using System.Diagnostics;

namespace Dada.Supervisor;

internal sealed class SupervisorRuntime : IAsyncDisposable
{
    private readonly ICredentialStore credentials;
    private ManagedComponentSupervisor? api;
    private ManagedComponentSupervisor? worker;
    private StructuredJsonlLogger? logger;

    internal SupervisorRuntime(ICredentialStore credentials)
    {
        this.credentials = credentials;
    }

    internal event Action<SupervisorState>? StateChanged;

    internal async Task<SupervisorState> StartAsync(CancellationToken cancellationToken = default)
    {
        if (LoopbackPortGuard.Check() == SupervisorState.PortInUse) return SupervisorState.PortInUse;
        var configuration = new InstanceConfigurationStore().Load();
        if (configuration.LocalDataRoot is null || configuration.AssetRoot is null ||
            !Directory.Exists(configuration.LocalDataRoot) || !Directory.Exists(configuration.AssetRoot))
        {
            return SupervisorState.StartupFailed;
        }
        try
        {
            logger = new StructuredJsonlLogger(Path.Combine(configuration.LocalDataRoot, "logs", "supervisor"), "supervisor");
            logger.Write(new StructuredLogEvent("starting", ErrorCategory: "none"));
        }
        catch (LogWriteException)
        {
            return SupervisorState.StorageUnavailable;
        }
        if (CredentialCatalog.RequiredFor(ChildRole.Api).Concat(CredentialCatalog.RequiredFor(ChildRole.Worker)).Any(target => !credentials.IsConfigured(target)))
        {
            return SupervisorState.StartupFailed;
        }

        var node = Path.Combine(AppContext.BaseDirectory, "runtime", "node.exe");
        var apiEntry = Path.Combine(AppContext.BaseDirectory, "server", "api.mjs");
        var workerEntry = Path.Combine(AppContext.BaseDirectory, "server", "worker.mjs");
        if (!File.Exists(node) || !File.Exists(apiEntry) || !File.Exists(workerEntry)) return SupervisorState.StartupFailed;

        api = CreateComponent(node, apiEntry, ChildRole.Api, SupervisorState.ApiDegraded);
        await api.StartAsync(cancellationToken);

        worker = CreateComponent(node, workerEntry, ChildRole.Worker, SupervisorState.WorkerDegraded);
        await worker.StartAsync(cancellationToken);
        return TryLog(new StructuredLogEvent("ready", ErrorCategory: "none")) ? SupervisorState.Ready : SupervisorState.StorageUnavailable;
    }

    private ManagedComponentSupervisor CreateComponent(string node, string entry, ChildRole role, SupervisorState degradedState)
    {
        var component = new ManagedComponentSupervisor(async cancellationToken =>
        {
            var startInfo = new ProcessStartInfo(node);
            startInfo.WorkingDirectory = AppContext.BaseDirectory;
            startInfo.Environment["DADA_SQLITE_NATIVE_BINDING"] = Path.Combine(AppContext.BaseDirectory, "server", "native", "better_sqlite3.node");
            startInfo.Environment["DADA_SUPPORT_GATE_ROOT"] = Path.Combine(AppContext.BaseDirectory, "web", "support-gate");
            startInfo.ArgumentList.Add(entry);
            var child = await ManagedChildProcess.StartAsync(startInfo, role, credentials, cancellationToken);
            child.StatusReceived += status =>
            {
                if (status == "storage_unavailable")
                {
                    TryLog(new StructuredLogEvent("unavailable", ErrorCategory: "log_write_failed"));
                    StateChanged?.Invoke(SupervisorState.StorageUnavailable);
                }
            };
            return child;
        }, degradedState);
        component.StateChanged += state =>
        {
            if (TryLog(new StructuredLogEvent("degraded", ErrorCategory: "service_unavailable"))) StateChanged?.Invoke(state);
        };
        return component;
    }

    private bool TryLog(StructuredLogEvent entry)
    {
        try
        {
            logger?.Write(entry);
            return true;
        }
        catch (LogWriteException)
        {
            StateChanged?.Invoke(SupervisorState.StorageUnavailable);
            return false;
        }
    }

    public async ValueTask DisposeAsync()
    {
        var stops = new List<Task>();
        if (worker is not null) stops.Add(worker.DisposeAsync().AsTask());
        if (api is not null) stops.Add(api.DisposeAsync().AsTask());
        await Task.WhenAll(stops);
    }
}