#region License Information
/* HeuristicLab
 * Copyright (C) 2002-2012 Heuristic and Evolutionary Algorithms Laboratory (HEAL)
 *
 * This file is part of HeuristicLab.
 *
 * HeuristicLab is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * HeuristicLab is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with HeuristicLab. If not, see <http://www.gnu.org/licenses/>.
 */
#endregion

using System;
using System.Collections.Generic;
using HeuristicLab.Common;
using HeuristicLab.Core;
using HeuristicLab.Data;
using HeuristicLab.Persistence.Default.CompositeSerializers.Storable;

namespace HeuristicLab.Algorithms.DataAnalysis {
  [StorableClass]
  [Item(Name = "CovarianceConst",
    Description = "Constant covariance function for Gaussian processes.")]
  public class CovarianceConst : CovarianceFunction {

    public IValueParameter<DoubleValue> ScaleParameter {
      get { return scaleParameter; }
    }

    [Storable]
    private readonly HyperParameter<DoubleValue> scaleParameter;

    [Storable]
    private double scale;

    [StorableConstructor]
    protected CovarianceConst(bool deserializing)
      : base(deserializing) {
    }

    protected CovarianceConst(CovarianceConst original, Cloner cloner)
      : base(original, cloner) {
      this.scaleParameter = cloner.Clone(original.scaleParameter);
      this.scale = original.scale;

      RegisterEvents();
    }

    public CovarianceConst()
      : base() {
      scaleParameter = new HyperParameter<DoubleValue>("Scale", "The scale of the constant covariance function.");
      Parameters.Add(scaleParameter);
      RegisterEvents();
    }

    [StorableHook(HookType.AfterDeserialization)]
    private void AfterDeserialization() {
      RegisterEvents();
    }

    // caching
    private void RegisterEvents() {
      AttachValueChangeHandler<DoubleValue, double>(scaleParameter, () => { scale = scaleParameter.Value.Value; });
    }


    public override IDeepCloneable Clone(Cloner cloner) {
      return new CovarianceConst(this, cloner);
    }

    public override int GetNumberOfParameters(int numberOfVariables) {
      return scaleParameter.Fixed ? 0 : 1;
    }

    public override void SetParameter(double[] hyp) {
      if (!scaleParameter.Fixed && hyp.Length == 1) {
        scaleParameter.SetValue(new DoubleValue(Math.Exp(2 * hyp[0])));
      } else {
        throw new ArgumentException("The length of the parameter vector does not match the number of free parameters for CovarianceConst", "hyp");
      }
    }

    public override double GetCovariance(double[,] x, int i, int j) {
      return scale;
    }

    public override IEnumerable<double> GetGradient(double[,] x, int i, int j) {
      yield return 2.0 * scale;
    }

    public override double GetCrossCovariance(double[,] x, double[,] xt, int i, int j) {
      return scale;
    }
  }
}