Abstract Publisher APIs from the router

1. Move fetchMetadata and serve static files to local publisher
2. Create factory class to create publishers based on app cofig

plugins/techdocs-backend/src/service/helpers.ts

@@ -15,7 +15,7 @@
  */
 import Docker from 'dockerode';
 import { Logger } from 'winston';
-import { Entity } from '@backstage/catalog-model';
+import { Entity, EntityName } from '@backstage/catalog-model';
 import {
   PreparerBuilder,
   PublisherBase,
@@ -127,3 +127,18 @@ export class DocsBuilder {
     return false;
   }
 }
+
+/**
+ * Using the path of the TechDocs page URL, return a structured EntityName type object with namespace,
+ * kind and name of the Entity.
+ * @param {string} path Example: default/Component/documented-component
+ */
+export const getEntityNameFromUrlPath = (path: string): EntityName => {
+  const [kind, namespace, name] = path.split('/');
+
+  return {
+    kind,
+    namespace,
+    name,
+  };
+};

plugins/techdocs-backend/src/service/router.ts

@@ -26,12 +26,9 @@ import {
   PublisherBase,
   getLocationForEntity,
 } from '@backstage/techdocs-common';
-import {
-  PluginEndpointDiscovery,
-  resolvePackagePath,
-} from '@backstage/backend-common';
+import { PluginEndpointDiscovery } from '@backstage/backend-common';
 import { Entity } from '@backstage/catalog-model';
-import { DocsBuilder } from './helpers';
+import { DocsBuilder, getEntityNameFromUrlPath } from './helpers';
 
 type RouterOptions = {
   preparers: PreparerBuilder;
@@ -44,11 +41,6 @@ type RouterOptions = {
   dockerClient: Docker;
 };
 
-const staticDocsDir = resolvePackagePath(
-  '@backstage/plugin-techdocs-backend',
-  'static/docs',
-);
-
 export async function createRouter({
   preparers,
   generators,
@@ -61,24 +53,18 @@ export async function createRouter({
   const router = Router();
 
   router.get('/metadata/techdocs/*', async (req, res) => {
-    let storageUrl = config.getString('techdocs.storageUrl');
-    if (publisher.isLocalPublisher()) {
-      storageUrl = new URL(
-        new URL(storageUrl).pathname,
-        await discovery.getBaseUrl('techdocs'),
-      ).toString();
-    }
+    // path is `:namespace/:kind:/:name`
     const { '0': path } = req.params;
+    const entityName = getEntityNameFromUrlPath(path);
 
-    const metadataURL = `${storageUrl}/${path}/techdocs_metadata.json`;
-
-    try {
-      const techdocsMetadata = await (await fetch(metadataURL)).json();
-      res.send(techdocsMetadata);
-    } catch (err) {
-      logger.info(`Unable to get metadata for ${path} with error ${err}`);
-      throw new Error(`Unable to get metadata for ${path} with error ${err}`);
-    }
+    publisher
+      .fetchTechDocsMetadata(entityName)
+      .then(techdocsMetadataJson => {
+        res.send(techdocsMetadataJson);
+      })
+      .catch(reason => {
+        res.status(500).send(`Unable to get Metadata. Reason: ${reason}`);
+      });
   });
 
   router.get('/metadata/entity/:namespace/:kind/:name', async (req, res) => {
@@ -139,9 +125,7 @@ export async function createRouter({
     res.redirect(`${storageUrl}${req.path.replace('/docs', '')}`);
   });
 
-  if (publisher.isLocalPublisher()) {
-    router.use('/static/docs', express.static(staticDocsDir));
-  }
+  router.use('/static/docs', publisher.docsRouter());
 
   return router;
 }

plugins/techdocs-backend/src/service/standaloneServer.ts

@@ -64,7 +64,7 @@ export async function startStandaloneServer(
   const techdocsGenerator = new TechdocsGenerator(logger, config);
   generators.register('techdocs', techdocsGenerator);
 
-  const publisher = new Publisher(logger, config, discovery);
+  const publisher = Publisher.fromConfig(config, logger, discovery);
 
   const dockerClient = new Docker();