// <copyright file="SbomExportService.cs" company="StellaOps">
// Copyright (c) StellaOps. Licensed under the BUSL-1.1.
// </copyright>


using Microsoft.Extensions.Logging;
using StellaOps.Canonical.Json;
using StellaOps.Scanner.Core.Contracts;
using StellaOps.Scanner.Emit.Composition;
using StellaOps.Scanner.Emit.Spdx;
using StellaOps.Scanner.WebService.Domain;
using StellaOps.Scanner.WebService.Endpoints;
using System.Collections.Immutable;

namespace StellaOps.Scanner.WebService.Services;

/// <summary>
/// Service for exporting SBOMs in multiple formats (SPDX 2.3, SPDX 3.0.1, CycloneDX).
/// Sprint: SPRINT_20260107_004_002 Tasks SG-010, SG-012
/// </summary>
public sealed class SbomExportService : ISbomExportService
{
    private readonly IScanCoordinator _coordinator;
    private readonly ISpdxComposer _spdxComposer;
    private readonly ILayerSbomService _layerSbomService;
    private readonly TimeProvider _timeProvider;
    private readonly ILogger<SbomExportService> _logger;

    public SbomExportService(
        IScanCoordinator coordinator,
        ISpdxComposer spdxComposer,
        ILayerSbomService layerSbomService,
        TimeProvider timeProvider,
        ILogger<SbomExportService> logger)
    {
        _coordinator = coordinator ?? throw new ArgumentNullException(nameof(coordinator));
        _spdxComposer = spdxComposer ?? throw new ArgumentNullException(nameof(spdxComposer));
        _layerSbomService = layerSbomService ?? throw new ArgumentNullException(nameof(layerSbomService));
        _timeProvider = timeProvider ?? throw new ArgumentNullException(nameof(timeProvider));
        _logger = logger ?? throw new ArgumentNullException(nameof(logger));
    }

    /// <inheritdoc />
    public async Task<SbomExportResult?> ExportAsync(
        ScanId scanId,
        SbomExportFormat format,
        Spdx3ProfileType profile,
        CancellationToken cancellationToken = default)
    {
        _logger.LogDebug(
            "Exporting SBOM for scan {ScanId} with format {Format} and profile {Profile}",
            scanId,
            format,
            profile);

        var snapshot = await _coordinator.GetAsync(scanId, cancellationToken).ConfigureAwait(false);
        if (snapshot is null)
        {
            _logger.LogWarning("Scan {ScanId} not found for SBOM export", scanId);
            return null;
        }

        // Get layer fragments for SBOM composition
        var layerFragments = await _layerSbomService.GetLayerFragmentsAsync(scanId, cancellationToken)
            .ConfigureAwait(false);

        if (layerFragments is null || layerFragments.Count == 0)
        {
            _logger.LogWarning("No layer fragments found for scan {ScanId}", scanId);
            return null;
        }

        return format switch
        {
            SbomExportFormat.Spdx3 => await ExportSpdx3Async(snapshot, layerFragments, profile, cancellationToken)
                .ConfigureAwait(false),
            SbomExportFormat.Spdx2 => await ExportSpdx2Async(snapshot, cancellationToken)
                .ConfigureAwait(false),
            SbomExportFormat.CycloneDx => await ExportCycloneDxAsync(snapshot, cancellationToken)
                .ConfigureAwait(false),
            _ => await ExportSpdx2Async(snapshot, cancellationToken).ConfigureAwait(false)
        };
    }

    private Task<SbomExportResult> ExportSpdx3Async(
        ScanSnapshot snapshot,
        IReadOnlyList<SbomLayerFragment> layerFragments,
        Spdx3ProfileType profile,
        CancellationToken cancellationToken)
    {
        _logger.LogDebug("Generating SPDX 3.0.1 SBOM with profile {Profile}", profile);

        // Build composition request from layer fragments
        var request = BuildCompositionRequest(snapshot, layerFragments);
        var options = new SpdxCompositionOptions
        {
            ProfileType = profile,
            IncludeFiles = profile != Spdx3ProfileType.Lite,
            IncludeTagValue = false
        };

        var artifact = _spdxComposer.Compose(request, options, cancellationToken);

        return Task.FromResult(new SbomExportResult(
            artifact.JsonBytes,
            SbomExportFormat.Spdx3,
            profile,
            artifact.JsonSha256,
            0)); // ComponentCount not available on SpdxArtifact
    }

    private async Task<SbomExportResult> ExportSpdx2Async(
        ScanSnapshot snapshot,
        CancellationToken cancellationToken)
    {
        _logger.LogDebug("Generating SPDX 2.3 SBOM");

        // For SPDX 2.3, we use the layer SBOM service's existing functionality
        var sbomBytes = await _layerSbomService.GetComposedSbomAsync(
            snapshot.ScanId,
            "spdx",
            cancellationToken).ConfigureAwait(false);

        if (sbomBytes is null || sbomBytes.Length == 0)
        {
            _logger.LogWarning("No SPDX 2.3 SBOM available for scan {ScanId}", snapshot.ScanId);
            return new SbomExportResult(
                Array.Empty<byte>(),
                SbomExportFormat.Spdx2,
                null,
                string.Empty,
                0);
        }

        var digest = CanonJson.Sha256Hex(sbomBytes);
        var componentCount = EstimateComponentCount(sbomBytes);

        return new SbomExportResult(
            sbomBytes,
            SbomExportFormat.Spdx2,
            null,
            digest,
            componentCount);
    }

    private async Task<SbomExportResult> ExportCycloneDxAsync(
        ScanSnapshot snapshot,
        CancellationToken cancellationToken)
    {
        _logger.LogDebug("Generating CycloneDX 1.7 SBOM");

        var sbomBytes = await _layerSbomService.GetComposedSbomAsync(
            snapshot.ScanId,
            "cdx",
            cancellationToken).ConfigureAwait(false);

        if (sbomBytes is null || sbomBytes.Length == 0)
        {
            _logger.LogWarning("No CycloneDX SBOM available for scan {ScanId}", snapshot.ScanId);
            return new SbomExportResult(
                Array.Empty<byte>(),
                SbomExportFormat.CycloneDx,
                null,
                string.Empty,
                0);
        }

        var digest = CanonJson.Sha256Hex(sbomBytes);
        var componentCount = EstimateComponentCount(sbomBytes);

        return new SbomExportResult(
            sbomBytes,
            SbomExportFormat.CycloneDx,
            null,
            digest,
            componentCount);
    }

    private SbomCompositionRequest BuildCompositionRequest(
        ScanSnapshot snapshot,
        IReadOnlyList<SbomLayerFragment> layerFragments)
    {
        // Convert SbomLayerFragment to LayerComponentFragment for SpdxComposer
        var fragments = layerFragments.Select(f => new LayerComponentFragment
        {
            LayerDigest = f.LayerDigest,
            Components = f.ComponentPurls
                .Select(purl => new ComponentRecord
                {
                    Identity = ComponentIdentity.Create(
                        key: purl,
                        name: ExtractNameFromPurl(purl),
                        version: ExtractVersionFromPurl(purl),
                        purl: purl),
                    LayerDigest = f.LayerDigest
                })
                .ToImmutableArray()
        }).ToImmutableArray();

        var image = new ImageArtifactDescriptor
        {
            ImageDigest = snapshot.Target.Digest ?? string.Empty,
            ImageReference = snapshot.Target.Reference
        };

        return SbomCompositionRequest.Create(
            image,
            fragments,
            _timeProvider.GetUtcNow(),
            generatorName: "StellaOps-Scanner",
            generatorVersion: "1.0");
    }

    private static string ExtractNameFromPurl(string purl)
    {
        // Basic PURL parsing: pkg:type/namespace/name@version
        // Returns the name portion
        try
        {
            var withoutScheme = purl.StartsWith("pkg:", StringComparison.OrdinalIgnoreCase)
                ? purl[4..]
                : purl;
            var atIndex = withoutScheme.IndexOf('@');
            var pathPart = atIndex >= 0 ? withoutScheme[..atIndex] : withoutScheme;
            var slashIndex = pathPart.LastIndexOf('/');
            return slashIndex >= 0 ? pathPart[(slashIndex + 1)..] : pathPart;
        }
        catch
        {
            return purl;
        }
    }

    private static string? ExtractVersionFromPurl(string purl)
    {
        // Basic PURL parsing: pkg:type/namespace/name@version
        // Returns the version portion
        try
        {
            var atIndex = purl.IndexOf('@');
            if (atIndex < 0) return null;
            var versionPart = purl[(atIndex + 1)..];
            var queryIndex = versionPart.IndexOf('?');
            return queryIndex >= 0 ? versionPart[..queryIndex] : versionPart;
        }
        catch
        {
            return null;
        }
    }

    private static int EstimateComponentCount(byte[] sbomBytes)
    {
        // Quick heuristic: count "purl" occurrences as proxy for component count
        var content = System.Text.Encoding.UTF8.GetString(sbomBytes);
        var count = 0;
        var index = 0;
        while ((index = content.IndexOf("\"purl\"", index, StringComparison.Ordinal)) != -1)
        {
            count++;
            index += 6;
        }
        return Math.Max(count, 1);
    }
}