using Microsoft.Extensions.Caching.Distributed;
using Microsoft.Extensions.Logging;
using StellaOps.SbomService.Lineage.Domain;
using StellaOps.SbomService.Lineage.Repositories;
using System.Text.Json;

namespace StellaOps.SbomService.Lineage.Services;

/// <summary>
/// Implementation of lineage graph service with caching and enrichment.
/// </summary>
public sealed class LineageGraphService : ILineageGraphService
{
    private readonly ISbomLineageEdgeRepository _edgeRepository;
    private readonly IVexDeltaRepository _deltaRepository;
    private readonly ISbomVerdictLinkRepository _verdictRepository;
    private readonly IDistributedCache? _cache;
    private readonly ILogger<LineageGraphService> _logger;

    private static readonly TimeSpan CacheExpiry = TimeSpan.FromMinutes(10);
    private static readonly JsonSerializerOptions SerializerOptions = new(JsonSerializerDefaults.Web);

    public LineageGraphService(
        ISbomLineageEdgeRepository edgeRepository,
        IVexDeltaRepository deltaRepository,
        ISbomVerdictLinkRepository verdictRepository,
        ILogger<LineageGraphService> logger,
        IDistributedCache? cache = null)
    {
        _edgeRepository = edgeRepository;
        _deltaRepository = deltaRepository;
        _verdictRepository = verdictRepository;
        _cache = cache;
        _logger = logger;
    }

    public async ValueTask<LineageGraphResponse> GetLineageAsync(
        string artifactDigest,
        Guid tenantId,
        LineageQueryOptions options,
        CancellationToken ct = default)
    {
        // Try cache first
        var cacheKey = $"lineage:{tenantId}:{artifactDigest}:{options.MaxDepth}";
        if (_cache != null)
        {
            var cached = await _cache.GetStringAsync(cacheKey, ct);
            if (cached != null)
            {
                var response = JsonSerializer.Deserialize<LineageGraphResponse>(cached, SerializerOptions);
                if (response != null)
                {
                    _logger.LogDebug("Cache hit for lineage {Digest}", artifactDigest);
                    return response;
                }
            }
        }

        // Build graph
        var graph = await _edgeRepository.GetGraphAsync(artifactDigest, tenantId, options.MaxDepth, ct);

        // Enrich with verdict data if requested
        var enrichment = new Dictionary<string, NodeEnrichment>();
        if (options.IncludeVerdicts)
        {
            foreach (var node in graph.Nodes.Where(n => n.SbomVersionId.HasValue))
            {
                var verdicts = await _verdictRepository.GetBySbomVersionAsync(
                    node.SbomVersionId!.Value,
                    tenantId,
                    ct);

                var affected = verdicts.Where(v => v.VerdictStatus == VexStatus.Affected).ToList();
                var high = affected.Where(v => v.ConfidenceScore >= 0.8m).ToList();

                enrichment[node.ArtifactDigest] = new NodeEnrichment(
                    VulnerabilityCount: verdicts.Count,
                    HighSeverityCount: high.Count,
                    AffectedCount: affected.Count,
                    TopCves: affected
                        .OrderByDescending(v => v.ConfidenceScore)
                        .Take(5)
                        .Select(v => v.Cve)
                        .ToList()
                );
            }
        }

        var result = new LineageGraphResponse(graph, enrichment);

        // Cache the result
        if (_cache != null)
        {
            var json = JsonSerializer.Serialize(result, SerializerOptions);
            await _cache.SetStringAsync(cacheKey, json, new DistributedCacheEntryOptions
            {
                AbsoluteExpirationRelativeToNow = CacheExpiry
            }, ct);
        }

        return result;
    }

    public async ValueTask<LineageDiffResponse> GetDiffAsync(
        string fromDigest,
        string toDigest,
        Guid tenantId,
        CancellationToken ct = default)
    {
        // Try cache first
        var cacheKey = $"lineage:compare:{tenantId}:{fromDigest}:{toDigest}";
        if (_cache != null)
        {
            var cached = await _cache.GetStringAsync(cacheKey, ct);
            if (cached != null)
            {
                var response = JsonSerializer.Deserialize<LineageDiffResponse>(cached, SerializerOptions);
                if (response != null)
                {
                    _logger.LogDebug("Cache hit for diff {From} -> {To}", fromDigest, toDigest);
                    return response;
                }
            }
        }

        // Get VEX deltas
        var deltas = await _deltaRepository.GetDeltasAsync(fromDigest, toDigest, tenantId, ct);

        var statusChanges = deltas.Where(d => d.FromStatus != d.ToStatus).ToList();
        var newVulns = deltas.Count(d => d.FromStatus == VexStatus.Unknown && d.ToStatus == VexStatus.Affected);
        var resolved = deltas.Count(d => d.FromStatus == VexStatus.Affected && d.ToStatus == VexStatus.Fixed);
        var affectedToNot = deltas.Count(d => d.FromStatus == VexStatus.Affected && d.ToStatus == VexStatus.NotAffected);
        var notToAffected = deltas.Count(d => d.FromStatus == VexStatus.NotAffected && d.ToStatus == VexStatus.Affected);

        var vexDiff = new VexDiff(
            StatusChanges: statusChanges,
            NewVulnerabilities: newVulns,
            ResolvedVulnerabilities: resolved,
            AffectedToNotAffected: affectedToNot,
            NotAffectedToAffected: notToAffected
        );

        // TODO: Implement SBOM diff by comparing component lists
        var sbomDiff = new SbomDiff([], [], []);

        // TODO: Implement reachability diff if requested
        ReachabilityDiff? reachDiff = null;

        var result = new LineageDiffResponse(
            FromDigest: fromDigest,
            ToDigest: toDigest,
            SbomDifferences: sbomDiff,
            VexDifferences: vexDiff,
            ReachabilityDifferences: reachDiff
        );

        // Cache the result
        if (_cache != null)
        {
            var json = JsonSerializer.Serialize(result, SerializerOptions);
            await _cache.SetStringAsync(cacheKey, json, new DistributedCacheEntryOptions
            {
                AbsoluteExpirationRelativeToNow = CacheExpiry
            }, ct);
        }

        return result;
    }

    public async ValueTask<ExportResult> ExportEvidencePackAsync(
        ExportRequest request,
        Guid tenantId,
        CancellationToken ct = default)
    {
        _logger.LogInformation("Exporting evidence pack for {Digest}", request.ArtifactDigest);

        // TODO: Implement evidence pack generation
        // 1. Get lineage graph if requested
        // 2. Get verdicts if requested
        // 3. Get reachability data if requested
        // 4. Bundle into archive (tar.gz or zip)
        // 5. Sign with Sigstore if requested
        // 6. Upload to storage and return download URL

        // Placeholder implementation
        var downloadUrl = $"https://evidence.stellaops.example/exports/{Guid.NewGuid()}.tar.gz";
        var expiresAt = DateTimeOffset.UtcNow.AddHours(24);

        return new ExportResult(
            DownloadUrl: downloadUrl,
            ExpiresAt: expiresAt,
            SizeBytes: 0,
            SignatureDigest: request.SignWithSigstore ? "sha256:placeholder" : null
        );
    }
}