cmd.go

package main

import (
	"flag"
	"fmt"
	"log"
	"os"
	"slices"
)

// command is a subcommand handler and its flag set.
type command struct {
	// flagSet is the flag set for the command.
	flagSet *flag.FlagSet

	// aliases for the command.
	aliases []string

	// handler is the function that is invoked to handle this command.
	handler func(args []string) error

	// flagSet.Usage function to invoke on e.g. -h flag. If nil, a default one is
	// used.
	usageFunc func()
}

// matches tells if the given name matches this command or one of its aliases.
func (c *command) matches(name string) bool {
	if name == c.flagSet.Name() {
		return true
	}
	return slices.Contains(c.aliases, name)
}

// commander represents a top-level command with subcommands.
type commander []*command

// run runs the command.
func (c commander) run(flagSet *flag.FlagSet, cmdName, usageText string, args []string) {
	// Parse flags.
	flagSet.Usage = func() {
		_, _ = fmt.Fprint(flag.CommandLine.Output(), usageText)
	}
	if !flagSet.Parsed() {
		_ = flagSet.Parse(args)
	}

	// Print usage if the command is "help".
	if flagSet.Arg(0) == "help" || flagSet.NArg() == 0 {
		flagSet.SetOutput(os.Stdout)
		flagSet.Usage()
		os.Exit(0)
	}

	// Configure default usage funcs for commands.
	for _, cmd := range c {
		if cmd.usageFunc != nil {
			cmd.flagSet.Usage = cmd.usageFunc
			continue
		}
		cmd.flagSet.Usage = func() {
			_, _ = fmt.Fprintf(flag.CommandLine.Output(), "Usage of '%s %s':\n", cmdName, cmd.flagSet.Name())
			cmd.flagSet.PrintDefaults()
		}
	}

	// Find the subcommand to execute.
	name := flagSet.Arg(0)

	// Command is legacy, so lets execute the old way
	for _, cmd := range c {
		if !cmd.matches(name) {
			continue
		}
		// Read global configuration now.
		var err error
		cfg, err = readConfig()
		if err != nil {
			log.Fatal("reading config: ", err)
		}

		exitCode, err := runLegacy(cmd, flagSet)
		if err != nil {
			log.Fatal(err)
		}
		os.Exit(exitCode)

	}
	log.Printf("%s: unknown subcommand %q", cmdName, name)
	log.Fatalf("Run '%s help' for usage.", cmdName)
}