New function to determine if an HTML blob is probably a newsletter based on its content

packages/api/test/utils/parser.test.ts

@@ -0,0 +1,21 @@
+import 'mocha'
+import { expect } from 'chai'
+import 'chai/register-should'
+import { JSDOM } from 'jsdom'
+import fs from 'fs'
+import { isProbablyNewsletter } from '../../src/utils/parser'
+
+describe('isProbablyNewsletter', () => {
+  const load = (path: string): JSDOM => {
+    const content = fs.readFileSync(path, 'utf8')
+    return new JSDOM(content);
+  }
+  it('returns true for substack newsletter', () => {
+    const dom = load('./test/utils/data/substack-forwarded-newsletter.html')
+    isProbablyNewsletter(dom.window).should.be.true
+  })
+  it('returns false for substack welcome email', () => {
+    const dom = load('./test/utils/data/substack-forwarded-welcome-email.html')
+    isProbablyNewsletter(dom.window).should.be.false
+  })
+})