/*
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 transip

import (
	"context"
	"errors"
	"fmt"
	"strings"

	log "github.com/sirupsen/logrus"
	"github.com/transip/gotransip"
	transip "github.com/transip/gotransip/domain"

	"sigs.k8s.io/external-dns/endpoint"
	"sigs.k8s.io/external-dns/plan"
	"sigs.k8s.io/external-dns/provider"
)

const (
	// 60 seconds is the current minimal TTL for TransIP and will replace unconfigured
	// TTL's for Endpoints
	transipMinimalValidTTL = 60
)

// TransIPProvider is an implementation of Provider for TransIP.
type TransIPProvider struct {
	provider.BaseProvider
	client       gotransip.SOAPClient
	domainFilter endpoint.DomainFilter
	dryRun       bool
}

// NewTransIPProvider initializes a new TransIP Provider.
func NewTransIPProvider(accountName, privateKeyFile string, domainFilter endpoint.DomainFilter, dryRun bool) (*TransIPProvider, error) {
	// check given arguments
	if accountName == "" {
		return nil, errors.New("required --transip-account not set")
	}

	if privateKeyFile == "" {
		return nil, errors.New("required --transip-keyfile not set")
	}

	var apiMode gotransip.APIMode
	if dryRun {
		apiMode = gotransip.APIModeReadOnly
	} else {
		apiMode = gotransip.APIModeReadWrite
	}

	// create new TransIP API client
	c, err := gotransip.NewSOAPClient(gotransip.ClientConfig{
		AccountName:    accountName,
		PrivateKeyPath: privateKeyFile,
		Mode:           apiMode,
	})
	if err != nil {
		return nil, fmt.Errorf("could not setup TransIP API client: %s", err.Error())
	}

	// return tipCloud struct
	return &TransIPProvider{
		client:       c,
		domainFilter: domainFilter,
		dryRun:       dryRun,
	}, nil
}

// ApplyChanges applies a given set of changes in a given zone.
func (p *TransIPProvider) ApplyChanges(ctx context.Context, changes *plan.Changes) error {
	// build zonefinder with all our zones so we can use FindZone
	// and a mapping of zones and their domain name
	zones, err := p.fetchZones()
	if err != nil {
		return err
	}

	zoneNameMapper := provider.ZoneIDName{}
	zonesByName := make(map[string]transip.Domain)
	updatedZones := make(map[string]bool)
	for _, zone := range zones {
		// TransIP API doesn't expose a unique identifier for zones, other than than
		// the domain name itself
		zoneNameMapper.Add(zone.Name, zone.Name)
		zonesByName[zone.Name] = zone
	}

	// first see if we need to delete anything
	for _, ep := range changes.Delete {
		log.WithFields(log.Fields{"record": ep.DNSName, "type": ep.RecordType}).Info("endpoint has to go")

		zone, err := p.zoneForZoneName(ep.DNSName, zoneNameMapper, zonesByName)
		if err != nil {
			log.Errorf("could not find zone for %s: %s", ep.DNSName, err.Error())
			continue
		}

		log.Debugf("removing records for %s", zone.Name)

		// remove current records from DNS entry set
		entries := p.removeEndpointFromEntries(ep, zone)

		// update zone in zone map
		zone.DNSEntries = entries
		zonesByName[zone.Name] = zone
		// flag zone for updating
		updatedZones[zone.Name] = true
	}

	for _, ep := range changes.Create {
		log.WithFields(log.Fields{"record": ep.DNSName, "type": ep.RecordType}).Info("endpoint is missing")

		zone, err := p.zoneForZoneName(ep.DNSName, zoneNameMapper, zonesByName)
		if err != nil {
			log.Errorf("could not find zone for %s: %s", ep.DNSName, err.Error())
			continue
		}

		log.Debugf("creating records for %s", zone.Name)

		// add new entries to set
		zone.DNSEntries = p.addEndpointToEntries(ep, zone, zone.DNSEntries)

		// update zone in zone map
		zonesByName[zone.Name] = zone
		// flag zone for updating
		updatedZones[zone.Name] = true
		log.WithFields(log.Fields{"zone": zone.Name}).Debug("flagging for update")
	}

	for _, ep := range changes.UpdateNew {
		log.WithFields(log.Fields{"record": ep.DNSName, "type": ep.RecordType}).Debug("needs updating")

		zone, err := p.zoneForZoneName(ep.DNSName, zoneNameMapper, zonesByName)
		if err != nil {
			log.WithFields(log.Fields{"record": ep.DNSName}).Warn(err.Error())
			continue
		}

		// updating the records is basically finding all matching records according
		// to the name and the type, removing them from the set and add the new
		// records
		log.WithFields(log.Fields{
			"zone":       zone.Name,
			"dnsname":    ep.DNSName,
			"recordtype": ep.RecordType,
		}).Debug("removing matching entries")

		// remove current records from DNS entry set
		entries := p.removeEndpointFromEntries(ep, zone)

		// add new entries to set
		entries = p.addEndpointToEntries(ep, zone, entries)

		// check to see if actually anything changed in the DNSEntry set
		if p.dnsEntriesAreEqual(entries, zone.DNSEntries) {
			log.WithFields(log.Fields{"zone": zone.Name}).Debug("not updating identical entries")
			continue
		}

		// update zone in zone map
		zone.DNSEntries = entries
		zonesByName[zone.Name] = zone
		// flag zone for updating
		updatedZones[zone.Name] = true

		log.WithFields(log.Fields{"zone": zone.Name}).Debug("flagging for update")
	}

	// go over all updated zones and set new DNSEntry set
	for uz := range updatedZones {
		zone, ok := zonesByName[uz]
		if !ok {
			log.WithFields(log.Fields{"zone": uz}).Debug("updated zone no longer found")
			continue
		}

		if p.dryRun {
			log.WithFields(log.Fields{"zone": zone.Name}).Info("not updating in dry-run mode")
			continue
		}

		log.WithFields(log.Fields{"zone": zone.Name}).Info("updating DNS entries")
		if err := transip.SetDNSEntries(p.client, zone.Name, zone.DNSEntries); err != nil {
			log.WithFields(log.Fields{"zone": zone.Name, "error": err.Error()}).Warn("failed to update")
		}
	}

	return nil
}

// fetchZones returns a list of all domains within the account
func (p *TransIPProvider) fetchZones() ([]transip.Domain, error) {
	domainNames, err := transip.GetDomainNames(p.client)
	if err != nil {
		return nil, err
	}

	domains, err := transip.BatchGetInfo(p.client, domainNames)
	if err != nil {
		return nil, err
	}

	var zones []transip.Domain
	for _, d := range domains {
		if !p.domainFilter.Match(d.Name) {
			continue
		}

		zones = append(zones, d)
	}

	return zones, nil
}

// Zones returns the list of hosted zones.
func (p *TransIPProvider) Zones() ([]transip.Domain, error) {
	zones, err := p.fetchZones()
	if err != nil {
		return nil, err
	}

	return zones, nil
}

// Records returns the list of records in a given zone.
func (p *TransIPProvider) Records(ctx context.Context) ([]*endpoint.Endpoint, error) {
	zones, err := p.Zones()
	if err != nil {
		return nil, err
	}

	var endpoints []*endpoint.Endpoint
	var name string
	// go over all zones and their DNS entries and create endpoints for them
	for _, zone := range zones {
		for _, r := range zone.DNSEntries {
			if !provider.SupportedRecordType(string(r.Type)) {
				continue
			}

			name = p.endpointNameForRecord(r, zone)
			endpoints = append(endpoints, endpoint.NewEndpointWithTTL(name, string(r.Type), endpoint.TTL(r.TTL), r.Content))
		}
	}

	return endpoints, nil
}

// endpointNameForRecord returns "www.example.org" for DNSEntry with Name "www" and
// Doman with Name "example.org"
func (p *TransIPProvider) endpointNameForRecord(r transip.DNSEntry, d transip.Domain) string {
	// root name is identified by "@" and should be translated to domain name for
	// the endpoint entry.
	if r.Name == "@" {
		return d.Name
	}

	return fmt.Sprintf("%s.%s", r.Name, d.Name)
}

// recordNameForEndpoint returns "www" for Endpoint with DNSName "www.example.org"
// and Domain with Name "example.org"
func (p *TransIPProvider) recordNameForEndpoint(ep *endpoint.Endpoint, d transip.Domain) string {
	// root name is identified by "@" and should be translated to domain name for
	// the endpoint entry.
	if ep.DNSName == d.Name {
		return "@"
	}

	return strings.TrimSuffix(ep.DNSName, "."+d.Name)
}

// getMinimalValidTTL returns max between given Endpoint's RecordTTL and
// transipMinimalValidTTL
func (p *TransIPProvider) getMinimalValidTTL(ep *endpoint.Endpoint) int64 {
	// TTL cannot be lower than transipMinimalValidTTL
	if ep.RecordTTL < transipMinimalValidTTL {
		return transipMinimalValidTTL
	}

	return int64(ep.RecordTTL)
}

// dnsEntriesAreEqual compares the entries in 2 sets and returns true if the
// content of the entries is equal
func (p *TransIPProvider) dnsEntriesAreEqual(a, b transip.DNSEntries) bool {
	if len(a) != len(b) {
		return false
	}

	match := 0
	for _, aa := range a {
		for _, bb := range b {
			if aa.Content != bb.Content {
				continue
			}

			if aa.Name != bb.Name {
				continue
			}

			if aa.TTL != bb.TTL {
				continue
			}

			if aa.Type != bb.Type {
				continue
			}

			match++
		}
	}

	return (len(a) == match)
}

// removeEndpointFromEntries removes DNS entries from zone's set that match the
// type and name from given endpoint and returns the resulting DNS entry set
func (p *TransIPProvider) removeEndpointFromEntries(ep *endpoint.Endpoint, zone transip.Domain) transip.DNSEntries {
	// create new entry set
	entries := transip.DNSEntries{}
	// go over each DNS entry to see if it is a match
	for _, e := range zone.DNSEntries {
		// if we have match, don't copy it to the new entry set
		if p.endpointNameForRecord(e, zone) == ep.DNSName && string(e.Type) == ep.RecordType {
			log.WithFields(log.Fields{
				"name":    e.Name,
				"content": e.Content,
				"type":    e.Type,
			}).Debug("found match")
			continue
		}

		entries = append(entries, e)
	}

	return entries
}

// addEndpointToEntries creates DNS entries for given endpoint and returns
// resulting DNS entry set
func (p *TransIPProvider) addEndpointToEntries(ep *endpoint.Endpoint, zone transip.Domain, entries transip.DNSEntries) transip.DNSEntries {
	ttl := p.getMinimalValidTTL(ep)
	for _, target := range ep.Targets {
		log.WithFields(log.Fields{
			"zone":       zone.Name,
			"dnsname":    ep.DNSName,
			"recordtype": ep.RecordType,
			"ttl":        ttl,
			"target":     target,
		}).Debugf("adding new record")
		entries = append(entries, transip.DNSEntry{
			Name:    p.recordNameForEndpoint(ep, zone),
			TTL:     ttl,
			Type:    transip.DNSEntryType(ep.RecordType),
			Content: target,
		})
	}

	return entries
}

// zoneForZoneName returns the zone mapped to given name or error if zone could
// not be found
func (p *TransIPProvider) zoneForZoneName(name string, m provider.ZoneIDName, z map[string]transip.Domain) (transip.Domain, error) {
	_, zoneName := m.FindZone(name)
	if zoneName == "" {
		return transip.Domain{}, fmt.Errorf("could not find zoneName for %s", name)
	}

	zone, ok := z[zoneName]
	if !ok {
		return zone, fmt.Errorf("could not find zone for %s", zoneName)
	}

	return zone, nil
}