using FluentAssertions;
using Microsoft.Extensions.Logging.Abstractions;
using Microsoft.Extensions.Options;
using StellaOps.Policy;
using StellaOps.Policy.Determinization;
using StellaOps.Policy.Determinization.Models;
using StellaOps.Policy.Engine.Policies;

namespace StellaOps.Policy.Engine.Tests.Policies;

public class DeterminizationPolicyTests
{
    private readonly DeterminizationPolicy _policy;

    public DeterminizationPolicyTests()
    {
        var options = Options.Create(new DeterminizationOptions());
        _policy = new DeterminizationPolicy(options, NullLogger<DeterminizationPolicy>.Instance);
    }

    [Fact]
    public void Evaluate_RuntimeEvidenceLoaded_ReturnsEscalated()
    {
        // Arrange
        var context = CreateContext(
            runtime: new SignalState<RuntimeEvidence>
            {
                HasValue = true,
                Value = new RuntimeEvidence { ObservedLoaded = true }
            });

        // Act
        var result = _policy.Evaluate(context);

        // Assert
        result.Status.Should().Be(PolicyVerdictStatus.Escalated);
        result.MatchedRule.Should().Be("RuntimeEscalation");
        result.Reason.Should().Contain("Runtime evidence shows vulnerable code loaded");
    }

    [Fact]
    public void Evaluate_HighEpss_ReturnsQuarantined()
    {
        // Arrange
        var context = CreateContext(
            epss: new SignalState<EpssEvidence>
            {
                HasValue = true,
                Value = new EpssEvidence { Score = 0.8 }
            },
            environment: DeploymentEnvironment.Production);

        // Act
        var result = _policy.Evaluate(context);

        // Assert
        result.Status.Should().Be(PolicyVerdictStatus.Blocked);
        result.MatchedRule.Should().Be("EpssQuarantine");
        result.Reason.Should().Contain("EPSS score");
    }

    [Fact]
    public void Evaluate_ReachableCode_ReturnsQuarantined()
    {
        // Arrange
        var context = CreateContext(
            reachability: new SignalState<ReachabilityEvidence>
            {
                HasValue = true,
                Value = new ReachabilityEvidence { IsReachable = true, Confidence = 0.9 }
            });

        // Act
        var result = _policy.Evaluate(context);

        // Assert
        result.Status.Should().Be(PolicyVerdictStatus.Blocked);
        result.MatchedRule.Should().Be("ReachabilityQuarantine");
        result.Reason.Should().Contain("reachable");
    }

    [Fact]
    public void Evaluate_HighEntropyInProduction_ReturnsQuarantined()
    {
        // Arrange
        var context = CreateContext(
            entropy: 0.5,
            environment: DeploymentEnvironment.Production);

        // Act
        var result = _policy.Evaluate(context);

        // Assert
        result.Status.Should().Be(PolicyVerdictStatus.Blocked);
        result.MatchedRule.Should().Be("ProductionEntropyBlock");
        result.Reason.Should().Contain("High uncertainty");
    }

    [Fact]
    public void Evaluate_StaleEvidence_ReturnsDeferred()
    {
        // Arrange
        var context = CreateContext(
            isStale: true);

        // Act
        var result = _policy.Evaluate(context);

        // Assert
        result.Status.Should().Be(PolicyVerdictStatus.Deferred);
        result.MatchedRule.Should().Be("StaleEvidenceDefer");
        result.Reason.Should().Contain("stale");
    }

    [Fact]
    public void Evaluate_ModerateUncertaintyInDev_ReturnsGuardedPass()
    {
        // Arrange
        var context = CreateContext(
            entropy: 0.5,
            trustScore: 0.3,
            environment: DeploymentEnvironment.Development);

        // Act
        var result = _policy.Evaluate(context);

        // Assert
        result.Status.Should().Be(PolicyVerdictStatus.GuardedPass);
        result.MatchedRule.Should().Be("GuardedAllowNonProd");
        result.GuardRails.Should().NotBeNull();
        result.GuardRails!.EnableMonitoring.Should().BeTrue();
    }

    [Fact]
    public void Evaluate_UnreachableWithHighConfidence_ReturnsAllowed()
    {
        // Arrange
        var context = CreateContext(
            reachability: new SignalState<ReachabilityEvidence>
            {
                HasValue = true,
                Value = new ReachabilityEvidence { IsReachable = false, Confidence = 0.9 }
            },
            trustScore: 0.8);

        // Act
        var result = _policy.Evaluate(context);

        // Assert
        result.Status.Should().Be(PolicyVerdictStatus.Pass);
        result.MatchedRule.Should().Be("UnreachableAllow");
        result.Reason.Should().Contain("unreachable");
    }

    [Fact]
    public void Evaluate_VexNotAffected_ReturnsAllowed()
    {
        // Arrange
        var context = CreateContext(
            vex: new SignalState<VexClaimSummary>
            {
                HasValue = true,
                Value = new VexClaimSummary { IsNotAffected = true, IssuerTrust = 0.9 }
            },
            trustScore: 0.8);

        // Act
        var result = _policy.Evaluate(context);

        // Assert
        result.Status.Should().Be(PolicyVerdictStatus.Pass);
        result.MatchedRule.Should().Be("VexNotAffectedAllow");
        result.Reason.Should().Contain("not_affected");
    }

    [Fact]
    public void Evaluate_SufficientEvidenceLowEntropy_ReturnsAllowed()
    {
        // Arrange
        var context = CreateContext(
            entropy: 0.2,
            trustScore: 0.8,
            environment: DeploymentEnvironment.Production);

        // Act
        var result = _policy.Evaluate(context);

        // Assert
        result.Status.Should().Be(PolicyVerdictStatus.Pass);
        result.MatchedRule.Should().Be("SufficientEvidenceAllow");
        result.Reason.Should().Contain("Sufficient evidence");
    }

    [Fact]
    public void Evaluate_ModerateUncertaintyTier_ReturnsGuardedPass()
    {
        // Arrange
        var context = CreateContext(
            tier: UncertaintyTier.Moderate,
            trustScore: 0.5,
            entropy: 0.5);

        // Act
        var result = _policy.Evaluate(context);

        // Assert
        result.Status.Should().Be(PolicyVerdictStatus.GuardedPass);
        result.MatchedRule.Should().Be("GuardedAllowModerateUncertainty");
        result.GuardRails.Should().NotBeNull();
    }

    [Fact]
    public void Evaluate_NoMatchingRule_ReturnsDeferred()
    {
        // Arrange
        var context = CreateContext(
            entropy: 0.9,
            trustScore: 0.1,
            environment: DeploymentEnvironment.Production);

        // Act
        var result = _policy.Evaluate(context);

        // Assert
        result.Status.Should().Be(PolicyVerdictStatus.Deferred);
        result.MatchedRule.Should().Be("DefaultDefer");
        result.Reason.Should().Contain("Insufficient evidence");
    }

    private static DeterminizationContext CreateContext(
        SignalState<EpssEvidence>? epss = null,
        SignalState<VexClaimSummary>? vex = null,
        SignalState<ReachabilityEvidence>? reachability = null,
        SignalState<RuntimeEvidence>? runtime = null,
        double entropy = 0.0,
        double trustScore = 0.0,
        UncertaintyTier tier = UncertaintyTier.Minimal,
        DeploymentEnvironment environment = DeploymentEnvironment.Development,
        bool isStale = false)
    {
        var snapshot = new SignalSnapshot
        {
            Cve = "CVE-2024-0001",
            Purl = "pkg:npm/test@1.0.0",
            Epss = epss ?? SignalState<EpssEvidence>.NotQueried(),
            Vex = vex ?? SignalState<VexClaimSummary>.NotQueried(),
            Reachability = reachability ?? SignalState<ReachabilityEvidence>.NotQueried(),
            Runtime = runtime ?? SignalState<RuntimeEvidence>.NotQueried(),
            Backport = SignalState<BackportEvidence>.NotQueried(),
            Sbom = SignalState<SbomLineageEvidence>.NotQueried(),
            Cvss = SignalState<CvssEvidence>.NotQueried(),
            SnapshotAt = DateTimeOffset.UtcNow
        };

        return new DeterminizationContext
        {
            SignalSnapshot = snapshot,
            UncertaintyScore = new UncertaintyScore
            {
                Entropy = entropy,
                Tier = tier,
                Completeness = 1.0 - entropy,
                MissingSignals = []
            },
            Decay = new ObservationDecay
            {
                LastSignalUpdate = DateTimeOffset.UtcNow.AddDays(-1),
                AgeDays = 1,
                DecayedMultiplier = isStale ? 0.3 : 0.9,
                IsStale = isStale
            },
            TrustScore = trustScore,
            Environment = environment
        };
    }
}