Enhance Spaced Repetition Algorithm with SM-2 Implementation

[Suraj-kumar00]

Enhance Spaced Repetition Algorithm with SM-2 Implementation

Description
The current spaced repetition system in src/components/study/StudyMode.tsx uses a basic implementation that updates nextReview dates based on difficulty ratings. This should be enhanced with a proper SM-2 algorithm for more effective learning scheduling.

Current Implementation
In StudyMode.tsx, the difficulty tracking updates the flashcard's nextReview field, but:

• The interval calculation is basic (not following SM-2 formula)
• repetitions count is not properly utilized
• No ease factor tracking
• Failed cards are not rescheduled optimally

What Needs to Be Done

1. Implement SM-2 Algorithm

Create a utility at src/lib/utils/spaced-repetition.ts:

• Calculate intervals based on: quality (0-5), repetitions, ease factor
• Formula: interval = previousInterval * easeFactor
• Ease factor adjustment based on response quality
• Reset to interval 1 on failure

2. Update Database Schema

Add to Prisma Flashcard model:

• easeFactor (Float, default 2.5)
• interval (Int, default 0)
• Update repetitions usage

3. Update Study Mode

• Apply SM-2 calculations when user rates difficulty
• Show next review date to user
• Add "Due for Review" filter to deck view
• Display mastery level per card (based on ease factor)

4. Study Analytics

• Track study streaks
• Show retention rate over time
• Daily review count vs. due cards
• Export study statistics

Files to Create/Modify

• Create: src/lib/utils/spaced-repetition.ts — SM-2 algorithm
• Modify: prisma/schema.prisma — Add easeFactor, interval fields
• Modify: src/components/study/StudyMode.tsx — Apply SM-2
• Modify: src/app/api/study/record/route.ts — Store SM-2 data

Acceptance Criteria

• SM-2 algorithm implemented and tested
• Database schema updated with new fields
• Study mode uses SM-2 for scheduling
• Next review date shown to user
• Due cards highlighted in deck view
• Study analytics/stats page