recursively hoist regions that duplicate their parent (#463)

* recursively hoist single-child nodes

* refactor and test

Author: joshreisner

public/app.js

@@ -16,5 +16,6 @@ export * from './get-index-by-key';
 export * from './load-meeting-data';
 export * from './query-string';
 export * from './settings';
+export * from './streamline-regions-index';
 export * from './translate-google-sheet';
 export * from './user-agent';

src/helpers/index.ts

@@ -5,6 +5,7 @@ import { formatAddress } from './format-address';
 import { formatConferenceProvider } from './format-conference-provider';
 import { formatSlug } from './format-slug';
 import { states } from './states';
+import { streamlineRegionsIndex } from './streamline-regions-index';
 
 import type { Index, JSONData, JSONDataFlat, Meeting, State } from '../types';
 
@@ -517,6 +518,8 @@ export function loadMeetingData(
 
   // determine capabilities (filter out options that apply to every meeting)
   const meetingsCount = Object.keys(meetings).length;
+  indexes.region = streamlineRegionsIndex(indexes.region, meetingsCount);
+
   ['region', 'weekday', 'time', 'type'].forEach(indexKey => {
     capabilities[indexKey as keyof typeof capabilities] = !!indexes[
       indexKey as keyof typeof indexes

src/helpers/load-meeting-data.ts

@@ -0,0 +1,22 @@
+import type { Index } from '../types';
+
+// clean up nodes that apply to all the parent's children
+export const streamlineRegionsIndex = (
+  indexes: Index[],
+  meetingsCount: number
+): Index[] =>
+  indexes
+    .filter(index => index.children || index.slugs.length < meetingsCount)
+    .flatMap(index => {
+      if (index.slugs.length === meetingsCount) {
+        // recursively process children, flattening the result
+        return streamlineRegionsIndex(index.children ?? [], index.slugs.length);
+      }
+      // return a new object with streamlined children if present
+      return {
+        ...index,
+        children: index.children
+          ? streamlineRegionsIndex(index.children, index.slugs.length)
+          : undefined,
+      };
+    });

src/helpers/streamline-regions-index.ts

@@ -0,0 +1,65 @@
+import { streamlineRegionsIndex } from '../../src/helpers';
+import type { Index } from '../../src/types';
+
+describe('streamlineRegionsIndex', () => {
+  it('removes top level regions that apply to all meetings', () => {
+    const mockIndexes: Index[] = [
+      {
+        key: 'usa',
+        name: 'United States',
+        slugs: ['meeting-1', 'meeting-2', 'meeting-3'],
+        children: [
+          {
+            key: 'california',
+            name: 'California',
+            slugs: ['meeting-1', 'meeting-2', 'meeting-3'],
+            children: [
+              {
+                key: 'los-angeles',
+                name: 'Los Angeles',
+                slugs: ['meeting-1', 'meeting-2'],
+              },
+              {
+                key: 'san-francisco',
+                name: 'San Francisco',
+                slugs: ['meeting-3'],
+              },
+            ],
+          },
+        ],
+      },
+    ];
+
+    expect(streamlineRegionsIndex(mockIndexes, 3)).toEqual([
+      {
+        key: 'los-angeles',
+        name: 'Los Angeles',
+        slugs: ['meeting-1', 'meeting-2'],
+      },
+      {
+        key: 'san-francisco',
+        name: 'San Francisco',
+        slugs: ['meeting-3'],
+      },
+    ]);
+  });
+
+  it("removes bottom regions that apply to all parent's meetings", () => {
+    const mockIndexes: Index[] = [
+      {
+        key: 'usa',
+        name: 'United States',
+        slugs: ['meeting-1', 'meeting-2', 'meeting-3'],
+        children: [
+          {
+            key: 'california',
+            name: 'California',
+            slugs: ['meeting-1', 'meeting-2', 'meeting-3'],
+          },
+        ],
+      },
+    ];
+
+    expect(streamlineRegionsIndex(mockIndexes, 3)).toEqual([]);
+  });
+});