Fix/if s<0.5, get_retrievability return NaN (#110)

* Fix/if s<0.5,get_retrievability return NaN

* update test

* use s.toFixed(2)

* bump version to 4.1.1

__tests__/FSRSV5.test.ts

@@ -116,8 +116,8 @@ describe('get retrievability', () => {
   test('return retrievability percentage for review cards', () => {
     const card = createEmptyCard('2023-12-01 04:00:00')
     const sc = fsrs.repeat(card, '2023-12-01 04:05:00')
-    const r = [undefined, undefined, undefined, '90.00%']
-    const r_number = [undefined, undefined, undefined, 0.9]
+    const r = [undefined, undefined, undefined, '90.26%']
+    const r_number = [undefined, undefined, undefined, 0.90260891]
     Grades.forEach((grade, index) => {
       expect(fsrs.get_retrievability(sc[grade].card, sc[grade].card.due)).toBe(
         r[index]

__tests__/impl/long-term_schduler.test.ts

@@ -1,13 +1,12 @@
 import {
+  CardInput,
   createEmptyCard,
   fsrs,
-  FSRSAlgorithm,
   generatorParameters,
   Grade,
   Rating,
   State,
 } from '../../src/fsrs'
-import LongTermScheduler from '../../src/fsrs/impl/long_term_schduler'
 
 describe('Long-term  schduler', () => {
   const w = [
@@ -282,4 +281,39 @@ describe('Long-term  schduler', () => {
       'Relearning',
     ])
   })
+
+  test('[Long-term]get_retrievability ', () => {
+    const f = fsrs({
+      w: [
+        0.4072, 1.1829, 3.1262, 15.4722, 7.2102, 0.5316, 1.0651, 0.0234, 1.616,
+        0.1544, 1.0824, 1.9813, 0.0953, 0.2975, 2.2042, 0.2407, 2.9466, 0.5034,
+        0.6567,
+      ],
+      enable_short_term: false,
+    })
+    const now = '2024-08-03T18:15:34.500Z'
+    const view_date = '2024-08-03T18:25:34.500Z'
+    let card: CardInput = createEmptyCard(now)
+    card = f.repeat(card, now)[Rating.Again].card
+    let r = f.get_retrievability(card, view_date)
+    expect(r).toEqual('100.00%')
+
+    card = {
+      cid: 81,
+      due: '2024-08-04T18:15:34.500Z',
+      stability: 0.4072,
+      difficulty: 7.2102,
+      elapsed_days: 0,
+      scheduled_days: 1,
+      reps: 1,
+      lapses: 0,
+      state: 'Review',
+      last_review: '2024-08-03T18:15:34.500Z',
+      nid: 82,
+      suspended: false,
+      deleted: false,
+    } as CardInput
+    r = f.get_retrievability(card, view_date)
+    expect(r).toEqual('100.00%')
+  })
 })

package.json

@@ -1,6 +1,6 @@
 {
   "name": "ts-fsrs",
-  "version": "4.1.0",
+  "version": "4.1.1",
   "description": "ts-fsrs is a versatile package based on TypeScript that supports ES modules, CommonJS, and UMD. It implements the Free Spaced Repetition Scheduler (FSRS) algorithm, enabling developers to integrate FSRS into their flashcard applications to enhance the user learning experience.",
   "main": "dist/index.cjs",
   "umd": "dist/index.umd.js",

src/fsrs/default.ts

@@ -11,7 +11,7 @@ export const default_w = [
 export const default_enable_fuzz = false
 export const defualt_enable_short_term = true
 
-export const FSRSVersion: string = 'v4.1.0 using FSRS V5.0'
+export const FSRSVersion: string = 'v4.1.1 using FSRS V5.0'
 
 export const generatorParameters = (
   props?: Partial<FSRSParameters>

src/fsrs/fsrs.ts

@@ -213,7 +213,7 @@ export class FSRS extends FSRSAlgorithm {
       return undefined
     }
     const t = Math.max(now.diff(processedCard.last_review as Date, 'days'), 0)
-    const r = this.forgetting_curve(t, Math.round(processedCard.stability))
+    const r = this.forgetting_curve(t, +processedCard.stability.toFixed(2))
     return (format ? `${(r * 100).toFixed(2)}%` : r) as T extends true
       ? string
       : number