Render html as png #43

package.json

@@ -13,6 +13,7 @@
   },
   "dependencies": {
     "@types/async": "~2.0.49",
+    "@types/async-lock": "^1.1.0",
     "@types/bcrypt": "~2.0.0",
     "@types/express": "^4.0.34",
     "@types/express-promise-router": "^2.0.0",
@@ -29,6 +30,7 @@
     "@types/sinon": "^5.0.1",
     "assert-rejects": "^0.1.1",
     "async": "~2.0.1",
+    "async-lock": "^1.1.3",
     "bcrypt": "~2.0.1",
     "body-parser": "~1.18.3",
     "cookie-parser": "~1.4.3",

src/api/routes/TimetableRouter.ts

@@ -3,6 +3,7 @@ var router = ExpressPromiseRouter();
 
 import TimetableService = require('@app/core/timetable/TimetableService');
 import TimetableLectureService = require('@app/core/timetable/TimetableLectureService');
+import TimetableImageRenderService = require('@app/core/timetable/TimetableImageRenderService');
 import User from '@app/core/user/model/User';
 import * as log4js from 'log4js';
 import DuplicateTimetableTitleError from '@app/core/timetable/error/DuplicateTimetableTitleError';
@@ -51,6 +52,19 @@ restGet(router, '/:id')(async function(context, req) {
   return result;
 });
 
+router.get('/:id/image', async function(req, res, next) {
+  let context: RequestContext = req['context'];
+  let user:User = context.user;
+
+  let table = await TimetableService.getByMongooseId(user._id, req.params.id);
+  if (!table) {
+    throw new ApiError(404, ErrorCode.TIMETABLE_NOT_FOUND, "timetable not found");
+  }
+  let imageBuffer = await TimetableImageRenderService.renderTimetableAsPng(table, 1920, 1080);
+  res.contentType('image/png');
+  res.send(imageBuffer);
+});
+
 restGet(router, '/:year/:semester')(async function(context, req) {
   let user:User = context.user;
   let result = await TimetableService.getBySemester(user._id, req.params.year, req.params.semester);

src/core/nightmare/NightmareService.ts

@@ -0,0 +1,30 @@
+import Nightmare = require('nightmare');
+import AsyncLock = require('async-lock');
+
+let nm = Nightmare({
+    show: false,
+    executionTimeout: 1000,
+    waitTimeout: 1000
+});
+
+let nmLock = new AsyncLock({maxPending : 100, timeout: 5000});
+const NM_LOCK_KEY = "NightmareServiceLock";
+
+function execute<T>(f: (Nightmare) => Promise<T>): Promise<T> {
+    return nmLock.acquire(NM_LOCK_KEY, function() {
+        return f(nm);
+    });
+}
+
+export function renderHtmlAsPng(html: string, width: number, height: number): Promise<Buffer> {
+    return execute(async function(nm) {
+        nm.viewport(width, height);
+        nm.goto("about:blank");
+        await nm.wait(function (html: string){
+            document.body.innerHTML = html;
+            return true;
+        }, html);
+        let buffer: Buffer = await nm.screenshot();
+        return buffer;
+    });
+}

src/core/timetable/TimetableImageRenderService.ts

@@ -0,0 +1,11 @@
+import log4js = require('log4js');
+
+import NightmareService = require('@app/core/nightmare/NightmareService');
+import Timetable from './model/Timetable';
+
+let logger = log4js.getLogger();
+
+export function renderTimetableAsPng(timetable: Timetable, width: number, height: number): Promise<Buffer> {
+    let html = "<p>Timetable title: " + timetable.title + "</p>";
+    return NightmareService.renderHtmlAsPng(html, width, height);
+}