package cron

import (
	"context"
	"database/sql"
	"fmt"
	"log/slog"
	"sync"
	"time"

	cf "goflare/internal/cloudflare"
	"goflare/internal/database/queries"
	"goflare/internal/ipfetcher"

	"github.com/robfig/cron/v3"
)

const (
	settingKeyCurrentIP         = "current_ip"
	settingKeyCurrentIPUpdatedAt = "current_ip_updated_at"
	settingKeyCurrentIPSource   = "current_ip_source"
)

type DDNSUpdater struct {
	q        *queries.Queries
	cron     *cron.Cron
	entryID  cron.EntryID
	schedule string
	mu       sync.Mutex
	lastIP   string
}

func NewDDNSUpdater(q *queries.Queries) *DDNSUpdater {
	return &DDNSUpdater{
		q:    q,
		cron: cron.New(),
	}
}

func (u *DDNSUpdater) Start(schedule string) error {
	id, err := u.cron.AddFunc(schedule, u.run)
	if err != nil {
		return fmt.Errorf("invalid cron schedule %q: %w", schedule, err)
	}
	u.entryID = id
	u.schedule = schedule
	u.cron.Start()

	ctx := context.Background()
	cached, err := u.q.GetSetting(ctx, settingKeyCurrentIP)
	if err == nil && cached != "" {
		u.mu.Lock()
		u.lastIP = cached
		u.mu.Unlock()
	}
	if err != nil && err != sql.ErrNoRows {
		slog.Warn("failed to load current_ip setting", "error", err)
	}

	slog.Info("ddns updater started", "schedule", schedule)
	return nil
}

func (u *DDNSUpdater) Stop() {
	u.cron.Stop()
	slog.Info("ddns updater stopped")
}

func (u *DDNSUpdater) Schedule() string {
	u.mu.Lock()
	defer u.mu.Unlock()
	return u.schedule
}

func (u *DDNSUpdater) Reschedule(schedule string) error {
	u.mu.Lock()
	defer u.mu.Unlock()

	id, err := u.cron.AddFunc(schedule, u.run)
	if err != nil {
		return fmt.Errorf("invalid cron schedule %q: %w", schedule, err)
	}

	u.cron.Remove(u.entryID)
	u.entryID = id
	u.schedule = schedule
	slog.Info("ddns updater rescheduled", "schedule", schedule)
	return nil
}

func (u *DDNSUpdater) run() {
	ctx := context.Background()

	urls, err := u.q.ListEnabledIpProviderUrls(ctx)
	if err != nil {
		slog.Error("failed to load IP providers", "error", err)
		return
	}
	var urlsOrNil []string
	if len(urls) > 0 {
		urlsOrNil = urls
	}
	res, err := ipfetcher.FetchPublicIPFrom(ctx, urlsOrNil)
	if err != nil {
		slog.Error("failed to fetch public IP", "error", err)
		return
	}
	ip := res.IP

	u.mu.Lock()
	lastIP := u.lastIP
	u.mu.Unlock()

	if ip == lastIP {
		slog.Debug("public IP unchanged", "ip", ip)
		return
	}

	slog.Info("public IP changed", "old", lastIP, "new", ip)

	records, err := u.q.ListNonStaticRecords(ctx)
	if err != nil {
		slog.Error("failed to list non-static records", "error", err)
		return
	}

	if len(records) == 0 {
		now := time.Now().UTC().Format(time.RFC3339)
		if err := u.q.UpsertSetting(ctx, queries.UpsertSettingParams{Key: settingKeyCurrentIP, Value: ip}); err != nil {
			slog.Error("failed to persist current_ip", "error", err)
		} else if err := u.q.UpsertSetting(ctx, queries.UpsertSettingParams{Key: settingKeyCurrentIPUpdatedAt, Value: now}); err != nil {
			slog.Error("failed to persist current_ip_updated_at", "error", err)
		} else if err := u.q.UpsertSetting(ctx, queries.UpsertSettingParams{Key: settingKeyCurrentIPSource, Value: res.Source}); err != nil {
			slog.Error("failed to persist current_ip_source", "error", err)
		}
		u.mu.Lock()
		u.lastIP = ip
		u.mu.Unlock()
		return
	}

	type zoneKey struct {
		apiKey string
		zoneID string
	}
	byZone := make(map[zoneKey][]queries.ListNonStaticRecordsRow)
	for _, rec := range records {
		k := zoneKey{apiKey: rec.ZoneApiKey, zoneID: rec.CfZoneID}
		byZone[k] = append(byZone[k], rec)
	}

	allOK := true
	for k, zoneRecs := range byZone {
		cfRecords := make([]cf.DNSRecord, len(zoneRecs))
		for i, rec := range zoneRecs {
			cfRecords[i] = cf.DNSRecord{
				ID:      rec.CfRecordID,
				Type:    rec.Type,
				Name:    rec.Name,
				Content: ip,
				Proxied: rec.Proxied == 1,
				TTL:     1, // auto
			}
		}

		if err := cf.BatchUpdateDNSRecords(ctx, k.apiKey, k.zoneID, cfRecords); err != nil {
			slog.Error("failed to batch update DNS records",
				"zone", k.zoneID,
				"count", len(zoneRecs),
				"error", err,
			)
			allOK = false
			continue
		}

		for _, rec := range zoneRecs {
			if err := u.q.UpdateRecordContent(ctx, queries.UpdateRecordContentParams{
				ID:      rec.ID,
				Content: ip,
			}); err != nil {
				slog.Error("failed to update local record content",
					"record", rec.Name,
					"error", err,
				)
				allOK = false
				continue
			}
			slog.Info("updated DNS record", "record", rec.Name, "ip", ip)
		}
	}

	if allOK {
		now := time.Now().UTC().Format(time.RFC3339)
		if err := u.q.UpsertSetting(ctx, queries.UpsertSettingParams{Key: settingKeyCurrentIP, Value: ip}); err != nil {
			slog.Error("failed to persist current_ip", "error", err)
		} else if err := u.q.UpsertSetting(ctx, queries.UpsertSettingParams{Key: settingKeyCurrentIPUpdatedAt, Value: now}); err != nil {
			slog.Error("failed to persist current_ip_updated_at", "error", err)
		} else if err := u.q.UpsertSetting(ctx, queries.UpsertSettingParams{Key: settingKeyCurrentIPSource, Value: res.Source}); err != nil {
			slog.Error("failed to persist current_ip_source", "error", err)
		}
		u.mu.Lock()
		u.lastIP = ip
		u.mu.Unlock()
	}
}