// -----------------------------------------------------------------------------
// VulnSurface.cs
// Sprint: SPRINT_3700_0002_0001_vuln_surfaces_core
// Description: Core models for vulnerability surface computation.
// -----------------------------------------------------------------------------

using System;
using System.Collections.Generic;
using System.Text.Json.Serialization;

namespace StellaOps.Scanner.VulnSurfaces.Models;

/// <summary>
/// A vulnerability surface represents the specific methods that changed
/// between a vulnerable and fixed version of a package.
/// </summary>
public sealed record VulnSurface
{
    /// <summary>
    /// Database ID.
    /// </summary>
    [JsonPropertyName("surface_id")]
    public long SurfaceId { get; init; }

    /// <summary>
    /// CVE ID (e.g., "CVE-2024-12345").
    /// </summary>
    [JsonPropertyName("cve_id")]
    public required string CveId { get; init; }

    /// <summary>
    /// Package identifier (PURL format preferred).
    /// </summary>
    [JsonPropertyName("package_id")]
    public required string PackageId { get; init; }

    /// <summary>
    /// Ecosystem (nuget, npm, maven, pypi).
    /// </summary>
    [JsonPropertyName("ecosystem")]
    public required string Ecosystem { get; init; }

    /// <summary>
    /// Vulnerable version analyzed.
    /// </summary>
    [JsonPropertyName("vuln_version")]
    public required string VulnVersion { get; init; }

    /// <summary>
    /// Fixed version used for diff.
    /// </summary>
    [JsonPropertyName("fixed_version")]
    public required string FixedVersion { get; init; }

    /// <summary>
    /// Sink methods (vulnerable code locations).
    /// </summary>
    [JsonPropertyName("sinks")]
    public IReadOnlyList<VulnSurfaceSink> Sinks { get; init; } = [];

    /// <summary>
    /// Number of trigger methods that can reach sinks.
    /// </summary>
    [JsonPropertyName("trigger_count")]
    public int TriggerCount { get; init; }

    /// <summary>
    /// Surface computation status.
    /// </summary>
    [JsonPropertyName("status")]
    public VulnSurfaceStatus Status { get; init; }

    /// <summary>
    /// Confidence score (0.0-1.0).
    /// </summary>
    [JsonPropertyName("confidence")]
    public double Confidence { get; init; } = 1.0;

    /// <summary>
    /// When the surface was computed.
    /// </summary>
    [JsonPropertyName("computed_at")]
    public DateTimeOffset ComputedAt { get; init; }

    /// <summary>
    /// Error message if computation failed.
    /// </summary>
    [JsonPropertyName("error")]
    public string? Error { get; init; }
}

/// <summary>
/// A sink method - a specific method that was modified in the security fix.
/// </summary>
public sealed record VulnSurfaceSink
{
    /// <summary>
    /// Database ID.
    /// </summary>
    [JsonPropertyName("sink_id")]
    public long SinkId { get; init; }

    /// <summary>
    /// Parent surface ID.
    /// </summary>
    [JsonPropertyName("surface_id")]
    public long SurfaceId { get; init; }

    /// <summary>
    /// Normalized method key.
    /// </summary>
    [JsonPropertyName("method_key")]
    public required string MethodKey { get; init; }

    /// <summary>
    /// Declaring type/class name.
    /// </summary>
    [JsonPropertyName("declaring_type")]
    public required string DeclaringType { get; init; }

    /// <summary>
    /// Method name.
    /// </summary>
    [JsonPropertyName("method_name")]
    public required string MethodName { get; init; }

    /// <summary>
    /// Method signature.
    /// </summary>
    [JsonPropertyName("signature")]
    public string? Signature { get; init; }

    /// <summary>
    /// Type of change detected.
    /// </summary>
    [JsonPropertyName("change_type")]
    public MethodChangeType ChangeType { get; init; }

    /// <summary>
    /// Hash of the method in vulnerable version.
    /// </summary>
    [JsonPropertyName("vuln_hash")]
    public string? VulnHash { get; init; }

    /// <summary>
    /// Hash of the method in fixed version.
    /// </summary>
    [JsonPropertyName("fixed_hash")]
    public string? FixedHash { get; init; }

    /// <summary>
    /// Whether this sink is directly exploitable.
    /// </summary>
    [JsonPropertyName("is_direct_exploit")]
    public bool IsDirectExploit { get; init; }
}

/// <summary>
/// Status of vulnerability surface computation.
/// </summary>
[JsonConverter(typeof(JsonStringEnumConverter))]
public enum VulnSurfaceStatus
{
    /// <summary>
    /// Computation pending.
    /// </summary>
    Pending,

    /// <summary>
    /// Computation in progress.
    /// </summary>
    Computing,

    /// <summary>
    /// Successfully computed.
    /// </summary>
    Computed,

    /// <summary>
    /// Computation failed.
    /// </summary>
    Failed,

    /// <summary>
    /// No diff detected (versions identical).
    /// </summary>
    NoDiff,

    /// <summary>
    /// Package not found.
    /// </summary>
    PackageNotFound
}

/// <summary>
/// Type of method change detected.
/// </summary>
[JsonConverter(typeof(JsonStringEnumConverter))]
public enum MethodChangeType
{
    /// <summary>
    /// Method body was modified.
    /// </summary>
    Modified,

    /// <summary>
    /// Method was added in fixed version.
    /// </summary>
    Added,

    /// <summary>
    /// Method was removed in fixed version.
    /// </summary>
    Removed,

    /// <summary>
    /// Method signature changed.
    /// </summary>
    SignatureChanged
}