package shortify

import (
	"errors"
	"log"

	"go.etcd.io/bbolt"
)

var bucketName = []byte("shorturls")

func (s *Shortener) get(shortID string) (string, error) {
	if val, ok := s.memStore.Load(shortID); ok {
		s.cache.Add(shortID, val.(string))
		return val.(string), nil
	}

	if val, ok := s.cache.Get(shortID); ok {
		return val.(string), nil
	}

	var longURL string
	err := s.db.View(func(tx *bbolt.Tx) error {
		b := tx.Bucket(bucketName)
		if b == nil {
			return errors.New("not found")
		}
		v := b.Get([]byte(shortID))
		if v != nil {
			longURL = string(v)
			s.cache.Add(shortID, longURL)
			return nil
		}
		return errors.New("not found")
	})

	return longURL, err
}

func (s *Shortener) put(shortID, longURL string) error {

	s.memStore.Store(shortID, longURL)
	s.cache.Add(shortID, longURL)

	// Queue write to DB (non-blocking)
	select {
	case s.writeChan <- [2]string{shortID, longURL}:
	default:
		log.Println("Warning: write queue full, short URL write may be dropped")
	}

	return nil
}

func (s *Shortener) asyncDBWriter() {
	for pair := range s.writeChan {
		shortID := pair[0]
		longURL := pair[1]

		err := s.db.Update(func(tx *bbolt.Tx) error {
			b, err := tx.CreateBucketIfNotExists(bucketName)
			if err != nil {
				return err
			}
			return b.Put([]byte(shortID), []byte(longURL))
		})
		if err != nil {
			log.Printf("DB write failed for %s: %v", shortID, err)
		}
	}
}