/* Copyright 2012 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 {
  getVisibleElements,
  isValidRotation,
  RenderingStates,
  scrollIntoView,
  watchScroll,
} from "./ui_utils.js";
import { PDFThumbnailView, TempImageFactory } from "./pdf_thumbnail_view.js";

const THUMBNAIL_SCROLL_MARGIN = -19;
const THUMBNAIL_SELECTED_CLASS = "selected";

/**
 * @typedef {Object} PDFThumbnailViewerOptions
 * @property {HTMLDivElement} container - The container for the thumbnail
 *   elements.
 * @property {EventBus} eventBus - The application event bus.
 * @property {IPDFLinkService} linkService - The navigation/linking service.
 * @property {PDFRenderingQueue} renderingQueue - The rendering queue object.
 * @property {IL10n} l10n - Localization service.
 */

/**
 * Viewer control to display thumbnails for pages in a PDF document.
 */
class PDFThumbnailViewer {
  /**
   * @param {PDFThumbnailViewerOptions} options
   */
  constructor({ container, eventBus, linkService, renderingQueue, l10n }) {
    this.container = container;
    this.linkService = linkService;
    this.renderingQueue = renderingQueue;
    this.l10n = l10n;

    this.scroll = watchScroll(this.container, this._scrollUpdated.bind(this));
    this._resetView();

    eventBus._on("optionalcontentconfigchanged", () => {
      // Ensure that the thumbnails always render with the *default* optional
      // content configuration.
      this._setImageDisabled = true;
    });
  }

  /**
   * @private
   */
  _scrollUpdated() {
    this.renderingQueue.renderHighestPriority();
  }

  getThumbnail(index) {
    return this._thumbnails[index];
  }

  /**
   * @private
   */
  _getVisibleThumbs() {
    return getVisibleElements({
      scrollEl: this.container,
      views: this._thumbnails,
    });
  }

  scrollThumbnailIntoView(pageNumber) {
    if (!this.pdfDocument) {
      return;
    }
    const thumbnailView = this._thumbnails[pageNumber - 1];

    if (!thumbnailView) {
      console.error('scrollThumbnailIntoView: Invalid "pageNumber" parameter.');
      return;
    }

    if (pageNumber !== this._currentPageNumber) {
      const prevThumbnailView = this._thumbnails[this._currentPageNumber - 1];
      // Remove the highlight from the previous thumbnail...
      prevThumbnailView.div.classList.remove(THUMBNAIL_SELECTED_CLASS);
      // ... and add the highlight to the new thumbnail.
      thumbnailView.div.classList.add(THUMBNAIL_SELECTED_CLASS);
    }
    const { first, last, views } = this._getVisibleThumbs();

    // If the thumbnail isn't currently visible, scroll it into view.
    if (views.length > 0) {
      let shouldScroll = false;
      if (pageNumber <= first.id || pageNumber >= last.id) {
        shouldScroll = true;
      } else {
        for (const { id, percent } of views) {
          if (id !== pageNumber) {
            continue;
          }
          shouldScroll = percent < 100;
          break;
        }
      }
      if (shouldScroll) {
        scrollIntoView(thumbnailView.div, { top: THUMBNAIL_SCROLL_MARGIN });
      }
    }

    this._currentPageNumber = pageNumber;
  }

  get pagesRotation() {
    return this._pagesRotation;
  }

  set pagesRotation(rotation) {
    if (!isValidRotation(rotation)) {
      throw new Error("Invalid thumbnails rotation angle.");
    }
    if (!this.pdfDocument) {
      return;
    }
    if (this._pagesRotation === rotation) {
      return; // The rotation didn't change.
    }
    this._pagesRotation = rotation;

    const updateArgs = { rotation };
    for (const thumbnail of this._thumbnails) {
      thumbnail.update(updateArgs);
    }
  }

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

  /**
   * @private
   */
  _resetView() {
    this._thumbnails = [];
    this._currentPageNumber = 1;
    this._pageLabels = null;
    this._pagesRotation = 0;
    this._optionalContentConfigPromise = null;
    this._setImageDisabled = false;

    // Remove the thumbnails from the DOM.
    this.container.textContent = "";
  }

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

    this.pdfDocument = pdfDocument;
    if (!pdfDocument) {
      return;
    }
    const firstPagePromise = pdfDocument.getPage(1);
    const optionalContentConfigPromise = pdfDocument.getOptionalContentConfig();

    firstPagePromise
    .then(firstPdfPage => {
      this._optionalContentConfigPromise = optionalContentConfigPromise;

      const pagesCount = pdfDocument.numPages;
      const viewport = firstPdfPage.getViewport({ scale: 1 });
      const checkSetImageDisabled = () => {
        return this._setImageDisabled;
      };

      for (let pageNum = 1; pageNum <= pagesCount; ++pageNum) {
        const thumbnail = new PDFThumbnailView({
          container: this.container,
          id: pageNum,
          defaultViewport: viewport.clone(),
          optionalContentConfigPromise,
          linkService: this.linkService,
          renderingQueue: this.renderingQueue,
          checkSetImageDisabled,
          l10n: this.l10n,
        });
        this._thumbnails.push(thumbnail);
      }
      // 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 firstThumbnailView = this._thumbnails[0];
      if (firstThumbnailView) {
        firstThumbnailView.setPdfPage(firstPdfPage);
      }

      // Ensure that the current thumbnail is always highlighted on load.
      const thumbnailView = this._thumbnails[this._currentPageNumber - 1];
      thumbnailView.div.classList.add(THUMBNAIL_SELECTED_CLASS);
    })
    .catch(reason => {
      console.error("Unable to initialize thumbnail viewer", reason);
    });
  }

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

  /**
   * @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("PDFThumbnailViewer_setPageLabels: Invalid page labels.");
    } else {
      this._pageLabels = labels;
    }
    // Update all the `PDFThumbnailView` instances.
    for (let i = 0, ii = this._thumbnails.length; i < ii; i++) {
      this._thumbnails[i].setPageLabel(this._pageLabels?.[i] ?? null);
    }
  }

  /**
   * @param {PDFThumbnailView} thumbView
   * @returns {Promise<PDFPageProxy | null>}
   */
  async #ensurePdfPageLoaded(thumbView) {
    if (thumbView.pdfPage) {
      return thumbView.pdfPage;
    }
    try {
      const pdfPage = await this.pdfDocument.getPage(thumbView.id);
      if (!thumbView.pdfPage) {
        thumbView.setPdfPage(pdfPage);
      }
      return pdfPage;
    } catch (reason) {
      console.error("Unable to get page for thumb view", reason);
      return null; // Page error -- there is nothing that can be done.
    }
  }

  #getScrollAhead(visible) {
    if (visible.first?.id === 1) {
      return true;
    } else if (visible.last?.id === this._thumbnails.length) {
      return false;
    }
    return this.scroll.down;
  }

  forceRendering() {
    const visibleThumbs = this._getVisibleThumbs();
    const scrollAhead = this.#getScrollAhead(visibleThumbs);
    const thumbView = this.renderingQueue.getHighestPriority(
      visibleThumbs,
      this._thumbnails,
      scrollAhead
    );
    if (thumbView) {
      this.#ensurePdfPageLoaded(thumbView).then(() => {
        this.renderingQueue.renderView(thumbView);
      });
      return true;
    }
    return false;
  }
}

export { PDFThumbnailViewer };
