// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
// See the LICENSE file in the project root for more information.
 
namespace Microsoft.ML;
 
/// <summary>
/// Type of prediction task. Note that this is a legacy structure and usage of this should generally be
/// discouraged in future projects. Its presence suggests that there are privileged and supported
/// tasks, and anything outside of this is unsupported. This runs rather contrary to the idea of this
/// being an expandable framework, and it is inappropriately limiting. For legacy pipelines based on
/// <see cref="ITrainer"/> and <see cref="IPredictor"/> it is still useful, but for things based on
/// the <see cref="IEstimator{TTransformer}"/> idiom, it is inappropriate.
/// </summary>
[BestFriend]
internal enum PredictionKind
{
    Unknown = 0,
    Custom = 1,
 
    BinaryClassification = 2,
    MulticlassClassification = 3,
    Regression = 4,
    MultiOutputRegression = 5,
    Ranking = 6,
    Recommendation = 7,
    AnomalyDetection = 8,
    Clustering = 9,
    SequenceClassification = 10,
 
    // More to be added later.
}
 
/// <summary>
/// Weakly typed version of IPredictor.
/// </summary>
[BestFriend]
internal interface IPredictor
{
    /// <summary>
    /// Return the type of prediction task.
    /// </summary>
    PredictionKind PredictionKind { get; }
}
 
/// <summary>
/// A predictor the produces values of the indicated type.
/// REVIEW: Determine whether this is just a temporary shim or long term solution.
/// </summary>
[BestFriend]
internal interface IPredictorProducing<out TResult> : IPredictor
{
}
 
/// <summary>
/// A predictor that produces values and distributions of the indicated types.
/// Note that from a public API perspective this is bad.
/// </summary>
[BestFriend]
internal interface IDistPredictorProducing<out TResult, out TResultDistribution> : IPredictorProducing<TResult>
{
}