Add getImageDataFromURL() implementation using fetch

src/utils/getImageDataFromURL.ts

@@ -1,12 +1,56 @@
+/* global fetch */
+// TODO: Read data:// URLs
+// TODO: Load node polyfill
+// TODO: Read from FS
 import sha1 from 'js-sha1';
 
+const ERROR_IMAGE =
+ 'iVBORw0KGgoAAAANSUhEUgAAAAEAAAABCAYAAAAfFcSJAAAADUlEQVR42mM8w8DwHwAEOQHNmnaaOAAAAABJRU5ErkJggg==';
+
+const ERROR_RESULT = {
+ data: ERROR_IMAGE,
+ sha1: sha1(ERROR_IMAGE),
+};
+
+const readBufferFromResponse = async (response: Response): Promise<Buffer> => {
+ const arrayBuffer = await response.arrayBuffer();
+ if (Buffer.isBuffer(arrayBuffer)) {
+ // skpm polyfill returns a Buffer instead of an ArrayBuffer
+ return arrayBuffer;
+ }
+ return Buffer.from(arrayBuffer);
+};
+
+const isImage = (buffer: Buffer): boolean => {
+ const firstByte = buffer[0];
+
+ // Check for first byte to see if we have an image.
+ // 0xFF = JPEG, 0x89 = PNG, 0x47 = GIF, 0x49 = TIFF, 0x4D = TIFF
+ return (
+ firstByte === 0xff ||
+ firstByte === 0x89 ||
+ firstByte === 0x47 ||
+ firstByte === 0x49 ||
+ firstByte === 0x4d
+ );
+};
+
 export default async function getImageDataFromURL(
  url?: string,
-): Promise<{ data: string; sha1: string }> {
- // FIXME: Mock
- console.log(url);
- const data =
- 'iVBORw0KGgoAAAANSUhEUgAAAAEAAAABCAYAAAAfFcSJAAAADUlEQVR42mM8w8DwHwAEOQHNmnaaOAAAAABJRU5ErkJggg==';
+): Promise<Readonly<{ data: string; sha1: string }>> {
+ if (!url) {
+ return ERROR_RESULT;
+ }
+
+ const response = await fetch(url);
+ if (!response.ok) {
+ return ERROR_RESULT;
+ }
+
+ const buffer = await readBufferFromResponse(response);
+ if (!isImage(buffer)) return ERROR_RESULT;
+
+ const data = buffer.toString('base64');
 
  return {
  data,