package store

import (
	"database/sql"
	"errors"
	"time"
)

var ErrInstanceLimit = errors.New("instance limit reached")

func reserveSlot(tx *sql.Tx, uid string) error {
	var count int
	if err := tx.QueryRow(`SELECT count(*) FROM instances WHERE uid=?`, uid).Scan(&count); err != nil {
		return err
	}
	if count >= 2 {
		return ErrInstanceLimit
	}
	return nil
}

func (s *Store) ReserveInstance(i Instance) error {
	tx, err := s.DB.Begin()
	if err != nil {
		return err
	}
	defer tx.Rollback()
	if err = reserveSlot(tx, i.UID); err != nil {
		return err
	}
	if err = insertInstance(tx, i); err != nil {
		return err
	}
	return tx.Commit()
}
func insertInstance(tx *sql.Tx, i Instance) error {
	_, err := tx.Exec(`INSERT INTO instances VALUES(?,?,?,?,?,?,?,?)`, i.ID, i.UID, i.Name, i.Version, i.ImageID, i.Status, i.ContainerID, time.Now().Unix())
	return err
}