kv

type Client interface {
	// Get a spefic key.  Will use a codec to deserialise key to appropriate type.
	Get(ctx context.Context, key string) (interface{}, error)

	// CAS stands for Compare-And-Swap.  Will call provided callback f with the
	// current value of the key and allow callback to return a different value.
	// Will then attempt to atomically swap the current value for the new value.
	// If that doesn't succeed will try again - callback will be called again
	// with new value etc.  Guarantees that only a single concurrent CAS
	// succeeds.  Callback can return nil to indicate it is happy with existing
	// value.
	CAS(ctx context.Context, key string, f func(in interface{}) (out interface{}, retry bool, err error)) error

	// WatchKey calls f whenever the value stored under key changes.
	WatchKey(ctx context.Context, key string, f func(interface{}) bool)

	// WatchPrefix calls f whenever any value stored under prefix changes.
	WatchPrefix(ctx context.Context, prefix string, f func(string, interface{}) bool)
}

type Config struct {
	Store  string        `yaml:"store,omitempty"`
	Consul consul.Config `yaml:"consul,omitempty"`
	Etcd   etcd.Config   `yaml:"etcd,omitempty"`
	Prefix string        `yaml:"prefix,omitempty"`

	Mock Client
}