optparse.go

package main

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

type Config struct {
	IndexDomain    string
	RegistryDomain string
}

type command struct {
	name     string
	argsdesc string
	desc     string
	nargs    int
	fn       func(*Config, []string)
}

var commands = [...]command{
	command{"info", "<repos_name>", "lookup repos meta-data", 1, CmdInfo},
	command{"layerinfo", "<repos_name> <layer_id>", "lookup layer meta-data", 2, CmdLayerInfo},
	command{"curlme", "<repos_name> <layer_id>", "print a curl command for fetching the layer", 2, CmdCurlme},
}

func OptParse() {
	flag.Usage = func() {
		fmt.Fprintf(os.Stderr, "Usage: %s [options] command\n", os.Args[0])
		fmt.Fprintln(os.Stderr, "")
		fmt.Fprintln(os.Stderr, "options:")
		flag.PrintDefaults()
		fmt.Fprintln(os.Stderr, "")
		fmt.Fprintln(os.Stderr, "commands:")
		for _, c := range commands {
			fmt.Fprintf(os.Stderr, "  %s %s: %s\n", c.name, c.argsdesc, c.desc)
		}
	}

	config := &Config{}
	flag.StringVar(&config.IndexDomain, "i", "https://index.docker.io", "override index endpoint")
	flag.StringVar(&config.RegistryDomain, "r", "", "override registry endpoint")
	flag.BoolVar(&Quiet, "q", false, "disable debug logs")
	flag.Parse()

	for _, c := range commands {
		if flag.Arg(0) == c.name {
			args := flag.Args()[1:]
			if len(args) != c.nargs {
				s := ""
				if c.nargs > 1 {
					s = "s"
				}
				fmt.Fprintf(os.Stderr, "%s takes %d argument%s: %s\n", c.name, c.nargs, s, c.argsdesc)
				os.Exit(2)
			}
			c.fn(config, args)
			return
		}
	}
	flag.Usage()
	os.Exit(2)
}