2 files changed, 46 insertions, 0 deletions
diff --git a/src/data/composite/things/art-tag/index.js b/src/data/composite/things/art-tag/index.js
new file mode 100644
index 00000000..aedc3a0c
--- /dev/null
+++ b/src/data/composite/things/art-tag/index.js
@@ -0,0 +1 @@
+export {default as withAllDescendantTags} from './withAllDescendantTags.js';
diff --git a/src/data/composite/things/art-tag/withAllDescendantTags.js b/src/data/composite/things/art-tag/withAllDescendantTags.js
new file mode 100644
index 00000000..b832e529
--- /dev/null
+++ b/src/data/composite/things/art-tag/withAllDescendantTags.js
@@ -0,0 +1,45 @@
+// Gets all the tags which descend from this one - that means its own direct
+// descendants, but also all the direct and indirect desceands of each of those!
+// The results aren't specially sorted, but they won't contain any duplicates
+// (for example if two descendant tags both route deeper to end up including
+// some of the same tags).
+
+import {input, templateCompositeFrom} from '#composite';
+import find from '#find';
+import {unique} from '#sugar';
+
+import {raiseOutputWithoutDependency} from '#composite/control-flow';
+import {withResolvedReferenceList} from '#composite/wiki-data';
+
+export default templateCompositeFrom({
+  annotation: `withAllDescendantTags`,
+
+  outputs: ['#allDescendantTags'],
+
+  steps: () => [
+    raiseOutputWithoutDependency({
+      dependency: 'directDescendantTags',
+      mode: input.value('empty'),
+      output: input.value({'#allDescendantTags': []})
+    }),
+
+    withResolvedReferenceList({
+      list: 'directDescendantTags',
+      data: 'artTagData',
+      find: input.value(find.artTag),
+    }),
+
+    {
+      dependencies: ['#resolvedReferenceList'],
+      compute: (continuation, {
+        ['#resolvedReferenceList']: directDescendantTags,
+      }) => continuation({
+        ['#allDescendantTags']:
+          unique([
+            ...directDescendantTags,
+            ...directDescendantTags.flatMap(tag => tag.allDescendantTags),
+          ]),
+      }),
+    },
+  ],
+})