using System.Collections.Immutable;
using Akka.Actor;
using Akka.Cluster;
using Akka.Cluster.Tools.Client;
using Akka.Cluster.Tools.Singleton;
using Akka.Configuration;
using Microsoft.Extensions.Options;
using ScadaLink.ClusterInfrastructure;
using ScadaLink.Communication;
using ScadaLink.Communication.Actors;
using ScadaLink.Host.Actors;
using ScadaLink.SiteRuntime;
using ScadaLink.SiteRuntime.Actors;
using ScadaLink.SiteRuntime.Messages;
using ScadaLink.SiteRuntime.Persistence;
using ScadaLink.SiteRuntime.Scripts;
using ScadaLink.SiteRuntime.Streaming;
using ScadaLink.StoreAndForward;

namespace ScadaLink.Host.Actors;

/// <summary>
/// Hosted service that manages the Akka.NET actor system lifecycle.
/// Creates the actor system on start, registers actors, and triggers
/// CoordinatedShutdown on stop.
///
/// WP-3: Transport heartbeat is explicitly configured in HOCON from CommunicationOptions.
/// </summary>
public class AkkaHostedService : IHostedService
{
    private readonly IServiceProvider _serviceProvider;
    private readonly NodeOptions _nodeOptions;
    private readonly ClusterOptions _clusterOptions;
    private readonly CommunicationOptions _communicationOptions;
    private readonly ILogger<AkkaHostedService> _logger;
    private ActorSystem? _actorSystem;

    public AkkaHostedService(
        IServiceProvider serviceProvider,
        IOptions<NodeOptions> nodeOptions,
        IOptions<ClusterOptions> clusterOptions,
        IOptions<CommunicationOptions> communicationOptions,
        ILogger<AkkaHostedService> logger)
    {
        _serviceProvider = serviceProvider;
        _nodeOptions = nodeOptions.Value;
        _clusterOptions = clusterOptions.Value;
        _communicationOptions = communicationOptions.Value;
        _logger = logger;
    }

    /// <summary>
    /// Gets the actor system once started. Null before StartAsync completes.
    /// </summary>
    public ActorSystem? ActorSystem => _actorSystem;

    public Task StartAsync(CancellationToken cancellationToken)
    {
        var seedNodesStr = string.Join(",",
            _clusterOptions.SeedNodes.Select(s => $"\"{s}\""));

        // For site nodes, include a site-specific role (e.g., "site-SiteA") alongside the base role
        var roles = BuildRoles();
        var rolesStr = string.Join(",", roles.Select(r => $"\"{r}\""));

        // WP-3: Transport heartbeat explicitly configured from CommunicationOptions (not framework defaults)
        var transportHeartbeatSec = _communicationOptions.TransportHeartbeatInterval.TotalSeconds;
        var transportFailureSec = _communicationOptions.TransportFailureThreshold.TotalSeconds;

        var hocon = $@"
akka {{
    actor {{
        provider = cluster
    }}
    remote {{
        dot-netty.tcp {{
            hostname = ""{_nodeOptions.NodeHostname}""
            port = {_nodeOptions.RemotingPort}
        }}
        transport-failure-detector {{
            heartbeat-interval = {transportHeartbeatSec:F0}s
            acceptable-heartbeat-pause = {transportFailureSec:F0}s
        }}
    }}
    cluster {{
        seed-nodes = [{seedNodesStr}]
        roles = [{rolesStr}]
        min-nr-of-members = {_clusterOptions.MinNrOfMembers}
        split-brain-resolver {{
            active-strategy = {_clusterOptions.SplitBrainResolverStrategy}
            stable-after = {_clusterOptions.StableAfter.TotalSeconds:F0}s
            keep-oldest {{
                down-if-alone = on
            }}
        }}
        failure-detector {{
            heartbeat-interval = {_clusterOptions.HeartbeatInterval.TotalSeconds:F0}s
            acceptable-heartbeat-pause = {_clusterOptions.FailureDetectionThreshold.TotalSeconds:F0}s
        }}
        run-coordinated-shutdown-when-down = on
    }}
    coordinated-shutdown {{
        run-by-clr-shutdown-hook = on
    }}
}}";

        var config = ConfigurationFactory.ParseString(hocon);
        _actorSystem = ActorSystem.Create("scadalink", config);

        _logger.LogInformation(
            "Akka.NET actor system 'scadalink' started. Role={Role}, Roles={Roles}, Hostname={Hostname}, Port={Port}, " +
            "TransportHeartbeat={TransportHeartbeat}s, TransportFailure={TransportFailure}s",
            _nodeOptions.Role,
            string.Join(", ", roles),
            _nodeOptions.NodeHostname,
            _nodeOptions.RemotingPort,
            transportHeartbeatSec,
            transportFailureSec);

        // Register the dead letter monitor actor
        var loggerFactory = _serviceProvider.GetRequiredService<ILoggerFactory>();
        var dlmLogger = loggerFactory.CreateLogger<DeadLetterMonitorActor>();
        var dlmHealthCollector = _serviceProvider.GetService<ScadaLink.HealthMonitoring.ISiteHealthCollector>();
        _actorSystem.ActorOf(
            Props.Create(() => new DeadLetterMonitorActor(dlmLogger, dlmHealthCollector)),
            "dead-letter-monitor");

        // Register role-specific actors
        if (_nodeOptions.Role.Equals("Central", StringComparison.OrdinalIgnoreCase))
        {
            RegisterCentralActors();
        }
        else if (_nodeOptions.Role.Equals("Site", StringComparison.OrdinalIgnoreCase))
        {
            RegisterSiteActors();
        }

        return Task.CompletedTask;
    }

    public async Task StopAsync(CancellationToken cancellationToken)
    {
        if (_actorSystem != null)
        {
            _logger.LogInformation("Shutting down Akka.NET actor system via CoordinatedShutdown...");
            var shutdown = Akka.Actor.CoordinatedShutdown.Get(_actorSystem);
            await shutdown.Run(Akka.Actor.CoordinatedShutdown.ClrExitReason.Instance);
            _logger.LogInformation("Akka.NET actor system shutdown complete.");
        }
    }

    /// <summary>
    /// Builds the list of cluster roles for this node. Site nodes get both "Site"
    /// and a site-specific role (e.g., "site-SiteA") to scope singleton placement.
    /// </summary>
    private List<string> BuildRoles()
    {
        var roles = new List<string> { _nodeOptions.Role };

        if (_nodeOptions.Role.Equals("Site", StringComparison.OrdinalIgnoreCase)
            && !string.IsNullOrEmpty(_nodeOptions.SiteId))
        {
            roles.Add($"site-{_nodeOptions.SiteId}");
        }

        return roles;
    }

    /// <summary>
    /// Registers central-side actors including the CentralCommunicationActor.
    /// WP-4: Central communication actor routes all 8 message patterns to sites.
    /// </summary>
    private void RegisterCentralActors()
    {
        var siteClientFactory = new DefaultSiteClientFactory();
        var centralCommActor = _actorSystem!.ActorOf(
            Props.Create(() => new CentralCommunicationActor(_serviceProvider, siteClientFactory)),
            "central-communication");

        // Register CentralCommunicationActor with ClusterClientReceptionist so site ClusterClients can reach it
        ClusterClientReceptionist.Get(_actorSystem).RegisterService(centralCommActor);
        _logger.LogInformation("CentralCommunicationActor registered with ClusterClientReceptionist");

        // Wire up the CommunicationService with the actor reference
        var commService = _serviceProvider.GetService<CommunicationService>();
        commService?.SetCommunicationActor(centralCommActor);

        // Management Service — accessible via ClusterClient
        var mgmtLogger = _serviceProvider.GetRequiredService<ILoggerFactory>()
            .CreateLogger<ScadaLink.ManagementService.ManagementActor>();
        var mgmtActor = _actorSystem!.ActorOf(
            Props.Create(() => new ScadaLink.ManagementService.ManagementActor(_serviceProvider, mgmtLogger)),
            "management");
        ClusterClientReceptionist.Get(_actorSystem).RegisterService(mgmtActor);
        _logger.LogInformation("ManagementActor registered with ClusterClientReceptionist");

        _logger.LogInformation("Central actors registered. CentralCommunicationActor created.");
    }

    /// <summary>
    /// Registers site-specific actors including the Deployment Manager cluster singleton
    /// and the SiteCommunicationActor.
    /// The singleton is scoped to the site-specific cluster role so it runs on exactly
    /// one node within this site's cluster.
    /// </summary>
    private void RegisterSiteActors()
    {
        var siteRole = $"site-{_nodeOptions.SiteId}";
        var storage = _serviceProvider.GetRequiredService<SiteStorageService>();
        var compilationService = _serviceProvider.GetRequiredService<ScriptCompilationService>();
        var sharedScriptLibrary = _serviceProvider.GetRequiredService<SharedScriptLibrary>();
        var streamManager = _serviceProvider.GetService<SiteStreamManager>();
        var siteRuntimeOptionsValue = _serviceProvider.GetService<IOptions<SiteRuntimeOptions>>()?.Value
            ?? new SiteRuntimeOptions();
        var dmLogger = _serviceProvider.GetRequiredService<ILoggerFactory>()
            .CreateLogger<DeploymentManagerActor>();

        // WP-34: Create DCL Manager Actor for tag subscriptions
        var dclFactory = _serviceProvider.GetService<ScadaLink.DataConnectionLayer.IDataConnectionFactory>();
        var dclOptions = _serviceProvider.GetService<IOptions<ScadaLink.DataConnectionLayer.DataConnectionOptions>>()?.Value
            ?? new ScadaLink.DataConnectionLayer.DataConnectionOptions();
        IActorRef? dclManager = null;
        if (dclFactory != null)
        {
            var healthCollector = _serviceProvider.GetRequiredService<ScadaLink.HealthMonitoring.ISiteHealthCollector>();
            dclManager = _actorSystem!.ActorOf(
                Props.Create(() => new ScadaLink.DataConnectionLayer.Actors.DataConnectionManagerActor(
                    dclFactory, dclOptions, healthCollector)),
                "dcl-manager");
            _logger.LogInformation("Data Connection Layer manager actor created");
        }

        // Resolve the health collector for the Deployment Manager
        var siteHealthCollector = _serviceProvider.GetService<ScadaLink.HealthMonitoring.ISiteHealthCollector>();

        // Create SiteReplicationActor on every node (not a singleton)
        var sfStorage = _serviceProvider.GetRequiredService<StoreAndForwardStorage>();
        var replicationService = _serviceProvider.GetRequiredService<ReplicationService>();
        var replicationLogger = _serviceProvider.GetRequiredService<ILoggerFactory>()
            .CreateLogger<SiteReplicationActor>();

        var replicationActor = _actorSystem!.ActorOf(
            Props.Create(() => new SiteReplicationActor(
                storage, sfStorage, replicationService, siteRole, replicationLogger)),
            "site-replication");

        // Wire S&F replication handler to forward operations via the replication actor
        replicationService.SetReplicationHandler(op =>
        {
            replicationActor.Tell(new ReplicateStoreAndForward(op));
            return Task.CompletedTask;
        });

        _logger.LogInformation("SiteReplicationActor created and S&F replication handler wired");

        // Create the Deployment Manager as a cluster singleton
        var singletonProps = ClusterSingletonManager.Props(
            singletonProps: Props.Create(() => new DeploymentManagerActor(
                storage,
                compilationService,
                sharedScriptLibrary,
                streamManager,
                siteRuntimeOptionsValue,
                dmLogger,
                dclManager,
                replicationActor,
                siteHealthCollector,
                _serviceProvider)),
            terminationMessage: PoisonPill.Instance,
            settings: ClusterSingletonManagerSettings.Create(_actorSystem!)
                .WithRole(siteRole)
                .WithSingletonName("deployment-manager"));

        _actorSystem!.ActorOf(singletonProps, "deployment-manager-singleton");

        // Create a proxy for other actors to communicate with the singleton
        var proxyProps = ClusterSingletonProxy.Props(
            singletonManagerPath: "/user/deployment-manager-singleton",
            settings: ClusterSingletonProxySettings.Create(_actorSystem)
                .WithRole(siteRole)
                .WithSingletonName("deployment-manager"));

        var dmProxy = _actorSystem.ActorOf(proxyProps, "deployment-manager-proxy");

        // WP-4: Create SiteCommunicationActor for receiving messages from central
        var siteCommActor = _actorSystem.ActorOf(
            Props.Create(() => new SiteCommunicationActor(
                _nodeOptions.SiteId!,
                _communicationOptions,
                dmProxy)),
            "site-communication");

        // Register local handlers with SiteCommunicationActor
        siteCommActor.Tell(new RegisterLocalHandler(LocalHandlerType.Artifacts, dmProxy));

        // Register SiteCommunicationActor with ClusterClientReceptionist so central ClusterClients can reach it
        ClusterClientReceptionist.Get(_actorSystem).RegisterService(siteCommActor);

        _logger.LogInformation(
            "Site actors registered. DeploymentManager singleton scoped to role={SiteRole}, SiteCommunicationActor created.",
            siteRole);

        // Create ClusterClient to central if contact points are configured
        if (_communicationOptions.CentralContactPoints.Count > 0)
        {
            var contacts = _communicationOptions.CentralContactPoints
                .Select(cp => ActorPath.Parse($"{cp}/system/receptionist"))
                .ToImmutableHashSet();
            var clientSettings = ClusterClientSettings.Create(_actorSystem)
                .WithInitialContacts(contacts);
            var centralClient = _actorSystem.ActorOf(
                ClusterClient.Props(clientSettings), "central-cluster-client");

            var siteCommSelection = _actorSystem.ActorSelection("/user/site-communication");
            siteCommSelection.Tell(new RegisterCentralClient(centralClient));

            _logger.LogInformation(
                "Created ClusterClient to central with {Count} contact point(s) for site {SiteId}",
                contacts.Count, _nodeOptions.SiteId);
        }
    }
}