refactor(webhook): type yes/no postback handlers

src/webhook/handlers/askingArticleSource.ts

@@ -1,5 +1,8 @@
 import { t } from 'ttag';
+import { Message } from '@line/bot-sdk';
+import { z } from 'zod';
 import ga from 'src/lib/ga';
+import { ChatbotPostbackHandler } from 'src/types/chatbotState';
 
 import {
   POSTBACK_YES,
@@ -12,14 +15,26 @@ import {
 } from './utils';
 
 import { TUTORIAL_STEPS } from './tutorial';
-import { ChatbotPostbackHandler } from 'src/types/chatbotState';
-import { Message } from '@line/bot-sdk';
+
+
+const inputSchema = z.enum([POSTBACK_NO, POSTBACK_YES]);
+
+/** Postback input type for ASKING_ARTICLE_SOURCE state handler */
+export type Input = z.infer<typeof inputSchema>;
 
 const askingArticleSource: ChatbotPostbackHandler = async ({
   data,
-  postbackData: { state, input },
+  postbackData: { state, input: postbackInput },
   userId,
 }) => {
+  let input: Input;
+  try {
+    input = inputSchema.parse(postbackInput);
+  } catch (e) {
+    console.error('[choosingReply]', e);
+    throw new ManipulationError(t`Please choose from provided options.`);
+  }
+
   let replies: Message[] = [];
 
   const visitor = ga(
@@ -29,8 +44,10 @@ const askingArticleSource: ChatbotPostbackHandler = async ({
   );
 
   switch (input) {
-    default:
-      throw new ManipulationError(t`Please choose from provided options.`);
+    default: {
+      // Exhaustive check
+      return input satisfies never;
+    }
 
     case POSTBACK_NO:
       replies = [

src/webhook/handlers/askingArticleSubmissionConsent.ts

@@ -1,10 +1,21 @@
 import { t } from 'ttag';
 import { Message } from '@line/bot-sdk';
+import { z } from 'zod';
 
 import { ChatbotPostbackHandler } from 'src/types/chatbotState';
 import ga from 'src/lib/ga';
 import gql from 'src/lib/gql';
 import { getArticleURL } from 'src/lib/sharedUtils';
+import UserSettings from 'src/database/models/userSettings';
+import UserArticleLink from 'src/database/models/userArticleLink';
+import {
+  ArticleTypeEnum,
+  SubmitMediaArticleUnderConsentMutation,
+  SubmitMediaArticleUnderConsentMutationVariables,
+  SubmitTextArticleUnderConsentMutation,
+  SubmitTextArticleUnderConsentMutationVariables,
+} from 'typegen/graphql';
+
 import {
   POSTBACK_YES,
   POSTBACK_NO,
@@ -16,25 +27,29 @@ import {
   getLineContentProxyURL,
   createAIReply,
 } from './utils';
-import UserSettings from 'src/database/models/userSettings';
-import UserArticleLink from 'src/database/models/userArticleLink';
-import {
-  ArticleTypeEnum,
-  SubmitMediaArticleUnderConsentMutation,
-  SubmitMediaArticleUnderConsentMutationVariables,
-  SubmitTextArticleUnderConsentMutation,
-  SubmitTextArticleUnderConsentMutationVariables,
-} from 'typegen/graphql';
+
+const inputSchema = z.enum([POSTBACK_NO, POSTBACK_YES]);
+
+/** Postback input type for ASKING_ARTICLE_SUBMISSION_CONSENT state handler */
+export type Input = z.infer<typeof inputSchema>;
 
 function uppercase<T extends string>(s: T) {
   return s.toUpperCase() as Uppercase<T>;
 }
 
 const askingArticleSubmissionConsent: ChatbotPostbackHandler = async ({
   data,
-  postbackData: { state, input },
+  postbackData: { state, input: postbackInput },
   userId,
 }) => {
+  let input: Input;
+  try {
+    input = inputSchema.parse(postbackInput);
+  } catch (e) {
+    console.error('[askingArticleSubmissionConsnet]', e);
+    throw new ManipulationError(t`Please choose from provided options.`);
+  }
+
   const visitor = ga(
     userId,
     state,
@@ -45,7 +60,8 @@ const askingArticleSubmissionConsent: ChatbotPostbackHandler = async ({
 
   switch (input) {
     default:
-      throw new ManipulationError(t`Please choose from provided options.`);
+      // Exhaustive check
+      return input satisfies never;
 
     case POSTBACK_NO:
       visitor.event({ ec: 'Article', ea: 'Create', el: 'No' });

src/webhook/handlers/utils.ts

@@ -11,7 +11,11 @@ import type {
 } from '@line/bot-sdk';
 import { t, msgid, ngettext } from 'ttag';
 import GraphemeSplitter from 'grapheme-splitter';
+
 import gql from 'src/lib/gql';
+import { getArticleURL, createTypeWords } from 'src/lib/sharedUtils';
+import { sign } from 'src/lib/jwt';
+import { ChatbotState, PostbackActionData } from 'src/types/chatbotState';
 
 import type {
   CreateHighlightContentsHighlightFragment,
@@ -21,26 +25,31 @@ import type {
   CreateAiReplyMutation,
   CreateAiReplyMutationVariables,
 } from 'typegen/graphql';
-import { getArticleURL, createTypeWords } from 'src/lib/sharedUtils';
-import { sign } from 'src/lib/jwt';
-import { ChatbotState, PostbackActionData } from 'src/types/chatbotState';
+
 import type { Input as ChoosingReplyInput } from './choosingReply';
+import type { Input as AskingArticleSourceInput } from './askingArticleSource';
+import type { Input as AskingArticleSubmissionConsentInput } from './askingArticleSubmissionConsent';
 
 const splitter = new GraphemeSplitter();
 
+/**
+ * Maps ChatbotState to the postback action data
+ */
 type StateInputMap = {
   __INIT__: string;
   TUTORIAL: string;
   CHOOSING_ARTICLE: string;
   CHOOSING_REPLY: ChoosingReplyInput;
-  ASKING_ARTICLE_SOURCE: string;
-  ASKING_ARTICLE_SUBMISSION_CONSENT: string;
+  ASKING_ARTICLE_SOURCE: AskingArticleSourceInput;
+  ASKING_ARTICLE_SUBMISSION_CONSENT: AskingArticleSubmissionConsentInput;
   Error: unknown;
 };
 
 /**
+ * Generate a postback action with a payload that the state handler can process properly.
+ *
  * @param label - Postback action button text, max 20 words
- * @param input - Input when pressed
+ * @param input - Input when pressed. The format must match the postback data type for that state.
  * @param displayText - Text to display in chat window.
  * @param sessionId - Current session ID
  * @param state - the state that processes the postback