check: description, externalSourceName, key

Bắt đầu tại src/Chroma/src/ChromaVectorCollection.cs, ở AddAsync, nơi TODO đánh dấu description, externalSourceName và key trong quá trình tạo MemoryRecord. Đọc cách sử dụng MemoryRecord và MemoryRecordMetadata hiện có trong repository này, đồng thời xác minh các trường đó cần nhận những giá trị nào; được xem là hoàn thành khi ba trường không còn chưa được giải quyết và collection vẫn bảo toàn các mã định danh của item cùng metadata.

https://github.com/tryAGI/LangChain.Databases/blob/709070b0226b59fe8eef116395b0e4ad1bd5df97/src/Chroma/src/ChromaVectorCollection.cs#L85

using System.Text.Json;
using System.Text.Json.Serialization;
using LangChain.Databases.JsonConverters;
using Microsoft.SemanticKernel.Connectors.Chroma;
using Microsoft.SemanticKernel.Memory;

namespace LangChain.Databases.Chroma;

/// <summary>
/// ChromaDB vector collection.
/// According: https://api.python.langchain.com/en/latest/_modules/langchain/vectorstores/chroma.html
/// </summary>
public class ChromaVectorCollection(
    ChromaMemoryStore store,
    string name = VectorCollection.DefaultName,
    string? id = null)
    : VectorCollection(name, id), IVectorCollection
{
    // TODO: SemanticKernel impl doesn't support collection metadata. Need changes when moved to another impl
    //private Dictionary<string, string> CollectionMetadata { get; } = [];

    /// <inheritdoc />
    public async Task<Vector?> GetAsync(string id, CancellationToken cancellationToken = default)
    {
        var record = await store.GetAsync(Name, id, withEmbedding: true, cancellationToken: cancellationToken).ConfigureAwait(false);
        if (record == null)
        {
            return null;
        }

        var text = record.Metadata.Text;
        var metadata = DeserializeMetadata(record.Metadata);

        return new Vector
        {
            Text = text,
            Metadata = metadata,
        };
    }

    /// <inheritdoc />
    public async Task<bool> DeleteAsync(
        IEnumerable<string> ids,
        CancellationToken cancellationToken = default)
    {
        await store.RemoveBatchAsync(Name, ids, cancellationToken).ConfigureAwait(false);

        return true;
    }

    private static float SelectRelevanceScoreFn(float distance)
    {
        //const string distanceKey = "hnsw:space";

        var distanceType = "l2";
        //if (CollectionMetadata.TryGetValue(distanceKey, out var value))
        //{
        //    distanceType = value;
        //}

        return distanceType switch
        {
            "cosine" => RelevanceScoreFunctions.Cosine(distance),
            "l2" => RelevanceScoreFunctions.Euclidean(distance),
            "ip" => RelevanceScoreFunctions.MaxInnerProduct(distance),

            _ => throw new ArgumentException(
                $@"No supported normalization function for distance metric of type: {distanceType}.
                Consider providing relevance_score_fn to Chroma constructor.")
        };
    }

    /// <inheritdoc />
    public async Task<IReadOnlyCollection<string>> AddAsync(
        IReadOnlyCollection<Vector> items,
        CancellationToken cancellationToken = default)
    {
        items = items ?? throw new ArgumentNullException(nameof(items));

        var records = new MemoryRecord[items.Count];
        for (var index = 0; index < items.Count; index++)
        {
            var item = items.ElementAt(index);

            // TODO: check: description, externalSourceName, key
            records[index] = new MemoryRecord
            (
                new MemoryRecordMetadata
                (
                    isReference: false,
                    id: item.Id,
                    text: item.Text,
                    description: string.Empty,
                    externalSourceName: string.Empty,
                    additionalMetadata: SerializeMetadata(item.Metadata ?? new Dictionary<string, object>())
                ),
                new ReadOnlyMemory<float>(item.Embedding ?? []),
                key: null
            );
        }

        var resultIds = new List<string>(items.Count);
        var resultIdsIterator = store.UpsertBatchAsync(Name, records, cancellationToken);
        await foreach (var item in resultIdsIterator.ConfigureAwait(false))
        {
            resultIds.Add(item);
        }

        return resultIds;
    }

    /// <inheritdoc />
    public async Task<VectorSearchResponse> SearchAsync(
        VectorSearchRequest request,
        VectorSearchSettings? settings = default,
        CancellationToken cancellationToken = default)
    {
        request = request ?? throw new ArgumentNullException(nameof(request));
        settings ??= new VectorSearchSettings();

        settings.RelevanceScoreFunc ??= SelectRelevanceScoreFn;

        var matches = await store
            .GetNearestMatchesAsync(
                collectionName: Name,
                embedding: new System.ReadOnlyMemory<float>(request.Embeddings.First()),
                limit: settings.NumberOfResults,
                cancellationToken: cancellationToken)
            .ToListAsync(cancellationToken)
            .ConfigureAwait(false);

        return new VectorSearchResponse
        {
            Items = matches
                .Select(record =>
                {
                    var text = record.Item1.Metadata.Text;
                    var metadata = DeserializeMetadata(record.Item1.Metadata);

                    return new Vector
                    {
                        Id = record.Item1.Metadata.Id,
                        Text = text,
                        Metadata = metadata,
                        Embedding = record.Item1.Embedding.ToArray(),
                        Distance = (float)record.Item2
                    };
                })
                .ToArray(),
        };
    }

    /// <inheritdoc />
    public Task<bool> IsEmptyAsync(CancellationToken cancellationToken = default)
    {
        throw new NotImplementedException();
    }

    private static string SerializeMetadata(IReadOnlyDictionary<string, object> metadata)
    {
        return JsonSerializer.Serialize(metadata, SourceGenerationContext.Default.IReadOnlyDictionaryStringObject);
    }

    private static IReadOnlyDictionary<string, object> DeserializeMetadata(MemoryRecordMetadata metadata)
    {
        return JsonSerializer.Deserialize(metadata.AdditionalMetadata, SourceGenerationContext.Default.IReadOnlyDictionaryStringObject)
               ?? new Dictionary<string, object>();
    }
}

[JsonSourceGenerationOptions(Converters = [typeof(ObjectAsPrimitiveConverter)])]
[JsonSerializable(typeof(IReadOnlyDictionary<string, object>))]
[JsonSerializable(typeof(double))]
[JsonSerializable(typeof(float))]
[JsonSerializable(typeof(int))]
[JsonSerializable(typeof(decimal))]
internal sealed partial class SourceGenerationContext : JsonSerializerContext;