Servers/MoonlightServers.Daemon/ServerSystem/Server.Power.cs

namespace MoonlightServers.Daemon.ServerSystem;

public partial class Server
{
    public async Task StartAsync()
    {
        await Lock.WaitAsync();

        try
        {
            if (State != ServerState.Offline)
                throw new InvalidOperationException("Server is not offline");

            // Check for any pre-existing runtime environment, if we don't have a reference already
            RuntimeEnvironment ??= await RuntimeEnvironmentService.FindAsync(Uuid);
            RuntimeStorage ??= await RuntimeStorageService.FindAsync(Uuid);

            // Remove any pre-existing environment
            if (RuntimeEnvironment != null)
            {
                Logger.LogTrace("Destroying pre-existing runtime environment");

                if (await RuntimeEnvironment.IsRunningAsync())
                {
                    Logger.LogTrace("Pre-existing runtime environment is still running, killing it");
                    await RuntimeEnvironment.KillAsync();
                }

                // Make sure no event handler is there anymore
                RuntimeEnvironment.Console.OnOutput -= OnConsoleMessageAsync;
                RuntimeEnvironment.Statistics.OnStatisticsReceived -= OnStatisticsReceivedAsync;
                RuntimeEnvironment.OnExited -= OnRuntimeExitedAsync;

                // Finally remove it
                await RuntimeEnvironmentService.DeleteAsync(RuntimeEnvironment);
                RuntimeEnvironment = null;

                Logger.LogTrace("Pre-existing runtime environment destroyed");
            }

            // Fetch the latest config
            Logger.LogTrace("Fetching latest configuration");
            RuntimeConfiguration = await ConfigurationService.GetRuntimeConfigurationAsync(Uuid);

            // Ensure runtime storage
            if (RuntimeStorage == null)
            {
                Logger.LogTrace("Creating runtime storage");
                RuntimeStorage = await RuntimeStorageService.CreateAsync(Uuid, RuntimeConfiguration);
            }
            else
            {
                Logger.LogTrace("Updating runtime storage");
                await RuntimeStorageService.UpdateAsync(RuntimeStorage, RuntimeConfiguration);
            }
            
            // Create the environment
            Logger.LogTrace("Creating runtime environment");

            RuntimeEnvironment = await RuntimeEnvironmentService.CreateAsync(Uuid, RuntimeConfiguration, RuntimeStorage);

            // Set event handlers
            Logger.LogTrace("Attaching to runtime environment");

            RuntimeEnvironment.Console.OnOutput += OnConsoleMessageAsync;
            RuntimeEnvironment.Statistics.OnStatisticsReceived += OnStatisticsReceivedAsync;
            RuntimeEnvironment.OnExited += OnRuntimeExitedAsync;

            // Attach console & statistics 
            await RuntimeEnvironment.Console.AttachAsync();
            await RuntimeEnvironment.Statistics.AttachAsync();

            // Start up
            Logger.LogTrace("Starting runtime environment");

            await RuntimeEnvironment.StartAsync();

            await ChangeStateAsync(ServerState.Starting);
        }
        finally
        {
            Lock.Release();
        }
    }

    public async Task StopAsync()
    {
        await Lock.WaitAsync();

        try
        {
            if (State is not (ServerState.Starting or ServerState.Online))
                throw new InvalidOperationException("Server is not starting or online");

            if (RuntimeEnvironment == null)
                throw new InvalidOperationException("Runtime environment is not set");

            Logger.LogTrace("Sending stop command to runtime environment");
            await RuntimeEnvironment.Console.WriteInputAsync("stop\n\r");

            await ChangeStateAsync(ServerState.Stopping);
        }
        finally
        {
            Lock.Release();
        }
    }

    public async Task KillAsync()
    {
        await Lock.WaitAsync();

        try
        {
            if (State is not (ServerState.Starting or ServerState.Online or ServerState.Stopping))
                throw new InvalidOperationException("Server is not starting, stopping or online");

            if (RuntimeEnvironment == null)
                throw new InvalidOperationException("Runtime environment is not set");

            Logger.LogTrace("Killing runtime environment");
            await RuntimeEnvironment.KillAsync();

            await ChangeStateAsync(ServerState.Stopping);
        }
        finally
        {
            Lock.Release();
        }
    }
    
    private async Task OnRuntimeExitedAsync()
    {
        Logger.LogTrace("Runtime environment exited, checking result and cleaning up");

        await Lock.WaitAsync();

        try
        {
            // TODO: Handle crash

            if (RuntimeEnvironment == null)
                throw new InvalidOperationException("Runtime environment is not set");

            // Make sure no event handler is there anymore
            RuntimeEnvironment.Console.OnOutput -= OnConsoleMessageAsync;
            RuntimeEnvironment.Statistics.OnStatisticsReceived -= OnStatisticsReceivedAsync;
            RuntimeEnvironment.OnExited -= OnRuntimeExitedAsync;

            // Finally remove it
            await RuntimeEnvironmentService.DeleteAsync(RuntimeEnvironment);
            RuntimeEnvironment = null;

            Logger.LogTrace("Runtime environment cleaned up");
        }
        finally
        {
            Lock.Release();
        }

        await ChangeStateAsync(ServerState.Offline);
    }
}