package app

import (
	"context"
	"crypto/sha256"
	"fmt"
	"os"
	"path/filepath"
	"sort"
	"time"
)

// watchLocalZones reloads projected ConfigMap files on every replica. A
// Kubernetes ConfigMap volume swaps its ..data symlink atomically when the UI
// edits a zone; polling the contents keeps both pods in sync without routing
// DNS changes through a single pod.
func (a *App) watchLocalZones(ctx context.Context) {
	if a.zones == nil {
		return
	}
	last, _ := a.localZoneFingerprint()
	ticker := time.NewTicker(2 * time.Second)
	defer ticker.Stop()
	for {
		select {
		case <-ctx.Done():
			return
		case <-ticker.C:
			next, err := a.localZoneFingerprint()
			if err != nil {
				a.log.Warn("local zone change check failed", "error", err)
				continue
			}
			if next == last {
				continue
			}
			a.reloadLocalZones()
			if a.cache != nil {
				a.cache.Flush()
			}
			last = next
		}
	}
}

func (a *App) localZoneFingerprint() (string, error) {
	paths := make([]string, 0)
	for _, configured := range a.cfg.Get().Block.LocalZones {
		path := a.cfg.Get().AbsPath(configured)
		if matches, err := filepath.Glob(path); err == nil && len(matches) > 0 {
			paths = append(paths, matches...)
			continue
		}
		if info, err := os.Stat(path); err == nil && info.IsDir() {
			matches, err := filepath.Glob(filepath.Join(path, "*.zone"))
			if err != nil {
				return "", err
			}
			paths = append(paths, matches...)
			continue
		}
	}
	sort.Strings(paths)
	h := sha256.New()
	for _, path := range paths {
		b, err := os.ReadFile(path)
		if err != nil {
			return "", fmt.Errorf("read %s: %w", path, err)
		}
		_, _ = h.Write([]byte(path))
		_, _ = h.Write([]byte{0})
		_, _ = h.Write(b)
		_, _ = h.Write([]byte{0})
	}
	return fmt.Sprintf("%x", h.Sum(nil)), nil
}