package client

import (
	"fmt"
	"regexp"
)

var instanceGroupIDRegex = regexp.MustCompile(`^projects/([^/]+)/zones/([^/]+)/instanceGroupManagers/([^/]+)$`)

// splitInstanceGroupID splits an instance group ID into core components.
func splitInstanceGroupID(instanceGroupID string) (project, zone, instanceGroup string, err error) {
	matches := instanceGroupIDRegex.FindStringSubmatch(instanceGroupID)
	if len(matches) != 4 {
		return "", "", "", fmt.Errorf("error splitting instanceGroupID: %v", instanceGroupID)
	}
	return matches[1], matches[2], matches[3], nil
}

// generateInstanceName generates a random instance name.
func generateInstanceName(baseInstanceName string, random prng) (string, error) {
	letters := []byte("abcdefghijklmnopqrstuvwxyz0123456789")
	const uidLen = 4
	uid := make([]byte, 0, uidLen)
	for i := 0; i < uidLen; i++ {
		n := random.Intn(len(letters))
		uid = append(uid, letters[n])
	}
	return baseInstanceName + "-" + string(uid), nil
}