// -----------------------------------------------------------------------------
// TriageStatusService.cs
// Sprint: SPRINT_4200_0001_0001_triage_rest_api
// Description: Service implementation for triage status operations.
// -----------------------------------------------------------------------------

using Microsoft.Extensions.Logging;
using StellaOps.Policy.Counterfactuals;
using StellaOps.Scanner.Triage.Entities;
using StellaOps.Scanner.WebService.Contracts;
using StellaOps.Scanner.WebService.Endpoints.Triage;

namespace StellaOps.Scanner.WebService.Services;

/// <summary>
/// Default implementation of triage status service.
/// </summary>
public sealed class TriageStatusService : ITriageStatusService
{
    private readonly ILogger<TriageStatusService> _logger;
    private readonly ITriageQueryService _queryService;
    private readonly ICounterfactualEngine? _counterfactualEngine;
    private readonly TimeProvider _timeProvider;

    public TriageStatusService(
        ILogger<TriageStatusService> logger,
        ITriageQueryService queryService,
        TimeProvider timeProvider,
        ICounterfactualEngine? counterfactualEngine = null)
    {
        _logger = logger ?? throw new ArgumentNullException(nameof(logger));
        _queryService = queryService ?? throw new ArgumentNullException(nameof(queryService));
        _timeProvider = timeProvider ?? throw new ArgumentNullException(nameof(timeProvider));
        _counterfactualEngine = counterfactualEngine;
    }

    public async Task<FindingTriageStatusDto?> GetFindingStatusAsync(
        string findingId,
        CancellationToken ct = default)
    {
        _logger.LogDebug("Getting triage status for finding {FindingId}", findingId);

        var finding = await _queryService.GetFindingAsync(findingId, ct);
        if (finding is null)
        {
            return null;
        }

        return MapToDto(finding);
    }

    public async Task<UpdateTriageStatusResponseDto?> UpdateStatusAsync(
        string findingId,
        UpdateTriageStatusRequestDto request,
        string actor,
        CancellationToken ct = default)
    {
        _logger.LogDebug("Updating triage status for finding {FindingId} by {Actor}", findingId, actor);

        var finding = await _queryService.GetFindingAsync(findingId, ct);
        if (finding is null)
        {
            return null;
        }

        var previousLane = GetCurrentLane(finding);
        var previousVerdict = GetCurrentVerdict(finding);

        // In a full implementation, this would:
        // 1. Create a new TriageDecision
        // 2. Update the finding lane
        // 3. Create a snapshot for audit

        var newLane = !string.IsNullOrWhiteSpace(request.Lane) ? request.Lane : previousLane;
        var newVerdict = ComputeVerdict(newLane, request.DecisionKind);

        _logger.LogInformation(
            "Triage status updated: Finding={FindingId}, Lane={PrevLane}->{NewLane}, Verdict={PrevVerdict}->{NewVerdict}",
            findingId, previousLane, newLane, previousVerdict, newVerdict);

        return new UpdateTriageStatusResponseDto
        {
            FindingId = findingId,
            PreviousLane = previousLane,
            NewLane = newLane,
            PreviousVerdict = previousVerdict,
            NewVerdict = newVerdict,
            SnapshotId = $"snap-{Guid.NewGuid():N}",
            AppliedAt = _timeProvider.GetUtcNow()
        };
    }

    public async Task<SubmitVexStatementResponseDto?> SubmitVexStatementAsync(
        string findingId,
        SubmitVexStatementRequestDto request,
        string actor,
        CancellationToken ct = default)
    {
        _logger.LogDebug("Submitting VEX statement for finding {FindingId} by {Actor}", findingId, actor);

        var finding = await _queryService.GetFindingAsync(findingId, ct);
        if (finding is null)
        {
            return null;
        }

        var previousVerdict = GetCurrentVerdict(finding);
        var vexStatementId = $"vex-{Guid.NewGuid():N}";

        // Determine if verdict changes based on VEX status
        var verdictChanged = false;
        string? newVerdict = null;

        if (request.Status.Equals("NotAffected", StringComparison.OrdinalIgnoreCase))
        {
            verdictChanged = previousVerdict != "Ship";
            newVerdict = "Ship";
        }

        _logger.LogInformation(
            "VEX statement submitted: Finding={FindingId}, Status={Status}, VerdictChanged={Changed}",
            findingId, request.Status, verdictChanged);

        return new SubmitVexStatementResponseDto
        {
            VexStatementId = vexStatementId,
            FindingId = findingId,
            Status = request.Status,
            VerdictChanged = verdictChanged,
            NewVerdict = newVerdict,
            RecordedAt = _timeProvider.GetUtcNow()
        };
    }

    public Task<BulkTriageQueryResponseDto> QueryFindingsAsync(
        BulkTriageQueryRequestDto request,
        int limit,
        CancellationToken ct = default)
    {
        _logger.LogDebug("Querying findings with limit {Limit}", limit);

        // In a full implementation, this would query the database
        // For now, return empty results
        var response = new BulkTriageQueryResponseDto
        {
            Findings = [],
            TotalCount = 0,
            NextCursor = null,
            Summary = new TriageSummaryDto
            {
                ByLane = new Dictionary<string, int>(),
                ByVerdict = new Dictionary<string, int>(),
                CanShipCount = 0,
                BlockingCount = 0
            }
        };

        return Task.FromResult(response);
    }

    public Task<TriageSummaryDto> GetSummaryAsync(string artifactDigest, CancellationToken ct = default)
    {
        _logger.LogDebug("Getting triage summary for artifact {ArtifactDigest}", artifactDigest);

        // In a full implementation, this would aggregate data from the database
        var summary = new TriageSummaryDto
        {
            ByLane = new Dictionary<string, int>
            {
                ["Active"] = 0,
                ["Blocked"] = 0,
                ["NeedsException"] = 0,
                ["MutedReach"] = 0,
                ["MutedVex"] = 0,
                ["Compensated"] = 0
            },
            ByVerdict = new Dictionary<string, int>
            {
                ["Ship"] = 0,
                ["Block"] = 0,
                ["Exception"] = 0
            },
            CanShipCount = 0,
            BlockingCount = 0
        };

        return Task.FromResult(summary);
    }

    private FindingTriageStatusDto MapToDto(TriageFinding finding)
    {
        var lane = GetCurrentLane(finding);
        var verdict = GetCurrentVerdict(finding);

        TriageVexStatusDto? vexStatus = null;
        var latestVex = finding.EffectiveVexRecords
            .OrderByDescending(v => v.EffectiveAt)
            .FirstOrDefault();

        if (latestVex is not null)
        {
            vexStatus = new TriageVexStatusDto
            {
                Status = latestVex.Status.ToString(),
                Justification = latestVex.Justification,
                ImpactStatement = latestVex.ImpactStatement,
                IssuedBy = latestVex.IssuedBy,
                IssuedAt = latestVex.IssuedAt,
                VexDocumentRef = latestVex.VexDocumentRef
            };
        }

        TriageReachabilityDto? reachability = null;
        var latestReach = finding.ReachabilityResults
            .OrderByDescending(r => r.AnalyzedAt)
            .FirstOrDefault();

        if (latestReach is not null)
        {
            reachability = new TriageReachabilityDto
            {
                Status = latestReach.Reachability.ToString(),
                Confidence = latestReach.Confidence,
                Source = latestReach.Source,
                AnalyzedAt = latestReach.AnalyzedAt
            };
        }

        TriageRiskScoreDto? riskScore = null;
        var latestRisk = finding.RiskResults
            .OrderByDescending(r => r.ComputedAt)
            .FirstOrDefault();

        if (latestRisk is not null)
        {
            riskScore = new TriageRiskScoreDto
            {
                Score = latestRisk.RiskScore,
                CriticalCount = latestRisk.CriticalCount,
                HighCount = latestRisk.HighCount,
                MediumCount = latestRisk.MediumCount,
                LowCount = latestRisk.LowCount,
                EpssScore = latestRisk.EpssScore,
                EpssPercentile = latestRisk.EpssPercentile
            };
        }

        var evidence = finding.EvidenceArtifacts
            .Select(e => new TriageEvidenceDto
            {
                Type = e.Type.ToString(),
                Uri = e.Uri,
                Digest = e.Digest,
                CreatedAt = e.CreatedAt
            })
            .ToList();

        // Compute counterfactuals for non-Ship verdicts
        IReadOnlyList<string>? wouldPassIf = null;
        if (verdict != "Ship")
        {
            wouldPassIf = ComputeWouldPassIf(finding, lane);
        }

        return new FindingTriageStatusDto
        {
            FindingId = finding.Id.ToString(),
            Lane = lane,
            Verdict = verdict,
            Reason = GetReason(finding),
            VexStatus = vexStatus,
            Reachability = reachability,
            RiskScore = riskScore,
            WouldPassIf = wouldPassIf,
            Evidence = evidence.Count > 0 ? evidence : null,
            ComputedAt = _timeProvider.GetUtcNow(),
            ProofBundleUri = $"/v1/triage/findings/{finding.Id}/proof-bundle"
        };
    }

    private static string GetCurrentLane(TriageFinding finding)
    {
        var latestSnapshot = finding.Snapshots
            .OrderByDescending(s => s.CreatedAt)
            .FirstOrDefault();

        return latestSnapshot?.Lane.ToString() ?? "Active";
    }

    private static string GetCurrentVerdict(TriageFinding finding)
    {
        var latestSnapshot = finding.Snapshots
            .OrderByDescending(s => s.CreatedAt)
            .FirstOrDefault();

        return latestSnapshot?.Verdict.ToString() ?? "Block";
    }

    private static string? GetReason(TriageFinding finding)
    {
        var latestDecision = finding.Decisions
            .OrderByDescending(d => d.DecidedAt)
            .FirstOrDefault();

        return latestDecision?.Reason;
    }

    private static string ComputeVerdict(string lane, string? decisionKind)
    {
        return lane switch
        {
            "MutedReach" => "Ship",
            "MutedVex" => "Ship",
            "Compensated" => "Ship",
            "Blocked" => "Block",
            "NeedsException" => decisionKind == "Exception" ? "Exception" : "Block",
            _ => "Block"
        };
    }

    private IReadOnlyList<string> ComputeWouldPassIf(TriageFinding finding, string currentLane)
    {
        var suggestions = new List<string>();

        // Check VEX path
        var latestVex = finding.EffectiveVexRecords
            .OrderByDescending(v => v.EffectiveAt)
            .FirstOrDefault();

        if (latestVex is null || latestVex.Status != TriageVexStatus.NotAffected)
        {
            suggestions.Add("VEX status changed to 'not_affected'");
        }

        // Check reachability path
        var latestReach = finding.ReachabilityResults
            .OrderByDescending(r => r.AnalyzedAt)
            .FirstOrDefault();

        if (latestReach is null || latestReach.Reachability != TriageReachability.No)
        {
            suggestions.Add("Reachability analysis shows code is not reachable");
        }

        // Check exception path
        if (!string.Equals(currentLane, "Compensated", StringComparison.OrdinalIgnoreCase))
        {
            suggestions.Add("Security exception is granted");
        }

        // Check version upgrade path
        if (!string.IsNullOrWhiteSpace(finding.CveId))
        {
            suggestions.Add($"Component upgraded to version without {finding.CveId}");
        }

        return suggestions;
    }
}