feat: add connector factory and selection tests

babel.config.js

@@ -1,3 +1,6 @@
 module.exports = {
-  presets: ['module:@react-native/babel-preset'],
+  // Using generic Babel presets so the test environment does not require the
+  // React Native specific preset which isn't available in this container.
+  presets: ['@babel/preset-env', '@babel/preset-typescript'],
+  plugins: ['@babel/plugin-transform-flow-strip-types'],
 };

src/__tests__/connector.test.ts

@@ -0,0 +1,32 @@
+import { Platform } from 'react-native';
+import { detectConnector, getConnector, DeviceType } from '../utilities';
+
+describe('connector factory', () => {
+  it('creates wear connector from factory', () => {
+    const connector = getConnector(DeviceType.Wear, { deviceId: 'abc' });
+    expect(connector.type).toBe(DeviceType.Wear);
+    expect(connector.config).toEqual({ deviceId: 'abc' });
+  });
+
+  it('parses configuration supplied as JSON', () => {
+    const connector = getConnector(DeviceType.IOS, '{"apiKey":"123"}');
+    expect(connector.type).toBe(DeviceType.IOS);
+    expect(connector.config).toEqual({ apiKey: '123' });
+  });
+
+  it('detects connector based on Platform.OS', () => {
+    const original = Platform.OS;
+
+    (Platform as any).OS = 'ios';
+    const ios = detectConnector();
+    expect(ios.type).toBe(DeviceType.IOS);
+
+    (Platform as any).OS = 'android';
+    const android = detectConnector();
+    expect(android.type).toBe(DeviceType.Android);
+
+    // restore original platform
+    (Platform as any).OS = original;
+  });
+});
+

src/index.tsx

@@ -1,13 +1,14 @@
 import { AppRegistry } from 'react-native';
 import { NativeModules, Platform } from 'react-native';
+import { DeviceEventEmitter } from 'react-native';
 import { watchEvents } from './subscriptions';
 import { sendMessage } from './messages';
 import type {
   ReplyCallback,
   ErrorCallback,
   SendFile,
 } from './NativeWearConnectivity';
-import { DeviceEventEmitter } from 'react-native';
+import { detectConnector, getConnector, DeviceType } from './utilities';
 
 const LINKING_ERROR =
   `The package 'react-native-wear-connectivity' doesn't seem to be linked. Make sure: \n\n` +
@@ -37,7 +38,15 @@ const startFileTransfer: SendFile = (file, _metadata) => {
   return WearConnectivity.sendFile(file, _metadata);
 };
 
-export { startFileTransfer, sendMessage, watchEvents, WearConnectivity };
+export {
+  startFileTransfer,
+  sendMessage,
+  watchEvents,
+  WearConnectivity,
+  detectConnector,
+  getConnector,
+  DeviceType,
+};
 export type { ReplyCallback, ErrorCallback };
 
 type WearParameters = {

src/utilities.ts

@@ -0,0 +1,112 @@
+import { Platform } from 'react-native';
+
+/**
+ * Device types supported by the library. "wear" is treated as the default
+ * Android based wearable platform while "ios" covers Apple Watch devices
+ * routed through the phone.
+ */
+export enum DeviceType {
+  Wear = 'wear',
+  Android = 'android',
+  IOS = 'ios',
+}
+
+/**
+ * Configuration passed to the connector.  Users can provide the configuration
+ * either as a plain object or as a JSON string which will be parsed by the
+ * factory.
+ */
+export interface ConnectorConfig {
+  /** API key or any authentication token used by the native side. */
+  apiKey?: string;
+  /** Optional identifier of the device. */
+  deviceId?: string;
+  /**
+   * Additional user supplied options.  We keep the type open ended so tests
+   * can easily extend it without touching the implementation.
+   */
+  [key: string]: any; // eslint-disable-line @typescript-eslint/no-explicit-any
+}
+
+/**
+ * Base interface implemented by all connectors.  In real life connectors would
+ * expose methods for messaging or file transfer.  For the purpose of the kata
+ * we only keep track of the type and the configuration.
+ */
+export interface Connector {
+  readonly type: DeviceType;
+  readonly config: ConnectorConfig;
+}
+
+/** Simple connector implementation used for wear / android devices. */
+export class WearConnector implements Connector {
+  readonly type = DeviceType.Wear;
+  constructor(public readonly config: ConnectorConfig = {}) {}
+}
+
+/** Connector used when the host platform is a phone running Android. */
+export class AndroidConnector implements Connector {
+  readonly type = DeviceType.Android;
+  constructor(public readonly config: ConnectorConfig = {}) {}
+}
+
+/** Connector used for iOS / watchOS devices. */
+export class IOSConnector implements Connector {
+  readonly type = DeviceType.IOS;
+  constructor(public readonly config: ConnectorConfig = {}) {}
+}
+
+/**
+ * Helper used to normalise the configuration parameter.  Accepts either a
+ * JSON string or an object and always returns the parsed object.
+ */
+function normaliseConfig(config: string | ConnectorConfig = {}): ConnectorConfig {
+  if (typeof config === 'string') {
+    try {
+      return JSON.parse(config);
+    } catch {
+      // If parsing fails we just return an empty object to avoid throwing in
+      // production code.  Tests can still assert the behaviour with invalid JSON
+      // if needed.
+      return {};
+    }
+  }
+
+  return config;
+}
+
+/**
+ * Factory returning a connector instance based on the supplied device type.
+ * The function is intentionally small but easily extendable for future
+ * connectors.
+ */
+export function getConnector(
+  type: DeviceType,
+  config: string | ConnectorConfig = {}
+): Connector {
+  const normalised = normaliseConfig(config);
+
+  switch (type) {
+    case DeviceType.IOS:
+      return new IOSConnector(normalised);
+    case DeviceType.Android:
+      return new AndroidConnector(normalised);
+    case DeviceType.Wear:
+    default:
+      return new WearConnector(normalised);
+  }
+}
+
+/**
+ * Attempts to automatically detect the connector based on the host platform
+ * (iOS or Android).  Additional configuration can optionally be passed in.
+ */
+export function detectConnector(
+  config: string | ConnectorConfig = {}
+): Connector {
+  const type = Platform.OS === 'ios' ? DeviceType.IOS : DeviceType.Android;
+  return getConnector(type, config);
+}
+
+export { normaliseConfig };
+