package app

import (
	"fmt"
	"regexp"
	"strconv"
	"strings"

	"github.com/golang/glog"
	kvalidation "k8s.io/kubernetes/pkg/util/validation"

	"github.com/openshift/origin/pkg/util/namer"
)

// the opposite of kvalidation.DNS1123LabelFmt
var invalidNameCharactersRegexp = regexp.MustCompile("[^-a-z0-9]")

// A UniqueNameGenerator is able to generate unique names from a given original
// name.
type UniqueNameGenerator interface {
	Generate(NameSuggester) (string, error)
}

// NewUniqueNameGenerator creates a new UniqueNameGenerator with the given
// original name.
func NewUniqueNameGenerator(name string) UniqueNameGenerator {
	return &uniqueNameGenerator{name, map[string]int{}}
}

type uniqueNameGenerator struct {
	originalName string
	names        map[string]int
}

// Generate returns a name that is unique within the set of names of this unique
// name generator. If the generator's original name is empty, a new name will be
// suggested.
func (ung *uniqueNameGenerator) Generate(suggester NameSuggester) (string, error) {
	name := ung.originalName
	if len(name) == 0 {
		var ok bool
		name, ok = suggester.SuggestName()
		if !ok {
			return "", ErrNameRequired
		}
	}
	return ung.ensureValidName(name)
}

// ensureValidName returns a new name based on the name given that is unique in
// the set of names of this unique name generator.
func (ung *uniqueNameGenerator) ensureValidName(name string) (string, error) {
	names := ung.names

	// Ensure that name meets length requirements
	if len(name) < 2 {
		return "", fmt.Errorf("invalid name: %s", name)
	}

	// Make all names lowercase
	name = strings.ToLower(name)

	// Remove everything except [-0-9a-z]
	name = invalidNameCharactersRegexp.ReplaceAllString(name, "")

	// Remove leading hyphen(s) that may be introduced by the previous step
	name = strings.TrimLeft(name, "-")

	if len(name) > kvalidation.DNS1123SubdomainMaxLength {
		glog.V(4).Infof("Trimming %s to maximum allowable length (%d)\n", name, kvalidation.DNS1123SubdomainMaxLength)
		name = name[:kvalidation.DNS1123SubdomainMaxLength]
	}

	count, existing := names[name]
	if !existing {
		names[name] = 0
		return name, nil
	}
	count++
	names[name] = count
	newName := namer.GetName(name, strconv.Itoa(count), kvalidation.DNS1123SubdomainMaxLength)
	return newName, nil
}
