Checked for existence of a resource to determine page existence

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

The existing implementation was a very basic check to get us to the
first milestone. By checking if the page points to a resource we can
know for sure the URL exists on the site.

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

@@ -1,5 +1,6 @@
 /**
  * @typedef {import('@tryghost/webmentions/lib/MentionsAPI').IRoutingService} IRoutingService
+ * @typedef {import('@tryghost/webmentions/lib/MentionsAPI').IResourceService} IResourceService
  */
 
 /**
@@ -15,12 +16,18 @@ module.exports = class RoutingService {
     /** @typedef {URL} */
     #siteUrl;
 
+    /** @typedef {IResourceService} */
+    #resourceService;
+
     /**
      * @param {object} deps
      * @param {URL} deps.siteUrl
+     * @param {IResourceService} deps.resourceService
+     * @param {import('got')} deps.externalRequest;
      */
     constructor(deps) {
         this.#siteUrl = deps.siteUrl;
+        this.#resourceService = deps.resourceService;
     }
 
     /**
@@ -35,8 +42,14 @@ module.exports = class RoutingService {
             return false;
         }
 
+        const resource = await this.#resourceService.getByURL(url);
+
+        if (resource) {
             return true;
         }
+
+        return false;
+    }
 };
 
 /**

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

@@ -35,7 +35,8 @@ module.exports = {
             urlService
         });
         const routingService = new RoutingService({
-            siteUrl: new URL(urlUtils.getSiteUrl())
+            siteUrl: new URL(urlUtils.getSiteUrl()),
+            resourceService
         });
 
         const api = new MentionsAPI({

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

@@ -1,12 +1,19 @@
 const assert = require('assert');
+const sinon = require('sinon');
+const ObjectID = require('bson-objectid').default;
 const RoutingService = require('../../../../../core/server/services/mentions/RoutingService');
 
 describe('RoutingService', function () {
     describe('pageExists', function () {
+        describe('URL checks', function () {
             it('Returns false if the url is from a different origin', async function () {
                 const siteUrl = new URL('https://website.com');
+                const resourceService = {
+                    getByURL: sinon.stub()
+                };
                 const routingService = new RoutingService({
-                siteUrl
+                    siteUrl,
+                    resourceService
                 });
 
                 const result = await routingService.pageExists(new URL('https://different-website.com'));
@@ -16,8 +23,12 @@ describe('RoutingService', function () {
 
             it('Returns false if the url is not on the correct subdirectory', async function () {
                 const siteUrl = new URL('https://website.com/subdir');
+                const resourceService = {
+                    getByURL: sinon.stub()
+                };
                 const routingService = new RoutingService({
-                siteUrl
+                    siteUrl,
+                    resourceService
                 });
 
                 checkNoSubdomain: {
@@ -32,24 +43,49 @@ describe('RoutingService', function () {
                     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
         });
 
+        describe('Resource checks', function () {
+            it('Returns true if a resource exists for the URL', async function () {
+                const siteUrl = new URL('https://website.com/subdir');
+                const resourceService = {
+                    getByURL: sinon.stub()
+                };
+                const routingService = new RoutingService({
+                    siteUrl,
+                    resourceService
+                });
+
+                resourceService.getByURL.resolves({type: 'post', id: new ObjectID});
+
+                const result = await routingService.pageExists(new URL('https://website.com/subdir/post'));
+                assert.equal(result, true);
+            });
+
+            it('Returns false if the url is on the correct origin and subdirectory and a resource does not exist', async function () {
+                const siteUrl = new URL('https://website.com/subdir');
+                const resourceService = {
+                    getByURL: sinon.stub()
+                };
+                const routingService = new RoutingService({
+                    siteUrl,
+                    resourceService
+                });
+
+                resourceService.getByURL.resolves(null);
+
                 checkJustSubdomain: {
                     const result = await routingService.pageExists(new URL('https://website.com/subdir'));
-                assert.equal(result, true);
+                    assert.equal(result, false);
                     break checkJustSubdomain;
                 }
 
                 checkLongerPath: {
                     const result = await routingService.pageExists(new URL('https://website.com/subdir/page'));
-                assert.equal(result, true);
+                    assert.equal(result, false);
                     break checkLongerPath;
                 }
             });
         });
+    });
 });