using FluentAssertions;
using Microsoft.Extensions.Logging.Abstractions;
using StellaOps.Policy.Determinization.Scoring;
using Xunit;

namespace StellaOps.Policy.Determinization.Tests;

public class DecayedConfidenceCalculatorTests
{
    private readonly DecayedConfidenceCalculator _calculator;

    public DecayedConfidenceCalculatorTests()
    {
        _calculator = new DecayedConfidenceCalculator(NullLogger<DecayedConfidenceCalculator>.Instance);
    }

    [Fact]
    public void Calculate_ZeroAge_ReturnsBaseConfidence()
    {
        // Arrange
        var baseConfidence = 0.8;
        var ageDays = 0.0;

        // Act
        var result = _calculator.Calculate(baseConfidence, ageDays);

        // Assert
        result.Should().Be(baseConfidence);
    }

    [Fact]
    public void Calculate_HalfLife_ReturnsHalfConfidence()
    {
        // Arrange
        var baseConfidence = 1.0;
        var halfLifeDays = 14.0;
        var ageDays = 14.0;

        // Act
        var result = _calculator.Calculate(baseConfidence, ageDays, halfLifeDays);

        // Assert
        result.Should().BeApproximately(0.5, 0.01);
    }

    [Fact]
    public void Calculate_TwoHalfLives_ReturnsQuarterConfidence()
    {
        // Arrange
        var baseConfidence = 1.0;
        var halfLifeDays = 14.0;
        var ageDays = 28.0;

        // Act
        var result = _calculator.Calculate(baseConfidence, ageDays, halfLifeDays);

        // Assert
        result.Should().BeApproximately(0.25, 0.01);
    }

    [Fact]
    public void Calculate_VeryOld_ReturnsFloor()
    {
        // Arrange
        var baseConfidence = 1.0;
        var halfLifeDays = 14.0;
        var ageDays = 200.0;
        var floor = 0.1;

        // Act
        var result = _calculator.Calculate(baseConfidence, ageDays, halfLifeDays, floor);

        // Assert
        result.Should().Be(floor);
    }

    [Fact]
    public void CalculateDecayFactor_ZeroAge_ReturnsOne()
    {
        // Act
        var factor = _calculator.CalculateDecayFactor(0.0);

        // Assert
        factor.Should().Be(1.0);
    }

    [Fact]
    public void CalculateDecayFactor_HalfLife_ReturnsHalf()
    {
        // Act
        var factor = _calculator.CalculateDecayFactor(14.0, 14.0);

        // Assert
        factor.Should().BeApproximately(0.5, 0.01);
    }

    [Theory]
    [InlineData(-0.1)]
    [InlineData(1.1)]
    public void Calculate_InvalidBaseConfidence_ThrowsArgumentOutOfRange(double invalidConfidence)
    {
        // Act & Assert
        var act = () => _calculator.Calculate(invalidConfidence, 10.0);
        act.Should().Throw<ArgumentOutOfRangeException>();
    }

    [Fact]
    public void Calculate_NegativeAge_ThrowsArgumentOutOfRange()
    {
        // Act & Assert
        var act = () => _calculator.Calculate(0.8, -1.0);
        act.Should().Throw<ArgumentOutOfRangeException>();
    }
}