesCapability.resolve();
                }
              },
              reason => {
                console.error(
                  `Unable to get page ${pageNum} to initialize viewer`,
                  reason
                );
                if (--getPagesLeft === 0) {
                  pagesCapability.resolve();
                }
              }
            );
          }
        });

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

        if (this.defaultRenderingQueue) {
          this.update();
        }
      })
      .catch(reason => {
        console.error("Unable to initialize viewer", reason);
      });
  }

  /**
   * @param {Array|null} labels
   */
  setPageLabels(labels) {
    if (!this.pdfDocument) {
      return;
    }
    if (!labels) {
      this._pageLabels = null;
    } else if (
      !(Array.isArray(labels) && this.pdfDocument.numPages === labels.length)
    ) {
      this._pageLabels = null;
      console.error(`${this._name}.setPageLabels: Invalid page labels.`);
    } else {
      this._pageLabels = labels;
    }
    // Update all the `PDFPageView` instances.
    for (let i = 0, ii = this._pages.length; i < ii; i++) {
      const pageView = this._pages[i];
      const label = this._pageLabels && this._pageLabels[i];
      pageView.setPageLabel(label);
    }
  }

  _resetView() {
    this._pages = [];
    this._currentPageNumber = 1;
    this._currentScale = UNKNOWN_SCALE;
    this._currentScaleValue = null;
    this._pageLabels = null;
    this._buffer = new PDFPageViewBuffer(DEFAULT_CACHE_SIZE);
    this._location = null;
    this._pagesRotation = 0;
    this._pagesRequests = new WeakMap();
    this._pageViewsReady = false;
    this._scrollMode = ScrollMode.VERTICAL;
    this._spreadMode = SpreadMode.NONE;

    if (this._onBeforeDraw) {
      this.eventBus.off("pagerender", this._onBeforeDraw);
      this._onBeforeDraw = null;
    }
    if (this._onAfterDraw) {
      this.eventBus.off("pagerendered", this._onAfterDraw);
      this._onAfterDraw = null;
    }
    // Remove the pages from the DOM...
    this.viewer.textContent = "";
    // ... and reset the Scroll mode CSS class(es) afterwards.
    this._updateScrollMode();
  }

  _scrollUpdate() {
    if (this.pagesCount === 0) {
      return;
    }
    this.update();
  }

  _scrollIntoView({ pageDiv, pageSpot = null, pageNumber = null }) {
    scrollIntoView(pageDiv, pageSpot);
  }

  _setScaleUpdatePages(newScale, newValue, noScroll = false, preset = false) {
    this._currentScaleValue = newValue.toString();

    if (isSameScale(this._currentScale, newScale)) {
      if (preset) {
        this.eventBus.dispatch("scalechanging", {
          source: this,
          scale: newScale,
          presetValue: newValue,
        });
      }
      return;
    }

    for (let i = 0, ii = this._pages.length; i < ii; i++) {
      this._pages[i].update(newScale);
    }
    this._currentScale = newScale;

    if (!noScroll) {
      let page = this._currentPageNumber,
        dest;
      if (
        this._location &&
        !(this.isInPresentationMode || this.isChangingPresentationMode)
      ) {
        page = this._location.pageNumber;
        dest = [
          null,
          { name: "XYZ" },
          this._location.left,
          this._location.top,
          null,
        ];
      }
      this.scrollPageIntoView({
        pageNumber: page,
        destArray: dest,
        allowNegativeOffset: true,
      });
    }

    this.eventBus.dispatch("scalechanging", {
      source: this,
      scale: newScale,
      presetValue: preset ? newValue : undefined,
    });

    if (this.defaultRenderingQueue) {
      this.update();
    }
  }

  _setScale(value, noScroll = false) {
    let scale = parseFloat(value);

    if (scale > 0) {
      this._setScaleUpdatePages(scale, value, noScroll, /* preset = */ false);
    } else {
      const currentPage = this._pages[this._currentPageNumber - 1];
      if (!currentPage) {
        return;
      }
      const noPadding = this.isInPresentationMode || this.removePageBorders;
      let hPadding = noPadding ? 0 : SCROLLBAR_PADDING;
      let vPadding = noPadding ? 0 : VERTICAL_PADDING;

      if (!noPadding && this._isScrollModeHorizontal) {
        [hPadding, vPadding] = [vPadding, hPadding]; // Swap the padding values.
      }
      const pageWidthScale =
        ((this.container.clientWidth - hPadding) / currentPage.width) *
        currentPage.scale;
      const pageHeightScale =
        ((this.container.clientHeight - vPadding) / currentPage.height) *
        currentPage.scale;
      switch (value) {
        case "page-actual":
          scale = 1;
          break;
        case "page-width":
          scale = pageWidthScale;
          break;
        case "page-height":
          scale = pageHeightScale;
          break;
        case "page-fit":
          scale = Math.min(pageWidthScale, pageHeightScale);
          break;
        case "auto":
          // For pages in landscape mode, fit the page height to the viewer
          // *unless* the page would thus become too wide to fit horizontally.
          const horizontalScale = isPortraitOrientation(currentPage)
            ? pageWidthScale
            : Math.min(pageHeightScale, pageWidthScale);
          scale = Math.min(MAX_AUTO_SCALE, horizontalScale);
          break;
        default:
          console.error(
            `${this._name}._setScale: "${value}" is an unknown zoom value.`
          );
          return;
      }
      this._setScaleUpdatePages(scale, value, noScroll, /* preset = */ true);
    }
  }

  /**
   * Refreshes page view: scrolls to the current page and updates the scale.
   * @private
   */
  _resetCurrentPageView() {
    if (this.isInPresentationMode) {
      // Fixes the case when PDF has different page sizes.
      this._setScale(this._currentScaleValue, true);
    }

    const pageView = this._pages[this._currentPageNumber - 1];
    this._scrollIntoView({ pageDiv: pageView.div });
  }

  /**
   * @typedef ScrollPageIntoViewParameters
   * @property {number} pageNumber - The page number.
   * @property {Array} [destArray] - The original PDF destination array, in the
   *   format: <page-ref> </XYZ|/FitXXX> <args..>
   * @property {boolean} [allowNegativeOffset] - Allow negative page offsets.
   *   The default value is `false`.
   */

  /**
   * Scrolls page into view.
   * @param {ScrollPageIntoViewParameters} params
   */
  scrollPageIntoView({
    pageNumber,
    destArray = null,
    allowNegativeOffset = false,
  }) {
    if (!this.pdfDocument) {
      return;
    }
    const pageView =
      Number.isInteger(pageNumber) && this._pages[pageNumber - 1];
    if (!pageView) {
      console.error(
        `${this._name}.scrollPageIntoView: ` +
          `"${pageNumber}" is not a valid pageNumber parameter.`
      );
      return;
    }

    if (this.isInPresentationMode || !destArray) {
      this._setCurrentPageNumber(pageNumber, /* resetCurrentPageView = */ true);
      return;
    }
    let x = 0,
      y = 0;
    let width = 0,
      height = 0,
      widthScale,
      heightScale;
    const changeOrientation = pageView.rotation % 180 === 0 ? false : true;
    const pageWidth =
      (changeOrientation ? pageView.height : pageView.width) /
      pageView.scale /
      CSS_UNITS;
    const pageHeight =
      (changeOrientation ? pageView.width : pageView.height) /
      pageView.scale /
      CSS_UNITS;
    let scale = 0;
    switch (destArray[1].name) {
      case "XYZ":
        x = destArray[2];
        y = destArray[3];
        scale = destArray[4];
        // If x and/or y coordinates are not supplied, default to
        // _top_ left of the page (not the obvious bottom left,
        // since aligning the bottom of the intended page with the
        // top of the window is rarely helpful).
        x = x !== null ? x : 0;
        y = y !== null ? y : pageHeight;
        break;
      case "Fit":
      case "FitB":
        scale = "page-fit";
        break;
      case "FitH":
      case "FitBH":
        y = destArray[2];
        scale = "page-width";
        // According to the PDF spec, section 12.3.2.2, a `null` value in the
        // parameter should maintain the position relative to the new page.
        if (y === null && this._location) {
          x = this._location.left;
          y = this._location.top;
        }
        break;
      case "FitV":
      case "FitBV":
        x = destArray[2];
        width = pageWidth;
        height = pageHeight;
        scale = "page-height";
        break;
      case "FitR":
        x = destArray[2];
        y = destArray[3];
        width = destArray[4] - x;
        height = destArray[5] - y;
        const hPadding = this.removePageBorders ? 0 : SCROLLBAR_PADDING;
        const vPadding = this.removePageBorders ? 0 : VERTICAL_PADDING;

        widthScale =
          (this.container.clientWidth - hPadding) / width / CSS_UNITS;
        heightScale =
          (this.container.clientHeight - vPadding) / height / CSS_UNITS;
        scale = Math.min(Math.abs(widthScale), Math.abs(heightScale));
        break;
      default:
        console.error(
          `${this._name}.scrollPageIntoView: ` +
            `"${destArray[1].name}" is not a valid destination type.`
        );
        return;
    }

    if (scale && scale !== this._currentScale) {
      this.currentScaleValue = scale;
    } else if (this._currentScale === UNKNOWN_SCALE) {
      this.currentScaleValue = DEFAULT_SCALE_VALUE;
    }

    if (scale === "page-fit" && !destArray[4]) {
      this._scrollIntoView({
        pageDiv: pageView.div,
        pageNumber,
      });
      return;
    }

    const boundingRect = [
      pageView.viewport.convertToViewportPoint(x, y),
      pageView.viewport.convertToViewportPoint(x + width, y + height),
    ];
    let left = Math.min(boundingRect[0][0], boundingRect[1][0]);
    let top = Math.min(boundingRect[0][1], boundingRect[1][1]);

    if (!allowNegativeOffset) {
      // Some bad PDF generators will create destinations with e.g. top values
      // that exceeds the page height. Ensure that offsets are not negative,
      // to prevent a previous page from becoming visible (fixes bug 874482).
      left = Math.max(left, 0);
      top = Math.max(top, 0);
    }
    this._scrollIntoView({
      pageDiv: pageView.div,
      pageSpot: { left, top },
      pageNumber,
    });
  }

  _updateLocation(firstPage) {
    const currentScale = this._currentScale;
    const currentScaleValue = this._currentScaleValue;
    const normalizedScaleValue =
      parseFloat(currentScaleValue) === currentScale
        ? Math.round(currentScale * 10000) / 100
        : currentScaleValue;

    const pageNumber = firstPage.id;
    let pdfOpenParams = "#page=" + pageNumber;
    pdfOpenParams += "&zoom=" + normalizedScaleValue;
    const currentPageView = this._pages[pageNumber - 1];
    const container = this.container;
    const topLeft = currentPageView.getPagePoint(
      container.scrollLeft - firstPage.x,
      container.scrollTop - firstPage.y
    );
    const intLeft = Math.round(topLeft[0]);
    const intTop = Math.round(topLeft[1]);
    pdfOpenParams += "," + intLeft + "," + intTop;

    this._location = {
      pageNumber,
      scale: normalizedScaleValue,
      top: intTop,
      left: intLeft,
      rotation: this._pagesRotation,
      pdfOpenParams,
    };
  }

  _updateHelper(visiblePages) {
    throw new Error("Not implemented: _updateHelper");
  }

  update() {
    const visible = this._getVisiblePages();
    const visiblePages = visible.views,
      numVisiblePages = visiblePages.length;

    if (numVisiblePages === 0) {
      return;
    }
    const newCacheSize = Math.max(DEFAULT_CACHE_SIZE, 2 * numVisiblePages + 1);
    this._buffer.resize(newCacheSize, visiblePages);

    this.renderingQueue.renderHighestPriority(visible);

    this._updateHelper(visiblePages); // Run any class-specific update code.

    this._updateLocation(visible.first);
    this.eventBus.dispatch("updateviewarea", {
      source: this,
      location: this._location,
    });
  }

  containsElement(element) {
    return this.container.contains(element);
  }

  focus() {
    this.container.focus();
  }

  get _isScrollModeHorizontal() {
    // Used to ensure that pre-rendering of the next/previous page works
    // correctly, since Scroll/Spread modes are ignored in Presentation Mode.
    return this.isInPresentationMode
      ? false
      : this._scrollMode === ScrollMode.HORIZONTAL;
  }

  get isInPresentationMode() {
    return this.presentationModeState === PresentationModeState.FULLSCREEN;
  }

  get isChangingPresentationMode() {
    return this.presentationModeState === PresentationModeState.CHANGING;
  }

  get isHorizontalScrollbarEnabled() {
    return this.isInPresentationMode
      ? false
      : this.container.scrollWidth > this.container.clientWidth;
  }

  get isVerticalScrollbarEnabled() {
    return this.isInPresentationMode
      ? false
      : this.container.scrollHeight > this.container.clientHeight;
  }

  /**
   * Helper method for `this._getVisiblePages`. Should only ever be used when
   * the viewer can only display a single page at a time, for example in:
   *  - `PDFSinglePageViewer`.
   *  - `PDFViewer` with Presentation Mode active.
   */
  _getCurrentVisiblePage() {
    if (!this.pagesCount) {
      return { views: [] };
    }
    const pageView = this._pages[this._currentPageNumber - 1];
    // NOTE: Compute the `x` and `y` properties of the current view,
    // since `this._updateLocation` depends of them being available.
    const element = pageView.div;

    const view = {
      id: pageView.id,
      x: element.offsetLeft + element.clientLeft,
      y: element.offsetTop + element.clientTop,
      view: pageView,
    };
    return { first: view, last: view, views: [view] };
  }

  _getVisiblePages() {
    return getVisibleElements(
      this.container,
      this._pages,
      true,
      this._isScrollModeHorizontal
    );
  }

  /**
   * @param {number} pageNumber
   */
  isPageVisible(pageNumber) {
    if (!this.pdfDocument) {
      return false;
    }
    if (pageNumber < 1 || pageNumber > this.pagesCount) {
      console.error(
        `${this._name}.isPageVisible: "${pageNumber}" is out of bounds.`
      );
      return false;
    }
    return this._getVisiblePages().views.some(function(view) {
      return view.id === pageNumber;
    });
  }

  cleanup() {
    for (let i = 0, ii = this._pages.length; i < ii; i++) {
      if (
        this._pages[i] &&
        this._pages[i].renderingState !== RenderingStates.FINISHED
      ) {
        this._pages[i].reset();
      }
    }
  }

  /**
   * @private
   */
  _cancelRendering() {
    for (let i = 0, ii = this._pages.length; i < ii; i++) {
      if (this._pages[i]) {
        this._pages[i].cancelRendering();
      }
    }
  }

  /**
   * @param {PDFPageView} pageView
   * @returns {Promise} Returns a promise containing a {PDFPageProxy} object.
   * @private
   */
  _ensurePdfPageLoaded(pageView) {
    if (pageView.pdfPage) {
      return Promise.resolve(pageView.pdfPage);
    }
    if (this._pagesRequests.has(pageView)) {
      return this._pagesRequests.get(pageView);
    }
    const promise = this.pdfDocument
      .getPage(pageView.id)
      .then(pdfPage => {
        if (!pageView.pdfPage) {
          pageView.setPdfPage(pdfPage);
        }
        this._pagesRequests.delete(pageView);
        return pdfPage;
      })
      .catch(reason => {
        console.error("Unable to get page for page view", reason);
        // Page error -- there is nothing that can be done.
        this._pagesRequests.delete(pageView);
      });
    this._pagesRequests.set(pageView, promise);
    return promise;
  }

  forceRendering(currentlyVisiblePages) {
    const visiblePages = currentlyVisiblePages || this._getVisiblePages();
    const scrollAhead = this._isScrollModeHorizontal
      ? this.scroll.right
      : this.scroll.down;
    const pageView = this.renderingQueue.getHighestPriority(
      visiblePages,
      this._pages,
      scrollAhead
    );
    if (pageView) {
      this._ensurePdfPageLoaded(pageView).then(() => {
        this.renderingQueue.renderView(pageView);
      });
      return true;
    }
    return false;
  }

  /**
   * @param {HTMLDivElement} textLayerDiv
   * @param {number} pageIndex
   * @param {PageViewport} viewport
   * @returns {TextLayerBuilder}
   */
  createTextLayerBuilder(
    textLayerDiv,
    pageIndex,
    viewport,
    enhanceTextSelection = false
  ) {
    return new TextLayerBuilder({
      textLayerDiv,
      eventBus: this.eventBus,
      pageIndex,
      viewport,
      findController: this.isInPresentationMode ? null : this.findController,
      enhanceTextSelection: this.isInPresentationMode
        ? false
        : enhanceTextSelection,
    });
  }

  /**
   * @param {HTMLDivElement} pageDiv
   * @param {PDFPage} pdfPage
   * @param {string} [imageResourcesPath] - Path for image resources, mainly
   *   for annotation icons. Include trailing slash.
   * @param {boolean} renderInteractiveForms
   * @param {IL10n} l10n
   * @returns {AnnotationLayerBuilder}
   */
  createAnnotationLayerBuilder(
    pageDiv,
    pdfPage,
    imageResourcesPath = "",
    renderInteractiveForms = false,
    l10n = NullL10n
  ) {
    return new AnnotationLayerBuilder({
      pageDiv,
      pdfPage,
      imageResourcesPath,
      renderInteractiveForms,
      linkService: this.linkService,
      downloadManager: this.downloadManager,
      l10n,
    });
  }

  /**
   * @type {boolean} Whether all pages of the PDF document have identical
   *   widths and heights.
   */
  get hasEqualPageSizes() {
    const firstPageView = this._pages[0];
    for (let i = 1, ii = this._pages.length; i < ii; ++i) {
      const pageView = this._pages[i];
      if (
        pageView.width !== firstPageView.width ||
        pageView.height !== firstPageView.height
      ) {
        return false;
      }
    }
    return true;
  }

  /**
   * Returns sizes of the pages.
   * @returns {Array} Array of objects with width/height/rotation fields.
   */
  getPagesOverview() {
    const pagesOverview = this._pages.map(function(pageView) {
      const viewport = pageView.pdfPage.getViewport({ scale: 1 });
      return {
        width: viewport.width,
        height: viewport.height,
        rotation: viewport.rotation,
      };
    });
    if (!this.enablePrintAutoRotate) {
      return pagesOverview;
    }
    const isFirstPagePortrait = isPortraitOrientation(pagesOverview[0]);
    return pagesOverview.map(function(size) {
      if (isFirstPagePortrait === isPortraitOrientation(size)) {
        return size;
      }
      return {
        width: size.height,
        height: size.width,
        rotation: (size.rotation + 90) % 360,
      };
    });
  }

  /**
   * @type {number} One of the values in {ScrollMode}.
   */
  get scrollMode() {
    return this._scrollMode;
  }

  /**
   * @param {number} mode - The direction in which the document pages should be
   *   laid out within the scrolling container.
   *   The constants from {ScrollMode} should be used.
   */
  set scrollMode(mode) {
    if (this._scrollMode === mode) {
      return; // The Scroll mode didn't change.
    }
    if (!isValidScrollMode(mode)) {
      throw new Error(`Invalid scroll mode: ${mode}`);
    }
    this._scrollMode = mode;
    this.eventBus.dispatch("scrollmodechanged", { source: this, mode });

    this._updateScrollMode(/* pageNumber = */ this._currentPageNumber);
  }

  _updateScrollMode(pageNumber = null) {
    const scrollMode = this._scrollMode,
      viewer = this.viewer;

    viewer.classList.toggle(
      "scrollHorizontal",
      scrollMode === ScrollMode.HORIZONTAL
    );
    viewer.classList.toggle("scrollWrapped", scrollMode === ScrollMode.WRAPPED);

    if (!this.pdfDocument || !pageNumber) {
      return;
    }
    // Non-numeric scale values can be sensitive to the scroll orientation.
    // Call this before re-scrolling to the current page, to ensure that any
    // changes in scale don't move the current page.
    if (this._currentScaleValue && isNaN(this._currentScaleValue)) {
      this._setScale(this._currentScaleValue, true);
    }
    this._setCurrentPageNumber(pageNumber, /* resetCurrentPageView = */ true);
    this.update();
  }

  /**
   * @type {number} One of the values in {SpreadMode}.
   */
  get spreadMode() {
    return this._spreadMode;
  }

  /**
   * @param {number} mode - Group the pages in spreads, starting with odd- or
   *   even-number pages (unless `SpreadMode.NONE` is used).
   *   The constants from {SpreadMode} should be used.
   */
  set spreadMode(mode) {
    if (this._spreadMode === mode) {
      return; // The Spread mode didn't change.
    }
    if (!isValidSpreadMode(mode)) {
      throw new Error(`Invalid spread mode: ${mode}`);
    }
    this._spreadMode = mode;
    this.eventBus.dispatch("spreadmodechanged", { source: this, mode });

    this._updateSpreadMode(/* pageNumber = */ this._currentPageNumber);
  }

  _updateSpreadMode(pageNumber = null) {
    if (!this.pdfDocument) {
      return;
    }
    const viewer = this.viewer,
      pages = this._pages;
    // Temporarily remove all the pages from the DOM.
    viewer.textContent = "";

    if (this._spreadMode === SpreadMode.NONE) {
      for (let i = 0, iMax = pages.length; i < iMax; ++i) {
        viewer.appendChild(pages[i].div);
      }
    } else {
      const parity = this._spreadMode - 1;
      let spread = null;
      for (let i = 0, iMax = pages.length; i < iMax; ++i) {
        if (spread === null) {
          spread = document.createElement("div");
          spread.className = "spread";
          viewer.appendChild(spread);
        } else if (i % 2 === parity) {
          spread = spread.cloneNode(false);
          viewer.appendChild(spread);
        }
        spread.appendChild(pages[i].div);
      }
    }

    if (!pageNumber) {
      return;
    }
    this._setCurrentPageNumber(pageNumber, /* resetCurrentPageView = */ true);
    this.update();
  }
}

export { BaseViewer };