/* -*- Mode: Java; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set shiftwidth=2 tabstop=2 autoindent cindent expandtab: */
/* 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.
 */
/* globals mozL10n, RenderingStates, Promise, scrollIntoView, PDFPageSource,
           watchScroll, getVisibleElements */

'use strict';

var THUMBNAIL_SCROLL_MARGIN = -19;

/**
 * @constructor
 * @param container
 * @param id
 * @param defaultViewport
 * @param linkService
 * @param renderingQueue
 * @param pageSource
 *
 * @implements {IRenderableView}
 */
var ThumbnailView = function thumbnailView(container, id, defaultViewport,
                                           linkService, renderingQueue,
                                           pageSource) {
  var anchor = document.createElement('a');
  anchor.href = linkService.getAnchorUrl('#page=' + id);
  anchor.title = mozL10n.get('thumb_page_title', {page: id}, 'Page {{page}}');
  anchor.onclick = function stopNavigation() {
    linkService.page = id;
    return false;
  };

  this.pdfPage = undefined;
  this.viewport = defaultViewport;
  this.pdfPageRotate = defaultViewport.rotation;

  this.rotation = 0;
  this.pageWidth = this.viewport.width;
  this.pageHeight = this.viewport.height;
  this.pageRatio = this.pageWidth / this.pageHeight;
  this.id = id;
  this.renderingId = 'thumbnail' + id;

  this.canvasWidth = 98;
  this.canvasHeight = this.canvasWidth / this.pageWidth * this.pageHeight;
  this.scale = (this.canvasWidth / this.pageWidth);

  var div = this.el = document.createElement('div');
  div.id = 'thumbnailContainer' + id;
  div.className = 'thumbnail';

  if (id === 1) {
    // Highlight the thumbnail of the first page when no page number is
    // specified (or exists in cache) when the document is loaded.
    div.classList.add('selected');
  }

  var ring = document.createElement('div');
  ring.className = 'thumbnailSelectionRing';
  ring.style.width = this.canvasWidth + 'px';
  ring.style.height = this.canvasHeight + 'px';

  div.appendChild(ring);
  anchor.appendChild(div);
  container.appendChild(anchor);

  this.hasImage = false;
  this.renderingState = RenderingStates.INITIAL;
  this.renderingQueue = renderingQueue;
  this.pageSource = pageSource;

  this.setPdfPage = function thumbnailViewSetPdfPage(pdfPage) {
    this.pdfPage = pdfPage;
    this.pdfPageRotate = pdfPage.rotate;
    var totalRotation = (this.rotation + this.pdfPageRotate) % 360;
    this.viewport = pdfPage.getViewport(1, totalRotation);
    this.update();
  };

  this.update = function thumbnailViewUpdate(rotation) {
    if (rotation !== undefined) {
      this.rotation = rotation;
    }
    var totalRotation = (this.rotation + this.pdfPageRotate) % 360;
    this.viewport = this.viewport.clone({
      scale: 1,
      rotation: totalRotation
    });
    this.pageWidth = this.viewport.width;
    this.pageHeight = this.viewport.height;
    this.pageRatio = this.pageWidth / this.pageHeight;

    this.canvasHeight = this.canvasWidth / this.pageWidth * this.pageHeight;
    this.scale = (this.canvasWidth / this.pageWidth);

    div.removeAttribute('data-loaded');
    ring.textContent = '';
    ring.style.width = this.canvasWidth + 'px';
    ring.style.height = this.canvasHeight + 'px';

    this.hasImage = false;
    this.renderingState = RenderingStates.INITIAL;
    this.resume = null;
  };

  this.getPageDrawContext = function thumbnailViewGetPageDrawContext() {
    var canvas = document.createElement('canvas');
    canvas.id = 'thumbnail' + id;

    canvas.width = this.canvasWidth;
    canvas.height = this.canvasHeight;
    canvas.className = 'thumbnailImage';
    canvas.setAttribute('aria-label', mozL10n.get('thumb_page_canvas',
      {page: id}, 'Thumbnail of Page {{page}}'));

    div.setAttribute('data-loaded', true);

    ring.appendChild(canvas);

    var ctx = canvas.getContext('2d');
    ctx.save();
    ctx.fillStyle = 'rgb(255, 255, 255)';
    ctx.fillRect(0, 0, this.canvasWidth, this.canvasHeight);
    ctx.restore();
    return ctx;
  };

  this.drawingRequired = function thumbnailViewDrawingRequired() {
    return !this.hasImage;
  };

  this.draw = function thumbnailViewDraw(callback) {
    if (!this.pdfPage) {
      var promise = this.pageSource.getPage(this.id);
      promise.then(function(pdfPage) {
        this.setPdfPage(pdfPage);
        this.draw(callback);
      }.bind(this));
      return;
    }

    if (this.renderingState !== RenderingStates.INITIAL) {
      console.error('Must be in new state before drawing');
    }

    this.renderingState = RenderingStates.RUNNING;
    if (this.hasImage) {
      callback();
      return;
    }

    var self = this;
    var ctx = this.getPageDrawContext();
    var drawViewport = this.viewport.clone({ scale: this.scale });
    var renderContext = {
      canvasContext: ctx,
      viewport: drawViewport,
      continueCallback: function(cont) {
        if (!self.renderingQueue.isHighestPriority(self)) {
          self.renderingState = RenderingStates.PAUSED;
          self.resume = function() {
            self.renderingState = RenderingStates.RUNNING;
            cont();
          };
          return;
        }
        cont();
      }
    };
    this.pdfPage.render(renderContext).promise.then(
      function pdfPageRenderCallback() {
        self.renderingState = RenderingStates.FINISHED;
        callback();
      },
      function pdfPageRenderError(error) {
        self.renderingState = RenderingStates.FINISHED;
        callback();
      }
    );
    this.hasImage = true;
  };

  function getTempCanvas(width, height) {
    var tempCanvas = ThumbnailView.tempImageCache;
    if (!tempCanvas) {
      tempCanvas = document.createElement('canvas');
      ThumbnailView.tempImageCache = tempCanvas;
    }
    tempCanvas.width = width;
    tempCanvas.height = height;
    return tempCanvas;
  }

  this.setImage = function thumbnailViewSetImage(img) {
    if (!this.pdfPage) {
      var promise = this.pageSource.getPage();
      promise.then(function(pdfPage) {
        this.setPdfPage(pdfPage);
        this.setImage(img);
      }.bind(this));
      return;
    }
    if (this.hasImage || !img) {
      return;
    }
    this.renderingState = RenderingStates.FINISHED;
    var ctx = this.getPageDrawContext();
    var canvas = ctx.canvas;

    if (img.width <= 2 * canvas.width) {
      ctx.drawImage(img, 0, 0, img.width, img.height,
                    0, 0, canvas.width, canvas.height);
    } else {
      // drawImage does an awful job of rescaling the image, doing it gradually
      var MAX_NUM_SCALING_STEPS = 3;
      var reducedWidth = canvas.width << MAX_NUM_SCALING_STEPS;
      var reducedHeight = canvas.height << MAX_NUM_SCALING_STEPS;
      var reducedImage = getTempCanvas(reducedWidth, reducedHeight);
      var reducedImageCtx = reducedImage.getContext('2d');

      while (reducedWidth > img.width || reducedHeight > img.height) {
        reducedWidth >>= 1;
        reducedHeight >>= 1;
      }
      reducedImageCtx.drawImage(img, 0, 0, img.width, img.height,
                                0, 0, reducedWidth, reducedHeight);
      while (reducedWidth > 2 * canvas.width) {
        reducedImageCtx.drawImage(reducedImage,
                                  0, 0, reducedWidth, reducedHeight,
                                  0, 0, reducedWidth >> 1, reducedHeight >> 1);
        reducedWidth >>= 1;
        reducedHeight >>= 1;
      }
      ctx.drawImage(reducedImage, 0, 0, reducedWidth, reducedHeight,
                    0, 0, canvas.width, canvas.height);
    }

    this.hasImage = true;
  };
};

ThumbnailView.tempImageCache = null;

/**
 * @typedef {Object} PDFThumbnailViewerOptions
 * @property {HTMLDivElement} container - The container for the thumbs elements.
 * @property {IPDFLinkService} linkService - The navigation/linking service.
 * @property {PDFRenderingQueue} renderingQueue - The rendering queue object.
 */

/**
 * Simple viewer control to display thumbs for pages.
 * @class
 */
var PDFThumbnailViewer = (function pdfThumbnailViewer() {
  /**
   * @constructs
   * @param {PDFThumbnailViewerOptions} options
   */
  function PDFThumbnailViewer(options) {
    this.container = options.container;
    this.renderingQueue = options.renderingQueue;
    this.linkService = options.linkService;

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

  PDFThumbnailViewer.prototype = {
    _scrollUpdated: function PDFThumbnailViewer_scrollUpdated() {
      this.renderingQueue.renderHighestPriority();
    },

    getThumbnail: function PDFThumbnailViewer_getThumbnail(index) {
      return this.thumbnails[index];
    },

    _getVisibleThumbs: function PDFThumbnailViewer_getVisibleThumbs() {
      return getVisibleElements(this.container, this.thumbnails);
    },

    scrollThumbnailIntoView: function (page) {
      var selected = document.querySelector('.thumbnail.selected');
      if (selected) {
        selected.classList.remove('selected');
      }
      var thumbnail = document.getElementById('thumbnailContainer' + page);
      thumbnail.classList.add('selected');
      var visibleThumbs = this._getVisibleThumbs();
      var numVisibleThumbs = visibleThumbs.views.length;

      // If the thumbnail isn't currently visible, scroll it into view.
      if (numVisibleThumbs > 0) {
        var first = visibleThumbs.first.id;
        // Account for only one thumbnail being visible.
        var last = (numVisibleThumbs > 1 ? visibleThumbs.last.id : first);
        if (page <= first || page >= last) {
          scrollIntoView(thumbnail, { top: THUMBNAIL_SCROLL_MARGIN });
        }
      }
    },

    get pagesRotation() {
      return this._pagesRotation;
    },

    set pagesRotation(rotation) {
      this._pagesRotation = rotation;
      for (var i = 0, l = this.thumbnails.length; i < l; i++) {
        var thumb = this.thumbnails[i];
        thumb.update(rotation);
      }
    },

    cleanup: function PDFThumbnailViewer_cleanup() {
      ThumbnailView.tempImageCache = null;
    },

    _resetView: function () {
      this.thumbnails = [];
      this._pagesRotation = 0;
    },

    setDocument: function (pdfDocument) {
      if (this.pdfDocument) {
        // cleanup of the elements and views
        var thumbsView = this.container;
        while (thumbsView.hasChildNodes()) {
          thumbsView.removeChild(thumbsView.lastChild);
        }
        this._resetView();
      }

      this.pdfDocument = pdfDocument;
      if (!pdfDocument) {
        return Promise.resolve();
      }

      return pdfDocument.getPage(1).then(function (firstPage) {
        var pagesCount = pdfDocument.numPages;
        var viewport = firstPage.getViewport(1.0);
        for (var pageNum = 1; pageNum <= pagesCount; ++pageNum) {
          var pageSource = new PDFPageSource(pdfDocument, pageNum);
          var thumbnail = new ThumbnailView(this.container, pageNum,
                                            viewport.clone(), this.linkService,
                                            this.renderingQueue, pageSource);
          this.thumbnails.push(thumbnail);
        }
      }.bind(this));
    },

    ensureThumbnailVisible:
        function PDFThumbnailViewer_ensureThumbnailVisible(page) {
      // Ensure that the thumbnail of the current page is visible
      // when switching from another view.
      scrollIntoView(document.getElementById('thumbnailContainer' + page));
    },

    forceRendering: function () {
      var visibleThumbs = this._getVisibleThumbs();
      var thumbView = this.renderingQueue.getHighestPriority(visibleThumbs,
                                                             this.thumbnails,
                                                             this.scroll.down);
      if (thumbView) {
        this.renderingQueue.renderView(thumbView);
        return true;
      }
      return false;
    }
  };

  return PDFThumbnailViewer;
})();