// <copyright file="LicenseEvidenceBuilderTests.cs" company="StellaOps">
// Copyright (c) StellaOps. Licensed under the AGPL-3.0-or-later.
// </copyright>

using System.Collections.Immutable;
using FluentAssertions;
using StellaOps.Scanner.Core.Contracts;
using StellaOps.Scanner.Emit.Evidence;
using Xunit;

namespace StellaOps.Scanner.Emit.Tests.Evidence;

/// <summary>
/// Unit tests for <see cref="LicenseEvidenceBuilder"/>.
/// Sprint: SPRINT_20260107_005_001 Task EV-011
/// </summary>
[Trait("Category", "Unit")]
public sealed class LicenseEvidenceBuilderTests
{
    private readonly LicenseEvidenceBuilder _sut = new();

    [Fact]
    public void Build_WithLicenseEvidence_ReturnsLicenseChoices()
    {
        // Arrange
        var evidence = ImmutableArray.Create(
            new ComponentEvidence { Kind = "license", Value = "MIT", Source = "/app/LICENSE" });
        var component = CreateComponent(evidence);

        // Act
        var result = _sut.Build(component);

        // Assert
        result.Should().HaveCount(1);
        result[0].License.Should().NotBeNull();
        result[0].License!.License.Should().NotBeNull();
        result[0].License!.License!.Id.Should().Be("MIT");
    }

    [Fact]
    public void Build_WithMultipleLicenses_ReturnsAllLicenses()
    {
        // Arrange
        var evidence = ImmutableArray.Create(
            new ComponentEvidence { Kind = "license", Value = "MIT", Source = "/app/LICENSE" },
            new ComponentEvidence { Kind = "license", Value = "Apache-2.0", Source = "/app/LICENSE.apache" },
            new ComponentEvidence { Kind = "license", Value = "GPL-3.0", Source = "/app/COPYING" });
        var component = CreateComponent(evidence);

        // Act
        var result = _sut.Build(component);

        // Assert
        result.Should().HaveCount(3);
    }

    [Fact]
    public void Build_WithNonLicenseEvidence_FiltersOutNonLicenses()
    {
        // Arrange
        var evidence = ImmutableArray.Create(
            new ComponentEvidence { Kind = "license", Value = "MIT", Source = "/app/LICENSE" },
            new ComponentEvidence { Kind = "file", Value = "readme.md", Source = "/app/README.md" });
        var component = CreateComponent(evidence);

        // Act
        var result = _sut.Build(component);

        // Assert
        result.Should().HaveCount(1);
        result[0].License!.License!.Id.Should().Be("MIT");
    }

    [Fact]
    public void Build_WithNoEvidence_ReturnsEmptyArray()
    {
        // Arrange
        var component = CreateComponent(ImmutableArray<ComponentEvidence>.Empty);

        // Act
        var result = _sut.Build(component);

        // Assert
        result.Should().BeEmpty();
    }

    [Fact]
    public void Build_NullComponent_ThrowsArgumentNullException()
    {
        // Act & Assert
        var act = () => _sut.Build(null!);
        act.Should().Throw<ArgumentNullException>();
    }

    [Fact]
    public void Build_WithExpression_ParsesAsExpression()
    {
        // Arrange
        var evidence = ImmutableArray.Create(
            new ComponentEvidence { Kind = "license", Value = "MIT OR Apache-2.0", Source = "/app/LICENSE" });
        var component = CreateComponent(evidence);

        // Act
        var result = _sut.Build(component);

        // Assert
        result.Should().HaveCount(1);
        // SPDX expressions are parsed as expression rather than ID
        result[0].License.Expression.Should().NotBeNullOrWhiteSpace();
    }

    [Fact]
    public void Build_DeduplicatesSameLicense()
    {
        // Arrange
        var evidence = ImmutableArray.Create(
            new ComponentEvidence { Kind = "license", Value = "MIT", Source = "/app/LICENSE" },
            new ComponentEvidence { Kind = "license", Value = "MIT", Source = "/app/package.json" }); // Same license
        var component = CreateComponent(evidence);

        // Act
        var result = _sut.Build(component);

        // Assert
        result.Should().HaveCount(1);
    }

    private static AggregatedComponent CreateComponent(ImmutableArray<ComponentEvidence> evidence)
    {
        var identity = ComponentIdentity.Create(
            key: "pkg:npm/lodash@4.17.21",
            name: "lodash",
            purl: "pkg:npm/lodash@4.17.21");

        return new AggregatedComponent
        {
            Identity = identity,
            Evidence = evidence,
        };
    }
}