using StellaOps.Excititor.Core;
using StellaOps.Excititor.Core.Storage;
using StellaOps.Excititor.WebService.Contracts;
using System;
using System.Collections.Generic;
using System.Collections.Immutable;
using System.Globalization;
using System.Linq;
using System.Threading;
using System.Threading.Tasks;

namespace StellaOps.Excititor.WebService.Services;

internal interface IVexEvidenceChunkService
{
    Task<VexEvidenceChunkResult> QueryAsync(VexEvidenceChunkRequest request, CancellationToken cancellationToken);
}

internal sealed record VexEvidenceChunkRequest(
    string Tenant,
    string VulnerabilityId,
    string ProductKey,
    ImmutableHashSet<string> ProviderIds,
    ImmutableHashSet<VexClaimStatus> Statuses,
    DateTimeOffset? Since,
    int Limit);

internal sealed record VexEvidenceChunkResult(
    IReadOnlyList<VexEvidenceChunkResponse> Chunks,
    bool Truncated,
    int TotalCount,
    DateTimeOffset GeneratedAtUtc);

internal sealed class VexEvidenceChunkService : IVexEvidenceChunkService
{
    private readonly IVexClaimStore _claimStore;
    private readonly TimeProvider _timeProvider;

    public VexEvidenceChunkService(IVexClaimStore claimStore, TimeProvider timeProvider)
    {
        _claimStore = claimStore ?? throw new ArgumentNullException(nameof(claimStore));
        _timeProvider = timeProvider ?? throw new ArgumentNullException(nameof(timeProvider));
    }

    public async Task<VexEvidenceChunkResult> QueryAsync(VexEvidenceChunkRequest request, CancellationToken cancellationToken)
    {
        ArgumentNullException.ThrowIfNull(request);

        var claims = await _claimStore
            .FindAsync(request.VulnerabilityId, request.ProductKey, request.Since, cancellationToken)
            .ConfigureAwait(false);

        var filtered = claims
            .Where(claim => MatchesProvider(claim, request.ProviderIds))
            .Where(claim => MatchesStatus(claim, request.Statuses))
            .OrderByDescending(claim => claim.LastSeen)
            .ToList();

        var total = filtered.Count;
        if (filtered.Count > request.Limit)
        {
            filtered = filtered.Take(request.Limit).ToList();
        }

        var chunks = filtered
            .Select(MapChunk)
            .ToList();

        return new VexEvidenceChunkResult(
            chunks,
            total > request.Limit,
            total,
            _timeProvider.GetUtcNow());
    }

    private static bool MatchesProvider(VexClaim claim, ImmutableHashSet<string> providers)
        => providers.Count == 0 || providers.Contains(claim.ProviderId, StringComparer.OrdinalIgnoreCase);

    private static bool MatchesStatus(VexClaim claim, ImmutableHashSet<VexClaimStatus> statuses)
        => statuses.Count == 0 || statuses.Contains(claim.Status);

    private static VexEvidenceChunkResponse MapChunk(VexClaim claim)
    {
        var observationId = string.Create(CultureInfo.InvariantCulture, $"{claim.ProviderId}:{claim.Document.Digest}");
        var linksetId = string.Create(CultureInfo.InvariantCulture, $"{claim.VulnerabilityId}:{claim.Product.Key}");

        var scope = new VexEvidenceChunkScope(
            claim.Product.Key,
            claim.Product.Name,
            claim.Product.Version,
            claim.Product.Purl,
            claim.Product.Cpe,
            claim.Product.ComponentIdentifiers);

        var document = new VexEvidenceChunkDocument(
            claim.Document.Digest,
            claim.Document.Format.ToString().ToLowerInvariant(),
            claim.Document.SourceUri.ToString(),
            claim.Document.Revision);

        var signature = claim.Document.Signature is null
            ? null
            : new VexEvidenceChunkSignature(
                claim.Document.Signature.Type,
                claim.Document.Signature.Subject,
                claim.Document.Signature.Issuer,
                claim.Document.Signature.KeyId,
                claim.Document.Signature.VerifiedAt,
                claim.Document.Signature.TransparencyLogReference);

        var scopeScore = claim.Confidence?.Score ?? claim.Signals?.Severity?.Score;

        return new VexEvidenceChunkResponse(
            observationId,
            linksetId,
            claim.VulnerabilityId,
            claim.Product.Key,
            claim.ProviderId,
            claim.Status.ToString(),
            claim.Justification?.ToString(),
            claim.Detail,
            scopeScore,
            claim.FirstSeen,
            claim.LastSeen,
            scope,
            document,
            signature,
            claim.AdditionalMetadata);
    }
}