Typescript-ify screenshot stitcher code in reporting

package.json

@@ -227,6 +227,8 @@
     "@kbn/plugin-generator": "link:packages/kbn-plugin-generator",
     "@kbn/test": "link:packages/kbn-test",
     "@types/angular": "^1.6.45",
+    "@types/babel-core": "^6.25.5",
+    "@types/bluebird": "^3.1.1",
     "@types/classnames": "^2.2.3",
     "@types/eslint": "^4.16.2",
     "@types/execa": "^0.9.0",

x-pack/package.json

@@ -28,6 +28,7 @@
     "@kbn/plugin-helpers": "link:../packages/kbn-plugin-helpers",
     "@kbn/test": "link:../packages/kbn-test",
     "@types/jest": "^22.2.3",
+    "@types/pngjs": "^3.3.1",
     "abab": "^1.0.4",
     "ansicolors": "0.3.2",
     "aws-sdk": "2.2.33",
@@ -82,6 +83,7 @@
     "@elastic/numeral": "2.3.2",
     "@kbn/datemath": "link:../packages/kbn-datemath",
     "@kbn/ui-framework": "link:../packages/kbn-ui-framework",
+    "@samverschueren/stream-to-observable": "^0.3.0",
     "@slack/client": "^4.2.2",
     "angular-paging": "2.2.1",
     "angular-resource": "1.4.9",
@@ -154,7 +156,6 @@
     "rison-node": "0.3.1",
     "rxjs": "^6.1.0",
     "semver": "5.1.0",
-    "@samverschueren/stream-to-observable": "^0.3.0",
     "styled-components": "2.3.2",
     "tar-fs": "1.13.0",
     "tinycolor2": "1.3.0",

x-pack/plugins/reporting/server/browsers/chromium/driver/index.js

@@ -101,7 +101,7 @@ export class HeadlessChromiumDriver {
           scale: 1
         }
       });
-      this._logger.debug(`captured screenshot clip ${JSON.stringify(screenshotClip)}`);
+      this._logger.debug(`Captured screenshot clip ${JSON.stringify(screenshotClip)}`);
       return data;
     }, this._logger);
   }
@@ -112,6 +112,7 @@ export class HeadlessChromiumDriver {
   }
 
   async setViewport({ width, height, zoom }) {
+    this._logger.debug(`Setting viewport to width: ${width}, height: ${height}, zoom: ${zoom}`);
     const { Emulation } = this._client;
 
     await Emulation.setDeviceMetricsOverride({

x-pack/plugins/reporting/server/browsers/chromium/driver/screenshot_stitcher/combine.ts

@@ -0,0 +1,116 @@
+/*
+ * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
+ * or more contributor license agreements. Licensed under the Elastic License;
+ * you may not use this file except in compliance with the Elastic License.
+ */
+
+// No types found for this package. May want to investigate an alternative with types.
+// @ts-ignore: implicit any for JS file
+import $streamToObservable from '@samverschueren/stream-to-observable';
+import { PNG } from 'pngjs';
+import * as Rx from 'rxjs';
+import { ObservableInput } from 'rxjs';
+import { map, mergeMap, reduce, switchMap, tap, toArray } from 'rxjs/operators';
+import { Logger, Screenshot, Size } from './types';
+
+// if we're only given one screenshot, and it matches the given size
+// we're going to skip the combination and just use it
+const canUseFirstScreenshot = (
+  screenshots: Screenshot[],
+  size: { width: number; height: number }
+) => {
+  if (screenshots.length !== 1) {
+    return false;
+  }
+
+  const firstScreenshot = screenshots[0];
+  return (
+    firstScreenshot.rectangle.width === size.width &&
+    firstScreenshot.rectangle.height === size.height
+  );
+};
+
+/**
+ * Combines the screenshot clips into a single screenshot of size `outputSize`.
+ * @param screenshots - Array of screenshots to combine
+ * @param outputSize - Final output size that the screenshots should match up with
+ * @param logger - logger for extra debug output
+ */
+export function $combine(
+  screenshots: Screenshot[],
+  outputSize: Size,
+  logger: Logger
+): Rx.Observable<string> {
+  logger.debug(
+    `Combining screenshot clips into final, scaled output dimension of ${JSON.stringify(
+      outputSize
+    )}`
+  );
+
+  if (screenshots.length === 0) {
+    return Rx.throwError('Unable to combine 0 screenshots');
+  }
+
+  if (canUseFirstScreenshot(screenshots, outputSize)) {
+    return Rx.of(screenshots[0].data);
+  }
+
+  // Turn the screenshot data into actual PNGs
+  const pngs$ = Rx.from(screenshots).pipe(
+    mergeMap(
+      (screenshot: Screenshot): ObservableInput<PNG> => {
+        const png = new PNG();
+        const buffer = Buffer.from(screenshot.data, 'base64');
+        const parseAsObservable = Rx.bindNodeCallback(png.parse.bind(png));
+        return parseAsObservable(buffer);
+      },
+      (screenshot: Screenshot, png: PNG) => {
+        if (
+          png.width !== screenshot.rectangle.width ||
+          png.height !== screenshot.rectangle.height
+        ) {
+          const errorMessage = `Screenshot captured with width:${
+            png.width
+          } and height: ${png.height}) is not of expected width: ${
+            screenshot.rectangle.width
+          } and height: ${screenshot.rectangle.height}`;
+
+          logger.error(errorMessage);
+          throw new Error(errorMessage);
+        }
+        return { screenshot, png };
+      }
+    )
+  );
+
+  const output$ = pngs$.pipe(
+    reduce((output: PNG, input: { screenshot: Screenshot; png: PNG }) => {
+      const { png, screenshot } = input;
+      // Spitting out a lot of output to help debug https://github.com/elastic/kibana/issues/19563. Once that is
+      // fixed, this should probably get pared down.
+      logger.debug(`Output dimensions is ${JSON.stringify(outputSize)}`);
+      logger.debug(`Input png w: ${png.width} and h: ${png.height}`);
+      logger.debug(
+        `Creating output png with ${JSON.stringify(screenshot.rectangle)}`
+      );
+      const { rectangle } = screenshot;
+      png.bitblt(
+        output,
+        0,
+        0,
+        rectangle.width,
+        rectangle.height,
+        rectangle.x,
+        rectangle.y
+      );
+      return output;
+    }, new PNG({ width: outputSize.width, height: outputSize.height }))
+  );
+
+  return output$.pipe(
+    tap(png => png.pack()),
+    switchMap<PNG, Buffer>($streamToObservable),
+    toArray(),
+    map((chunks: Buffer[]) => Buffer.concat(chunks).toString('base64'))
+  );
+}