refactor: Simplify API calls

API calls can now make with a simple wrapper function.

Additionally, the error code "200" now means success for all API calls.

backend/src/algorithms/sm2/index.ts

@@ -1,11 +1,15 @@
-import { dayInNDays } from "../../utils/date";
-
 export interface ISchedulingData {
     easiness: number;
     consecutiveCorrectAnswers: number;
     nextDueDate: number;
 };
 
+function dateInNDays(n: number): number {
+    let today = new Date();
+    today.setDate(today.getDate() + n);
+    return Date.parse(today.toString());
+}
+
 export enum AnswerType {
     CORRECT,
     WRONG,
@@ -28,8 +32,8 @@ export function updateSchedulingData(data: ISchedulingData, answer: AnswerType):
         data.consecutiveCorrectAnswers + 1
     ) : 0;
     data.nextDueDate = answer === AnswerType.CORRECT ? (
-        dayInNDays(6 * Math.pow(data.easiness, data.consecutiveCorrectAnswers - 1))
-    ) : dayInNDays(1);
+        dateInNDays(6 * Math.pow(data.easiness, data.consecutiveCorrectAnswers - 1))
+    ) : dateInNDays(1);
 
     return data;
 }