refactor

src/images.ts

@@ -0,0 +1,48 @@
+
+import sharp from "sharp";
+import fse from "fs-extra";
+import path from "path";
+import { Md5 } from "ts-md5/dist/md5";
+import axios from "axios";
+
+import { CoverArt } from "./music_service";
+import { BROWSER_HEADERS } from "./utils";
+
+export type ImageFetcher = (url: string) => Promise<CoverArt | undefined>;
+
+export const cachingImageFetcher =
+  (cacheDir: string, delegate: ImageFetcher) =>
+  async (url: string): Promise<CoverArt | undefined> => {
+    const filename = path.join(cacheDir, `${Md5.hashStr(url)}.png`);
+    return fse
+      .readFile(filename)
+      .then((data) => ({ contentType: "image/png", data }))
+      .catch(() =>
+        delegate(url).then((image) => {
+          if (image) {
+            return sharp(image.data)
+              .png()
+              .toBuffer()
+              .then((png) => {
+                return fse
+                  .writeFile(filename, png)
+                  .then(() => ({ contentType: "image/png", data: png }));
+              });
+          } else {
+            return undefined;
+          }
+        })
+      );
+  };
+
+export const axiosImageFetcher = (url: string): Promise<CoverArt | undefined> =>
+  axios
+    .get(url, {
+      headers: BROWSER_HEADERS,
+      responseType: "arraybuffer",
+    })
+    .then((res) => ({
+      contentType: res.headers["content-type"],
+      data: Buffer.from(res.data, "binary"),
+    }))
+    .catch(() => undefined);