Merge pull request #53 from robertying/discriminate-return-types

Discriminate `getAllContents` return type based on input content type
Harry-Chen · Oct 29, 2023 · ad1a6b0 · ad1a6b0
2 parents 1b914c0 + bdec610
commit ad1a6b0
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Showing 2 changed files with 35 additions and 28 deletions.
diff --git a/src/index.ts b/src/index.ts
@@ -8,7 +8,6 @@ import {
   CredentialProvider,
   Fetch,
   HelperConfig,
-  Content,
   ContentType,
   CourseContent,
   CourseInfo,
@@ -33,6 +32,7 @@ import {
   Language,
   HomeworkTA,
   UserInfo,
+  ContentTypeMap,
 } from './types';
 import {
   decodeHTML,
@@ -322,36 +322,37 @@ export class Learn2018Helper {
    * Get certain type of content of all specified courses.
    * It actually wraps around other `getXXX` functions. You can ignore the failure caused by certain courses.
    */
-  public async getAllContents(
+  public async getAllContents<T extends ContentType>(
     courseIDs: string[],
-    type: ContentType,
+    type: T,
     courseType: CourseType = CourseType.STUDENT,
     allowFailure = false,
-  ): Promise<CourseContent> {
-    let fetchFunc: (courseID: string, courseType: CourseType) => Promise<Content[]>;
-    switch (type) {
-      case ContentType.NOTIFICATION:
-        fetchFunc = this.getNotificationList;
-        break;
-      case ContentType.FILE:
-        fetchFunc = this.getFileList;
-        break;
-      case ContentType.HOMEWORK:
-        fetchFunc = this.getHomeworkList;
-        break;
-      case ContentType.DISCUSSION:
-        fetchFunc = this.getDiscussionList;
-        break;
-      case ContentType.QUESTION:
-        fetchFunc = this.getAnsweredQuestionList;
-        break;
-    }
+  ) {
+    const fetchContentForCourse = <T extends ContentType>(type: T, id: string, courseType: CourseType) => {
+      switch (type) {
+        case ContentType.NOTIFICATION:
+          return this.getNotificationList(id, courseType) as Promise<ContentTypeMap[T][]>;
+        case ContentType.FILE:
+          return this.getFileList(id, courseType) as Promise<ContentTypeMap[T][]>;
+        case ContentType.HOMEWORK:
+          return this.getHomeworkList(id) as Promise<ContentTypeMap[T][]>;
+        case ContentType.DISCUSSION:
+          return this.getDiscussionList(id, courseType) as Promise<ContentTypeMap[T][]>;
+        case ContentType.QUESTION:
+          return this.getAnsweredQuestionList(id, courseType) as Promise<ContentTypeMap[T][]>;
+        default:
+          return Promise.reject({
+            reason: FailReason.NOT_IMPLEMENTED,
+            extra: 'Unknown content type',
+          } as ApiError);
+      }
+    };
 
-    const contents: CourseContent = {};
+    const contents: CourseContent<T> = {};
 
     const results = await Promise.allSettled(
       courseIDs.map(async (id) => {
-        contents[id] = await fetchFunc.bind(this)(id, courseType);
+        contents[id] = await fetchContentForCourse(type, id, courseType);
       }),
     );
 

diff --git a/src/types.ts b/src/types.ts
@@ -268,13 +268,19 @@ interface IQuestion extends IDiscussionBase {
 
 export type Question = IQuestion;
 
-export type Content = Notification | File | Homework | Discussion | Question;
+export type ContentTypeMap = {
+  [ContentType.NOTIFICATION]: Notification;
+  [ContentType.FILE]: File;
+  [ContentType.HOMEWORK]: Homework;
+  [ContentType.DISCUSSION]: Discussion;
+  [ContentType.QUESTION]: Question;
+};
 
-interface ICourseContent {
-  [id: string]: Content[];
+interface ICourseContent<T extends ContentType> {
+  [id: string]: ContentTypeMap[T][];
 }
 
-export type CourseContent = ICourseContent;
+export type CourseContent<T extends ContentType> = ICourseContent<T>;
 
 export interface CalendarEvent {
   location: string;