package dns

import (
	"bytes"
	"fmt"
	"io"
	"net/netip"
	"sort"
	"time"

	"darvaza.org/core"
	"github.com/libdns/libdns"
)

func (mgr *Manager) fqdn(name string) string {
	return fmt.Sprintf("%s.%s.", name, mgr.domain)
}

// SortAddrSlice sorts a slice of [netip.Addr]
func SortAddrSlice(s []netip.Addr) []netip.Addr {
	sort.Slice(s, func(i, j int) bool {
		return s[i].Less(s[j])
	})
	return s
}

// SortAddrRecords sorts a slice of [AddrRecord]
// by Name and Address
func SortAddrRecords(s []AddrRecord) []AddrRecord {
	sort.Slice(s, func(i, j int) bool {
		return s[i].Name < s[j].Name
	})

	for _, p := range s {
		SortAddrSlice(p.Addr)
	}

	return s
}

// SortRegions sorts regions. first by length those 3-character
// or shorter, and then by length. It's mostly aimed at
// supporting ISO-3166 order
func SortRegions(regions []string) []string {
	sort.Slice(regions, func(i, j int) bool {
		r1, r2 := regions[i], regions[j]

		switch {
		case len(r1) < 4:
			switch {
			case len(r1) < len(r2):
				return true
			case len(r1) > len(r2):
				return false
			default:
				return r1 < r2
			}
		case len(r2) < 4:
			return false
		default:
			return r1 < r2
		}
	})
	return regions
}

// AddrRecord represents an A or AAAA record
type AddrRecord struct {
	Name string
	Addr []netip.Addr
}

// Sort sorts the addresses of the record
func (rr *AddrRecord) Sort() {
	SortAddrSlice(rr.Addr)
}

// Export converts the record into libdns.Record
func (rr *AddrRecord) Export() []libdns.Record {
	out := make([]libdns.Record, len(rr.Addr))
	for i, addr := range rr.Addr {
		out[i] = libdns.Record{
			Name:  rr.Name,
			TTL:   time.Second * 1,
			Type:  core.IIf(addr.Is6(), "AAAA", "A"),
			Value: addr.String(),
		}
	}

	return out
}

// WriteTo writes the record in BIND notation
func (rr *AddrRecord) WriteTo(w io.Writer) (int64, error) {
	var total int
	for _, addr := range rr.Addr {
		n, err := fmt.Fprint(w,
			rr.Name, "\t",
			1, "\t",
			core.IIf(addr.Is6(), "AAAA", "A"), "\t",
			addr.String(), "\n")

		switch {
		case err != nil:
			return 0, err
		case n > 0:
			total += n
		}
	}

	return int64(total), nil
}

// String converts the record into BIND entries
func (rr *AddrRecord) String() string {
	var buf bytes.Buffer
	_, _ = rr.WriteTo(&buf)
	return buf.String()
}

func (mgr *Manager) genRegionsSorted() []string {
	regions := make([]string, 0, len(mgr.regions))
	for name := range mgr.regions {
		regions = append(regions, name)
	}

	return SortRegions(regions)
}

func (mgr *Manager) genAllAddrRecords() []AddrRecord {
	var out []AddrRecord

	cache := make(map[string][]netip.Addr)

	// zones
	for _, z := range mgr.zones {
		// hosts
		s := mgr.genZoneHostRecords(z)
		out = append(out, s...)

		// zone alias
		addrs := mgr.genZoneAddresses(z)
		name := z.Name

		out = append(out, AddrRecord{
			Name: name + mgr.suffix,
			Addr: addrs,
		})

		// and cache for regions
		cache[name] = addrs
	}

	for _, name := range mgr.genRegionsSorted() {
		var addrs []netip.Addr

		for _, z := range mgr.regions[name] {
			addrs = append(addrs, cache[z]...)
		}

		rec := AddrRecord{
			Name: name + mgr.suffix,
			Addr: addrs,
		}
		rec.Sort()

		out = append(out, rec)
	}

	SortAddrRecords(out)
	return out
}

func (*Manager) genZoneAddresses(z *Zone) []netip.Addr {
	var out []netip.Addr

	for _, p := range z.Hosts {
		if p.Active {
			out = append(out, p.Addrs...)
		}
	}

	SortAddrSlice(out)
	return out
}

func (mgr *Manager) genZoneHostRecords(z *Zone) []AddrRecord {
	out := make([]AddrRecord, 0, len(z.Hosts))

	for _, p := range z.Hosts {
		rec := AddrRecord{
			Name: p.String() + mgr.suffix,
			Addr: p.Addrs,
		}
		out = append(out, rec)
	}

	SortAddrRecords(out)
	return out
}

func (mgr *Manager) genRegionAddressesCached(name string,
	zones map[string][]netip.Addr) []netip.Addr {
	//
	var addrs []netip.Addr

	for _, zoneName := range mgr.regions[name] {
		addrs = append(addrs, zones[zoneName]...)
	}

	SortAddrSlice(addrs)
	return addrs
}