5 files changed, 33 insertions, 158 deletions

diff --git a/src/data/composite/things/album/index.js b/src/data/composite/things/album/index.js
index 8139f10e..8b5098f0 100644
--- a/src/data/composite/things/album/index.js
+++ b/src/data/composite/things/album/index.js
@@ -1,2 +1 @@
 export {default as withTracks} from './withTracks.js';
-export {default as withTrackSections} from './withTrackSections.js';
diff --git a/src/data/composite/things/album/withTrackSections.js b/src/data/composite/things/album/withTrackSections.js
deleted file mode 100644
index 0a1ebebc..00000000
--- a/src/data/composite/things/album/withTrackSections.js
+++ /dev/null
@@ -1,127 +0,0 @@
-import {input, templateCompositeFrom} from '#composite';
-import find from '#find';
-import {empty, filterMultipleArrays, stitchArrays} from '#sugar';
-import {isTrackSectionList} from '#validators';
-
-import {exitWithoutDependency, exitWithoutUpdateValue}
-  from '#composite/control-flow';
-import {withResolvedReferenceList} from '#composite/wiki-data';
-
-import {
-  fillMissingListItems,
-  withFlattenedList,
-  withPropertiesFromList,
-  withUnflattenedList,
-} from '#composite/data';
-
-export default templateCompositeFrom({
-  annotation: `withTrackSections`,
-
-  outputs: ['#trackSections'],
-
-  steps: () => [
-    exitWithoutDependency({
-      dependency: 'ownTrackData',
-      value: input.value([]),
-    }),
-
-    exitWithoutUpdateValue({
-      mode: input.value('empty'),
-      value: input.value([]),
-    }),
-
-    // TODO: input.updateValue description down here is a kludge.
-    withPropertiesFromList({
-      list: input.updateValue({
-        validate: isTrackSectionList,
-      }),
-      prefix: input.value('#sections'),
-      properties: input.value([
-        'tracks',
-        'dateOriginallyReleased',
-        'isDefaultTrackSection',
-        'name',
-        'color',
-      ]),
-    }),
-
-    fillMissingListItems({
-      list: '#sections.tracks',
-      fill: input.value([]),
-    }),
-
-    fillMissingListItems({
-      list: '#sections.isDefaultTrackSection',
-      fill: input.value(false),
-    }),
-
-    fillMissingListItems({
-      list: '#sections.name',
-      fill: input.value('Unnamed Track Section'),
-    }),
-
-    fillMissingListItems({
-      list: '#sections.color',
-      fill: input.dependency('color'),
-    }),
-
-    withFlattenedList({
-      list: '#sections.tracks',
-    }).outputs({
-      ['#flattenedList']: '#trackRefs',
-      ['#flattenedIndices']: '#sections.startIndex',
-    }),
-
-    withResolvedReferenceList({
-      list: '#trackRefs',
-      data: 'ownTrackData',
-      notFoundMode: input.value('null'),
-      find: input.value(find.track),
-    }).outputs({
-      ['#resolvedReferenceList']: '#tracks',
-    }),
-
-    withUnflattenedList({
-      list: '#tracks',
-      indices: '#sections.startIndex',
-    }).outputs({
-      ['#unflattenedList']: '#sections.tracks',
-    }),
-
-    {
-      dependencies: [
-        '#sections.tracks',
-        '#sections.name',
-        '#sections.color',
-        '#sections.dateOriginallyReleased',
-        '#sections.isDefaultTrackSection',
-        '#sections.startIndex',
-      ],
-
-      compute: (continuation, {
-        '#sections.tracks': tracks,
-        '#sections.name': name,
-        '#sections.color': color,
-        '#sections.dateOriginallyReleased': dateOriginallyReleased,
-        '#sections.isDefaultTrackSection': isDefaultTrackSection,
-        '#sections.startIndex': startIndex,
-      }) => {
-        filterMultipleArrays(
-          tracks, name, color, dateOriginallyReleased, isDefaultTrackSection, startIndex,
-          tracks => !empty(tracks));
-
-        return continuation({
-          ['#trackSections']:
-            stitchArrays({
-              tracks,
-              name,
-              color,
-              dateOriginallyReleased,
-              isDefaultTrackSection,
-              startIndex,
-            }),
-        });
-      },
-    },
-  ],
-});
diff --git a/src/data/composite/things/album/withTracks.js b/src/data/composite/things/album/withTracks.js
index fff3d5ae..05f5b24d 100644
--- a/src/data/composite/things/album/withTracks.js
+++ b/src/data/composite/things/album/withTracks.js
@@ -1,9 +1,8 @@
 import {input, templateCompositeFrom} from '#composite';
-import find from '#find';
 
 import {exitWithoutDependency, raiseOutputWithoutDependency}
   from '#composite/control-flow';
-import {withResolvedReferenceList} from '#composite/wiki-data';
+import {withFlattenedList, withPropertyFromList} from '#composite/data';
 
 export default templateCompositeFrom({
   annotation: `withTracks`,
@@ -11,41 +10,22 @@ export default templateCompositeFrom({
   outputs: ['#tracks'],
 
   steps: () => [
-    exitWithoutDependency({
-      dependency: 'ownTrackData',
-      value: input.value([]),
-    }),
-
     raiseOutputWithoutDependency({
       dependency: 'trackSections',
-      mode: input.value('empty'),
       output: input.value({
-        ['#tracks']: [],
+        '#tracks': [],
       }),
     }),
 
-    {
-      dependencies: ['trackSections'],
-      compute: (continuation, {trackSections}) =>
-        continuation({
-          '#trackRefs': trackSections
-            .flatMap(section => section.tracks ?? []),
-        }),
-    },
-
-    withResolvedReferenceList({
-      list: '#trackRefs',
-      data: 'ownTrackData',
-      find: input.value(find.track),
+    withPropertyFromList({
+      list: 'trackSections',
+      property: input.value('tracks'),
     }),
 
-    {
-      dependencies: ['#resolvedReferenceList'],
-      compute: (continuation, {
-        ['#resolvedReferenceList']: resolvedReferenceList,
-      }) => continuation({
-        ['#tracks']: resolvedReferenceList,
-      })
-    },
+    withFlattenedList({
+      list: '#trackSections.tracks',
+    }).outputs({
+      ['#flattenedList']: '#tracks',
+    }),
   ],
 });
diff --git a/src/data/composite/things/track-section/index.js b/src/data/composite/things/track-section/index.js
new file mode 100644
index 00000000..3202ed49
--- /dev/null
+++ b/src/data/composite/things/track-section/index.js
@@ -0,0 +1 @@
+export {default as withAlbum} from './withAlbum.js';
diff --git a/src/data/composite/things/track-section/withAlbum.js b/src/data/composite/things/track-section/withAlbum.js
new file mode 100644
index 00000000..608cc0cd
--- /dev/null
+++ b/src/data/composite/things/track-section/withAlbum.js
@@ -0,0 +1,22 @@
+// Gets the track section's album. This will early exit if ownAlbumData is
+// missing. If there's no album whose list of track sections includes this one,
+// the output dependency will be null.
+
+import {input, templateCompositeFrom} from '#composite';
+
+import {withUniqueReferencingThing} from '#composite/wiki-data';
+
+export default templateCompositeFrom({
+  annotation: `withAlbum`,
+
+  outputs: ['#album'],
+
+  steps: () => [
+    withUniqueReferencingThing({
+      data: 'ownAlbumData',
+      list: input.value('trackSections'),
+    }).outputs({
+      ['#uniqueReferencingThing']: '#album',
+    }),
+  ],
+});