goshort/cmd/main.go

//nolint:forbidigo // This is part of the CLI and the errors will be written as fmt.Pxxx
package cmd

import (
	"context"
	"errors"
	"flag"
	"fmt"
	"os"
	"os/signal"
	"syscall"

	devcmd "git.maronato.dev/maronato/goshort/cmd/dev"
	healthcheckcmd "git.maronato.dev/maronato/goshort/cmd/healthcheck"
	servecmd "git.maronato.dev/maronato/goshort/cmd/serve"
	"git.maronato.dev/maronato/goshort/cmd/shared"
	"git.maronato.dev/maronato/goshort/internal/config"
	"git.maronato.dev/maronato/goshort/internal/util/logging"
	"git.maronato.dev/maronato/goshort/internal/util/tracing"
	"github.com/peterbourgon/ff/v3/ffcli"
)

var (
	// ErrUnknownCommand is returned when the user tries to run an unknown command.
	ErrUnknownCommand = errors.New("unknown command")
	// ErrUnknownHelpTopic is returned when the user tries to run an unknown help topic.
	ErrUnknownHelpTopic = errors.New("unknown help topic")
)

func NewUnknownCommand(cmd string) error {
	return fmt.Errorf("%q: %w\nRun 'goshort help' for usage", cmd, ErrUnknownCommand)
}

func NewUnknownHelpTopic(topic string) error {
	return fmt.Errorf("%q: %w. Run 'goshort help'", topic, ErrUnknownHelpTopic)
}

func Run(version string) error {
	// Create the application-wide context, and
	// implement graceful shutdown.
	ctx, cancel := context.WithCancel(context.Background())
	defer cancel()

	trapSignalsCrossPlatform(cancel)

	// Create the root command and register subcommands.
	rootCmd, cfg := newRootCmd(version)
	rootCmd.Subcommands = append(
		rootCmd.Subcommands,
		servecmd.New(cfg),
		healthcheckcmd.New(cfg),
	)

	// Look for the env ENV_DOCKER=true to disable the dev command
	// since the docker image won't have node installed.
	if os.Getenv("ENV_DOCKER") != "true" {
		rootCmd.Subcommands = append(rootCmd.Subcommands, devcmd.New(cfg))
	}

	// Parse the command-line arguments.
	if err := rootCmd.Parse(os.Args[1:]); err != nil {
		if errors.Is(err, flag.ErrHelp) {
			return nil
		}

		return fmt.Errorf("%w", err)
	}

	// Validate config
	if err := config.Validate(cfg); err != nil {
		if errors.Is(err, flag.ErrHelp) {
			return nil
		}

		return fmt.Errorf("%w", err)
	}

	// Create system logger
	l := logging.NewLogger(cfg)
	ctx = logging.WithLogger(ctx, l)

	// Initialize tracing
	ctx, stopTracing, err := tracing.InitTracer(ctx, cfg, version)
	if err != nil {
		return fmt.Errorf("%w", err)
	}

	// Close the tracer when the application exits
	defer stopTracing()

	// Run the command.
	if err := rootCmd.Run(ctx); err != nil {
		if errors.Is(err, flag.ErrHelp) {
			return nil
		}

		return fmt.Errorf("%w", err)
	}

	return nil
}

// newRootCmd constructs a root command from the provided options.
func newRootCmd(version string) (*ffcli.Command, *config.Config) {
	var cfg config.Config

	fs := flag.NewFlagSet("goshort", flag.ContinueOnError)

	cmd := &ffcli.Command{
		Name:       "goshort",
		ShortUsage: "goshort <subcommand> [flags]",
		ShortHelp:  "goshort is a tiny URL shortener",
		FlagSet:    fs,
		Exec: func(_ context.Context, args []string) error {
			// If the user didn't provide any subcommand, then
			// we'll just show the help message.
			if len(args) == 0 {
				return flag.ErrHelp
			}

			return NewUnknownCommand(args[0])
		},
	}

	cmd.Subcommands = []*ffcli.Command{
		// Register help command
		{
			Name:       "help",
			ShortUsage: "help [command]",
			ShortHelp:  "Show help for a command",
			Exec: func(ctx context.Context, args []string) error {
				if len(args) == 0 || args[0] == "help" {
					cmd.FlagSet.Usage()

					fmt.Printf("\nUse 'goshort help <command>' for more information about that command.\n\n")

					return nil
				}

				for _, c := range cmd.Subcommands {
					if c.Name == args[0] {
						return c.ParseAndRun(ctx, []string{"-h"}) //nolint:wrapcheck // We don't want to wrap the error here
					}
				}

				return NewUnknownHelpTopic(args[0])
			},
		},

		// Register version command
		{
			Name:       "version",
			ShortUsage: "version",
			ShortHelp:  "Show version information",
			Exec: func(_ context.Context, _ []string) error {
				fmt.Printf("goshort version %s\n", version)

				return nil
			},
		},

		// Register config command
		NewConfigCmd(&cfg),
	}

	return cmd, &cfg
}

// https://github.com/caddyserver/caddy/blob/fbb0ecfa322aa7710a3448453fd3ae40f037b8d1/sigtrap.go#L37
// trapSignalsCrossPlatform captures SIGINT or interrupt (depending
// on the OS), which initiates a graceful shutdown. A second SIGINT
// or interrupt will forcefully exit the process immediately.
func trapSignalsCrossPlatform(cancel context.CancelFunc) {
	go func() {
		shutdown := make(chan os.Signal, 1)
		signal.Notify(shutdown, os.Interrupt, syscall.SIGINT)

		for i := 0; true; i++ {
			<-shutdown

			if i > 0 {
				fmt.Printf("\nForce quit\n")
				os.Exit(1)
			}

			fmt.Printf("\nGracefully shutting down. Press Ctrl+C again to force quit\n")
			cancel()
		}
	}()
}

func NewConfigCmd(cfg *config.Config) *ffcli.Command {
	// Create the flagset and register the flags.
	fs := flag.NewFlagSet("goshort serve", flag.ContinueOnError)

	shared.RegisterBaseFlags(fs, cfg)
	shared.RegisterServerFlags(fs, cfg)
	fs.BoolVar(&cfg.Prod, "prod", config.DefaultProd, "run in production mode")

	// Return the ffcli command.
	return &ffcli.Command{
		Name:       "config",
		ShortUsage: "goshort config [flags]",
		ShortHelp:  "Prints the current config",
		FlagSet:    fs,
		Exec: func(_ context.Context, _ []string) error {
			cfg.PrettyPrint()

			return nil
		},
		Options: shared.NewSharedCmdOptions(),
	}
}