From b6be163ccb8e4b9de9afe25900850b6b4657cd1c Mon Sep 17 00:00:00 2001
From: David Lechner <david@pybricks.com>
Date: Mon, 8 Jun 2020 19:36:59 -0500
Subject: [PATCH] refactor lookup function

---
 src/components/button.test.ts       | 11 +----------
 src/components/editor.test.ts       | 11 +----------
 src/components/notification.test.ts | 11 +----------
 src/utils/index.test.ts             |  8 +++++++-
 src/utils/index.ts                  | 15 +++++++++++++++
 5 files changed, 25 insertions(+), 31 deletions(-)

diff --git a/src/components/button.test.ts b/src/components/button.test.ts
index 1483a68e..8b6ce7ff 100644
--- a/src/components/button.test.ts
+++ b/src/components/button.test.ts
@@ -1,19 +1,10 @@
 // SPDX-License-Identifier: MIT
 // Copyright (c) 2020 The Pybricks Authors
 
+import { lookup } from '../utils';
 import { TooltipId } from './button';
 import en from './button.en.json';
 
-function lookup(obj: object, id: string): string | undefined {
-    const value = id
-        .split('.')
-        .reduce((pv, cv) => pv && (pv as Record<string, object>)[cv], obj);
-    if (typeof value === 'string') {
-        return value;
-    }
-    return undefined;
-}
-
 describe('Ensure .json file has matches for TooltipIds', () => {
     test.each(Object.values(TooltipId))('%s', (id) => {
         expect(lookup(en, id)).toBeDefined();
diff --git a/src/components/editor.test.ts b/src/components/editor.test.ts
index 0db32b08..bc5d3eda 100644
--- a/src/components/editor.test.ts
+++ b/src/components/editor.test.ts
@@ -1,19 +1,10 @@
 // SPDX-License-Identifier: MIT
 // Copyright (c) 2020 The Pybricks Authors
 
+import { lookup } from '../utils';
 import { EditorStringId } from './editor';
 import en from './editor.en.json';
 
-function lookup(obj: object, id: string): string | undefined {
-    const value = id
-        .split('.')
-        .reduce((pv, cv) => pv && (pv as Record<string, object>)[cv], obj);
-    if (typeof value === 'string') {
-        return value;
-    }
-    return undefined;
-}
-
 describe('Ensure .json file has matches for EditorStringId', () => {
     test.each(Object.values(EditorStringId))('%s', (id) => {
         expect(lookup(en, id)).toBeDefined();
diff --git a/src/components/notification.test.ts b/src/components/notification.test.ts
index 12b7c6aa..fe69432d 100644
--- a/src/components/notification.test.ts
+++ b/src/components/notification.test.ts
@@ -2,18 +2,9 @@
 // Copyright (c) 2020 The Pybricks Authors
 
 import { MessageId } from '../reducers/notification';
+import { lookup } from '../utils';
 import en from './notification.en.json';
 
-function lookup(obj: object, id: string): string | undefined {
-    const value = id
-        .split('.')
-        .reduce((pv, cv) => pv && (pv as Record<string, object>)[cv], obj);
-    if (typeof value === 'string') {
-        return value;
-    }
-    return undefined;
-}
-
 describe('Ensure .json file has matches for MessageIds', () => {
     test.each(Object.values(MessageId))('%s', (id) => {
         expect(lookup(en, id)).toBeDefined();
diff --git a/src/utils/index.test.ts b/src/utils/index.test.ts
index 203ceede..9f69757c 100644
--- a/src/utils/index.test.ts
+++ b/src/utils/index.test.ts
@@ -1,7 +1,7 @@
 // SPDX-License-Identifier: MIT
 // Copyright (c) 2020 The Pybricks Authors
 
-import { assert, hex } from '.';
+import { assert, hex, lookup } from '.';
 
 test('assert', () => {
     const assertTrue = jest.fn(() => assert(true, 'should not throw'));
@@ -16,3 +16,9 @@ test('hex', () => {
     expect(hex(1, 4)).toBe('0x0001');
     expect(hex(2, 8)).toBe('0x00000002');
 });
+
+test('lookup', () => {
+    const obj = { a: { b: { c: 'd' } } };
+    expect(lookup(obj, 'a.b.c')).toBe('d');
+    expect(lookup(obj, 'a.x.y')).toBeUndefined();
+});
diff --git a/src/utils/index.ts b/src/utils/index.ts
index ea7af95f..7695b84a 100644
--- a/src/utils/index.ts
+++ b/src/utils/index.ts
@@ -21,3 +21,18 @@ export function assert(condition: boolean, message: string): void {
 export function hex(n: number, pad: number): string {
     return `0x${n.toString(16).padStart(pad, '0')}`;
 }
+
+/**
+ * Looks up a nested property in an object.
+ * @param obj The object
+ * @param id The property path
+ */
+export function lookup(obj: object, id: string): string | undefined {
+    const value = id
+        .split('.')
+        .reduce((pv, cv) => pv && (pv as Record<string, object>)[cv], obj);
+    if (typeof value === 'string') {
+        return value;
+    }
+    return undefined;
+}