package main

import (
	"bytes"
	"flag"
	"fmt"
)

type arrayFlags struct {
	name      string
	v         *[]string
	setCalled bool
}

func (i *arrayFlags) String() string {
	if i.v == nil {
		return ""
	}
	var buffer bytes.Buffer
	for _, cmd := range *i.v {
		if _, err := buffer.WriteString(fmt.Sprintf("-%s %s ", i.name, cmd)); err != nil {
			panic("error parsing array flags")
		}
	}
	return buffer.String()
}

func (i *arrayFlags) Set(value string) error {
	if !i.setCalled {
		*i.v = (*i.v)[:0]
		i.setCalled = true
	}
	*i.v = append(*i.v, value)
	return nil
}

func newArrayFlag(name string, val []string, p *[]string) *arrayFlags {
	*p = val
	a := &arrayFlags{name: name, v: p}
	return a
}

// ArrayVar defines an []string flag with specified name, default value, and usage string.
// The return value is the address of an []string variable that stores the value of the flag.
func ArrayVar(name string, value []string, usage string) *[]string {
	p := new([]string)
	flag.CommandLine.Var(newArrayFlag(name, value, p), name, usage)
	return p
}