step3/api/QuestionsApi/Services/Flashcards/FlashcardMediaStore.cs

using MongoDB.Bson;
using MongoDB.Driver;
using QuestionsApi.Models;

namespace QuestionsApi.Services.Flashcards;

public sealed class FlashcardMediaStore
{
    private readonly IMongoCollection<FlashcardMediaAsset> _assets;

    public FlashcardMediaStore(MongoDatabaseProvider mongo)
    {
        _assets = mongo.Database.GetCollection<FlashcardMediaAsset>("FlashcardMediaAssets");
        _assets.Indexes.CreateOne(new CreateIndexModel<FlashcardMediaAsset>(
            Builders<FlashcardMediaAsset>.IndexKeys.Ascending(v => v.UserId),
            new CreateIndexOptions { Name = "flashcard_media_user" }));
    }

    public async Task<FlashcardMediaAsset> CreateAsync(string userId, string fileName, string contentType, byte[] bytes)
    {
        var asset = new FlashcardMediaAsset
        {
            UserId = userId,
            FileName = fileName,
            ContentType = contentType,
            Bytes = bytes,
            CreatedUtc = DateTime.UtcNow
        };
        await _assets.InsertOneAsync(asset);
        return asset;
    }

    public async Task<FlashcardMediaAsset?> GetAsync(string userId, string id)
    {
        if (!ObjectId.TryParse(id, out _)) return null;
        return await _assets.Find(v => v.UserId == userId && v.Id == id).FirstOrDefaultAsync();
    }

    public Task<long> DeleteAsync(string userId, string id) =>
        _assets.DeleteOneAsync(v => v.UserId == userId && v.Id == id).ContinueWith(t => t.Result.DeletedCount);
}