data: track: withDate

1 files changed, 34 insertions, 0 deletions

diff --git a/src/data/composite/things/track/withDate.js b/src/data/composite/things/track/withDate.js
new file mode 100644
index 00000000..b5a770e9
--- /dev/null
+++ b/src/data/composite/things/track/withDate.js
@@ -0,0 +1,34 @@
+// Gets the track's own date. This is either its dateFirstReleased property
+// or, if unset, the album's date.
+
+import {input, templateCompositeFrom} from '#composite';
+
+import withPropertyFromAlbum from './withPropertyFromAlbum.js';
+
+export default templateCompositeFrom({
+  annotation: `withDate`,
+
+  outputs: ['#date'],
+
+  steps: () => [
+    {
+      dependencies: ['dateFirstReleased'],
+      compute: (continuation, {dateFirstReleased}) =>
+        (dateFirstReleased
+          ? continuation.raiseOutput({'#date': dateFirstReleased})
+          : continuation()),
+    },
+
+    withPropertyFromAlbum({
+      property: input.value('date'),
+    }),
+
+    {
+      dependencies: ['#album.date'],
+      compute: (continuation, {['#album.date']: albumDate}) =>
+        (albumDate
+          ? continuation.raiseOutput({'#date': albumDate})
+          : continuation.raiseOutput({'#date': null})),
+    },
+  ],
+})