package main

import (
	"PangolinDNS/pangolin"
	"context"
	"fmt"
	"net/netip"
	"os"
	"reflect"
	"time"

	"github.com/go-playground/validator/v10"
	_ "github.com/joho/godotenv/autoload"
	"github.com/libdns/cloudflare"
	"github.com/libdns/libdns"
	"github.com/libdns/route53"
	"github.com/samber/lo"
	log "github.com/sirupsen/logrus"
	"github.com/spf13/viper"
)

const (
	defaultTTL = 60 * 24 * time.Minute
)

type Config struct {
	Interval   time.Duration    `mapstructure:"interval" validate:"required"`
	DNS        DNSConfig        `mapstructure:"dns" validate:"required"`
	Pangolin   PangolinConfig   `mapstructure:"pangolin" validate:"required"`
	Cloudflare CloudflareConfig `mapstructure:"cloudflare" validate:"-"`
	Route53    Route53Config    `mapstructure:"route53" validate:"-"`
}

type PangolinConfig struct {
	URL           string   `mapstructure:"url" validate:"required,url"`
	Key           string   `mapstructure:"key" validate:"required"`
	Organizations []string `mapstructure:"orgs" validate:"required"`
}

type CloudflareConfig struct {
	Token string `mapstructure:"token" validate:"required"`
}

type Route53Config struct {
	Region    string `mapstructure:"region" validate:"required"`
	AccessKey string `mapstructure:"access_key" validate:"required"`
	SecretKey string `mapstructure:"secret_key" validate:"required"`
}

type DNSConfig struct {
	Provider string               `mapstructure:"provider" validate:"required"`
	Default  DNSTarget            `mapstructure:"default" validate:"required"`
	Domains  map[string]DNSTarget `mapstructure:"domains" validate:"dive"`
}

type DNSTarget struct {
	CNAME   string        `mapstructure:"cname" validate:"required_without=Address,omitempty,hostname|fqdn"`
	Address string        `mapstructure:"address" validate:"required_without=CNAME,omitempty,ip"`
	TTL     time.Duration `mapstructure:"ttl"`
}

type DNSSync struct {
	cfg           Config
	pangolin      *pangolin.Client
	provider      libdns.RecordSetter
	resourceCache map[string]bool
}

func main() {
	var provider libdns.RecordSetter

	v := viper.NewWithOptions(viper.KeyDelimiter("::"))
	v.SetConfigFile("config.yaml")

	if err := v.ReadInConfig(); err != nil {
		log.WithError(err).Fatal("Error reading config")
	}

	var cfg Config

	if err := v.Unmarshal(&cfg); err != nil {
		log.WithError(err).Fatal("Error unmarshalling config")
	}

	validate := validator.New()

	validate.RegisterStructValidation(func(sl validator.StructLevel) {
		cfg := sl.Current().Interface().(Config)

		t := reflect.TypeOf(cfg)
		cfgValue := reflect.ValueOf(cfg)

		for i := 0; i < t.NumField(); i++ {
			field := t.Field(i)
			fieldName := field.Tag.Get("mapstructure")

			if fieldName != cfg.DNS.Provider {
				continue
			}

			if err := validate.Struct(cfgValue.Field(i).Interface()); err != nil {
				for _, e := range err.(validator.ValidationErrors) {
					sl.ReportError(
						e.Value(),
						fieldName+"."+e.Field(),
						e.StructField(),
						e.Tag(),
						e.Param(),
					)
				}
			}

			break
		}
	}, Config{})

	if err := validate.Struct(cfg); err != nil {
		fmt.Println(err)
		os.Exit(1)
	}

	switch cfg.DNS.Provider {
	case "cloudflare":
		provider = &cloudflare.Provider{
			APIToken: cfg.Cloudflare.Token,
		}
	case "route53":
		provider = &route53.Provider{
			Region:          cfg.Route53.Region,
			AccessKeyId:     cfg.Route53.AccessKey,
			SecretAccessKey: cfg.Route53.SecretKey,
		}
	case "example":
		provider = &ExampleSetter{}
	default:
		log.Fatalf("Unsupported provider %s", cfg.DNS.Provider)
	}

	p := pangolin.New(cfg.Pangolin.URL, cfg.Pangolin.Key)

	s := &DNSSync{
		cfg:           cfg,
		provider:      provider,
		pangolin:      p,
		resourceCache: make(map[string]bool),
	}

	// On initial startup, always push domains
	s.checkResources(true)

	if cfg.Interval <= 0 {
		return
	}

	t := time.NewTicker(cfg.Interval)
	for {
		<-t.C

		s.checkResources(false)
	}
}

func (d *DNSSync) checkResources(force bool) {
	for _, org := range d.cfg.Pangolin.Organizations {
		log.Infof("Reading domains from org %s", org)
		domains, err := d.pangolin.Domains(org)

		if err != nil {
			log.WithFields(log.Fields{
				"error": err,
				"org":   org,
			}).Fatal("Unable to fetch domains for org")
		}

		resources, err := d.pangolin.Resources(org)

		if err != nil {
			log.WithFields(log.Fields{
				"error": err,
				"org":   org,
			}).Fatal("Unable to fetch resources for org")
		}

		log.Info("Mapping domains to keys")

		domainKeys := lo.Associate(domains, func(domain pangolin.Domain) (string, string) {
			return domain.ID, domain.BaseDomain
		})

		log.Info("Mapping records to domains")

		recordMap := lo.GroupBy(resources, func(record pangolin.Resource) string {
			return domainKeys[record.DomainID]
		})

		for domain, res := range recordMap {
			log.Infof("Building domain list for %s", domain)
			zone := domain + "."

			if !force {
				res = lo.Filter(res, func(record pangolin.Resource, _ int) bool {
					_, ok := d.resourceCache[record.FullDomain]
					return !ok
				})
			}

			records := lo.Map(res, func(resource pangolin.Resource, _ int) libdns.Record {
				if target, ok := d.cfg.DNS.Domains[domain]; ok {
					return recordFromTarget(resource.FullDomain, target)
				}

				return recordFromTarget(resource.FullDomain, d.cfg.DNS.Default)
			})

			changed, err := d.provider.SetRecords(context.Background(), zone, records)

			if err != nil {
				log.WithFields(log.Fields{
					"error":  err,
					"org":    org,
					"domain": domain,
				}).Fatal("Unable to set records for domain")
			}

			for _, changed := range changed {
				log.Infof("Updated record %s", changed.RR())
			}

			// Ensure all resources we checked are set in the cache for future runs
			for _, res := range resources {
				d.resourceCache[res.FullDomain] = true
			}
		}
	}
}

func recordFromTarget(name string, target DNSTarget) libdns.Record {
	ttl := defaultTTL

	if target.TTL > 0 {
		ttl = target.TTL
	}

	if target.CNAME != "" {
		return libdns.CNAME{
			Name:   name,
			TTL:    ttl,
			Target: target.CNAME,
		}
	}

	if target.Address != "" {
		return libdns.Address{
			Name: name,
			TTL:  ttl,
			IP:   netip.MustParseAddr(target.Address),
		}
	}

	panic("no target defined for domain")
}