// SPDX-License-Identifier: BUSL-1.1
// Sprint: SPRINT_4100_0004_0001 - Security State Delta & Verdict
// Task: T6 - Add Delta API endpoints

using StellaOps.Policy.Deltas;
using StellaOps.Policy.Snapshots;

namespace StellaOps.Policy.Gateway.Services;

/// <summary>
/// Adapter that bridges between the KnowledgeSnapshotManifest-based snapshot store
/// and the SnapshotData interface required by the DeltaComputer.
/// </summary>
public sealed class DeltaSnapshotServiceAdapter : StellaOps.Policy.Deltas.ISnapshotService
{
    private readonly ISnapshotStore _snapshotStore;
    private readonly ILogger<DeltaSnapshotServiceAdapter> _logger;

    public DeltaSnapshotServiceAdapter(
        ISnapshotStore snapshotStore,
        ILogger<DeltaSnapshotServiceAdapter> logger)
    {
        _snapshotStore = snapshotStore ?? throw new ArgumentNullException(nameof(snapshotStore));
        _logger = logger ?? throw new ArgumentNullException(nameof(logger));
    }

    /// <summary>
    /// Gets snapshot data by ID, converting from KnowledgeSnapshotManifest.
    /// </summary>
    public async Task<SnapshotData?> GetSnapshotAsync(string snapshotId, CancellationToken ct = default)
    {
        if (string.IsNullOrWhiteSpace(snapshotId))
        {
            return null;
        }

        var manifest = await _snapshotStore.GetAsync(snapshotId, ct).ConfigureAwait(false);
        if (manifest is null)
        {
            _logger.LogDebug("Snapshot {SnapshotId} not found in store", snapshotId);
            return null;
        }

        return ConvertToSnapshotData(manifest);
    }

    private static SnapshotData ConvertToSnapshotData(KnowledgeSnapshotManifest manifest)
    {
        // Get policy version from manifest sources
        var policySource = manifest.Sources.FirstOrDefault(s => s.Type == KnowledgeSourceTypes.Policy);
        var policyVersion = policySource?.Digest;

        // Note: In a full implementation, we would fetch and parse the bundled content
        // from each source to extract packages, reachability, VEX statements, etc.
        // For now, we return the manifest metadata only.
        return new SnapshotData
        {
            SnapshotId = manifest.SnapshotId,
            Packages = [],
            Reachability = [],
            VexStatements = [],
            PolicyViolations = [],
            Unknowns = [],
            PolicyVersion = policyVersion
        };
    }
}