Ability to cache subsonic artist images locally on disk (#61)

README.md

@@ -150,6 +150,7 @@ BNB_SONOS_SERVICE_NAME | bonob | service name for sonos
 BNB_SONOS_SERVICE_ID | 246 | service id for sonos
 BNB_SUBSONIC_URL | http://$(hostname):4533 | URL for subsonic clone
 BNB_SUBSONIC_CUSTOM_CLIENTS | undefined | Comma delimeted mime types for custom subsonic clients when streaming. ie. "audio/flac,audio/ogg" would use client = 'bonob+audio/flac' for flacs, and 'bonob+audio/ogg' for oggs.
+BNB_SUBSONIC_ARTIST_IMAGE_CACHE | undefined | Path for caching of artist images as are sourced externally.  ie. Navidrome provides spotify URLs
 BNB_SCROBBLE_TRACKS | true | Whether to scrobble the playing of a track if it has been played for >30s
 BNB_REPORT_NOW_PLAYING | true | Whether to report a track as now playing
 BNB_ICON_FOREGROUND_COLOR | undefined | Icon foreground color in sonos app, must be a valid [svg color](https://www.december.com/html/spec/colorsvg.html)

package.json

@@ -8,6 +8,7 @@
   "dependencies": {
     "@svrooij/sonos": "^2.4.0",
     "@types/express": "^4.17.13",
+    "@types/fs-extra": "^9.0.13",
     "@types/morgan": "^1.9.3",
     "@types/node": "^16.7.13",
     "@types/sharp": "^0.28.6",
@@ -18,6 +19,7 @@
     "eta": "^1.12.3",
     "express": "^4.17.1",
     "fp-ts": "^2.11.1",
+    "fs-extra": "^10.0.0",
     "libxmljs2": "^0.28.0",
     "morgan": "^1.10.0",
     "node-html-parser": "^4.1.4",
@@ -35,12 +37,14 @@
     "@types/jest": "^27.0.1",
     "@types/mocha": "^9.0.0",
     "@types/supertest": "^2.0.11",
+    "@types/tmp": "^0.2.1",
     "chai": "^4.3.4",
     "get-port": "^5.1.1",
     "image-js": "^0.33.0",
     "jest": "^27.1.0",
     "nodemon": "^2.0.12",
     "supertest": "^6.1.6",
+    "tmp": "^0.2.1",
     "ts-jest": "^27.0.5",
     "ts-mockito": "^2.6.1",
     "ts-node": "^10.2.1",

src/app.ts

@@ -2,7 +2,13 @@ import path from "path";
 import fs from "fs";
 import server from "./server";
 import logger from "./logger";
-import { appendMimeTypeToClientFor, DEFAULT, Subsonic } from "./subsonic";
+import {
+  appendMimeTypeToClientFor,
+  axiosImageFetcher,
+  cachingImageFetcher,
+  DEFAULT,
+  Subsonic,
+} from "./subsonic";
 import encryption from "./encryption";
 import { InMemoryAccessTokens, sha256 } from "./access_tokens";
 import { InMemoryLinkCodes } from "./link_codes";
@@ -28,10 +34,15 @@ const streamUserAgent = config.subsonic.customClientsFor
   ? appendMimeTypeToClientFor(config.subsonic.customClientsFor.split(","))
   : DEFAULT;
 
+const artistImageFetcher = config.subsonic.artistImageCache
+  ? cachingImageFetcher(config.subsonic.artistImageCache, axiosImageFetcher)
+  : axiosImageFetcher;
+
 const subsonic = new Subsonic(
   config.subsonic.url,
   encryption(config.secret),
-  streamUserAgent
+  streamUserAgent,
+  artistImageFetcher
 );
 
 const featureFlagAwareMusicService: MusicService = {
@@ -60,7 +71,9 @@ const featureFlagAwareMusicService: MusicService = {
 
 export const GIT_INFO = path.join(__dirname, "..", ".gitinfo");
 
-const version = fs.existsSync(GIT_INFO) ? fs.readFileSync(GIT_INFO).toString().trim() : "v??"
+const version = fs.existsSync(GIT_INFO)
+  ? fs.readFileSync(GIT_INFO).toString().trim()
+  : "v??";
 
 const app = server(
   sonosSystem,
@@ -74,7 +87,7 @@ const app = server(
     iconColors: config.icons,
     applyContextPath: true,
     logRequests: true,
-    version
+    version,
   }
 );
 
@@ -90,12 +103,12 @@ if (config.sonos.autoRegister) {
       );
     }
   });
-} else if(config.sonos.discovery.enabled) {
+} else if (config.sonos.discovery.enabled) {
-  sonosSystem.devices().then(devices => {
+  sonosSystem.devices().then((devices) => {
-    devices.forEach(d => {
+    devices.forEach((d) => {
-      logger.info(`Found device ${d.name}(${d.group}) @ ${d.ip}:${d.port}`)
+      logger.info(`Found device ${d.name}(${d.group}) @ ${d.ip}:${d.port}`);
-    })
+    });
-  })
+  });
 }
 
 export default app;

src/config.ts

@@ -84,6 +84,7 @@ export default function () {
     subsonic: {
       url: bnbEnvVar("SUBSONIC_URL", { legacy: ["BONOB_NAVIDROME_URL"], default: `http://${hostname()}:4533` })!,
       customClientsFor: bnbEnvVar("SUBSONIC_CUSTOM_CLIENTS", { legacy: ["BONOB_NAVIDROME_CUSTOM_CLIENTS"] }),
+      artistImageCache: bnbEnvVar("SUBSONIC_ARTIST_IMAGE_CACHE"),
     },
     scrobbleTracks: bnbEnvVar("SCROBBLE_TRACKS", { default: "true" }) == "true",
     reportNowPlaying:

src/subsonic.ts

@@ -18,10 +18,13 @@ import {
   AlbumSummary,
   Genre,
   Track,
+  CoverArt,
 } from "./music_service";
 import X2JS from "x2js";
 import sharp from "sharp";
 import _ from "underscore";
+import fse from "fs-extra";
+import path from "path";
 
 import axios, { AxiosRequestConfig } from "axios";
 import { Encryption } from "./encryption";
@@ -311,19 +314,61 @@ export const asURLSearchParams = (q: any) => {
   return urlSearchParams;
 };
 
+export type ImageFetcher = (url: string) => Promise<CoverArt | undefined>;
+
+export const cachingImageFetcher =
+  (cacheDir: string, delegate: ImageFetcher) =>
+  (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);
+
 export class Subsonic implements MusicService {
   url: string;
   encryption: Encryption;
   streamClientApplication: StreamClientApplication;
+  externalImageFetcher: ImageFetcher;
 
   constructor(
     url: string,
     encryption: Encryption,
-    streamClientApplication: StreamClientApplication = DEFAULT
+    streamClientApplication: StreamClientApplication = DEFAULT,
+    externalImageFetcher: ImageFetcher = axiosImageFetcher
   ) {
     this.url = url;
     this.encryption = encryption;
     this.streamClientApplication = streamClientApplication;
+    this.externalImageFetcher = externalImageFetcher;
   }
 
   get = async (
@@ -630,28 +675,21 @@ export class Subsonic implements MusicService {
                 (it) => it.coverArt
               );
               if (artist.image.large) {
-                return axios
+                return this.externalImageFetcher(artist.image.large!).then(
-                  .get(artist.image.large!, {
+                  (image) => {
-                    headers: BROWSER_HEADERS,
+                    if (image && size) {
-                    responseType: "arraybuffer",
+                      return sharp(image.data)
-                  })
-                  .then((res) => {
-                    const image = Buffer.from(res.data, "binary");
-                    if (size) {
-                      return sharp(image)
                         .resize(size)
                         .toBuffer()
                         .then((resized) => ({
-                          contentType: res.headers["content-type"],
+                          contentType: image.contentType,
                           data: resized,
                         }));
                     } else {
-                      return {
+                      return image;
-                        contentType: res.headers["content-type"],
-                        data: image,
-                      };
                     }
-                  });
+                  }
+                );
               } else if (albumsWithCoverArt.length > 0) {
                 return subsonic
                   .getCoverArt(

tests/builders.ts

@@ -3,7 +3,15 @@ import { v4 as uuid } from "uuid";
 import { Credentials } from "../src/smapi";
 
 import { Service, Device } from "../src/sonos";
-import { Album, Artist, Track, albumToAlbumSummary, artistToArtistSummary, PlaylistSummary, Playlist } from "../src/music_service";
+import {
+  Album,
+  Artist,
+  Track,
+  albumToAlbumSummary,
+  artistToArtistSummary,
+  PlaylistSummary,
+  Playlist,
+} from "../src/music_service";
 import randomString from "../src/random_string";
 import { b64Encode } from "../src/b64";
 
@@ -29,12 +37,14 @@ export const aService = (fields: Partial<Service> = {}): Service => ({
   ...fields,
 });
 
-export function aPlaylistSummary(fields: Partial<PlaylistSummary> = {}): PlaylistSummary {
+export function aPlaylistSummary(
+  fields: Partial<PlaylistSummary> = {}
+): PlaylistSummary {
   return {
     id: `playlist-${uuid()}`,
     name: `playlistname-${randomString()}`,
-    ...fields
+    ...fields,
-  }
+  };
 }
 
 export function aPlaylist(fields: Partial<Playlist> = {}): Playlist {
@@ -42,8 +52,8 @@ export function aPlaylist(fields: Partial<Playlist> = {}): Playlist {
     id: `playlist-${uuid()}`,
     name: `playlist-${randomString()}`,
     entries: [aTrack(), aTrack()],
-    ...fields
+    ...fields,
-  }
+  };
 }
 
 export function aDevice(fields: Partial<Device> = {}): Device {
@@ -105,14 +115,14 @@ export function anArtist(fields: Partial<Artist> = {}): Artist {
     ],
     ...fields,
   };
-  artist.albums.forEach(album => {
+  artist.albums.forEach((album) => {
     album.artistId = artist.id;
     album.artistName = artist.name;
-  })
+  });
   return artist;
 }
 
-export const aGenre = (name: string) => ({ id: b64Encode(name), name })
+export const aGenre = (name: string) => ({ id: b64Encode(name), name });
 
 export const HIP_HOP = aGenre("Hip-Hop");
 export const METAL = aGenre("Metal");
@@ -125,7 +135,16 @@ export const SKA = aGenre("Ska");
 export const PUNK = aGenre("Punk");
 export const TRIP_HOP = aGenre("Trip Hop");
 
-export const SAMPLE_GENRES = [HIP_HOP, METAL, NEW_WAVE, POP, POP_ROCK, REGGAE, ROCK, SKA];
+export const SAMPLE_GENRES = [
+  HIP_HOP,
+  METAL,
+  NEW_WAVE,
+  POP,
+  POP_ROCK,
+  REGGAE,
+  ROCK,
+  SKA,
+];
 export const randomGenre = () => SAMPLE_GENRES[randomInt(SAMPLE_GENRES.length)];
 
 export function aTrack(fields: Partial<Track> = {}): Track {
@@ -140,7 +159,9 @@ export function aTrack(fields: Partial<Track> = {}): Track {
     number: randomInt(100),
     genre,
     artist: artistToArtistSummary(artist),
-    album: albumToAlbumSummary(anAlbum({ artistId: artist.id, artistName: artist.name, genre })),
+    album: albumToAlbumSummary(
+      anAlbum({ artistId: artist.id, artistName: artist.name, genre })
+    ),
     coverArt: `coverArt:${uuid()}`,
     ...fields,
   };
@@ -173,7 +194,7 @@ export const BLONDIE: Artist = {
       genre: NEW_WAVE,
       artistId: BLONDIE_ID,
       artistName: BLONDIE_NAME,
-      coverArt: `coverArt:${uuid()}`
+      coverArt: `coverArt:${uuid()}`,
     },
     {
       id: uuid(),
@@ -182,7 +203,7 @@ export const BLONDIE: Artist = {
       genre: POP_ROCK,
       artistId: BLONDIE_ID,
       artistName: BLONDIE_NAME,
-      coverArt: `coverArt:${uuid()}`
+      coverArt: `coverArt:${uuid()}`,
     },
   ],
   image: {
@@ -199,9 +220,33 @@ export const BOB_MARLEY: Artist = {
   id: BOB_MARLEY_ID,
   name: BOB_MARLEY_NAME,
   albums: [
-    { id: uuid(), name: "Burin'", year: "1973", genre: REGGAE, artistId: BOB_MARLEY_ID, artistName: BOB_MARLEY_NAME, coverArt: `coverArt:${uuid()}` },
+    {
-    { id: uuid(), name: "Exodus", year: "1977", genre: REGGAE, artistId: BOB_MARLEY_ID, artistName: BOB_MARLEY_NAME, coverArt: `coverArt:${uuid()}` },
+      id: uuid(),
-    { id: uuid(), name: "Kaya", year: "1978", genre: SKA, artistId: BOB_MARLEY_ID, artistName: BOB_MARLEY_NAME, coverArt: `coverArt:${uuid()}` },
+      name: "Burin'",
+      year: "1973",
+      genre: REGGAE,
+      artistId: BOB_MARLEY_ID,
+      artistName: BOB_MARLEY_NAME,
+      coverArt: `coverArt:${uuid()}`,
+    },
+    {
+      id: uuid(),
+      name: "Exodus",
+      year: "1977",
+      genre: REGGAE,
+      artistId: BOB_MARLEY_ID,
+      artistName: BOB_MARLEY_NAME,
+      coverArt: `coverArt:${uuid()}`,
+    },
+    {
+      id: uuid(),
+      name: "Kaya",
+      year: "1978",
+      genre: SKA,
+      artistId: BOB_MARLEY_ID,
+      artistName: BOB_MARLEY_NAME,
+      coverArt: `coverArt:${uuid()}`,
+    },
   ],
   image: {
     small: "http://localhost/BOB_MARLEY/sml",
@@ -238,7 +283,7 @@ export const METALLICA: Artist = {
       genre: METAL,
       artistId: METALLICA_ID,
       artistName: METALLICA_NAME,
-      coverArt: `coverArt:${uuid()}`
+      coverArt: `coverArt:${uuid()}`,
     },
     {
       id: uuid(),
@@ -247,7 +292,7 @@ export const METALLICA: Artist = {
       genre: METAL,
       artistId: METALLICA_ID,
       artistName: METALLICA_NAME,
-      coverArt: `coverArt:${uuid()}`
+      coverArt: `coverArt:${uuid()}`,
     },
   ],
   image: {
@@ -261,3 +306,4 @@ export const METALLICA: Artist = {
 export const ALL_ARTISTS = [BOB_MARLEY, BLONDIE, MADONNA, METALLICA];
 
 export const ALL_ALBUMS = ALL_ARTISTS.flatMap((it) => it.albums || []);
+

tests/config.test.ts

@@ -66,11 +66,13 @@ describe("envVar", () => {
 
   describe("validationPattern", () => {
     it("should fail when the value does not match the pattern", () => {
-      expect(
+      expect(() =>
-        () => envVar("bnb-var", {
+        envVar("bnb-var", {
           validationPattern: /^foobar$/,
         })
-      ).toThrowError(`Invalid value specified for 'bnb-var', must match ${/^foobar$/}`)
+      ).toThrowError(
+        `Invalid value specified for 'bnb-var', must match ${/^foobar$/}`
+      );
     });
   });
 });
@@ -117,7 +119,7 @@ describe("config", () => {
   }
 
   describe("bonobUrl", () => {
-    ["BNB_URL", "BONOB_URL", "BONOB_WEB_ADDRESS"].forEach(key => {
+    ["BNB_URL", "BONOB_URL", "BONOB_WEB_ADDRESS"].forEach((key) => {
       describe(`when ${key} is specified`, () => {
         it("should be used", () => {
           const url = "http://bonob1.example.com:8877/";
@@ -163,7 +165,8 @@ describe("config", () => {
 
   describe("icons", () => {
     describe("foregroundColor", () => {
-      ["BNB_ICON_FOREGROUND_COLOR", "BONOB_ICON_FOREGROUND_COLOR"].forEach(k => {
+      ["BNB_ICON_FOREGROUND_COLOR", "BONOB_ICON_FOREGROUND_COLOR"].forEach(
+        (k) => {
           describe(`when ${k} is not specified`, () => {
             it(`should default to undefined`, () => {
               expect(config().icons.foregroundColor).toEqual(undefined);
@@ -192,11 +195,13 @@ describe("config", () => {
               );
             });
           });
-      });
+        }
+      );
     });
 
     describe("backgroundColor", () => {
-      ["BNB_ICON_BACKGROUND_COLOR", "BONOB_ICON_BACKGROUND_COLOR"].forEach(k => {
+      ["BNB_ICON_BACKGROUND_COLOR", "BONOB_ICON_BACKGROUND_COLOR"].forEach(
+        (k) => {
           describe(`when ${k} is not specified`, () => {
             it(`should default to undefined`, () => {
               expect(config().icons.backgroundColor).toEqual(undefined);
@@ -225,7 +230,8 @@ describe("config", () => {
               );
             });
           });
-      });
+        }
+      );
     });
   });
 
@@ -234,7 +240,7 @@ describe("config", () => {
       expect(config().secret).toEqual("bonob");
     });
 
-    ["BNB_SECRET", "BONOB_SECRET"].forEach(key => {
+    ["BNB_SECRET", "BONOB_SECRET"].forEach((key) => {
       it(`should be overridable using ${key}`, () => {
         process.env[key] = "new secret";
         expect(config().secret).toEqual("new secret");
@@ -248,7 +254,7 @@ describe("config", () => {
         expect(config().sonos.serviceName).toEqual("bonob");
       });
 
-      ["BNB_SONOS_SERVICE_NAME", "BONOB_SONOS_SERVICE_NAME"].forEach(k => {
+      ["BNB_SONOS_SERVICE_NAME", "BONOB_SONOS_SERVICE_NAME"].forEach((k) => {
         it("should be overridable", () => {
           process.env[k] = "foobar1000";
           expect(config().sonos.serviceName).toEqual("foobar1000");
@@ -256,21 +262,23 @@ describe("config", () => {
       });
     });
 
-    ["BNB_SONOS_DEVICE_DISCOVERY", "BONOB_SONOS_DEVICE_DISCOVERY"].forEach(k => {
+    ["BNB_SONOS_DEVICE_DISCOVERY", "BONOB_SONOS_DEVICE_DISCOVERY"].forEach(
+      (k) => {
         describeBooleanConfigValue(
           "deviceDiscovery",
           k,
           true,
           (config) => config.sonos.discovery.enabled
         );
-    });
+      }
+    );
 
     describe("seedHost", () => {
       it("should default to undefined", () => {
         expect(config().sonos.discovery.seedHost).toBeUndefined();
       });
 
-      ["BNB_SONOS_SEED_HOST", "BONOB_SONOS_SEED_HOST"].forEach(k => {
+      ["BNB_SONOS_SEED_HOST", "BONOB_SONOS_SEED_HOST"].forEach((k) => {
         it("should be overridable", () => {
           process.env[k] = "123.456.789.0";
           expect(config().sonos.discovery.seedHost).toEqual("123.456.789.0");
@@ -278,7 +286,7 @@ describe("config", () => {
       });
     });
 
-    ["BNB_SONOS_AUTO_REGISTER", "BONOB_SONOS_AUTO_REGISTER"].forEach(k => {
+    ["BNB_SONOS_AUTO_REGISTER", "BONOB_SONOS_AUTO_REGISTER"].forEach((k) => {
       describeBooleanConfigValue(
         "autoRegister",
         k,
@@ -287,13 +295,12 @@ describe("config", () => {
       );
     });
 
-
     describe("sid", () => {
       it("should default to 246", () => {
         expect(config().sonos.sid).toEqual(246);
       });
 
-      ["BNB_SONOS_SERVICE_ID", "BONOB_SONOS_SERVICE_ID"].forEach(k => {
+      ["BNB_SONOS_SERVICE_ID", "BONOB_SONOS_SERVICE_ID"].forEach((k) => {
         it("should be overridable", () => {
           process.env[k] = "786";
           expect(config().sonos.sid).toEqual(786);
@@ -304,17 +311,22 @@ describe("config", () => {
 
   describe("subsonic", () => {
     describe("url", () => {
-      ["BNB_SUBSONIC_URL", "BONOB_SUBSONIC_URL", "BONOB_NAVIDROME_URL"].forEach(k => {
+      ["BNB_SUBSONIC_URL", "BONOB_SUBSONIC_URL", "BONOB_NAVIDROME_URL"].forEach(
+        (k) => {
           describe(`when ${k} is not specified`, () => {
             it(`should default to http://${hostname()}:4533`, () => {
-            expect(config().subsonic.url).toEqual(`http://${hostname()}:4533`);
+              expect(config().subsonic.url).toEqual(
+                `http://${hostname()}:4533`
+              );
             });
           });
 
           describe(`when ${k} is ''`, () => {
             it(`should default to http://${hostname()}:4533`, () => {
               process.env[k] = "";
-            expect(config().subsonic.url).toEqual(`http://${hostname()}:4533`);
+              expect(config().subsonic.url).toEqual(
+                `http://${hostname()}:4533`
+              );
             });
           });
 
@@ -325,7 +337,8 @@ describe("config", () => {
               expect(config().subsonic.url).toEqual(url);
             });
           });
-      });
+        }
+      );
     });
 
     describe("customClientsFor", () => {
@@ -333,17 +346,31 @@ describe("config", () => {
         expect(config().subsonic.customClientsFor).toBeUndefined();
       });
 
-      ["BNB_SUBSONIC_CUSTOM_CLIENTS", "BONOB_SUBSONIC_CUSTOM_CLIENTS", "BONOB_NAVIDROME_CUSTOM_CLIENTS"].forEach(k => {
+      [
+        "BNB_SUBSONIC_CUSTOM_CLIENTS",
+        "BONOB_SUBSONIC_CUSTOM_CLIENTS",
+        "BONOB_NAVIDROME_CUSTOM_CLIENTS",
+      ].forEach((k) => {
         it(`should be overridable for ${k}`, () => {
           process.env[k] = "whoop/whoop";
           expect(config().subsonic.customClientsFor).toEqual("whoop/whoop");
         });
       });
     });
+
+    describe("artistImageCache", () => {
+      it("should default to undefined", () => {
+        expect(config().subsonic.artistImageCache).toBeUndefined();
       });
 
+      it(`should be overridable for BNB_SUBSONIC_ARTIST_IMAGE_CACHE`, () => {
+        process.env["BNB_SUBSONIC_ARTIST_IMAGE_CACHE"] = "/some/path";
+        expect(config().subsonic.artistImageCache).toEqual("/some/path");
+      });
+    });
+  });
 
-  ["BNB_SCROBBLE_TRACKS", "BONOB_SCROBBLE_TRACKS"].forEach(k => {
+  ["BNB_SCROBBLE_TRACKS", "BONOB_SCROBBLE_TRACKS"].forEach((k) => {
     describeBooleanConfigValue(
       "scrobbleTracks",
       k,
@@ -352,7 +379,7 @@ describe("config", () => {
     );
   });
 
-  ["BNB_REPORT_NOW_PLAYING", "BONOB_REPORT_NOW_PLAYING"].forEach(k => {
+  ["BNB_REPORT_NOW_PLAYING", "BONOB_REPORT_NOW_PLAYING"].forEach((k) => {
     describeBooleanConfigValue(
       "reportNowPlaying",
       k,

tests/subsonic.test.ts

@@ -1,5 +1,8 @@
 import { Md5 } from "ts-md5/dist/md5";
 import { v4 as uuid } from "uuid";
+import tmp from "tmp";
+import fse from "fs-extra";
+import path from "path";
 
 import {
   isDodgyImage,
@@ -11,6 +14,7 @@ import {
   appendMimeTypeToClientFor,
   asURLSearchParams,
   splitCoverArtId,
+  cachingImageFetcher,
 } from "../src/subsonic";
 import encryption from "../src/encryption";
 
@@ -158,6 +162,74 @@ describe("asURLSearchParams", () => {
   });
 });
 
+describe("cachingImageFetcher", () => {
+  const delegate = jest.fn();
+  const url = "http://test.example.com/someimage.jpg";
+
+  beforeEach(() => {
+    jest.clearAllMocks();
+    jest.resetAllMocks();
+  });
+
+  describe("when there is no image in the cache", () => {
+    it.only("should fetch the image from the source and then cache and return it", async () => {
+      const dir = tmp.dirSync();
+      const cacheFile = path.join(dir.name, `${Md5.hashStr(url)}.png`);
+      const jpgImage = Buffer.from("jpg-image", 'utf-8');
+      const pngImage = Buffer.from("png-image", 'utf-8');
+
+      delegate.mockResolvedValue({ contentType: "image/jpeg", data: jpgImage });
+      const png = jest.fn();
+      (sharp as unknown as jest.Mock).mockReturnValue({ png });
+      png.mockReturnValue({
+        toBuffer: () => Promise.resolve(pngImage),
+      });
+
+      const result = await cachingImageFetcher(dir.name, delegate)(url);
+
+      expect(result!.contentType).toEqual("image/png");
+      expect(result!.data).toEqual(pngImage);
+
+      expect(delegate).toHaveBeenCalledWith(url);
+      expect(fse.existsSync(cacheFile)).toEqual(true);
+      expect(fse.readFileSync(cacheFile)).toEqual(pngImage);
+    });
+  });
+
+  describe("when the image is already in the cache", () => {
+    it.only("should fetch the image from the cache and return it", async () => {
+      const dir = tmp.dirSync();
+      const cacheFile = path.join(dir.name, `${Md5.hashStr(url)}.png`);
+      const data = Buffer.from("foobar2", "utf-8");
+
+      fse.writeFileSync(cacheFile, data);
+
+      const result = await cachingImageFetcher(dir.name, delegate)(url);
+
+      expect(result!.contentType).toEqual("image/png");
+      expect(result!.data).toEqual(data);
+
+      expect(delegate).not.toHaveBeenCalled();
+    });
+  });
+
+  describe("when the delegate returns undefined", () => {
+    it.only("should return undefined", async () => {
+      const dir = tmp.dirSync();
+      const cacheFile = path.join(dir.name, `${Md5.hashStr(url)}.png`);
+
+      delegate.mockResolvedValue(undefined);
+
+      const result = await cachingImageFetcher(dir.name, delegate)(url);
+
+      expect(result).toBeUndefined();
+
+      expect(delegate).toHaveBeenCalledWith(url);
+      expect(fse.existsSync(cacheFile)).toEqual(false);
+    });
+  });
+});
+
 const ok = (data: string) => ({
   status: 200,
   data,

yarn.lock

@@ -1131,6 +1131,15 @@ __metadata:
   languageName: node
   linkType: hard
 
+"@types/fs-extra@npm:^9.0.13":
+  version: 9.0.13
+  resolution: "@types/fs-extra@npm:9.0.13"
+  dependencies:
+    "@types/node": "*"
+  checksum: add79e212acd5ac76b97b9045834e03a7996aef60a814185e0459088fd290519a3c1620865d588fa36c4498bf614210d2a703af5cf80aa1dbc125db78f6edac3
+  languageName: node
+  linkType: hard
+
 "@types/graceful-fs@npm:^4.1.2":
   version: 4.1.5
   resolution: "@types/graceful-fs@npm:4.1.5"
@@ -1303,6 +1312,13 @@ __metadata:
   languageName: node
   linkType: hard
 
+"@types/tmp@npm:^0.2.1":
+  version: 0.2.1
+  resolution: "@types/tmp@npm:0.2.1"
+  checksum: 2617d2a04811ca78a8d21f5ffc3bd7c392e03c440053a615b091f3e3726540d36babffc750614a803c81b9f2c5f218cdafc748d8cf4638eade2962f8ccddd2fa
+  languageName: node
+  linkType: hard
+
 "@types/underscore@npm:^1.11.3":
   version: 1.11.3
   resolution: "@types/underscore@npm:1.11.3"
@@ -1764,12 +1780,14 @@ __metadata:
     "@svrooij/sonos": ^2.4.0
     "@types/chai": ^4.2.21
     "@types/express": ^4.17.13
+    "@types/fs-extra": ^9.0.13
     "@types/jest": ^27.0.1
     "@types/mocha": ^9.0.0
     "@types/morgan": ^1.9.3
     "@types/node": ^16.7.13
     "@types/sharp": ^0.28.6
     "@types/supertest": ^2.0.11
+    "@types/tmp": ^0.2.1
     "@types/underscore": ^1.11.3
     "@types/uuid": ^8.3.1
     axios: ^0.21.4
@@ -1778,6 +1796,7 @@ __metadata:
     eta: ^1.12.3
     express: ^4.17.1
     fp-ts: ^2.11.1
+    fs-extra: ^10.0.0
     get-port: ^5.1.1
     image-js: ^0.33.0
     jest: ^27.1.0
@@ -1788,6 +1807,7 @@ __metadata:
     sharp: ^0.29.1
     soap: ^0.42.0
     supertest: ^6.1.6
+    tmp: ^0.2.1
     ts-jest: ^27.0.5
     ts-md5: ^1.2.9
     ts-mockito: ^2.6.1
@@ -3162,6 +3182,17 @@ __metadata:
   languageName: node
   linkType: hard
 
+"fs-extra@npm:^10.0.0":
+  version: 10.0.0
+  resolution: "fs-extra@npm:10.0.0"
+  dependencies:
+    graceful-fs: ^4.2.0
+    jsonfile: ^6.0.1
+    universalify: ^2.0.0
+  checksum: 5285a3d8f34b917cf2b66af8c231a40c1623626e9d701a20051d3337be16c6d7cac94441c8b3732d47a92a2a027886ca93c69b6a4ae6aee3c89650d2a8880c0a
+  languageName: node
+  linkType: hard
+
 "fs-minipass@npm:^2.0.0":
   version: 2.1.0
   resolution: "fs-minipass@npm:2.1.0"
@@ -3362,7 +3393,7 @@ __metadata:
   languageName: node
   linkType: hard
 
-"graceful-fs@npm:^4.2.6":
+"graceful-fs@npm:^4.1.6, graceful-fs@npm:^4.2.0, graceful-fs@npm:^4.2.6":
   version: 4.2.8
   resolution: "graceful-fs@npm:4.2.8"
   checksum: 5d224c8969ad0581d551dfabdb06882706b31af2561bd5e2034b4097e67cc27d05232849b8643866585fd0a41c7af152950f8776f4dd5579e9853733f31461c6
@@ -4598,6 +4629,19 @@ __metadata:
   languageName: node
   linkType: hard
 
+"jsonfile@npm:^6.0.1":
+  version: 6.1.0
+  resolution: "jsonfile@npm:6.1.0"
+  dependencies:
+    graceful-fs: ^4.1.6
+    universalify: ^2.0.0
+  dependenciesMeta:
+    graceful-fs:
+      optional: true
+  checksum: 7af3b8e1ac8fe7f1eccc6263c6ca14e1966fcbc74b618d3c78a0a2075579487547b94f72b7a1114e844a1e15bb00d440e5d1720bfc4612d790a6f285d5ea8354
+  languageName: node
+  linkType: hard
+
 "keyv@npm:^3.0.0":
   version: 3.1.0
   resolution: "keyv@npm:3.1.0"
@@ -6685,6 +6729,15 @@ resolve@^1.20.0:
   languageName: node
   linkType: hard
 
+"tmp@npm:^0.2.1":
+  version: 0.2.1
+  resolution: "tmp@npm:0.2.1"
+  dependencies:
+    rimraf: ^3.0.0
+  checksum: 8b1214654182575124498c87ca986ac53dc76ff36e8f0e0b67139a8d221eaecfdec108c0e6ec54d76f49f1f72ab9325500b246f562b926f85bcdfca8bf35df9e
+  languageName: node
+  linkType: hard
+
 "tmpl@npm:1.0.x":
   version: 1.0.4
   resolution: "tmpl@npm:1.0.4"
@@ -6992,6 +7045,13 @@ typescript@^4.4.2:
   languageName: node
   linkType: hard
 
+"universalify@npm:^2.0.0":
+  version: 2.0.0
+  resolution: "universalify@npm:2.0.0"
+  checksum: 2406a4edf4a8830aa6813278bab1f953a8e40f2f63a37873ffa9a3bc8f9745d06cc8e88f3572cb899b7e509013f7f6fcc3e37e8a6d914167a5381d8440518c44
+  languageName: node
+  linkType: hard
+
 "unpipe@npm:1.0.0, unpipe@npm:~1.0.0":
   version: 1.0.0
   resolution: "unpipe@npm:1.0.0"