using System.Collections.Generic;
using System.Security.Cryptography;
using System.Text;
using StellaOps.Zastava.Core.Contracts;
using StellaOps.Zastava.Observer.Configuration;
using StellaOps.Zastava.Observer.ContainerRuntime;
using StellaOps.Zastava.Observer.ContainerRuntime.Cri;
using StellaOps.Zastava.Observer.Runtime;

namespace StellaOps.Zastava.Observer.Worker;

internal static class RuntimeEventFactory
{
    public static RuntimeEventEnvelope Create(
        ContainerLifecycleEvent lifecycleEvent,
        ContainerRuntimeEndpointOptions endpoint,
        CriRuntimeIdentity identity,
        string tenant,
        string nodeName,
        RuntimeProcessCapture? capture = null,
        RuntimePosture? posture = null,
        IReadOnlyList<RuntimeEvidence>? additionalEvidence = null)
    {
        ArgumentNullException.ThrowIfNull(lifecycleEvent);
        ArgumentNullException.ThrowIfNull(endpoint);
        ArgumentNullException.ThrowIfNull(identity);
        ArgumentNullException.ThrowIfNull(tenant);
        ArgumentNullException.ThrowIfNull(nodeName);

        var snapshot = lifecycleEvent.Snapshot;
        var workloadLabels = snapshot.Labels ?? new Dictionary<string, string>(StringComparer.Ordinal);
        var annotations = snapshot.Annotations is null
            ? new Dictionary<string, string>(StringComparer.Ordinal)
            : new Dictionary<string, string>(snapshot.Annotations, StringComparer.Ordinal);

        var platform = ResolvePlatform(workloadLabels, endpoint);
        var runtimeEvent = new RuntimeEvent
        {
            EventId = ComputeEventId(nodeName, lifecycleEvent),
            When = lifecycleEvent.Timestamp,
            Kind = lifecycleEvent.Kind == ContainerLifecycleEventKind.Start
                ? RuntimeEventKind.ContainerStart
                : RuntimeEventKind.ContainerStop,
            Tenant = tenant,
            Node = nodeName,
            Runtime = new RuntimeEngine
            {
                Engine = endpoint.Engine.ToEngineString(),
                Version = identity.RuntimeVersion
            },
            Workload = new RuntimeWorkload
            {
                Platform = platform,
                Namespace = TryGet(workloadLabels, CriLabelKeys.PodNamespace),
                Pod = TryGet(workloadLabels, CriLabelKeys.PodName),
                Container = TryGet(workloadLabels, CriLabelKeys.ContainerName) ?? snapshot.Name,
                ContainerId = $"{endpoint.Engine.ToEngineString()}://{snapshot.Id}",
                ImageRef = ResolveImageRef(snapshot),
                Owner = null
            },
            Process = capture?.Process,
            LoadedLibraries = capture?.Libraries ?? Array.Empty<RuntimeLoadedLibrary>(),
            Posture = posture,
            Evidence = MergeEvidence(capture?.Evidence, additionalEvidence),
            Annotations = annotations.Count == 0 ? null : new SortedDictionary<string, string>(annotations, StringComparer.Ordinal)
        };

        return RuntimeEventEnvelope.Create(runtimeEvent, ZastavaContractVersions.RuntimeEvent);
    }

    private static string ResolvePlatform(IReadOnlyDictionary<string, string> labels, ContainerRuntimeEndpointOptions endpoint)
    {
        if (labels.ContainsKey(CriLabelKeys.PodName))
        {
            return "kubernetes";
        }

        return endpoint.Engine.ToEngineString();
    }

    private static IReadOnlyList<RuntimeEvidence> MergeEvidence(
        IReadOnlyList<RuntimeEvidence>? primary,
        IReadOnlyList<RuntimeEvidence>? secondary)
    {
        if ((primary is null || primary.Count == 0) && (secondary is null || secondary.Count == 0))
        {
            return Array.Empty<RuntimeEvidence>();
        }

        if (secondary is null || secondary.Count == 0)
        {
            return primary ?? Array.Empty<RuntimeEvidence>();
        }

        if (primary is null || primary.Count == 0)
        {
            return secondary;
        }

        var merged = new List<RuntimeEvidence>(primary.Count + secondary.Count);
        merged.AddRange(primary);
        merged.AddRange(secondary);
        return merged;
    }

    private static string? ResolveImageRef(CriContainerInfo snapshot)
    {
        if (!string.IsNullOrWhiteSpace(snapshot.ImageRef))
        {
            return snapshot.ImageRef;
        }

        return snapshot.Image;
    }

    private static string? TryGet(IReadOnlyDictionary<string, string> dictionary, string key)
    {
        if (dictionary.TryGetValue(key, out var value) && !string.IsNullOrWhiteSpace(value))
        {
            return value;
        }

        return null;
    }

    private static string ComputeEventId(string nodeName, ContainerLifecycleEvent lifecycleEvent)
    {
        var builder = new StringBuilder()
            .Append(nodeName)
            .Append('|')
            .Append(lifecycleEvent.Snapshot.Id)
            .Append('|')
            .Append(lifecycleEvent.Timestamp.ToUniversalTime().Ticks)
            .Append('|')
            .Append((int)lifecycleEvent.Kind);

        var bytes = Encoding.UTF8.GetBytes(builder.ToString());
        Span<byte> hash = stackalloc byte[16];
        if (!MD5.TryHashData(bytes, hash, out _))
        {
            using var md5 = MD5.Create();
            hash = md5.ComputeHash(bytes).AsSpan(0, 16);
        }

        var guid = new Guid(hash);
        return guid.ToString("N");
    }
}