Simplify config type

Use separate config type for client and middleware.

Author: Hyunje Jun

lib/client.ts

@@ -6,7 +6,7 @@ import { toArray } from "./util";
 export default class Client {
   public config: Types.ClientConfig;
 
-  constructor(config: Types.Config & Types.ClientConfig) {
+  constructor(config: Types.ClientConfig) {
     if (!config.channelAccessToken) {
       throw new Error("no channel access token");
     }

lib/middleware.ts

@@ -14,9 +14,7 @@ export type Middleware = (
   next: NextCallback,
 ) => void;
 
-export default function middleware(
-  config: Types.Config & Types.MiddlewareConfig,
-): Middleware {
+export default function middleware(config: Types.MiddlewareConfig): Middleware {
   if (!config.channelSecret) {
     throw new Error("no channel secret");
   }

lib/types.ts

@@ -1,12 +1,15 @@
-export type ClientConfig = {
+export interface Config {
+  channelAccessToken?: string;
+  channelSecret?: string;
+}
+
+export interface ClientConfig extends Config {
   channelAccessToken: string;
-};
+}
 
-export type MiddlewareConfig = {
+export interface MiddlewareConfig extends Config {
   channelSecret: string;
-};
-
-export type Config = ClientConfig | MiddlewareConfig;
+}
 
 export type Profile = {
   displayName: string;