meeting-assistant/MeetingAssistant/Speakers/SpeakerIdentityMerger.cs

namespace MeetingAssistant.Speakers;

internal static class SpeakerIdentityMerger
{
    public static void MergeIntoAndPrune(
        SpeakerIdentity target,
        SpeakerIdentity source,
        int maxSnippets,
        int maxVoiceVectors,
        ResemblyzerVoiceVectorOutlierPruner outlierPruner)
    {
        outlierPruner.Prune(target);
        outlierPruner.Prune(source);
        MergeInto(target, source, maxSnippets, maxVoiceVectors);
        outlierPruner.Prune(target);
    }

    public static void MergeInto(
        SpeakerIdentity target,
        SpeakerIdentity source,
        int maxSnippets,
        int maxVoiceVectors = int.MaxValue)
    {
        AddAlias(target, source.CanonicalName);
        foreach (var alias in source.Aliases)
        {
            AddAlias(target, alias.Name);
        }

        foreach (var candidate in source.CandidateNames)
        {
            AddAlias(target, candidate.Name);
        }

        foreach (var reference in source.References)
        {
            SpeakerIdentityReferences.AddIfMissing(target, reference);
        }

        var retainedSnippets = target.Snippets
            .Concat(source.Snippets)
            .OrderBy(snippet => StableSnippetKey(snippet.WavBytes))
            .Take(Math.Max(1, maxSnippets))
            .Select(snippet => new SpeakerSnippet
            {
                WavBytes = snippet.WavBytes,
                CreatedAt = snippet.CreatedAt
            })
            .ToList();
        target.Snippets.Clear();
        target.Snippets.AddRange(retainedSnippets);

        var retainedVectors = target.VoiceVectors
            .Concat(source.VoiceVectors)
            .GroupBy(vector => vector.Fingerprint, StringComparer.Ordinal)
            .Select(group => group.OrderByDescending(vector => vector.CreatedAt).First())
            .OrderByDescending(vector => vector.CreatedAt)
            .ThenBy(vector => vector.Fingerprint, StringComparer.Ordinal)
            .Take(Math.Max(1, maxVoiceVectors))
            .Select(vector => new SpeakerVoiceVector
            {
                SpeakerIdentity = target,
                ModelId = vector.ModelId,
                Dimensions = vector.Dimensions,
                VectorBytes = vector.VectorBytes.ToArray(),
                Fingerprint = vector.Fingerprint,
                CreatedAt = vector.CreatedAt
            })
            .ToList();
        target.VoiceVectors.Clear();
        target.VoiceVectors.AddRange(retainedVectors);
        target.UpdatedAt = DateTimeOffset.UtcNow;
    }

    private static void AddAlias(SpeakerIdentity identity, string? alias)
    {
        if (string.IsNullOrWhiteSpace(alias) ||
            string.Equals(identity.CanonicalName, alias, StringComparison.OrdinalIgnoreCase) ||
            identity.Aliases.Any(existing => string.Equals(existing.Name, alias, StringComparison.OrdinalIgnoreCase)))
        {
            return;
        }

        identity.Aliases.Add(new SpeakerAlias { Name = alias.Trim() });
    }

    private static int StableSnippetKey(byte[] snippet)
    {
        var hash = new HashCode();
        foreach (var value in snippet)
        {
            hash.Add(value);
        }

        return hash.ToHashCode();
    }
}