package server

import (
	"errors"
	"fmt"
)

type automap map[string]interface{}

var errExists = errors.New("already exists")
var errNotFound = errors.New("no such entry")

func (m automap) add(v interface{}) string {
	for n := 1;; n++ {
		k := fmt.Sprintf("%d", n)
		if _, ok := m[k]; !ok {
			m[k] = v
			return k
		}
	}
}

func (m automap) rename(old string, new string) (interface{}, error) {
	if _, ok := m[old]; !ok {
		return nil, errNotFound
	}

	if _, ok := m[new]; ok {
		return nil, errExists
	}

	v := m[old]
	m[new] = v

	delete(m, old)
	return v, nil
}