using HeuristicLab.Problems.DataAnalysis;
using System;
using System.Linq;

namespace HeuristicLab.Algorithms.DataAnalysis.FastFunctionExtraction {
    internal struct ProductBaseFunction : IBasisFunction {
        public IBasisFunction B1 { get; set; }
        public IBasisFunction B2 { get; set; }

        public int Complexity => 1 + B1.Complexity + B2.Complexity;

        public bool IsDenominator { get; set; }

        public ProductBaseFunction(IBasisFunction b1, IBasisFunction b2, bool isDenominator) {
            B1 = b1 ?? throw new ArgumentNullException(nameof(b1));
            B2 = b2 ?? throw new ArgumentNullException(nameof(b2));
            IsDenominator = isDenominator;
        }

        public double[] Evaluate(IRegressionProblemData data) {
            return B1.Evaluate(data).Zip(B2.Evaluate(data), (a, b) => a * b).ToArray();
        }

        public override string ToString() {
            return $"{B1} * {B2}";
        }

        public IBasisFunction DeepCopy() {
            return new ProductBaseFunction(B1, B2, IsDenominator);
        }
    }
}