/*
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 provider

import (
	"fmt"
	"strings"

	"cloud.google.com/go/compute/metadata"
	"github.com/linki/instrumented_http"
	log "github.com/sirupsen/logrus"

	dns "google.golang.org/api/dns/v1"

	"golang.org/x/net/context"
	"golang.org/x/oauth2/google"

	googleapi "google.golang.org/api/googleapi"

	"github.com/kubernetes-incubator/external-dns/endpoint"
	"github.com/kubernetes-incubator/external-dns/plan"
)

const (
	googleRecordTTL = 300
)

type managedZonesCreateCallInterface interface {
	Do(opts ...googleapi.CallOption) (*dns.ManagedZone, error)
}

type managedZonesListCallInterface interface {
	Pages(ctx context.Context, f func(*dns.ManagedZonesListResponse) error) error
}

type managedZonesServiceInterface interface {
	Create(project string, managedzone *dns.ManagedZone) managedZonesCreateCallInterface
	List(project string) managedZonesListCallInterface
}

type resourceRecordSetsListCallInterface interface {
	Pages(ctx context.Context, f func(*dns.ResourceRecordSetsListResponse) error) error
}

type resourceRecordSetsClientInterface interface {
	List(project string, managedZone string) resourceRecordSetsListCallInterface
}

type changesCreateCallInterface interface {
	Do(opts ...googleapi.CallOption) (*dns.Change, error)
}

type changesServiceInterface interface {
	Create(project string, managedZone string, change *dns.Change) changesCreateCallInterface
}

type resourceRecordSetsService struct {
	service *dns.ResourceRecordSetsService
}

func (r resourceRecordSetsService) List(project string, managedZone string) resourceRecordSetsListCallInterface {
	return r.service.List(project, managedZone)
}

type managedZonesService struct {
	service *dns.ManagedZonesService
}

func (m managedZonesService) Create(project string, managedzone *dns.ManagedZone) managedZonesCreateCallInterface {
	return m.service.Create(project, managedzone)
}

func (m managedZonesService) List(project string) managedZonesListCallInterface {
	return m.service.List(project)
}

type changesService struct {
	service *dns.ChangesService
}

func (c changesService) Create(project string, managedZone string, change *dns.Change) changesCreateCallInterface {
	return c.service.Create(project, managedZone, change)
}

// GoogleProvider is an implementation of Provider for Google CloudDNS.
type GoogleProvider struct {
	// The Google project to work in
	project string
	// Enabled dry-run will print any modifying actions rather than execute them.
	dryRun bool
	// only consider hosted zones managing domains ending in this suffix
	domainFilter DomainFilter
	// only consider hosted zones ending with this zone id
	zoneIDFilter ZoneIDFilter
	// A client for managing resource record sets
	resourceRecordSetsClient resourceRecordSetsClientInterface
	// A client for managing hosted zones
	managedZonesClient managedZonesServiceInterface
	// A client for managing change sets
	changesClient changesServiceInterface
}

// NewGoogleProvider initializes a new Google CloudDNS based Provider.
func NewGoogleProvider(project string, domainFilter DomainFilter, zoneIDFilter ZoneIDFilter, dryRun bool) (*GoogleProvider, error) {
	gcloud, err := google.DefaultClient(context.TODO(), dns.NdevClouddnsReadwriteScope)
	if err != nil {
		return nil, err
	}

	gcloud = instrumented_http.NewClient(gcloud, &instrumented_http.Callbacks{
		PathProcessor: func(path string) string {
			parts := strings.Split(path, "/")
			return parts[len(parts)-1]
		},
	})

	dnsClient, err := dns.New(gcloud)
	if err != nil {
		return nil, err
	}

	if project == "" {
		mProject, mErr := metadata.ProjectID()
		if mErr == nil {
			log.Infof("Google project auto-detected: %s", mProject)
			project = mProject
		}
	}

	provider := &GoogleProvider{
		project:                  project,
		dryRun:                   dryRun,
		domainFilter:             domainFilter,
		zoneIDFilter:             zoneIDFilter,
		resourceRecordSetsClient: resourceRecordSetsService{dnsClient.ResourceRecordSets},
		managedZonesClient:       managedZonesService{dnsClient.ManagedZones},
		changesClient:            changesService{dnsClient.Changes},
	}

	return provider, nil
}

// Zones returns the list of hosted zones.
func (p *GoogleProvider) Zones() (map[string]*dns.ManagedZone, error) {
	zones := make(map[string]*dns.ManagedZone)

	f := func(resp *dns.ManagedZonesListResponse) error {
		for _, zone := range resp.ManagedZones {
			if p.domainFilter.Match(zone.DnsName) && p.zoneIDFilter.Match(fmt.Sprintf("%v", zone.Id)) {
				zones[zone.Name] = zone
				log.Debugf("Matched %s (zone: %s)", zone.DnsName, zone.Name)
			} else {
				log.Debugf("Filtered %s (zone: %s)", zone.DnsName, zone.Name)
			}
		}

		return nil
	}

	log.Debugf("Matching zones against domain filters: %v", p.domainFilter.filters)
	if err := p.managedZonesClient.List(p.project).Pages(context.TODO(), f); err != nil {
		return nil, err
	}

	if len(zones) == 0 {
		if p.domainFilter.IsConfigured() {
			log.Warnf("No zones in the project, %s, match domain filters: %v", p.project, p.domainFilter.filters)
		} else {
			log.Warnf("No zones found in the project, %s", p.project)
		}
	}

	for _, zone := range zones {
		log.Debugf("Considering zone: %s (domain: %s)", zone.Name, zone.DnsName)
	}

	return zones, nil
}

// Records returns the list of records in all relevant zones.
func (p *GoogleProvider) Records() (endpoints []*endpoint.Endpoint, _ error) {
	zones, err := p.Zones()
	if err != nil {
		return nil, err
	}

	f := func(resp *dns.ResourceRecordSetsListResponse) error {
		for _, r := range resp.Rrsets {
			if !supportedRecordType(r.Type) {
				continue
			}
			endpoints = append(endpoints, endpoint.NewEndpointWithTTL(r.Name, r.Type, endpoint.TTL(r.Ttl), r.Rrdatas...))
		}

		return nil
	}

	for _, z := range zones {
		if err := p.resourceRecordSetsClient.List(p.project, z.Name).Pages(context.TODO(), f); err != nil {
			return nil, err
		}
	}

	return endpoints, nil
}

// CreateRecords creates a given set of DNS records in the given hosted zone.
func (p *GoogleProvider) CreateRecords(endpoints []*endpoint.Endpoint) error {
	change := &dns.Change{}

	change.Additions = append(change.Additions, p.newFilteredRecords(endpoints)...)

	return p.submitChange(change)
}

// UpdateRecords updates a given set of old records to a new set of records in a given hosted zone.
func (p *GoogleProvider) UpdateRecords(records, oldRecords []*endpoint.Endpoint) error {
	change := &dns.Change{}

	change.Additions = append(change.Additions, p.newFilteredRecords(records)...)
	change.Deletions = append(change.Deletions, p.newFilteredRecords(oldRecords)...)

	return p.submitChange(change)
}

// DeleteRecords deletes a given set of DNS records in a given zone.
func (p *GoogleProvider) DeleteRecords(endpoints []*endpoint.Endpoint) error {
	change := &dns.Change{}

	change.Deletions = append(change.Deletions, p.newFilteredRecords(endpoints)...)

	return p.submitChange(change)
}

// ApplyChanges applies a given set of changes in a given zone.
func (p *GoogleProvider) ApplyChanges(changes *plan.Changes) error {
	change := &dns.Change{}

	change.Additions = append(change.Additions, p.newFilteredRecords(changes.Create)...)

	change.Additions = append(change.Additions, p.newFilteredRecords(changes.UpdateNew)...)
	change.Deletions = append(change.Deletions, p.newFilteredRecords(changes.UpdateOld)...)

	change.Deletions = append(change.Deletions, p.newFilteredRecords(changes.Delete)...)

	return p.submitChange(change)
}

// newFilteredRecords returns a collection of RecordSets based on the given endpoints and domainFilter.
func (p *GoogleProvider) newFilteredRecords(endpoints []*endpoint.Endpoint) []*dns.ResourceRecordSet {
	records := []*dns.ResourceRecordSet{}

	for _, endpoint := range endpoints {
		if p.domainFilter.Match(endpoint.DNSName) {
			records = append(records, newRecord(endpoint))
		}
	}

	return records
}

// submitChange takes a zone and a Change and sends it to Google.
func (p *GoogleProvider) submitChange(change *dns.Change) error {
	if len(change.Additions) == 0 && len(change.Deletions) == 0 {
		log.Info("All records are already up to date")
		return nil
	}

	zones, err := p.Zones()
	if err != nil {
		return err
	}

	// separate into per-zone change sets to be passed to the API.
	changes := separateChange(zones, change)

	for z, c := range changes {
		log.Infof("Change zone: %v", z)
		for _, del := range c.Deletions {
			log.Infof("Del records: %s %s %s %d", del.Name, del.Type, del.Rrdatas, del.Ttl)
		}
		for _, add := range c.Additions {
			log.Infof("Add records: %s %s %s %d", add.Name, add.Type, add.Rrdatas, add.Ttl)
		}
	}

	if p.dryRun {
		return nil
	}

	for z, c := range changes {
		if _, err := p.changesClient.Create(p.project, z, c).Do(); err != nil {
			return err
		}
	}

	return nil
}

// separateChange separates a multi-zone change into a single change per zone.
func separateChange(zones map[string]*dns.ManagedZone, change *dns.Change) map[string]*dns.Change {
	changes := make(map[string]*dns.Change)
	zoneNameIDMapper := zoneIDName{}
	for _, z := range zones {
		zoneNameIDMapper[z.Name] = z.DnsName
		changes[z.Name] = &dns.Change{
			Additions: []*dns.ResourceRecordSet{},
			Deletions: []*dns.ResourceRecordSet{},
		}
	}
	for _, a := range change.Additions {
		if zoneName, _ := zoneNameIDMapper.FindZone(ensureTrailingDot(a.Name)); zoneName != "" {
			changes[zoneName].Additions = append(changes[zoneName].Additions, a)
		} else {
			log.Warnf("No matching zone for record addition: %s %s %s %d", a.Name, a.Type, a.Rrdatas, a.Ttl)
		}
	}

	for _, d := range change.Deletions {
		if zoneName, _ := zoneNameIDMapper.FindZone(ensureTrailingDot(d.Name)); zoneName != "" {
			changes[zoneName].Deletions = append(changes[zoneName].Deletions, d)
		} else {
			log.Warnf("No matching zone for record deletion: %s %s %s %d", d.Name, d.Type, d.Rrdatas, d.Ttl)
		}
	}

	// separating a change could lead to empty sub changes, remove them here.
	for zone, change := range changes {
		if len(change.Additions) == 0 && len(change.Deletions) == 0 {
			delete(changes, zone)
		}
	}

	return changes
}

// newRecord returns a RecordSet based on the given endpoint.
func newRecord(ep *endpoint.Endpoint) *dns.ResourceRecordSet {
	// TODO(linki): works around appending a trailing dot to TXT records. I think
	// we should go back to storing DNS names with a trailing dot internally. This
	// way we can use it has is here and trim it off if it exists when necessary.
	targets := make([]string, len(ep.Targets))
	copy(targets, []string(ep.Targets))
	if ep.RecordType == endpoint.RecordTypeCNAME {
		targets[0] = ensureTrailingDot(targets[0])
	}

	// no annotation results in a Ttl of 0, default to 300 for backwards-compatability
	var ttl int64 = googleRecordTTL
	if ep.RecordTTL.IsConfigured() {
		ttl = int64(ep.RecordTTL)
	}

	return &dns.ResourceRecordSet{
		Name:    ensureTrailingDot(ep.DNSName),
		Rrdatas: targets,
		Ttl:     ttl,
		Type:    ep.RecordType,
	}
}