/*
Copyright 2017 The Kubernetes Authors.

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/

package endpoint

import (
	"fmt"
	"sort"
	"strings"
)

const (
	// RecordTypeA is a RecordType enum value
	RecordTypeA = "A"
	// RecordTypeCNAME is a RecordType enum value
	RecordTypeCNAME = "CNAME"
	// RecordTypeTXT is a RecordType enum value
	RecordTypeTXT = "TXT"
	// RecordTypeSRV is a RecordType enum value
	RecordTypeSRV = "SRV"
)

// TTL is a structure defining the TTL of a DNS record
type TTL int64

// IsConfigured returns true if TTL is configured, false otherwise
func (ttl TTL) IsConfigured() bool {
	return ttl > 0
}

// Targets is a representation of a list of targets for an endpoint.
type Targets []string

// NewTargets is a convenience method to create a new Targets object from a vararg of strings
func NewTargets(target ...string) Targets {
	t := make(Targets, 0, len(target))
	t = append(t, target...)
	return t
}

func (t Targets) String() string {
	return strings.Join(t, ";")
}

func (t Targets) Len() int {
	return len(t)
}

func (t Targets) Less(i, j int) bool {
	return t[i] < t[j]
}

func (t Targets) Swap(i, j int) {
	t[i], t[j] = t[j], t[i]
}

// Same compares to Targets and returns true if they are completely identical
func (t Targets) Same(o Targets) bool {
	if len(t) != len(o) {
		return false
	}
	sort.Stable(t)
	sort.Stable(o)

	for i, e := range t {
		if e != o[i] {
			return false
		}
	}
	return true
}

// IsLess should fulfill the requirement to compare two targets and chosse the 'lesser' one.
// In the past target was a simple string so simple string comparison could be used. Now we define 'less'
// as either being the shorter list of targets or where the first entry is less.
// FIXME We really need to define under which circumstances a list Targets is considered 'less'
// than another.
func (t Targets) IsLess(o Targets) bool {
	if len(t) < len(o) {
		return true
	}
	if len(t) > len(o) {
		return false
	}

	sort.Sort(t)
	sort.Sort(o)

	for i, e := range t {
		if e != o[i] {
			return e < o[i]
		}
	}
	return false
}

// Endpoint is a high-level way of a connection between a service and an IP
type Endpoint struct {
	// The hostname of the DNS record
	DNSName string
	// The targets the DNS record points to
	Targets Targets
	// RecordType type of record, e.g. CNAME, A, TXT etc
	RecordType string
	// TTL for the record
	RecordTTL TTL
	// Labels stores labels defined for the Endpoint
	Labels Labels
}

// NewEndpoint initialization method to be used to create an endpoint
func NewEndpoint(dnsName, recordType string, targets ...string) *Endpoint {
	return NewEndpointWithTTL(dnsName, recordType, TTL(0), targets...)
}

// NewEndpointWithTTL initialization method to be used to create an endpoint with a TTL struct
func NewEndpointWithTTL(dnsName, recordType string, ttl TTL, targets ...string) *Endpoint {
	cleanTargets := make([]string, len(targets))
	for idx, target := range targets {
		cleanTargets[idx] = strings.TrimSuffix(target, ".")
	}

	return &Endpoint{
		DNSName:    strings.TrimSuffix(dnsName, "."),
		Targets:    cleanTargets,
		RecordType: recordType,
		Labels:     NewLabels(),
		RecordTTL:  ttl,
	}
}

func (e *Endpoint) String() string {
	return fmt.Sprintf("%s %d IN %s %s", e.DNSName, e.RecordTTL, e.RecordType, e.Targets)
}