mfgames-toolbuilder-cil/src/MfGames.ToolBuilder/ToolBuilder.cs

using System;
using System.IO;
using System.Threading.Tasks;

using Autofac;
using Autofac.Extensions.DependencyInjection;

using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Hosting;

using Serilog;

namespace MfGames.ToolBuilder
{
    /// <summary>
    /// A builder pattern for creating the tool. This wraps much of the hosting
    /// infrastructure with some opinionated decisions and reduces the amount of
    /// boilerplate needed to configure the tool.
    /// </summary>
    public class ToolBuilder
    {
        private readonly string[] arguments;

        private readonly ConfigToolService configService;

        private readonly IHostBuilder hostBuilder;

        private readonly LoggingToolService loggingService;

        public ToolBuilder(
            string applicationName,
            string internalName,
            string[] arguments)
        {
            // Create our various services.
            this.arguments = arguments;
            this.ApplicationName = applicationName;
            this.InternalName = internalName;
            this.configService = new ConfigToolService()
                .WithInternalName(this.InternalName);
            this.loggingService = new LoggingToolService();

            // Set up logging first so we can report the loading process. This
            // sets up the Serilog.Log.Logger which means we can use that for
            // everything beyond this point.
            this.loggingService.Configure(arguments);

            // Start up the basic configuration.
            this.hostBuilder = Host
                .CreateDefaultBuilder(arguments)
                .UseConsoleLifetime()
                .ConfigureAppConfiguration(this.ConfigureAppConfiguration)
                .UseSerilog()
                .UseServiceProviderFactory(new AutofacServiceProviderFactory())
                .ConfigureServices(this.ConfigureServices)
                .ConfigureContainer<ContainerBuilder>(this.ConfigureContainer);
        }

        /// <summary>
        /// Gets the human-readable name of the application.
        /// </summary>
        public string ApplicationName { get; }

        /// <summary>
        /// Gets the internal name of the application.
        /// </summary>
        public string InternalName { get; }

        public static ToolBuilder Create(
            string applicationName,
            string internalName,
            string[] arguments)
        {
            return new ToolBuilder(applicationName, internalName, arguments);
        }

        public ToolBuilder ConfigureContainer(
            Action<ContainerBuilder> configure)
        {
            this.hostBuilder.ConfigureContainer(configure);
            return this;
        }

        public ToolBuilder ConfigureServices(
            Action<IServiceCollection> configure)
        {
            this.hostBuilder.ConfigureServices(configure);
            return this;
        }

        /// <summary>
        /// Finishes building the tool, parses the arguments, and runs the
        /// command.
        /// </summary>
        /// <returns>An error code, 0 for successful, otherwise false.</returns>
        public async Task<int> RunAsync()
        {
            try
            {
                await this.hostBuilder
                    .RunConsoleAsync()
                    .ConfigureAwait(false);
            }
            catch (Exception exception)
            {
                Log.Fatal(
                    exception,
                    "There was a problem running the command: {Arguments}",
                    this.arguments);

                return Environment.ExitCode == 0 ? 1 : Environment.ExitCode;
            }

            // Get the exit code and return it.
            return Environment.ExitCode;
        }

        private void ConfigureAppConfiguration(
            HostBuilderContext context,
            IConfigurationBuilder builder)
        {
            builder.SetBasePath(Directory.GetCurrentDirectory());
            this.configService.Configure(builder, this.arguments);
        }

        private void ConfigureContainer(
            HostBuilderContext context,
            ContainerBuilder builder)
        {
            // We want to get logging up and running as soon as possible. We
            // also hook up the logging to the process exit in an attempt to
            // make sure the logger is properly flushed before exiting.
            builder.RegisterInstance(Log.Logger).As<ILogger>().SingleInstance();

            AppDomain.CurrentDomain.ProcessExit +=
                (_, _) => Log.CloseAndFlush();

            // Register the components required to make the CLI work.
            builder.RegisterModule<ToolBuilderModule>();
        }

        private void ConfigureServices(
            HostBuilderContext context,
            IServiceCollection services)
        {
            services.AddAutofac();
            services.AddHostedService<ToolService>();
        }
    }
}