main.go

package main

import (
	"flag"
	"fmt"
	"os"
)

type Command struct {
	Name      string
	Usage     string
	ShortHelp string
	LongHelp  string
	Run       func(args []string)
	Flag      flag.FlagSet
}

var commands = []*Command{
	eval,
	serve,
}

func main() {
	flag.Usage = usage
	flag.Parse()
	args := flag.Args()

	if len(args) < 1 {
		usage()
		return
	}

	for _, cmd := range commands {
		if cmd.Name == args[0] && cmd.Run != nil {
			cmd.Flag.Parse(args[1:])
			cmd_args := cmd.Flag.Args()
			cmd.Run(cmd_args)
			os.Exit(0)
		}
	}

	fmt.Fprintf(os.Stderr, "Unknown subcommand %q\n", args[0])
}

func usage() {
	fmt.Printf("usage: %s\n\n", os.Args[0])

	for _, cmd := range commands {
		if cmd.Usage != "" {
			fmt.Printf("    %s\n", cmd.Usage)
		}
	}
	fmt.Printf("\n")
}