using System;
using System.Collections.Generic;
using System.Linq;
using HeuristicLab.Core;
using HeuristicLab.Problems.Instances.DataAnalysis;
using HeuristicLab.Random;
using Irony.Interpreter;

namespace HeuristicLab.BenchmarkGenerator {
  public static class Functions {
    private static readonly IRandom Random = new MersenneTwister();

    public static void SetSeed(int seed) { Random.Reset(seed); }

    public static object NormalDouble(ScriptThread thread, object[] args) {
      if (args.Length != 2) throw new ArgumentException("The NormalDouble function accepts exactly two arguments.");
      var mu = (double)args[0];
      var sigma = (double)args[1];
      return NormalDouble(mu, sigma);
    }

    public static object UniformDouble(ScriptThread thread, object[] args) {
      if (args.Length != 2) throw new ArgumentException("The UniformDouble function accepts exactly two arguments.");
      var a = (double)args[0];
      var b = (double)args[1];
      return UniformDouble(a, b);
    }

    public static object NormalDistribution(ScriptThread thread, object[] args) {
      if (args.Length != 3) throw new ArgumentException("The dnormal function accepts exactly three arguments.");
      var n = (int)(double)args[0];
      var start = (double)args[1];
      var end = (double)args[2];
      return NormalDistribution(n, start, end).Cast<object>().ToArray();
    }

    public static object UniformDistribution(ScriptThread thread, object[] args) {
      if (args.Length != 3) throw new ArgumentException("The duniform function accepts exactly three arguments.");
      var n = (int)(double)args[0];
      var start = (double)args[1];
      var end = (double)args[2];
      return UniformDistribution(n, start, end).Cast<object>().ToArray();
    }

    public static object[] Steps(ScriptThread thread, object[] args) {
      if (args.Length != 3) throw new ArgumentException("The Steps function accepts exactly three arguments.");
      var start = (double)args[0];
      var end = (double)args[1];
      var step = (double)args[2];
      return Steps(start, end, step).Cast<object>().ToArray();
    }

    public static object[] Sin(ScriptThread thread, object[] args) {
      if (args.Length != 1) throw new ArgumentException("The Sin function accepts exactly one argument.");
      var values = (object[])args[0];
      return values.Cast<double>().Select(Math.Sin).Cast<object>().ToArray();
    }

    public static object[] Cos(ScriptThread thread, object[] args) {
      if (args.Length != 1) throw new ArgumentException("The Cos function accepts exactly one argument.");
      var values = (object[])args[0];
      return values.Cast<double>().Select(Math.Cos).Cast<object>().ToArray();
    }

    public static object Length(ScriptThread thread, object[] args) {
      if (args.Length != 1) throw new ArgumentException("The Length function accepts exactly one argument which must be an object array.");
      var values = (object[])args[0];
      return (double)values.Length;
    }

    public static object DotProduct(ScriptThread thread, object[] args) {
      if (args.Length != 2) throw new ArgumentException("The DotProduct function accepts exactly two arguments which must be object arrays of the same length.");
      var a = (object[])args[0];
      var b = (object[])args[1];
      return DotProduct(a.Cast<double>(), b.Cast<double>());
    }

    public static object[] Abs(ScriptThread thread, object[] args) {
      if (args.Length != 1) throw new ArgumentException("The Length function accepts exactly one argument which must be an object array.");
      var values = (object[])args[0];
      return values.Cast<double>().Select(Math.Abs).Cast<object>().ToArray();
    }

    public static object[] Repeat(ScriptThread thread, object[] args) {
      if (args.Length != 2) throw new ArgumentException("The Repeat function accepts exactly two arguments.");
      var n = (int)(double)args[0];
      var v = (double)args[1];
      return Enumerable.Repeat(v, n).Cast<object>().ToArray();
    }

    #region convenience methods for less typing
    private static double UniformDouble(double min, double max) {
      return UniformDistributedRandom.NextDouble(Random, min, max);
    }
    private static double NormalDouble(double mu, double sigma) {
      return NormalDistributedRandom.NextDouble(Random, mu, sigma);
    }
    private static IEnumerable<double> Steps(double start, double end, double step) {
      return ValueGenerator.GenerateSteps(start, end, step);
    }
    private static IEnumerable<double> UniformDistribution(int n, double start, double end) {
      return ValueGenerator.GenerateUniformDistributedValues(n, start, end);
    }
    private static IEnumerable<double> NormalDistribution(int n, double start, double end) {
      return ValueGenerator.GenerateNormalDistributedValues(n, start, end);
    }
    private static double DotProduct(IEnumerable<double> a, IEnumerable<double> b) {
      return a.Zip(b, (x, y) => x * y).Sum();
    }
    #endregion
  }
}