CliFx/CliFx/CliApplication.cs

using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.Linq;
using System.Threading.Tasks;
using CliFx.Exceptions;
using CliFx.Formatting;
using CliFx.Infrastructure;
using CliFx.Input;
using CliFx.Schema;
using CliFx.Utils;
using CliFx.Utils.Extensions;

namespace CliFx;

/// <summary>
/// Command line application facade.
/// </summary>
public class CliApplication
{
    /// <summary>
    /// Application metadata.
    /// </summary>
    public ApplicationMetadata Metadata { get; }

    /// <summary>
    /// Application configuration.
    /// </summary>
    public ApplicationConfiguration Configuration { get; }

    private readonly IConsole _console;
    private readonly ITypeActivator _typeActivator;

    private readonly CommandBinder _commandBinder;

    /// <summary>
    /// Initializes an instance of <see cref="CliApplication"/>.
    /// </summary>
    public CliApplication(
        ApplicationMetadata metadata,
        ApplicationConfiguration configuration,
        IConsole console,
        ITypeActivator typeActivator)
    {
        Metadata = metadata;
        Configuration = configuration;
        _console = console;
        _typeActivator = typeActivator;

        _commandBinder = new CommandBinder(typeActivator);
    }

    private bool IsDebugModeEnabled(CommandInput commandInput) =>
        Configuration.IsDebugModeAllowed && commandInput.IsDebugDirectiveSpecified;

    private bool IsPreviewModeEnabled(CommandInput commandInput) =>
        Configuration.IsPreviewModeAllowed && commandInput.IsPreviewDirectiveSpecified;

    private bool ShouldShowHelpText(CommandSchema commandSchema, CommandInput commandInput) =>
        commandSchema.IsHelpOptionAvailable && commandInput.IsHelpOptionSpecified ||
        // Show help text also in case the fallback default command is
        // executed without any arguments.
        commandSchema == FallbackDefaultCommand.Schema &&
        string.IsNullOrWhiteSpace(commandInput.CommandName) &&
        !commandInput.Parameters.Any() &&
        !commandInput.Options.Any();

    private bool ShouldShowVersionText(CommandSchema commandSchema, CommandInput commandInput) =>
        commandSchema.IsVersionOptionAvailable && commandInput.IsVersionOptionSpecified;

    private async ValueTask PromptDebuggerAsync()
    {
        using (_console.WithForegroundColor(ConsoleColor.Green))
        {
            var processId = ProcessEx.GetCurrentProcessId();

            _console.Output.WriteLine(
                $"Attach debugger to PID {processId} to continue."
            );
        }

        // Try to also launch debugger ourselves (only works if VS is installed)
        Debugger.Launch();

        while (!Debugger.IsAttached)
        {
            await Task.Delay(100);
        }
    }

    private async ValueTask<int> RunAsync(ApplicationSchema applicationSchema, CommandInput commandInput)
    {
        // Handle debug directive
        if (IsDebugModeEnabled(commandInput))
        {
            await PromptDebuggerAsync();
        }

        // Handle preview directive
        if (IsPreviewModeEnabled(commandInput))
        {
            _console.Output.WriteCommandInput(commandInput);
            return 0;
        }

        // Try to get the command schema that matches the input
        var commandSchema =
            applicationSchema.TryFindCommand(commandInput.CommandName) ??
            applicationSchema.TryFindDefaultCommand() ??
            FallbackDefaultCommand.Schema;

        // Activate command instance
        var commandInstance = commandSchema == FallbackDefaultCommand.Schema
            ? new FallbackDefaultCommand() // bypass activator
            : (ICommand)_typeActivator.CreateInstance(commandSchema.Type);

        // Assemble help context
        var helpContext = new HelpContext(
            Metadata,
            applicationSchema,
            commandSchema,
            commandSchema.GetValues(commandInstance)
        );

        // Handle help option
        if (ShouldShowHelpText(commandSchema, commandInput))
        {
            _console.Output.WriteHelpText(helpContext);
            return 0;
        }

        // Handle version option
        if (ShouldShowVersionText(commandSchema, commandInput))
        {
            _console.Output.WriteLine(Metadata.Version);
            return 0;
        }

        // Starting from this point, we may produce exceptions that are meant for the
        // end user of the application (i.e. invalid input, command exception, etc).
        // Catch these exceptions here, print them to the console, and don't let them
        // propagate further.
        try
        {
            // Bind and execute command
            _commandBinder.Bind(commandInput, commandSchema, commandInstance);
            await commandInstance.ExecuteAsync(_console);

            return 0;
        }
        catch (CliFxException ex)
        {
            _console.Error.WriteException(ex);

            if (ex.ShowHelp)
            {
                _console.Output.WriteLine();
                _console.Output.WriteHelpText(helpContext);
            }

            return ex.ExitCode;
        }
    }

    /// <summary>
    /// Runs the application with the specified command line arguments and environment variables.
    /// Returns an exit code which indicates whether the application completed successfully.
    /// </summary>
    /// <remarks>
    /// When running WITHOUT debugger (i.e. in production), this method swallows all exceptions and
    /// reports them to the console.
    /// </remarks>
    public async ValueTask<int> RunAsync(
        IReadOnlyList<string> commandLineArguments,
        IReadOnlyDictionary<string, string> environmentVariables)
    {
        try
        {
            // Console colors may have already been overridden by the parent process,
            // so we need to reset it to make sure that everything we write looks properly.
            _console.ResetColor();

            var applicationSchema = ApplicationSchema.Resolve(Configuration.CommandTypes);

            var commandInput = CommandInput.Parse(
                commandLineArguments,
                environmentVariables,
                applicationSchema.GetCommandNames()
            );

            return await RunAsync(applicationSchema, commandInput);
        }
        // To prevent the app from showing the annoying troubleshooting dialog on Windows,
        // we handle all exceptions ourselves and print them to the console.
        //
        // We only want to do that if the app is running in production, which we infer
        // based on whether a debugger is attached to the process.
        //
        // When not running in production, we want the IDE to show exceptions to the
        // developer, so we don't swallow them in that case.
        catch (Exception ex) when (!Debugger.IsAttached)
        {
            _console.Error.WriteException(ex);
            return 1;
        }
    }

    /// <summary>
    /// Runs the application with the specified command line arguments.
    /// Environment variables are resolved automatically.
    /// Returns an exit code which indicates whether the application completed successfully.
    /// </summary>
    /// <remarks>
    /// When running WITHOUT debugger (i.e. in production), this method swallows all exceptions and
    /// reports them to the console.
    /// </remarks>
    public async ValueTask<int> RunAsync(IReadOnlyList<string> commandLineArguments) => await RunAsync(
        commandLineArguments,
        // Use case-sensitive comparison because environment variables are
        // case-sensitive on Linux and macOS (but not on Windows).
        Environment
            .GetEnvironmentVariables()
            .ToDictionary<string, string>(StringComparer.Ordinal)
    );

    /// <summary>
    /// Runs the application.
    /// Command line arguments and environment variables are resolved automatically.
    /// Returns an exit code which indicates whether the application completed successfully.
    /// </summary>
    /// <remarks>
    /// When running WITHOUT debugger (i.e. in production), this method swallows all exceptions and
    /// reports them to the console.
    /// </remarks>
    public async ValueTask<int> RunAsync() => await RunAsync(
        Environment.GetCommandLineArgs()
            .Skip(1) // first element is the file path
            .ToArray()
    );
}