1 files changed, 63 insertions, 0 deletions
diff --git a/src/data/composite/things/track/withContainingTrackSection.js b/src/data/composite/things/track/withContainingTrackSection.js
new file mode 100644
index 0000000..b2e5f2b
--- /dev/null
+++ b/src/data/composite/things/track/withContainingTrackSection.js
@@ -0,0 +1,63 @@
+// Gets the track section containing this track from its album's track list.
+// If notFoundMode is set to 'exit', this will early exit if the album can't be
+// found or if none of its trackSections includes the track for some reason.
+
+import {input, templateCompositeFrom} from '#composite';
+import {is} from '#validators';
+
+import withPropertyFromAlbum from './withPropertyFromAlbum.js';
+
+export default templateCompositeFrom({
+  annotation: `withContainingTrackSection`,
+
+  inputs: {
+    notFoundMode: input({
+      validate: is('exit', 'null'),
+      defaultValue: 'null',
+    }),
+  },
+
+  outputs: ['#trackSection'],
+
+  steps: () => [
+    withPropertyFromAlbum({
+      property: input.value('trackSections'),
+      notFoundMode: input('notFoundMode'),
+    }),
+
+    {
+      dependencies: [
+        input.myself(),
+        input('notFoundMode'),
+        '#album.trackSections',
+      ],
+
+      compute(continuation, {
+        [input.myself()]: track,
+        [input('notFoundMode')]: notFoundMode,
+        ['#album.trackSections']: trackSections,
+      }) {
+        if (!trackSections) {
+          return continuation.raiseOutput({
+            ['#trackSection']: null,
+          });
+        }
+
+        const trackSection =
+          trackSections.find(({tracks}) => tracks.includes(track));
+
+        if (trackSection) {
+          return continuation.raiseOutput({
+            ['#trackSection']: trackSection,
+          });
+        } else if (notFoundMode === 'exit') {
+          return continuation.exit(null);
+        } else {
+          return continuation.raiseOutput({
+            ['#trackSection']: null,
+          });
+        }
+      },
+    },
+  ],
+});