package storage

import (
	"errors"
	"sync"
)

var (
	ErrNoSuchKey = errors.New("no such key in store")
	ErrKeyExists = errors.New("key already exists")
)

// Item is an item in a datastore.
type Item interface {
	// Item is lockable if updating data item directly.
	sync.Locker

	// Dirty sets the dirty flag for the item so it will be flushed.
	Dirty()

	// IsDirty gets the dirty flag for the item.
	IsDirty() bool

	// GetData gets the data for the item.
	GetData() interface{}

	// GetData sets the data for the item.
	SetData(interface{})

	// ItemKey gets the key of the item.
	ItemKey() string
}

// Store represents a datastore.
type Store interface {
	// GetItem loads the specified key from the store into data and returns the Item.
	// If err is ErrKeyExists, Item will be the existing item.
	GetItem(key string, data interface{}) (Item, error)

	// Get is the same as GetItem, but only returns error.
	Get(key string, data interface{}) error

	// Put puts the specified key into the store. If the key already exists, it clobbers.
	// Note that any existing items will then dangle.
	Put(key string, version, minorVersion int, secretMode bool, data interface{}) (Item, error)

	// FlushAll flushes the store to backing.
	FlushAll() []error

	// Flush flushes a single key to backing.
	Flush(key string) error

	// Shutdown is called to quiesce and shutdown the store.
	Shutdown()
}