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

using System.Globalization;
using StellaOps.Spdx3.Model.Security;

namespace StellaOps.VexLens.Spdx3;

/// <summary>
/// Maps CVSS scores to SPDX 3.0.1 Security profile assessment relationships.
/// Sprint: SPRINT_20260107_004_004 Task SP-007
/// </summary>
public static class CvssMapper
{
    /// <summary>
    /// Maps a CVSS v3 score to an SPDX 3.0.1 CVSS vulnerability assessment relationship.
    /// </summary>
    /// <param name="cvssData">The CVSS v3 data to map.</param>
    /// <param name="vulnerabilitySpdxId">SPDX ID of the vulnerability being assessed.</param>
    /// <param name="assessedElementSpdxId">SPDX ID of the element being assessed.</param>
    /// <param name="spdxIdPrefix">Prefix for generating relationship SPDX IDs.</param>
    /// <returns>The mapped CVSS assessment relationship.</returns>
    public static Spdx3CvssV3VulnAssessmentRelationship MapToSpdx3(
        CvssV3Data cvssData,
        string vulnerabilitySpdxId,
        string assessedElementSpdxId,
        string spdxIdPrefix)
    {
        ArgumentNullException.ThrowIfNull(cvssData);
        ArgumentException.ThrowIfNullOrWhiteSpace(vulnerabilitySpdxId);
        ArgumentException.ThrowIfNullOrWhiteSpace(assessedElementSpdxId);
        ArgumentException.ThrowIfNullOrWhiteSpace(spdxIdPrefix);

        var spdxId = GenerateSpdxId(spdxIdPrefix, vulnerabilitySpdxId, assessedElementSpdxId, "cvss");

        return new Spdx3CvssV3VulnAssessmentRelationship
        {
            SpdxId = spdxId,
            Type = Spdx3CvssV3VulnAssessmentRelationship.TypeName,
            AssessedElement = assessedElementSpdxId,
            From = vulnerabilitySpdxId,
            To = [assessedElementSpdxId],
            RelationshipType = "hasAssessmentFor",
            Score = cvssData.BaseScore,
            Severity = MapSeverity(cvssData.BaseScore),
            VectorString = cvssData.VectorString,
            PublishedTime = cvssData.PublishedTime,
            ModifiedTime = cvssData.ModifiedTime,
            SuppliedBy = cvssData.Source
        };
    }

    /// <summary>
    /// Maps an EPSS score to an SPDX 3.0.1 EPSS vulnerability assessment relationship.
    /// </summary>
    /// <param name="epssData">The EPSS data to map.</param>
    /// <param name="vulnerabilitySpdxId">SPDX ID of the vulnerability being assessed.</param>
    /// <param name="assessedElementSpdxId">SPDX ID of the element being assessed.</param>
    /// <param name="spdxIdPrefix">Prefix for generating relationship SPDX IDs.</param>
    /// <returns>The mapped EPSS assessment relationship.</returns>
    public static Spdx3EpssVulnAssessmentRelationship MapEpssToSpdx3(
        EpssData epssData,
        string vulnerabilitySpdxId,
        string assessedElementSpdxId,
        string spdxIdPrefix)
    {
        ArgumentNullException.ThrowIfNull(epssData);
        ArgumentException.ThrowIfNullOrWhiteSpace(vulnerabilitySpdxId);
        ArgumentException.ThrowIfNullOrWhiteSpace(assessedElementSpdxId);
        ArgumentException.ThrowIfNullOrWhiteSpace(spdxIdPrefix);

        var spdxId = GenerateSpdxId(spdxIdPrefix, vulnerabilitySpdxId, assessedElementSpdxId, "epss");

        return new Spdx3EpssVulnAssessmentRelationship
        {
            SpdxId = spdxId,
            Type = Spdx3EpssVulnAssessmentRelationship.TypeName,
            AssessedElement = assessedElementSpdxId,
            From = vulnerabilitySpdxId,
            To = [assessedElementSpdxId],
            RelationshipType = "hasAssessmentFor",
            Probability = epssData.Probability,
            Percentile = epssData.Percentile,
            PublishedTime = epssData.ScoreDate,
            SuppliedBy = "https://www.first.org/epss"
        };
    }

    /// <summary>
    /// Maps a CVSS v3 base score to severity level.
    /// </summary>
    /// <param name="score">The CVSS v3 base score (0.0-10.0).</param>
    /// <returns>The severity level.</returns>
    public static Spdx3CvssSeverity MapSeverity(decimal? score)
    {
        return score switch
        {
            null => Spdx3CvssSeverity.None,
            0.0m => Spdx3CvssSeverity.None,
            >= 0.1m and <= 3.9m => Spdx3CvssSeverity.Low,
            >= 4.0m and <= 6.9m => Spdx3CvssSeverity.Medium,
            >= 7.0m and <= 8.9m => Spdx3CvssSeverity.High,
            >= 9.0m => Spdx3CvssSeverity.Critical,
            _ => Spdx3CvssSeverity.None
        };
    }

    /// <summary>
    /// Parses a CVSS v3 vector string to extract component scores.
    /// </summary>
    /// <param name="vectorString">The CVSS v3 vector string (e.g., "CVSS:3.1/AV:N/AC:L/...").</param>
    /// <returns>Parsed vector components, or null if parsing fails.</returns>
    public static CvssVectorComponents? ParseVectorString(string? vectorString)
    {
        if (string.IsNullOrWhiteSpace(vectorString))
        {
            return null;
        }

        try
        {
            var parts = vectorString.Split('/');
            var components = new Dictionary<string, string>(StringComparer.OrdinalIgnoreCase);

            foreach (var part in parts)
            {
                var kv = part.Split(':');
                if (kv.Length == 2)
                {
                    components[kv[0]] = kv[1];
                }
            }

            return new CvssVectorComponents
            {
                Version = components.GetValueOrDefault("CVSS", "3.1"),
                AttackVector = components.GetValueOrDefault("AV"),
                AttackComplexity = components.GetValueOrDefault("AC"),
                PrivilegesRequired = components.GetValueOrDefault("PR"),
                UserInteraction = components.GetValueOrDefault("UI"),
                Scope = components.GetValueOrDefault("S"),
                ConfidentialityImpact = components.GetValueOrDefault("C"),
                IntegrityImpact = components.GetValueOrDefault("I"),
                AvailabilityImpact = components.GetValueOrDefault("A")
            };
        }
        catch
        {
            return null;
        }
    }

    private static string GenerateSpdxId(
        string prefix,
        string vulnerabilityId,
        string elementId,
        string assessmentType)
    {
        using var sha = System.Security.Cryptography.SHA256.Create();
        var input = $"{vulnerabilityId}:{elementId}:{assessmentType}";
        var hash = sha.ComputeHash(System.Text.Encoding.UTF8.GetBytes(input));
        var shortHash = Convert.ToHexStringLower(hash)[..12];
        return $"{prefix.TrimEnd('/')}/{assessmentType}/{shortHash}";
    }
}

/// <summary>
/// CVSS v3 data input model.
/// Sprint: SPRINT_20260107_004_004 Task SP-007
/// </summary>
public sealed record CvssV3Data
{
    /// <summary>
    /// Gets or sets the CVSS v3 base score (0.0-10.0).
    /// </summary>
    public decimal? BaseScore { get; init; }

    /// <summary>
    /// Gets or sets the CVSS v3 vector string.
    /// </summary>
    public string? VectorString { get; init; }

    /// <summary>
    /// Gets or sets the temporal score.
    /// </summary>
    public decimal? TemporalScore { get; init; }

    /// <summary>
    /// Gets or sets the environmental score.
    /// </summary>
    public decimal? EnvironmentalScore { get; init; }

    /// <summary>
    /// Gets or sets when the score was published.
    /// </summary>
    public DateTimeOffset? PublishedTime { get; init; }

    /// <summary>
    /// Gets or sets when the score was modified.
    /// </summary>
    public DateTimeOffset? ModifiedTime { get; init; }

    /// <summary>
    /// Gets or sets the source of the CVSS data.
    /// </summary>
    public string? Source { get; init; }
}

/// <summary>
/// EPSS data input model.
/// Sprint: SPRINT_20260107_004_004 Task SP-007
/// </summary>
public sealed record EpssData
{
    /// <summary>
    /// Gets or sets the EPSS probability (0.0-1.0).
    /// </summary>
    public decimal? Probability { get; init; }

    /// <summary>
    /// Gets or sets the EPSS percentile (0.0-1.0).
    /// </summary>
    public decimal? Percentile { get; init; }

    /// <summary>
    /// Gets or sets the date of the EPSS score.
    /// </summary>
    public DateTimeOffset? ScoreDate { get; init; }
}

/// <summary>
/// Parsed CVSS v3 vector components.
/// Sprint: SPRINT_20260107_004_004 Task SP-007
/// </summary>
public sealed record CvssVectorComponents
{
    /// <summary>Gets or sets the CVSS version.</summary>
    public string? Version { get; init; }

    /// <summary>Gets or sets the Attack Vector (AV).</summary>
    public string? AttackVector { get; init; }

    /// <summary>Gets or sets the Attack Complexity (AC).</summary>
    public string? AttackComplexity { get; init; }

    /// <summary>Gets or sets the Privileges Required (PR).</summary>
    public string? PrivilegesRequired { get; init; }

    /// <summary>Gets or sets the User Interaction (UI).</summary>
    public string? UserInteraction { get; init; }

    /// <summary>Gets or sets the Scope (S).</summary>
    public string? Scope { get; init; }

    /// <summary>Gets or sets the Confidentiality Impact (C).</summary>
    public string? ConfidentialityImpact { get; init; }

    /// <summary>Gets or sets the Integrity Impact (I).</summary>
    public string? IntegrityImpact { get; init; }

    /// <summary>Gets or sets the Availability Impact (A).</summary>
    public string? AvailabilityImpact { get; init; }
}