using System;
using System.Collections.Generic;
using System.Utility;
using Chernobyl.Collections.Generic;
using Chernobyl.Extensions;
using NUnit.Framework;
using Enumerable = System.Linq.Enumerable;

namespace Chernobyl.Mathematics.Space
{
    [TestFixture, Description("Tests for the Wave type.")]
    public class WaveTests
    {
        [Test, Description("Ensures Step starts at the expected value and increases that " +
                           "value at the expected rate.")]
        public void StepStartsAndIncreasesAtExpectedValues()
        {
            var result = Wave.Step(1, 5);

            result().IsEqualTo(5, "first invoke");
            result().IsEqualTo(6, "second invoke");
            result().IsEqualTo(7, "third invoke");
            result().IsEqualTo(8, "fourth invoke");
            result().IsEqualTo(9, "fifth invoke");
        }

        [Test, Description("Ensures Step starts at the expected value and increases that " +
                           "value at the expected rate.")]
        public void StepResetsCorrectly()
        {
            var result = Wave.Step(1, 5, current => current >= 8);

            result().IsEqualTo(5, "first invoke");
            result().IsEqualTo(6, "second invoke");
            result().IsEqualTo(7, "third invoke");
            result().IsEqualTo(5, "fourth invoke");
            result().IsEqualTo(6, "fifth invoke");
        }

        [Test, Description("Ensures Multiply returns the expected value.")]
        public void AmplifyReturnsExpectedValues()
        {
            var result = Wave.Step(1, 5).Multiply(2);

            result().IsEqualTo(10, "first invoke");
            result().IsEqualTo(12, "second invoke");
            result().IsEqualTo(14, "third invoke");
            result().IsEqualTo(16, "fourth invoke");
            result().IsEqualTo(18, "fifth invoke");
        }

        [Test, Description("Ensures Square returns the expected value.")]
        public void SquareReturnsExpectedValues()
        {
            var items = new List<Tuple<double, int>> { Tuple.Create(1.0, 1), Tuple.Create(2.0, 3), Tuple.Create(3.0, 2) };
            var squareFunction = items.GetEnumerator().AsFunc(Tuple.Create(1.0, 0)).Square();

            squareFunction().IsEqualTo(1.0, "first invoke");
            squareFunction().IsEqualTo(2.0, "second invoke");
            squareFunction().IsEqualTo(2.0, "third invoke");
            squareFunction().IsEqualTo(2.0, "fourth invoke");
            squareFunction().IsEqualTo(3.0, "fifth invoke");
            squareFunction().IsEqualTo(3.0, "sixth invoke");
        }

        [Test, Description("Ensures Square skips values marked with zero.")]
        public void SquareSkipsValuesMarkedWithZero()
        {
            var items = new List<Tuple<double, int>> { Tuple.Create(1.0, 1), Tuple.Create(2.0, 0), Tuple.Create(3.0, 2) };
            var squareFunction = items.GetEnumerator().AsFunc(Tuple.Create(1.0, 0)).Square();

            squareFunction().IsEqualTo(1.0, "first invoke");
            squareFunction().IsEqualTo(3.0, "second invoke");
            squareFunction().IsEqualTo(3.0, "third invoke");
        }
    }
}