// <copyright file="IdentityEvidenceBuilderTests.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="IdentityEvidenceBuilder"/>.
/// Sprint: SPRINT_20260107_005_001 Task EV-011
/// </summary>
[Trait("Category", "Unit")]
public sealed class IdentityEvidenceBuilderTests
{
    private readonly IdentityEvidenceBuilder _sut = new();

    [Fact]
    public void Build_WithPurl_ReturnsFieldAsPurl()
    {
        // Arrange
        var component = CreateComponent(purl: "pkg:npm/lodash@4.17.21");

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

        // Assert
        result.Should().NotBeNull();
        result!.Field.Should().Be("purl");
    }

    [Fact]
    public void Build_WithNameOnly_ReturnsFieldAsName()
    {
        // Arrange
        var component = CreateComponent(name: "my-package");

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

        // Assert
        result.Should().NotBeNull();
        result!.Field.Should().Be("name");
    }

    [Fact]
    public void Build_WithManifestEvidence_IncludesManifestAnalysisMethod()
    {
        // Arrange
        var evidence = ImmutableArray.Create(
            new ComponentEvidence { Kind = "manifest", Value = "package.json", Source = "/app/package.json" });
        var component = CreateComponent(purl: "pkg:npm/lodash@4.17.21", evidence: evidence);

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

        // Assert
        result!.Methods.Should().ContainSingle(m =>
            m.Technique == IdentityEvidenceTechnique.ManifestAnalysis);
        result.Methods![0].Confidence.Should().Be(0.95);
    }

    [Fact]
    public void Build_WithBinaryEvidence_IncludesBinaryAnalysisMethod()
    {
        // Arrange
        var evidence = ImmutableArray.Create(
            new ComponentEvidence { Kind = "binary", Value = "lodash.dll", Source = "/app/lodash.dll" });
        var component = CreateComponent(purl: "pkg:npm/lodash@4.17.21", evidence: evidence);

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

        // Assert
        result!.Methods.Should().ContainSingle(m =>
            m.Technique == IdentityEvidenceTechnique.BinaryAnalysis);
        result.Methods![0].Confidence.Should().Be(0.80);
    }

    [Fact]
    public void Build_WithHashEvidence_IncludesHighConfidenceMethod()
    {
        // Arrange
        var evidence = ImmutableArray.Create(
            new ComponentEvidence { Kind = "hash", Value = "sha256:abc123", Source = "/app/lib.so" });
        var component = CreateComponent(purl: "pkg:npm/lodash@4.17.21", evidence: evidence);

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

        // Assert
        result!.Methods.Should().ContainSingle(m =>
            m.Technique == IdentityEvidenceTechnique.HashComparison);
        result.Methods![0].Confidence.Should().Be(0.99);
    }

    [Fact]
    public void Build_WithMultipleSources_IncludesAllMethods()
    {
        // Arrange
        var evidence = ImmutableArray.Create(
            new ComponentEvidence { Kind = "manifest", Value = "package.json", Source = "/app/package.json" },
            new ComponentEvidence { Kind = "binary", Value = "lib.dll", Source = "/app/lib.dll" },
            new ComponentEvidence { Kind = "hash", Value = "sha256:abc", Source = "/app/lib.so" });
        var component = CreateComponent(purl: "pkg:npm/lodash@4.17.21", evidence: evidence);

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

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

    [Fact]
    public void Build_CalculatesOverallConfidenceFromHighestMethod()
    {
        // Arrange
        var evidence = ImmutableArray.Create(
            new ComponentEvidence { Kind = "binary", Value = "lib.dll", Source = "/app/lib.dll" },
            new ComponentEvidence { Kind = "hash", Value = "sha256:abc", Source = "/app/lib.so" });
        var component = CreateComponent(purl: "pkg:npm/lodash@4.17.21", evidence: evidence);

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

        // Assert
        result!.Confidence.Should().Be(0.99); // Hash match has highest confidence
    }

    [Fact]
    public void Build_WithNoIdentifyingData_ReturnsNull()
    {
        // Arrange - unknown name means no identification
        var component = new AggregatedComponent
        {
            Identity = ComponentIdentity.Create("unknown", "unknown"),
        };

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

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

    [Fact]
    public void Build_WithPurlNoEvidence_ReturnsAttestationMethod()
    {
        // Arrange
        var component = CreateComponent(purl: "pkg:npm/lodash@4.17.21");

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

        // Assert
        result!.Methods.Should().ContainSingle(m =>
            m.Technique == IdentityEvidenceTechnique.Attestation);
        result.Methods![0].Confidence.Should().Be(0.70);
    }

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

    private static AggregatedComponent CreateComponent(
        string? purl = null,
        string? name = null,
        ImmutableArray<ComponentEvidence> evidence = default)
    {
        var identity = ComponentIdentity.Create(
            key: purl ?? name ?? "unknown",
            name: name ?? "test-component",
            purl: purl);

        return new AggregatedComponent
        {
            Identity = identity,
            Evidence = evidence.IsDefault ? ImmutableArray<ComponentEvidence>.Empty : evidence,
        };
    }
}