// Package updater runs dynamic DNS update passes across all configured entries.
package updater

import (
	"fmt"
	"log"
	"net"

	"git.aehoo.net/alphard/he-dydns/internal/config"
	"git.aehoo.net/alphard/he-dydns/internal/hedns"
	"git.aehoo.net/alphard/he-dydns/internal/network"
)

type cacheKey struct {
	hostname   string
	recordType config.RecordType
}

// Updater runs update passes and remembers the last address successfully
// published for each entry, so unchanged addresses aren't re-sent upstream.
type Updater struct {
	last map[cacheKey]net.IP
}

// New returns an Updater with no cached state; its first Run always
// publishes every entry that has a usable address.
func New() *Updater {
	return &Updater{last: make(map[cacheKey]net.IP)}
}

// Run discovers the current address(es) and updates entries whose address
// changed since the last successful update. It returns an error only when
// address discovery itself fails outright; per-entry update failures are
// logged and aggregated but do not stop other entries from being attempted.
func (u *Updater) Run(cfg *config.Config) error {
	addrs, err := network.Discover(cfg.Interface)
	if err != nil {
		return fmt.Errorf("discovering address: %w", err)
	}

	if addrs.Empty() {
		log.Printf("no address found (interface=%q); skipping update", cfg.Interface)
		return nil
	}

	if addrs.IPv4 != nil {
		log.Printf("discovered IPv4 address %s", addrs.IPv4)
	}
	if addrs.IPv6 != nil {
		log.Printf("discovered IPv6 address %s", addrs.IPv6)
	}

	var failures int
	for _, entry := range cfg.Entries {
		var ip net.IP
		switch entry.RecordType {
		case config.RecordTypeAAAA:
			ip = addrs.IPv6
		default:
			ip = addrs.IPv4
		}

		if ip == nil {
			log.Printf("no %s address available for %s; skipping", entry.RecordType, entry.Hostname)
			continue
		}

		key := cacheKey{hostname: entry.Hostname, recordType: entry.RecordType}
		if last, ok := u.last[key]; ok && last.Equal(ip) {
			log.Printf("%s (%s) unchanged at %s; skipping update", entry.Hostname, entry.RecordType, ip)
			continue
		}

		if err := hedns.Update(entry.Hostname, entry.Token, ip); err != nil {
			log.Printf("error: %v", err)
			failures++
			continue
		}

		log.Printf("updated %s (%s) -> %s", entry.Hostname, entry.RecordType, ip)
		u.last[key] = ip
	}

	if failures > 0 {
		return fmt.Errorf("%d update(s) failed", failures)
	}
	return nil
}