using System.Diagnostics;

namespace Dada.Supervisor;

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

    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;
        }
        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, "apps", "api", "dist", "main.js");
        var workerEntry = Path.Combine(AppContext.BaseDirectory, "apps", "worker", "dist", "worker.js");
        if (!File.Exists(node) || !File.Exists(apiEntry) || !File.Exists(workerEntry)) return SupervisorState.StartupFailed;

        api = CreateComponent(node, apiEntry, ChildRole.Api, SupervisorState.ApiDegraded);
        api.StateChanged += state => StateChanged?.Invoke(state);
        await api.StartAsync(cancellationToken);

        worker = CreateComponent(node, workerEntry, ChildRole.Worker, SupervisorState.WorkerDegraded);
        worker.StateChanged += state => StateChanged?.Invoke(state);
        await worker.StartAsync(cancellationToken);
        return SupervisorState.Ready;
    }

    private ManagedComponentSupervisor CreateComponent(string node, string entry, ChildRole role, SupervisorState degradedState) =>
        new(async cancellationToken =>
        {
            var startInfo = new ProcessStartInfo(node);
            startInfo.ArgumentList.Add(entry);
            return await ManagedChildProcess.StartAsync(startInfo, role, credentials, cancellationToken);
        }, degradedState);

    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);
    }
}