using ErsatzTV.Infrastructure.Streaming.Graphics;
using NCalc;
using NUnit.Framework;
using Shouldly;

namespace ErsatzTV.Infrastructure.Tests.Streaming.Graphics;

[TestFixture]
public class OpacityExpressionHelperTests
{
    // Exercises the NCalc custom-function wiring (FunctionEventArgs / FunctionData under NCalc 6.x)
    // exactly the way the graphics elements do: build an Expression, hook EvaluateFunction, evaluate.
    private static float Evaluate(string expressionString, TimeSpan timeOfDay)
    {
        var expression = new Expression(expressionString);
        expression.EvaluateFunction += OpacityExpressionHelper.EvaluateFunction;
        return OpacityExpressionHelper.GetOpacity(
            expression,
            timeOfDay,
            TimeSpan.Zero,
            TimeSpan.Zero,
            TimeSpan.Zero);
    }

    // LinearFadePoints(time, start=0, peakStart=10, peakEnd=20, end=30)
    [TestCase(5, 0.5)]   // fade in:  (5-0)/(10-0)
    [TestCase(15, 1.0)]  // solid
    [TestCase(25, 0.5)]  // fade out: (30-25)/(30-20)
    [TestCase(35, 0.0)]  // past end
    public void LinearFadePoints_ReturnsExpectedOpacity(int timeOfDaySeconds, double expected)
    {
        float opacity = Evaluate(
            "LinearFadePoints(time_of_day_seconds, 0, 10, 20, 30)",
            TimeSpan.FromSeconds(timeOfDaySeconds));

        opacity.ShouldBe((float)expected, 0.0001);
    }

    // LinearFadeDuration(time, start=0, fadeSeconds=10, peakSeconds=10)
    // -> peakStart=10, peakEnd=20, end=30 (same curve as the LinearFadePoints case above)
    [TestCase(5, 0.5)]   // mid fade in
    [TestCase(15, 1.0)]  // solid
    [TestCase(25, 0.5)]  // mid fade out
    public void LinearFadeDuration_ReturnsExpectedOpacity(int timeOfDaySeconds, double expected)
    {
        float opacity = Evaluate(
            "LinearFadeDuration(time_of_day_seconds, 0, 10, 10)",
            TimeSpan.FromSeconds(timeOfDaySeconds));

        opacity.ShouldBe((float)expected, 0.0001);
    }
}