From bb5055aeea70f4463c00392e57a3f2465541959b Mon Sep 17 00:00:00 2001
From: Johan Haals <johan.haals@gmail.com>
Date: Wed, 14 Apr 2021 09:59:00 +0200
Subject: [PATCH] Catalog-model: Add getEntitySourceLocation helper

Co-authored-by: Patrik Oldsberg <poldsberg@gmail.com>
Signed-off-by: Johan Haals <johan.haals@gmail.com>
---
 .changeset/metal-foxes-speak.md               |  5 ++
 .../src/location/helpers.test.ts              | 51 ++++++++++++++++++-
 .../catalog-model/src/location/helpers.ts     | 26 ++++++++++
 packages/catalog-model/src/location/index.ts  |  6 ++-
 4 files changed, 86 insertions(+), 2 deletions(-)
 create mode 100644 .changeset/metal-foxes-speak.md

diff --git a/.changeset/metal-foxes-speak.md b/.changeset/metal-foxes-speak.md
new file mode 100644
index 0000000000..45b8ae3c7c
--- /dev/null
+++ b/.changeset/metal-foxes-speak.md
@@ -0,0 +1,5 @@
+---
+'@backstage/catalog-model': patch
+---
+
+Add getEntitySourceLocation helper
diff --git a/packages/catalog-model/src/location/helpers.test.ts b/packages/catalog-model/src/location/helpers.test.ts
index 888c79b328..3b5994b956 100644
--- a/packages/catalog-model/src/location/helpers.test.ts
+++ b/packages/catalog-model/src/location/helpers.test.ts
@@ -14,7 +14,11 @@
  * limitations under the License.
  */
 
-import { parseLocationReference, stringifyLocationReference } from './helpers';
+import {
+  getEntitySourceLocation,
+  parseLocationReference,
+  stringifyLocationReference,
+} from './helpers';
 
 describe('parseLocationReference', () => {
   it('works for the simple case', () => {
@@ -68,3 +72,48 @@ describe('stringifyLocationReference', () => {
     ).toThrow('Unable to stringify location reference, empty target');
   });
 });
+
+describe('getEntitySourceLocation', () => {
+  it('returns the source-location', () => {
+    expect(
+      getEntitySourceLocation({
+        apiVersion: 'backstage.io/v1alpha1',
+        kind: 'Location',
+        metadata: {
+          name: 'test',
+          namespace: 'default',
+          annotations: {
+            'backstage.io/source-location': 'url:https://backstage.io/foo.yaml',
+            'backstage.io/managed-by-location': 'url:https://spotify.com',
+          },
+        },
+      }),
+    ).toEqual({ target: 'https://backstage.io/foo.yaml', type: 'url' });
+  });
+
+  it('returns the managed-by-location', () => {
+    expect(
+      getEntitySourceLocation({
+        apiVersion: 'backstage.io/v1alpha1',
+        kind: 'Location',
+        metadata: {
+          name: 'test',
+          namespace: 'default',
+          annotations: {
+            'backstage.io/managed-by-location': 'url:https://spotify.com',
+          },
+        },
+      }),
+    ).toEqual({ target: 'https://spotify.com', type: 'url' });
+  });
+
+  it('rejects missing location annotation', () => {
+    expect(() =>
+      getEntitySourceLocation({
+        apiVersion: 'backstage.io/v1alpha1',
+        kind: 'Location',
+        metadata: { name: 'test', namespace: 'default' },
+      }),
+    ).toThrow(`Entity 'location:default/test' is missing location`);
+  });
+});
diff --git a/packages/catalog-model/src/location/helpers.ts b/packages/catalog-model/src/location/helpers.ts
index fb1be5abad..9dce67d054 100644
--- a/packages/catalog-model/src/location/helpers.ts
+++ b/packages/catalog-model/src/location/helpers.ts
@@ -14,6 +14,9 @@
  * limitations under the License.
  */
 
+import { Entity, stringifyEntityRef } from '../entity';
+import { LOCATION_ANNOTATION, SOURCE_LOCATION_ANNOTATION } from './annotation';
+
 /**
  * Parses a string form location reference.
  *
@@ -80,3 +83,26 @@ export function stringifyLocationReference(ref: {
 
   return `${type}:${target}`;
 }
+
+/**
+ * Returns the source code location of the Entity, to the extend which one exists.
+ *
+ * If the returned location type is of type 'url', the target should be readable at least
+ * using the UrlReader from @backstage/backend-common. If it is not of type 'url', the caller
+ * needs to have explicit handling of each location type or signal that it is not supported.
+ */
+export function getEntitySourceLocation(
+  entity: Entity,
+): { type: string; target: string } {
+  const locationRef =
+    entity.metadata?.annotations?.[SOURCE_LOCATION_ANNOTATION] ??
+    entity.metadata?.annotations?.[LOCATION_ANNOTATION];
+
+  if (!locationRef) {
+    throw new Error(
+      `Entity '${stringifyEntityRef(entity)}' is missing location`,
+    );
+  }
+
+  return parseLocationReference(locationRef);
+}
diff --git a/packages/catalog-model/src/location/index.ts b/packages/catalog-model/src/location/index.ts
index fddc8bde37..751172c6ba 100644
--- a/packages/catalog-model/src/location/index.ts
+++ b/packages/catalog-model/src/location/index.ts
@@ -19,7 +19,11 @@ export {
   ORIGIN_LOCATION_ANNOTATION,
   SOURCE_LOCATION_ANNOTATION,
 } from './annotation';
-export { parseLocationReference, stringifyLocationReference } from './helpers';
+export {
+  parseLocationReference,
+  stringifyLocationReference,
+  getEntitySourceLocation,
+} from './helpers';
 export type { Location, LocationSpec } from './types';
 export {
   analyzeLocationSchema,