package dns

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

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

// 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()
}