From 7de3cedb15032c7ef21a5ec3106b4465876a7d8d Mon Sep 17 00:00:00 2001
From: Alexander Polynomdivision <polynomdivision+dev@protonmail.ch>
Date: Wed, 17 Oct 2018 14:40:21 +0200
Subject: [PATCH] refactor: Move the SM2 implementation to the backend

---
 .../src/algorithms/sm2/index.ts               |  0
 backend/src/api/user.ts                       | 33 +++++++++----------
 2 files changed, 16 insertions(+), 17 deletions(-)
 rename {frontend => backend}/src/algorithms/sm2/index.ts (100%)

diff --git a/frontend/src/algorithms/sm2/index.ts b/backend/src/algorithms/sm2/index.ts
similarity index 100%
rename from frontend/src/algorithms/sm2/index.ts
rename to backend/src/algorithms/sm2/index.ts
diff --git a/backend/src/api/user.ts b/backend/src/api/user.ts
index d334544..2670117 100644
--- a/backend/src/api/user.ts
+++ b/backend/src/api/user.ts
@@ -8,7 +8,9 @@ import { authRoute } from "../security/token";
 import { userFromSession } from "../utils/user";
 
 import { IUser, IUserDBModel } from "../models/user";
-import { ISM2Metadata } from "../models/review";
+import {
+    ISchedulingData, AnswerType, updateSchedulingData
+} from "../algorithms/sm2";
 import { LRequest } from "../types/express";
 
 const userRouter = express.Router();
@@ -190,34 +192,31 @@ userRouter.post("/lastReview", async (req: LRequest, res) => {
         return;
     }
 
+    // NOTE: Oh oh
+    // Update the user's score based on what they sent us
     user.score += parseInt(req.body.delta);
 
+    // Itterate over all of the vocabulary that needs to have its
+    // metadata updated.
+    // Use our SM2 implementation to update the vocabulary and modify our
+    // copy of the user object, so that we can write the copied (and modified)
+    // user object back into the database.
     Object.keys(req.body.sm2).forEach((id: string) => {
         const vocabId = parseInt(id);
         const correct: boolean = req.body.sm2[id];
-        let vocab_sm2: ISM2Metadata = Object.assign({},
+        let vocab_sm2: ISchedulingData = Object.assign({},
             user.vocabMetadata[vocabId]);
 
-        // TODO: Tuning?
-        // TODO: Move into another module
-        const perf = correct ? 3 : 1;
-        vocab_sm2.easiness += -0.8 + 0.28 * perf + 0.02 * Math.pow(perf, 2);
-        // Update the consecutive correct answers and the due date
-        if (correct) {
-            vocab_sm2.consecutiveCorrectAnswers += 1;
-            vocab_sm2.nextDueDate = dateInNDays(6 * Math.pow(vocab_sm2.easiness, vocab_sm2.consecutiveCorrectAnswers - 1));
-        } else {
-            vocab_sm2.consecutiveCorrectAnswers = 0;
-            vocab_sm2.nextDueDate = dateInNDays(1);
-        }
-
-        user.vocabMetadata[vocabId] = vocab_sm2;
+        const answer = correct ? AnswerType.CORRECT : AnswerType.WRONG;
+        user.vocabMetadata[vocabId] = updateSchedulingData(vocab_sm2, answer);
     });
 
     // Update the last review
     user.lastReview = req.body.meta;
 
-    // TODO: Error handling
+    // NOTE: Error handling could be implemented here, but we can ensure that
+    //       the user exists, as we just got his username (and entire data)
+    //       from `userFromSession`.
     await db.collection("users").updateOne({
         username: user.username,
     }, {