AccessTokens class for generating temporary tokens for retrieving images etc

src/access_tokens.ts

@@ -0,0 +1,50 @@
+import dayjs, { Dayjs } from 'dayjs';
+import { v4 as uuid } from 'uuid';
+
+export interface Clock {
+  now(): Dayjs
+}
+
+type AccessToken = {
+  value: string;
+  authToken: string;
+  expiry: Dayjs;
+};
+
+export interface AccessTokens {
+  mint(authToken: string): string;
+  authTokenFor(value: string): string | undefined;
+}
+
+export class ExpiringAccessTokens implements AccessTokens {
+  tokens = new Map<string, AccessToken>();
+  clock: Clock;
+  
+  constructor(clock : Clock = { now: () => dayjs() }) {
+    this.clock = clock
+  }
+
+  mint(authToken: string): string {
+    this.clearOutExpired();
+    const accessToken = {
+      value: uuid(),
+      authToken,
+      expiry: this.clock.now().add(12, 'hours')
+    };
+    this.tokens.set(accessToken.value, accessToken);
+    return accessToken.value;
+  }
+
+  authTokenFor(value: string): string | undefined {
+    this.clearOutExpired();
+    return this.tokens.get(value)?.authToken;
+  }
+
+  clearOutExpired() {
+    Array.from(this.tokens.values()).filter(it => it.expiry.isBefore(this.clock.now())).forEach(expired => {
+      this.tokens.delete(expired.value);
+    })
+  }
+
+  count = () => this.tokens.size;
+}