package hetznerv2

import (
	"context"
	"encoding/json"
	"errors"

	"github.com/hetznercloud/hcloud-go/v2/hcloud"
	"golang.org/x/net/idna"

	"github.com/StackExchange/dnscontrol/v4/models"
	"github.com/StackExchange/dnscontrol/v4/pkg/diff2"
	"github.com/StackExchange/dnscontrol/v4/pkg/txtutil"
	"github.com/StackExchange/dnscontrol/v4/pkg/version"
	"github.com/StackExchange/dnscontrol/v4/pkg/zonecache"
	"github.com/StackExchange/dnscontrol/v4/providers"
)

var features = providers.DocumentationNotes{
	// The default for unlisted capabilities is 'Cannot'.
	// See providers/capabilities.go for the entire list of capabilities.
	providers.CanAutoDNSSEC:          providers.Cannot(),
	providers.CanConcur:              providers.Can(),
	providers.CanGetZones:            providers.Can(),
	providers.CanOnlyDiff1Features:   providers.Can(),
	providers.CanUseAlias:            providers.Cannot(),
	providers.CanUseCAA:              providers.Can(),
	providers.CanUseDS:               providers.Can(),
	providers.CanUseDSForChildren:    providers.Cannot(),
	providers.CanUseLOC:              providers.Cannot(),
	providers.CanUseNAPTR:            providers.Cannot(),
	providers.CanUsePTR:              providers.Can(),
	providers.CanUseSOA:              providers.Cannot(),
	providers.CanUseSRV:              providers.Can(),
	providers.CanUseSVCB:             providers.Can(),
	providers.CanUseHTTPS:            providers.Can(),
	providers.CanUseSSHFP:            providers.Cannot(),
	providers.CanUseTLSA:             providers.Can(),
	providers.DocCreateDomains:       providers.Can(),
	providers.DocOfficiallySupported: providers.Cannot(),
	providers.DocDualHost:            providers.Can(),
}

func init() {
	const providerName = "HETZNER_V2"
	const providerMaintainer = "@das7pad"
	fns := providers.DspFuncs{
		Initializer:   New,
		RecordAuditor: AuditRecords,
	}
	providers.RegisterDomainServiceProviderType(providerName, fns, features)
	providers.RegisterMaintainer(providerName, providerMaintainer)
}

// New creates a new API handle.
func New(settings map[string]string, _ json.RawMessage) (providers.DNSServiceProvider, error) {
	apiToken := settings["api_token"]
	if apiToken == "" {
		return nil, errors.New("missing HETZNER_V2 api_token")
	}

	h := &hetznerv2Provider{
		client: hcloud.NewClient(
			hcloud.WithToken(apiToken),
			hcloud.WithApplication("dnscontrol", version.Version()),
		),
	}
	h.zoneCache = zonecache.New(h.fetchAllZones)
	return h, nil
}

type hetznerv2Provider struct {
	zoneCache zonecache.ZoneCache[*hcloud.Zone]
	client    *hcloud.Client
}

// fetchAllZones is used by the zonecache.ZoneCache.
func (h *hetznerv2Provider) fetchAllZones() (map[string]*hcloud.Zone, error) {
	flat, err := h.client.Zone.All(context.Background())
	if err != nil {
		return nil, err
	}
	zones := make(map[string]*hcloud.Zone, len(flat))
	for _, z := range flat {
		zones[z.Name] = z
	}
	return zones, nil
}

// EnsureZoneExists creates a zone if it does not exist
func (h *hetznerv2Provider) EnsureZoneExists(domain string, _ map[string]string) error {
	encoded, err := idna.ToASCII(domain)
	if err != nil {
		return err
	}
	if ok, err2 := h.zoneCache.HasZone(encoded); err2 != nil || ok {
		return err2
	}
	result, _, err := h.client.Zone.Create(context.Background(), hcloud.ZoneCreateOpts{
		Name: encoded,
		Mode: hcloud.ZoneModePrimary,
	})
	if err != nil {
		return err
	}
	err = h.client.Action.WaitFor(context.Background(), result.Action)
	if err != nil {
		return err
	}
	z, _, err := h.client.Zone.GetByID(context.Background(), result.Zone.ID)
	if err != nil {
		return err
	}
	h.zoneCache.SetZone(encoded, z)
	return nil
}

// GetZoneRecordsCorrections returns a list of corrections that will turn existing records into dc.Records.
func (h *hetznerv2Provider) GetZoneRecordsCorrections(dc *models.DomainConfig, existingRecords models.Records) ([]*models.Correction, int, error) {
	encoded, err := idna.ToASCII(dc.Name)
	if err != nil {
		return nil, 0, err
	}

	z, err := h.zoneCache.GetZone(encoded)
	if err != nil {
		return nil, 0, err
	}

	// Hetzner Cloud has a "ByRecordSet" API for DNS.
	// At each label:rtype pair, we either delete all records or UPSERT the desired records.
	instructions, actualChangeCount, err := diff2.ByRecordSet(existingRecords, dc, nil)
	if err != nil {
		return nil, 0, err
	}

	var reports []*models.Correction
	for _, instruction := range instructions {
		switch instruction.Type {
		case diff2.REPORT:
			reports = append(reports, &models.Correction{
				Msg: instruction.MsgsJoined,
			})
			continue
		case diff2.CREATE:
			first := instruction.New[0]
			ttl := int(first.TTL)
			opts := hcloud.ZoneRRSetCreateOpts{
				Name: first.Name,
				Type: hcloud.ZoneRRSetType(first.Type),
				TTL:  &ttl,
			}
			for _, r := range instruction.New {
				opts.Records = append(opts.Records, hcloud.ZoneRRSetRecord{
					Value: r.GetTargetCombinedFunc(txtutil.EncodeQuoted),
				})
			}
			reports = append(reports, &models.Correction{
				F: func() error {
					_, _, err2 := h.client.Zone.CreateRRSet(context.Background(), z, opts)
					return err2
				},
				Msg: instruction.MsgsJoined,
			})
		case diff2.CHANGE:
			rrSet := instruction.Old[0].Original.(*hcloud.ZoneRRSet)
			reports = append(reports, &models.Correction{
				F: func() error {
					if instruction.New[0].TTL != instruction.Old[0].TTL {
						ttl := int(instruction.New[0].TTL)
						opts := hcloud.ZoneRRSetChangeTTLOpts{TTL: &ttl}
						_, _, err2 := h.client.Zone.ChangeRRSetTTL(context.Background(), rrSet, opts)
						if err2 != nil {
							return err2
						}
					}

					opts := hcloud.ZoneRRSetSetRecordsOpts{}
					for _, r := range instruction.New {
						opts.Records = append(opts.Records, hcloud.ZoneRRSetRecord{
							Value: r.GetTargetCombinedFunc(txtutil.EncodeQuoted),
						})
					}
					_, _, err2 := h.client.Zone.SetRRSetRecords(context.Background(), rrSet, opts)
					return err2
				},
				Msg: instruction.MsgsJoined,
			})
		case diff2.DELETE:
			reports = append(reports, &models.Correction{
				F: func() error {
					rc := instruction.Old[0].Original.(*hcloud.ZoneRRSet)
					_, _, err2 := h.client.Zone.DeleteRRSet(context.Background(), rc)
					return err2
				},
				Msg: instruction.MsgsJoined,
			})
		}
	}

	return reports, actualChangeCount, nil
}

// GetNameservers returns the nameservers for a domain.
func (h *hetznerv2Provider) GetNameservers(domain string) ([]*models.Nameserver, error) {
	encoded, err := idna.ToASCII(domain)
	if err != nil {
		return nil, err
	}
	z, err := h.zoneCache.GetZone(encoded)
	if err != nil {
		return nil, err
	}
	return models.ToNameserversStripTD(z.AuthoritativeNameservers.Assigned)
}

// GetZoneRecords gets the records of a zone and returns them in RecordConfig format.
func (h *hetznerv2Provider) GetZoneRecords(domain string, _ map[string]string) (models.Records, error) {
	encoded, err := idna.ToASCII(domain)
	if err != nil {
		return nil, err
	}
	z, err := h.zoneCache.GetZone(encoded)
	if err != nil {
		return nil, err
	}
	opts := hcloud.ZoneRRSetListOpts{}
	opts.PerPage = 100
	records, err := h.client.Zone.AllRRSetsWithOpts(context.Background(), z, opts)
	if err != nil {
		return nil, err
	}
	existingRecords := make([]*models.RecordConfig, 0, len(records))
	for _, rrSet := range records {
		if rrSet.Type == hcloud.ZoneRRSetTypeSOA {
			// SOA records are not available for editing, hide them.
			continue
		}
		base := models.RecordConfig{
			Type:     string(rrSet.Type),
			Original: rrSet,
		}
		base.SetLabel(rrSet.Name, z.Name)
		if rrSet.TTL != nil {
			base.TTL = uint32(*rrSet.TTL)
		} else {
			base.TTL = uint32(z.TTL)
		}

		for _, r := range rrSet.Records {
			rc := base
			if err = rc.PopulateFromStringFunc(rc.Type, r.Value, z.Name, txtutil.ParseQuoted); err != nil {
				return nil, err
			}
			existingRecords = append(existingRecords, &rc)
		}
	}
	return existingRecords, nil
}

// ListZones lists the zones on this account.
func (h *hetznerv2Provider) ListZones() ([]string, error) {
	return h.zoneCache.GetZoneNames()
}