// SPDX-License-Identifier: BUSL-1.1
// SPDX-FileCopyrightText: 2025 StellaOps Contributors

using FluentAssertions;
using StellaOps.TestKit.Assertions;
using Xunit;

namespace StellaOps.Policy.Engine.Tests.Snapshots;

/// <summary>
/// Snapshot tests for policy evaluation trace summaries.
/// Ensures evaluation traces have stable structure for debugging and auditing.
/// </summary>
public sealed class PolicyEvaluationTraceSnapshotTests
{
    private static readonly DateTimeOffset FrozenTime = DateTimeOffset.Parse("2025-12-24T12:00:00Z");

    /// <summary>
    /// Verifies that a simple evaluation trace produces stable structure.
    /// </summary>
    [Fact]
    public void SimpleEvaluationTrace_ProducesStableStructure()
    {
        // Arrange
        var trace = CreateSimpleEvaluationTrace();

        // Act
        SnapshotAssert.MatchesSnapshot(trace, "SimpleEvaluationTrace");
    }

    /// <summary>
    /// Verifies that an evaluation trace with multiple rule evaluations produces stable structure.
    /// </summary>
    [Fact]
    public void MultiRuleEvaluationTrace_ProducesStableStructure()
    {
        // Arrange
        var trace = CreateMultiRuleEvaluationTrace();

        // Act
        SnapshotAssert.MatchesSnapshot(trace, "MultiRuleEvaluationTrace");
    }

    /// <summary>
    /// Verifies that an evaluation trace with VEX resolution produces stable structure.
    /// </summary>
    [Fact]
    public void VexResolutionTrace_ProducesStableStructure()
    {
        // Arrange
        var trace = CreateVexResolutionTrace();

        // Act
        SnapshotAssert.MatchesSnapshot(trace, "VexResolutionTrace");
    }

    /// <summary>
    /// Verifies that an evaluation trace with profile application produces stable structure.
    /// </summary>
    [Fact]
    public void ProfileApplicationTrace_ProducesStableStructure()
    {
        // Arrange
        var trace = CreateProfileApplicationTrace();

        // Act
        SnapshotAssert.MatchesSnapshot(trace, "ProfileApplicationTrace");
    }

    /// <summary>
    /// Verifies that an evaluation trace with severity escalation produces stable structure.
    /// </summary>
    [Fact]
    public void SeverityEscalationTrace_ProducesStableStructure()
    {
        // Arrange
        var trace = CreateSeverityEscalationTrace();

        // Act
        SnapshotAssert.MatchesSnapshot(trace, "SeverityEscalationTrace");
    }

    /// <summary>
    /// Verifies that evaluation trace steps are ordered by priority.
    /// </summary>
    [Fact]
    public void EvaluationTrace_StepsOrderedByPriority()
    {
        // Arrange
        var trace = CreateMultiRuleEvaluationTrace();

        // Assert
        var priorities = trace.Steps.Select(s => s.Priority).ToList();
        priorities.Should().BeInDescendingOrder("Steps should be ordered by priority (highest first)");
    }

    /// <summary>
    /// Verifies that evaluation trace includes timing information.
    /// </summary>
    [Fact]
    public void EvaluationTrace_IncludesTimingInformation()
    {
        // Arrange
        var trace = CreateSimpleEvaluationTrace();

        // Assert
        trace.StartedAt.Should().Be(FrozenTime);
        trace.CompletedAt.Should().BeAfter(trace.StartedAt);
        trace.DurationMs.Should().BeGreaterThanOrEqualTo(0);
        trace.Steps.Should().AllSatisfy(s => s.DurationMs.Should().BeGreaterThanOrEqualTo(0));
    }

    #region Trace Factories

    private static PolicyEvaluationTrace CreateSimpleEvaluationTrace()
    {
        return new PolicyEvaluationTrace
        {
            TraceId = "TRACE-2025-001",
            PolicyId = "POL-PROD-001",
            PolicyName = "Production Baseline Policy",
            EvaluationContext = new EvaluationContext
            {
                DigestEvaluated = "sha256:abc123def456",
                TenantId = "TENANT-001",
                Environment = "production",
                Exposure = "internet"
            },
            StartedAt = FrozenTime,
            CompletedAt = FrozenTime.AddMilliseconds(42),
            DurationMs = 42,
            Outcome = "Pass",
            Steps =
            [
                new EvaluationStep
                {
                    StepNumber = 1,
                    RuleName = "block_critical",
                    Priority = 5,
                    Phase = EvaluationPhase.RuleMatch,
                    Condition = "severity.normalized >= \"Critical\"",
                    ConditionResult = false,
                    Action = null,
                    Explanation = "No critical vulnerabilities found in scan",
                    DurationMs = 15
                },
                new EvaluationStep
                {
                    StepNumber = 2,
                    RuleName = "allow_low_severity",
                    Priority = 1,
                    Phase = EvaluationPhase.RuleMatch,
                    Condition = "severity.normalized <= \"Low\"",
                    ConditionResult = true,
                    Action = "status := \"allowed\"",
                    Explanation = "All findings are Low severity or below",
                    DurationMs = 12
                }
            ],
            FinalStatus = "allowed",
            MatchedRuleCount = 1,
            TotalRuleCount = 2
        };
    }

    private static PolicyEvaluationTrace CreateMultiRuleEvaluationTrace()
    {
        return new PolicyEvaluationTrace
        {
            TraceId = "TRACE-2025-002",
            PolicyId = "POL-COMPLEX-001",
            PolicyName = "Complex Multi-Rule Policy",
            EvaluationContext = new EvaluationContext
            {
                DigestEvaluated = "sha256:xyz789",
                TenantId = "TENANT-002",
                Environment = "staging",
                Exposure = "internal"
            },
            StartedAt = FrozenTime,
            CompletedAt = FrozenTime.AddMilliseconds(89),
            DurationMs = 89,
            Outcome = "Warn",
            Steps =
            [
                new EvaluationStep
                {
                    StepNumber = 1,
                    RuleName = "block_critical",
                    Priority = 5,
                    Phase = EvaluationPhase.RuleMatch,
                    Condition = "severity.normalized >= \"Critical\"",
                    ConditionResult = false,
                    Action = null,
                    Explanation = "No critical vulnerabilities",
                    DurationMs = 10
                },
                new EvaluationStep
                {
                    StepNumber = 2,
                    RuleName = "escalate_high_internet",
                    Priority = 4,
                    Phase = EvaluationPhase.RuleMatch,
                    Condition = "severity.normalized == \"High\" and env.exposure == \"internet\"",
                    ConditionResult = false,
                    Action = null,
                    Explanation = "Not internet-exposed, skipping escalation",
                    DurationMs = 8
                },
                new EvaluationStep
                {
                    StepNumber = 3,
                    RuleName = "block_ruby_dev",
                    Priority = 4,
                    Phase = EvaluationPhase.RuleMatch,
                    Condition = "sbom.any_component(ruby.group(\"development\"))",
                    ConditionResult = false,
                    Action = null,
                    Explanation = "No development-only Ruby gems",
                    DurationMs = 12
                },
                new EvaluationStep
                {
                    StepNumber = 4,
                    RuleName = "require_vex_justification",
                    Priority = 3,
                    Phase = EvaluationPhase.RuleMatch,
                    Condition = "vex.any(status in [\"not_affected\",\"fixed\"])",
                    ConditionResult = true,
                    Action = "status := vex.status",
                    Explanation = "VEX statement found: not_affected (component_not_present)",
                    DurationMs = 25
                },
                new EvaluationStep
                {
                    StepNumber = 5,
                    RuleName = "warn_eol_runtime",
                    Priority = 1,
                    Phase = EvaluationPhase.RuleMatch,
                    Condition = "severity.normalized <= \"Medium\" and sbom.has_tag(\"runtime:eol\")",
                    ConditionResult = true,
                    Action = "warn message \"Runtime marked as EOL; upgrade recommended.\"",
                    Explanation = "EOL runtime detected: python3.9",
                    DurationMs = 15
                }
            ],
            FinalStatus = "warning",
            MatchedRuleCount = 2,
            TotalRuleCount = 5
        };
    }

    private static PolicyEvaluationTrace CreateVexResolutionTrace()
    {
        return new PolicyEvaluationTrace
        {
            TraceId = "TRACE-2025-003",
            PolicyId = "POL-VEX-001",
            PolicyName = "VEX-Aware Policy",
            EvaluationContext = new EvaluationContext
            {
                DigestEvaluated = "sha256:vex123",
                TenantId = "TENANT-001",
                Environment = "production",
                Exposure = "internet"
            },
            StartedAt = FrozenTime,
            CompletedAt = FrozenTime.AddMilliseconds(67),
            DurationMs = 67,
            Outcome = "Pass",
            Steps =
            [
                new EvaluationStep
                {
                    StepNumber = 1,
                    RuleName = "vex_merge_resolution",
                    Priority = 10,
                    Phase = EvaluationPhase.VexMerge,
                    Condition = "vex.statements.count > 1",
                    ConditionResult = true,
                    Action = null,
                    Explanation = "Multiple VEX statements found; merging via K4 lattice",
                    DurationMs = 20,
                    VexMergeDetail = new VexMergeDetail
                    {
                        VulnerabilityId = "CVE-2024-0001",
                        StatementCount = 3,
                        Sources =
                        [
                            new VexSourceInfo { Source = "vendor", Status = "not_affected", Trust = 1.0m },
                            new VexSourceInfo { Source = "maintainer", Status = "affected", Trust = 0.9m },
                            new VexSourceInfo { Source = "scanner", Status = "unknown", Trust = 0.5m }
                        ],
                        WinningSource = "vendor",
                        WinningStatus = "not_affected",
                        ResolutionReason = "TrustWeight",
                        ConflictsResolved = 2
                    }
                },
                new EvaluationStep
                {
                    StepNumber = 2,
                    RuleName = "require_vex_justification",
                    Priority = 3,
                    Phase = EvaluationPhase.RuleMatch,
                    Condition = "vex.justification in [\"component_not_present\",\"vulnerable_code_not_present\"]",
                    ConditionResult = true,
                    Action = "status := vex.status",
                    Explanation = "VEX justification accepted: component_not_present",
                    DurationMs = 12
                }
            ],
            FinalStatus = "allowed",
            MatchedRuleCount = 2,
            TotalRuleCount = 2
        };
    }

    private static PolicyEvaluationTrace CreateProfileApplicationTrace()
    {
        return new PolicyEvaluationTrace
        {
            TraceId = "TRACE-2025-004",
            PolicyId = "POL-PROFILE-001",
            PolicyName = "Profile-Based Policy",
            EvaluationContext = new EvaluationContext
            {
                DigestEvaluated = "sha256:profile123",
                TenantId = "TENANT-003",
                Environment = "production",
                Exposure = "internet"
            },
            StartedAt = FrozenTime,
            CompletedAt = FrozenTime.AddMilliseconds(55),
            DurationMs = 55,
            Outcome = "Pass",
            Steps =
            [
                new EvaluationStep
                {
                    StepNumber = 1,
                    RuleName = "profile_severity",
                    Priority = 100,
                    Phase = EvaluationPhase.ProfileApplication,
                    Condition = "profile.severity.enabled",
                    ConditionResult = true,
                    Action = null,
                    Explanation = "Applying severity profile adjustments",
                    DurationMs = 18,
                    ProfileApplicationDetail = new ProfileApplicationDetail
                    {
                        ProfileName = "severity",
                        Adjustments =
                        [
                            new ProfileAdjustment
                            {
                                Finding = "CVE-2024-0001",
                                OriginalSeverity = "High",
                                AdjustedSeverity = "Critical",
                                Reason = "GHSA source weight +0.5, internet exposure +0.5"
                            }
                        ]
                    }
                },
                new EvaluationStep
                {
                    StepNumber = 2,
                    RuleName = "block_critical",
                    Priority = 5,
                    Phase = EvaluationPhase.RuleMatch,
                    Condition = "severity.normalized >= \"Critical\"",
                    ConditionResult = false,
                    Action = null,
                    Explanation = "Post-profile: no critical vulnerabilities (VEX override applied)",
                    DurationMs = 10
                }
            ],
            FinalStatus = "allowed",
            MatchedRuleCount = 1,
            TotalRuleCount = 2
        };
    }

    private static PolicyEvaluationTrace CreateSeverityEscalationTrace()
    {
        return new PolicyEvaluationTrace
        {
            TraceId = "TRACE-2025-005",
            PolicyId = "POL-ESCALATE-001",
            PolicyName = "Escalation Policy",
            EvaluationContext = new EvaluationContext
            {
                DigestEvaluated = "sha256:escalate123",
                TenantId = "TENANT-001",
                Environment = "production",
                Exposure = "internet"
            },
            StartedAt = FrozenTime,
            CompletedAt = FrozenTime.AddMilliseconds(45),
            DurationMs = 45,
            Outcome = "Fail",
            Steps =
            [
                new EvaluationStep
                {
                    StepNumber = 1,
                    RuleName = "escalate_high_internet",
                    Priority = 4,
                    Phase = EvaluationPhase.SeverityEscalation,
                    Condition = "severity.normalized == \"High\" and env.exposure == \"internet\"",
                    ConditionResult = true,
                    Action = "escalate to severity_band(\"Critical\")",
                    Explanation = "High severity on internet-exposed asset escalated to Critical",
                    DurationMs = 15,
                    EscalationDetail = new EscalationDetail
                    {
                        Finding = "CVE-2024-0001",
                        OriginalSeverity = "High",
                        EscalatedSeverity = "Critical",
                        Reason = "Internet exposure triggers escalation per policy rule"
                    }
                },
                new EvaluationStep
                {
                    StepNumber = 2,
                    RuleName = "block_critical",
                    Priority = 5,
                    Phase = EvaluationPhase.RuleMatch,
                    Condition = "severity.normalized >= \"Critical\"",
                    ConditionResult = true,
                    Action = "status := \"blocked\"",
                    Explanation = "Critical severity (post-escalation) triggers block",
                    DurationMs = 10
                }
            ],
            FinalStatus = "blocked",
            MatchedRuleCount = 2,
            TotalRuleCount = 2
        };
    }

    #endregion
}

#region Trace Models

public sealed record PolicyEvaluationTrace
{
    public required string TraceId { get; init; }
    public required string PolicyId { get; init; }
    public required string PolicyName { get; init; }
    public required EvaluationContext EvaluationContext { get; init; }
    public required DateTimeOffset StartedAt { get; init; }
    public required DateTimeOffset CompletedAt { get; init; }
    public required int DurationMs { get; init; }
    public required string Outcome { get; init; }
    public required IReadOnlyList<EvaluationStep> Steps { get; init; }
    public required string FinalStatus { get; init; }
    public required int MatchedRuleCount { get; init; }
    public required int TotalRuleCount { get; init; }
}

public sealed record EvaluationContext
{
    public required string DigestEvaluated { get; init; }
    public required string TenantId { get; init; }
    public required string Environment { get; init; }
    public required string Exposure { get; init; }
}

public sealed record EvaluationStep
{
    public required int StepNumber { get; init; }
    public required string RuleName { get; init; }
    public required int Priority { get; init; }
    public required EvaluationPhase Phase { get; init; }
    public required string Condition { get; init; }
    public required bool ConditionResult { get; init; }
    public string? Action { get; init; }
    public required string Explanation { get; init; }
    public required int DurationMs { get; init; }
    public VexMergeDetail? VexMergeDetail { get; init; }
    public ProfileApplicationDetail? ProfileApplicationDetail { get; init; }
    public EscalationDetail? EscalationDetail { get; init; }
}

public enum EvaluationPhase
{
    ProfileApplication,
    VexMerge,
    SeverityEscalation,
    RuleMatch
}

public sealed record VexMergeDetail
{
    public required string VulnerabilityId { get; init; }
    public required int StatementCount { get; init; }
    public required IReadOnlyList<VexSourceInfo> Sources { get; init; }
    public required string WinningSource { get; init; }
    public required string WinningStatus { get; init; }
    public required string ResolutionReason { get; init; }
    public required int ConflictsResolved { get; init; }
}

public sealed record VexSourceInfo
{
    public required string Source { get; init; }
    public required string Status { get; init; }
    public required decimal Trust { get; init; }
}

public sealed record ProfileApplicationDetail
{
    public required string ProfileName { get; init; }
    public required IReadOnlyList<ProfileAdjustment> Adjustments { get; init; }
}

public sealed record ProfileAdjustment
{
    public required string Finding { get; init; }
    public required string OriginalSeverity { get; init; }
    public required string AdjustedSeverity { get; init; }
    public required string Reason { get; init; }
}

public sealed record EscalationDetail
{
    public required string Finding { get; init; }
    public required string OriginalSeverity { get; init; }
    public required string EscalatedSeverity { get; init; }
    public required string Reason { get; init; }
}

#endregion