namespace StellaOps.Interop.Tests.Analysis;

/// <summary>
/// Analyzes and categorizes differences between tool findings.
/// </summary>
public sealed class FindingsParityAnalyzer
{
    /// <summary>
    /// Categorizes differences between tools.
    /// </summary>
    public ParityAnalysisReport Analyze(
        IReadOnlyList<Finding> stellaFindings,
        IReadOnlyList<GrypeFinding> grypeFindings)
    {
        var differences = new List<FindingDifference>();

        // Category 1: Version matching differences
        // (e.g., semver vs non-semver interpretation)
        var versionDiffs = AnalyzeVersionMatchingDifferences(stellaFindings, grypeFindings);
        differences.AddRange(versionDiffs);

        // Category 2: Feed coverage differences
        // (e.g., Stella has feed X, Grype doesn't)
        var feedDiffs = AnalyzeFeedCoverageDifferences(stellaFindings, grypeFindings);
        differences.AddRange(feedDiffs);

        // Category 3: Package identification differences
        // (e.g., different PURL generation)
        var purlDiffs = AnalyzePurlDifferences(stellaFindings, grypeFindings);
        differences.AddRange(purlDiffs);

        // Category 4: VEX application differences
        // (e.g., Stella applies VEX, Grype doesn't)
        var vexDiffs = AnalyzeVexDifferences(stellaFindings, grypeFindings);
        differences.AddRange(vexDiffs);

        return new ParityAnalysisReport
        {
            TotalDifferences = differences.Count,
            VersionMatchingDifferences = versionDiffs,
            FeedCoverageDifferences = feedDiffs,
            PurlDifferences = purlDiffs,
            VexDifferences = vexDiffs,
            AcceptableDifferences = differences.Count(d => d.IsAcceptable),
            RequiresInvestigation = differences.Count(d => !d.IsAcceptable)
        };
    }

    private static List<FindingDifference> AnalyzeVersionMatchingDifferences(
        IReadOnlyList<Finding> stellaFindings,
        IReadOnlyList<GrypeFinding> grypeFindings)
    {
        var differences = new List<FindingDifference>();

        // TODO: Implement version matching analysis
        // Compare how Stella and Grype interpret version ranges
        // e.g., >=1.0.0 vs ^1.0.0

        return differences;
    }

    private static List<FindingDifference> AnalyzeFeedCoverageDifferences(
        IReadOnlyList<Finding> stellaFindings,
        IReadOnlyList<GrypeFinding> grypeFindings)
    {
        var differences = new List<FindingDifference>();

        // TODO: Implement feed coverage analysis
        // Identify which vulnerabilities come from feeds only one tool has
        // e.g., Stella has GHSA, Grype doesn't, or vice versa

        return differences;
    }

    private static List<FindingDifference> AnalyzePurlDifferences(
        IReadOnlyList<Finding> stellaFindings,
        IReadOnlyList<GrypeFinding> grypeFindings)
    {
        var differences = new List<FindingDifference>();

        // TODO: Implement PURL difference analysis
        // Compare how packages are identified
        // e.g., pkg:npm/package vs pkg:npm/package@version

        return differences;
    }

    private static List<FindingDifference> AnalyzeVexDifferences(
        IReadOnlyList<Finding> stellaFindings,
        IReadOnlyList<GrypeFinding> grypeFindings)
    {
        var differences = new List<FindingDifference>();

        // TODO: Implement VEX application analysis
        // Stella applies VEX documents, Grype may not
        // This is an acceptable difference

        return differences;
    }
}

public sealed class ParityAnalysisReport
{
    public int TotalDifferences { get; init; }
    public IReadOnlyList<FindingDifference> VersionMatchingDifferences { get; init; } = [];
    public IReadOnlyList<FindingDifference> FeedCoverageDifferences { get; init; } = [];
    public IReadOnlyList<FindingDifference> PurlDifferences { get; init; } = [];
    public IReadOnlyList<FindingDifference> VexDifferences { get; init; } = [];
    public int AcceptableDifferences { get; init; }
    public int RequiresInvestigation { get; init; }
}

public sealed record FindingDifference(
    string Category,
    string Description,
    bool IsAcceptable,
    string? Reason = null);