using Microsoft.Extensions.Options;

namespace MeetingAssistant.Speakers;

public sealed record SpeakerSampleCollectionPolicy(
    int MinimumRetainedSamples,
    bool RequireNonOverlappingSamples)
{
    public static SpeakerSampleCollectionPolicy ExistingBackend { get; } = new(1, false);

    public static SpeakerSampleCollectionPolicy IndependentVectors(int maximumVectors)
    {
        return new SpeakerSampleCollectionPolicy(Math.Max(1, maximumVectors), true);
    }

    public int ResolveRetainedSampleLimit(int configuredLimit)
    {
        return Math.Max(Math.Max(1, configuredLimit), MinimumRetainedSamples);
    }
}

internal static class SpeakerSampleDurationConfiguration
{
    public static void ValidateOrThrow(
        SpeakerIdentificationOptions options,
        string context)
    {
        ValidateOrThrow(
            options.MinimumSampleSpeechDuration,
            options.MaximumSampleDuration,
            context);
    }

    public static void ValidateOrThrow(
        TimeSpan minimumDuration,
        TimeSpan maximumDuration,
        string context)
    {
        var error = GetError(minimumDuration, maximumDuration);
        if (error is not null)
        {
            throw new InvalidOperationException($"{context}: {error}");
        }
    }

    public static string? GetError(
        TimeSpan minimumDuration,
        TimeSpan maximumDuration)
    {
        if (minimumDuration < TimeSpan.Zero)
        {
            return "SpeakerIdentification:MinimumSampleSpeechDuration must not be negative.";
        }

        if (maximumDuration <= TimeSpan.Zero)
        {
            return "SpeakerIdentification:MaximumSampleDuration must be greater than zero.";
        }

        return minimumDuration > maximumDuration
            ? "SpeakerIdentification:MinimumSampleSpeechDuration must not exceed SpeakerIdentification:MaximumSampleDuration."
            : null;
    }
}

internal static class ResemblyzerSpeakerRecognitionConfiguration
{
    public static void ValidateOrThrow(
        ResemblyzerSpeakerRecognitionOptions options,
        string context)
    {
        var error = GetError(options);
        if (error is not null)
        {
            throw new InvalidOperationException($"{context}: {error}");
        }
    }

    public static string? GetError(ResemblyzerSpeakerRecognitionOptions options)
    {
        if (options.RequiredVectorsPerSpeaker < 1)
        {
            return "SpeakerIdentification:Resemblyzer:RequiredVectorsPerSpeaker must be at least one.";
        }

        if (options.MaxVectorsPerIdentity < options.RequiredVectorsPerSpeaker)
        {
            return "SpeakerIdentification:Resemblyzer:MaxVectorsPerIdentity must not be less than RequiredVectorsPerSpeaker.";
        }

        if (options.OutlierPruningMinimumVectors < options.RequiredVectorsPerSpeaker)
        {
            return "SpeakerIdentification:Resemblyzer:OutlierPruningMinimumVectors must not be less than RequiredVectorsPerSpeaker.";
        }

        if (options.OutlierPruningMinimumVectors > options.MaxVectorsPerIdentity)
        {
            return "SpeakerIdentification:Resemblyzer:OutlierPruningMinimumVectors must not exceed MaxVectorsPerIdentity.";
        }

        if (options.OutlierPruningMinimumNeighbors < 1 ||
            options.OutlierPruningMinimumNeighbors > options.OutlierPruningMinimumVectors)
        {
            return "SpeakerIdentification:Resemblyzer:OutlierPruningMinimumNeighbors must be between one and OutlierPruningMinimumVectors.";
        }

        if (!IsCosine(options.OutlierPruningNeighborSimilarity))
        {
            return "SpeakerIdentification:Resemblyzer:OutlierPruningNeighborSimilarity must be finite and between -1 and 1.";
        }

        if (!double.IsFinite(options.OutlierPruningMinimumClusterRatio) ||
            options.OutlierPruningMinimumClusterRatio is <= 0 or > 1)
        {
            return "SpeakerIdentification:Resemblyzer:OutlierPruningMinimumClusterRatio must be finite, greater than zero, and at most one.";
        }

        if (!IsCosine(options.MinimumClusterCohesion))
        {
            return "SpeakerIdentification:Resemblyzer:MinimumClusterCohesion must be finite and between -1 and 1.";
        }

        if (!IsCosine(options.MinimumIdentitySimilarity))
        {
            return "SpeakerIdentification:Resemblyzer:MinimumIdentitySimilarity must be finite and between -1 and 1.";
        }

        return !double.IsFinite(options.MinimumSimilarityMargin) ||
            options.MinimumSimilarityMargin is < 0 or > 2
            ? "SpeakerIdentification:Resemblyzer:MinimumSimilarityMargin must be finite and between 0 and 2."
            : null;
    }

    private static bool IsCosine(double value)
    {
        return double.IsFinite(value) && value is >= -1 and <= 1;
    }
}

internal sealed class MeetingAssistantSpeakerSampleOptionsValidator
    : IValidateOptions<MeetingAssistantOptions>
{
    public ValidateOptionsResult Validate(string? name, MeetingAssistantOptions options)
    {
        var error = SpeakerSampleDurationConfiguration.GetError(
            options.SpeakerIdentification.MinimumSampleSpeechDuration,
            options.SpeakerIdentification.MaximumSampleDuration) ??
            ResemblyzerSpeakerRecognitionConfiguration.GetError(
                options.SpeakerIdentification.Resemblyzer);
        return error is null
            ? ValidateOptionsResult.Success
            : ValidateOptionsResult.Fail(error);
    }
}