Implemented and tested RoutingService as separate class

refs https://github.com/TryGhost/Team/issues/2466

This code is still in the Ghost package for now as it's essentially glue code.

ghost/core/core/server/services/mentions/RoutingService.js

@@ -0,0 +1,47 @@
+/**
+ * @typedef {import('@tryghost/webmentions/lib/MentionsAPI').IRoutingService} IRoutingService
+ */
+
+/**
+ * @typedef {object} IUrlUtils
+ * @prop {() => string} getSiteUrl
+ * @prop {() => string} getSubdir
+ */
+
+/**
+ * @implements {IRoutingService}
+ */
+module.exports = class RoutingService {
+    /** @typedef {URL} */
+    #siteUrl;
+
+    /**
+     * @param {object} deps
+     * @param {URL} deps.siteUrl
+     */
+    constructor(deps) {
+        this.#siteUrl = deps.siteUrl;
+    }
+
+    /**
+     * @param {URL} url
+     */
+    async pageExists(url) {
+        if (this.#siteUrl.origin !== url.origin) {
+            return false;
+        }
+        const subdir = removeTrailingSlash(this.#siteUrl.pathname);
+        if (subdir && !url.pathname.startsWith(subdir)) {
+            return false;
+        }
+
+        return true;
+    }
+};
+
+/**
+ * @param {string} str
+ */
+function removeTrailingSlash(str) {
+    return str.replace(/\/$/, '');
+}

ghost/core/core/server/services/mentions/service.js

@@ -7,6 +7,8 @@ const {
     MentionDiscoveryService
 } = require('@tryghost/webmentions');
 const BookshelfMentionRepository = require('./BookshelfMentionRepository');
+const RoutingService = require('./RoutingService');
+
 const models = require('../../models');
 const events = require('../../lib/common/events');
 const externalRequest = require('../../../server/lib/request-external.js');
@@ -28,6 +30,10 @@ module.exports = {
         });
         const webmentionMetadata = new WebmentionMetadata();
         const discoveryService = new MentionDiscoveryService({externalRequest});
+        const routingService = new RoutingService({
+            siteUrl: new URL(urlUtils.getSiteUrl())
+        });
+
         const api = new MentionsAPI({
             repository,
             webmentionMetadata,
@@ -47,20 +53,7 @@ module.exports = {
                     };
                 }
             },
-            routingService: {
-                async pageExists(url) {
-                    const siteUrl = new URL(urlUtils.getSiteUrl());
-                    if (siteUrl.origin !== url.origin) {
-                        return false;
-                    }
-                    const subdir = urlUtils.getSubdir();
-                    if (subdir && !url.pathname.startsWith(subdir)) {
-                        return false;
-                    }
-
-                    return true;
-                }
-            }
+            routingService
         });
 
         this.controller.init({api});

ghost/core/test/unit/server/services/mentions/RoutingService.test.js

@@ -0,0 +1,55 @@
+const assert = require('assert');
+const RoutingService = require('../../../../../core/server/services/mentions/RoutingService');
+
+describe('RoutingService', function () {
+    describe('pageExists', function () {
+        it('Returns false if the url is from a different origin', async function () {
+            const siteUrl = new URL('https://website.com');
+            const routingService = new RoutingService({
+                siteUrl
+            });
+
+            const result = await routingService.pageExists(new URL('https://different-website.com'));
+
+            assert.equal(result, false);
+        });
+
+        it('Returns false if the url is not on the correct subdirectory', async function () {
+            const siteUrl = new URL('https://website.com/subdir');
+            const routingService = new RoutingService({
+                siteUrl
+            });
+
+            checkNoSubdomain: {
+                const result = await routingService.pageExists(new URL('https://website.com'));
+                assert.equal(result, false);
+                break checkNoSubdomain;
+            }
+
+            checkIncorrectSubdomain: {
+                const result = await routingService.pageExists(new URL('https://website.com/different'));
+                assert.equal(result, false);
+                break checkIncorrectSubdomain;
+            }
+        });
+
+        it('Returns true if the url is on the correct origin and subdirectory', async function () {
+            const siteUrl = new URL('https://website.com/subdir');
+            const routingService = new RoutingService({
+                siteUrl
+            });
+
+            checkJustSubdomain: {
+                const result = await routingService.pageExists(new URL('https://website.com/subdir'));
+                assert.equal(result, true);
+                break checkJustSubdomain;
+            }
+
+            checkLongerPath: {
+                const result = await routingService.pageExists(new URL('https://website.com/subdir/page'));
+                assert.equal(result, true);
+                break checkLongerPath;
+            }
+        });
+    });
+});