plugins/catalog-backend: add gitlab reader processor

plugins/catalog-backend/src/ingestion/LocationReaders.ts

@@ -26,6 +26,7 @@ import { AnnotateLocationEntityProcessor } from './processors/AnnotateLocationEn
 import { EntityPolicyProcessor } from './processors/EntityPolicyProcessor';
 import { FileReaderProcessor } from './processors/FileReaderProcessor';
 import { GithubReaderProcessor } from './processors/GithubReaderProcessor';
+import { GitlabReaderProcessor } from './processors/GitlabReaderProcessor';
 import { LocationRefProcessor } from './processors/LocationEntityProcessor';
 import * as result from './processors/results';
 import {
@@ -56,6 +57,7 @@ export class LocationReaders implements LocationReader {
     return [
       new FileReaderProcessor(),
       new GithubReaderProcessor(),
+      new GitlabReaderProcessor(),
       new YamlProcessor(),
       new EntityPolicyProcessor(entityPolicy),
       new LocationRefProcessor(),

plugins/catalog-backend/src/ingestion/processors/GitlabReaderProcessor.ts

@@ -0,0 +1,93 @@
+/*
+ * Copyright 2020 Spotify AB
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+import { LocationSpec } from '@backstage/catalog-model';
+import fetch from 'node-fetch';
+import * as result from './results';
+import { LocationProcessor, LocationProcessorEmit } from './types';
+
+export class GitlabReaderProcessor implements LocationProcessor {
+  async readLocation(
+    location: LocationSpec,
+    optional: boolean,
+    emit: LocationProcessorEmit,
+  ): Promise<boolean> {
+    if (location.type !== 'gitlab') {
+      return false;
+    }
+
+    try {
+      const url = this.buildRawUrl(location.target);
+
+      const response = await fetch(url.toString());
+
+      if (response.ok) {
+        const data = await response.buffer();
+        emit(result.data(location, data));
+      } else {
+        const message = `${location.target} could not be read as ${url}, ${response.status} ${response.statusText}`;
+        if (response.status === 404) {
+          if (!optional) {
+            throw result.notFoundError(location, message);
+          }
+        } else {
+          throw result.generalError(location, message);
+        }
+      }
+    } catch (e) {
+      const message = `Unable to read ${location.type} ${location.target}, ${e}`;
+      emit(result.generalError(location, message));
+    }
+
+    return true;
+  }
+
+  // Converts
+  // from: https://gitlab.example.com/a/b/blob/master/c.yaml
+  // to:   https://gitlab.example.com/a/b/raw/master/c.yaml
+  private buildRawUrl(target: string): URL {
+    try {
+      const url = new URL(target);
+
+      const [
+        empty,
+        userOrOrg,
+        repoName,
+        blobKeyword,
+        ...restOfPath
+      ] = url.pathname.split('/');
+
+      if (
+        empty !== '' ||
+        userOrOrg === '' ||
+        repoName === '' ||
+        blobKeyword !== 'blob' ||
+        !restOfPath.join('/').match(/\.yaml$/)
+      ) {
+        throw new Error('Wrong Gitlab URL');
+      }
+
+      // Replace 'blob' with 'raw'
+      url.pathname = [empty, userOrOrg, repoName, 'raw', ...restOfPath].join(
+        '/',
+      );
+
+      return url;
+    } catch (e) {
+      throw new Error(`Incorrect url: ${target}, ${e}`);
+    }
+  }
+}