refactor(context): typing postback action

- Default as string
- Enable different type of postback action
- Simplify handlePostback() argument with SDK types

src/types/chatbotState.ts

@@ -1,4 +1,4 @@
-import type { Message, MessageEvent } from '@line/bot-sdk';
+import type { Message, MessageEvent, PostbackEvent } from '@line/bot-sdk';
 
 export type ChatbotState =
   | '__INIT__'
@@ -28,18 +28,9 @@ type ArgumentedEventParams = {
   input: string;
 };
 
-export type ChatbotEvent = (
-  | MessageEvent
-  | ServerChooseEvent
-  /**
-   * A special format of postback that Chatbot actually uses: postback + input (provided in `ArgumentedEventParams`)
-   * @FIXME Replace with original PostbackEvent and parse its action to support passing more thing than a string
-   */
-  | {
-      type: 'postback';
-    }
-) &
-  ArgumentedEventParams;
+export type ChatbotEvent =
+  | ((MessageEvent | ServerChooseEvent) & ArgumentedEventParams)
+  | PostbackEvent;
 
 export type Context = {
   /** Used to differientiate different search sessions (searched text or media) */
@@ -82,8 +73,8 @@ export type ChatbotStateHandler = (
  *
  * @FIXME Replace input: string with something that is more structured
  */
-export type PostbackActionData = {
-  input: string;
+export type PostbackActionData<T> = {
+  input: T;
   sessionId: number;
   state: ChatbotState;
 };

src/webhook/handlePostback.ts

@@ -11,6 +11,7 @@ import {
   ChatbotState,
   ChatbotStateHandlerParams,
   ChatbotStateHandlerReturnType,
+  PostbackActionData,
 } from 'src/types/chatbotState';
 import { Message } from '@line/bot-sdk';
 
@@ -24,23 +25,15 @@ import { Message } from '@line/bot-sdk';
  */
 export default async function handlePostback(
   { data = {} },
-  state: ChatbotState,
+  postbackData: PostbackActionData<unknown>,
   event: ChatbotEvent,
   userId: string
 ) {
   let replies: Message[] = [];
 
-  if (event.input === undefined) {
-    throw new Error('input undefined');
-  }
-
-  if (event.type !== 'postback') {
-    throw new Error('wrong event type');
-  }
-
   let params: ChatbotStateHandlerParams | ChatbotStateHandlerReturnType = {
     data,
-    state,
+    state: postbackData.state,
     event,
     userId,
     replies,

src/webhook/handlers/utils.ts

@@ -34,15 +34,15 @@ const splitter = new GraphemeSplitter();
  * @param sessionId - Current session ID
  * @param state - the state that processes the postback
  */
-export function createPostbackAction(
+export function createPostbackAction<INPUT = string>(
   label: string,
-  input: string,
+  input: INPUT,
   displayText: string,
   sessionId: number,
   state: ChatbotState
 ): Action {
   // Ensure the data type before stringification
-  const data: PostbackActionData = {
+  const data: PostbackActionData<INPUT> = {
     input,
     sessionId,
     state,

src/webhook/index.ts

@@ -152,12 +152,9 @@ const singleUserHandler = async (
       })
       .send();
   } else if (webhookEvent.type === 'postback') {
-    /**
-     * @FIXME Replace with runtime type check to be future-proof
-     */
     const postbackData = JSON.parse(
       webhookEvent.postback.data
-    ) as PostbackActionData;
+    ) as PostbackActionData<unknown>;
 
     // Handle the case when user context in redis is expired
     if (!context.data) {
@@ -195,9 +192,7 @@ const singleUserHandler = async (
       return;
     }
 
-    const input = postbackData.input;
-    const event: ChatbotEvent = { type: webhookEvent.type, input };
-    result = await handlePostback(context, postbackData.state, event, userId);
+    result = await handlePostback(context, postbackData, webhookEvent, userId);
   }
 
   if (isReplied) {