1 files changed, 46 insertions, 0 deletions
diff --git a/src/data/composite/wiki-properties/singleReference.js b/src/data/composite/wiki-properties/singleReference.js
new file mode 100644
index 0000000..db4fc9f
--- /dev/null
+++ b/src/data/composite/wiki-properties/singleReference.js
@@ -0,0 +1,46 @@
+// Stores and exposes one connection, or reference, to another data object.
+// The reference must be to a specific type, which is specified on the class
+// input.
+//
+// See also:
+//  - referenceList
+//  - withResolvedReference
+//
+
+import {input, templateCompositeFrom} from '#composite';
+import {isThingClass, validateReference} from '#validators';
+
+import {exposeDependency} from '#composite/control-flow';
+import {inputWikiData, withResolvedReference} from '#composite/wiki-data';
+
+export default templateCompositeFrom({
+  annotation: `singleReference`,
+
+  compose: false,
+
+  inputs: {
+    class: input.staticValue({validate: isThingClass}),
+
+    find: input({type: 'function'}),
+
+    data: inputWikiData({allowMixedTypes: false}),
+  },
+
+  update: ({
+    [input.staticValue('class')]: thingClass,
+  }) => ({
+    validate:
+      validateReference(
+        thingClass[Symbol.for('Thing.referenceType')]),
+  }),
+
+  steps: () => [
+    withResolvedReference({
+      ref: input.updateValue(),
+      data: input('data'),
+      find: input('find'),
+    }),
+
+    exposeDependency({dependency: '#resolvedReference'}),
+  ],
+});