1+ 'use server' ;
2+
3+ import { ObjectId } from 'mongodb' ;
4+ import { connectToDatabase } from '@/lib/db' ;
5+ import { ReviewEventDocument , ReviewResult , CardDocument } from '@/types' ;
6+
7+ interface LastReviewResult {
8+ cardId : string ;
9+ lastResult : ReviewResult ;
10+ timestamp : Date ;
11+ }
12+
13+ // Fetches the most recent review event for each card within a specific deck.
14+ export async function getLastReviewEventPerCard ( deckId : string ) : Promise < Map < string , LastReviewResult > > {
15+ if ( ! deckId || ! ObjectId . isValid ( deckId ) ) {
16+ throw new Error ( 'Invalid Deck ID provided.' ) ;
17+ }
18+
19+ const { db } = await connectToDatabase ( ) ;
20+ const reviewEventsCollection = db . collection < ReviewEventDocument > ( 'review_events' ) ;
21+ const cardsCollection = db . collection < CardDocument > ( 'cards' ) ;
22+
23+ try {
24+ // 1. Find all card IDs belonging to the deck
25+ const cardIdsInDeck = await cardsCollection
26+ . find ( { deck_id : new ObjectId ( deckId ) } , { projection : { _id : 1 } } )
27+ . map ( ( doc : { _id : ObjectId } ) => doc . _id )
28+ . toArray ( ) ;
29+
30+ if ( cardIdsInDeck . length === 0 ) {
31+ return new Map ( ) ; // No cards in deck, so no review history
32+ }
33+
34+ // 2. Use aggregation to find the last review event for each relevant card
35+ const aggregationPipeline = [
36+ // Match only events for cards in the target deck
37+ { $match : { card_id : { $in : cardIdsInDeck } } } ,
38+ // Sort by timestamp descending to get the latest first
39+ { $sort : { timestamp : - 1 } } ,
40+ // Group by card_id and take the first document (which is the latest due to sorting)
41+ {
42+ $group : {
43+ _id : "$card_id" ,
44+ lastEvent : { $first : "$$ROOT" } // Get the whole document
45+ }
46+ } ,
47+ // Reshape the output
48+ {
49+ $project : {
50+ _id : 0 , // Exclude the grouping _id
51+ cardId : { $toString : "$_id" } , // Convert card_id ObjectId to string
52+ lastResult : "$lastEvent.result" ,
53+ timestamp : "$lastEvent.timestamp"
54+ }
55+ }
56+ ] ;
57+
58+ const results : LastReviewResult [ ] = await reviewEventsCollection . aggregate < LastReviewResult > ( aggregationPipeline ) . toArray ( ) ;
59+
60+ // Convert the array of results into a Map for easy lookup by cardId
61+ const resultMap = new Map < string , LastReviewResult > ( ) ;
62+ results . forEach ( item => {
63+ resultMap . set ( item . cardId , item ) ;
64+ } ) ;
65+
66+ return resultMap ;
67+
68+ } catch ( error ) {
69+ console . error ( "Error fetching last review events:" , error ) ;
70+ throw new Error ( "Failed to fetch review history." ) ;
71+ }
72+ }
0 commit comments