/* Copyright 2017 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.
 */

var Canvas = require('canvas');
var assert = require('assert');
var fs = require('fs');

function NodeCanvasFactory() {}
NodeCanvasFactory.prototype = {
  create: function NodeCanvasFactory_create(width, height) {
    assert(width > 0 && height > 0, 'Invalid canvas size');
    var canvas = new Canvas(width, height);
    var context = canvas.getContext('2d');
    return {
      canvas: canvas,
      context: context,
    };
  },

  reset: function NodeCanvasFactory_reset(canvasAndContext, width, height) {
    assert(canvasAndContext.canvas, 'Canvas is not specified');
    assert(width > 0 && height > 0, 'Invalid canvas size');
    canvasAndContext.canvas.width = width;
    canvasAndContext.canvas.height = height;
  },

  destroy: function NodeCanvasFactory_destroy(canvasAndContext) {
    assert(canvasAndContext.canvas, 'Canvas is not specified');

    // Zeroing the width and height cause Firefox to release graphics
    // resources immediately, which can greatly reduce memory consumption.
    canvasAndContext.canvas.width = 0;
    canvasAndContext.canvas.height = 0;
    canvasAndContext.canvas = null;
    canvasAndContext.context = null;
  },
};

var pdfjsLib = require('pdfjs-dist');

// Relative path of the PDF file.
var pdfURL = '../../helloworld/helloworld.pdf';

// Read the PDF file into a typed array so PDF.js can load it.
var rawData = new Uint8Array(fs.readFileSync(pdfURL));

// Load the PDF file.
pdfjsLib.getDocument(rawData).then(function (pdfDocument) {
  console.log('# PDF document loaded.');

  // Get the first page.
  pdfDocument.getPage(1).then(function (page) {
    // Render the page on a Node canvas with 100% scale.
    var viewport = page.getViewport(1.0);
    var canvasFactory = new NodeCanvasFactory();
    var canvasAndContext = canvasFactory.create(viewport.width, viewport.height);
    var renderContext = {
      canvasContext: canvasAndContext.context,
      viewport: viewport,
      canvasFactory: canvasFactory
    };

    page.render(renderContext).then(function () {
      // Convert the canvas to an image buffer.
      var image = canvasAndContext.canvas.toBuffer();
      fs.writeFile('output.png', image, function (error) {
        if (error) {
          console.error('Error: ' + error);
        } else {
          console.log('Finished converting first page of PDF file to a PNG image.');
        }
      });
    });
  });
}).catch(function(reason) {
  console.log(reason);
});