storage

type Event struct {
	Key       string
	Value     []byte
	Revision  int64
	IsCreated bool
	IsDeleted bool

	// Error management
	Error   error
	IsError bool
}

type Filter interface {
	// Filter is a predicate that inspects a value (protocol buffer message instance) and returns true if and only if the value should remain in the set
	Filter(val proto.Message) bool
}

type Interface interface {
	// Endpoints returns an array of endpoints for the storage
	Endpoints() []string

	// Connect to etcd using client v3 api
	Connect() error

	// Close connection to etcd
	Close() error

	// Create adds a new object at a key unless it already exists. 'ttl' is time-to-live
	// in seconds (0 means forever). If no error is returned and out is not nil, out will be
	// set to the read value from database.
	Create(ctx context.Context, key string, val proto.Message, out proto.Message, ttl int64) error

	// Put adds a new value to a key if the key does not already exist; else it updates the value passed
	// to the specified key. 'ttl' is time-to-live in seconds (0 means forever).
	Put(ctx context.Context, key string, val proto.Message, ttl int64) error

	// Get unmarshals the protocol buffer message found at key into out, if found.
	// If not found and ignoreNotFound is set, then out will be a zero object, otherwise
	// error will be set to not found. A non-existing node or an empty response are both
	// treated as not found.
	Get(ctx context.Context, key string, out proto.Message, ignoreNotFound bool) error

	// Delete(ctx context.Context, key string, recurse bool, out proto.Message) error
	// TODO: will need to add preconditions support
	// if recurse then all the key having the same path under 'key' are going to be deleted
	// if !recurse then only 'key' is going to be deleted
	Delete(ctx context.Context, key string, recurse bool, out proto.Message) error

	// Update performs a guaranteed update, which means it will continue to retry until an update succeeds or the request is canceled.
	// Update(ctx context.Context, key string, type interface, ignoreNotFound bool, preconditions *Preconditions, tryUpdate UpdateFunc) error
	// TODO: the following is a temporary interface
	Update(ctx context.Context, key string, val proto.Message, ttl int64) error

	// List returns all the values that match the filter.
	List(ctx context.Context, key string, filter Filter, obj proto.Message, out *[]proto.Message) error

	// Watch begins watching the specified key.
	Watch(ctx context.Context, key string, resourceVersion int64, filter Filter) (WatchInterface, error)

	// WatchList begins watching the specified key's items.
	WatchList(ctx context.Context, key string, resourceVersion int64, filter Filter) (WatchInterface, error)

	// CompareAndSet atomically sets the value to the given updated value if the current value == the expected value
	CompareAndSet(ctx context.Context, key string, expect proto.Message, update proto.Message) error
}

type WatchInterface interface {
	// Stops watching. Will close the channel returned by ResultChan(). Releases
	// any resources used by the watch.
	Stop()

	// Returns a chan which will receive all the events. If an error occurs
	// or Stop() is called, this channel will be closed, in which case the
	// watch should be completely cleaned up.
	ResultChan() <-chan Event
}