// Adapter is the interface for configuration retrieving.
type Adapter interface {
	// Available checks and returns the configuration service is available.
	// The optional parameter `resource` specifies certain configuration resource.
	//
	// It returns true if configuration file is present in default AdapterFile, or else false.
	// Note that this function does not return error as it just does simply check for backend configuration service.
	Available(ctx context.Context, resource ...string) (ok bool)

	// Get retrieves and returns value by specified `pattern`.
	Get(ctx context.Context, pattern string) (value interface{}, err error)

	// Data retrieves and returns all configuration data as map type.
	// Note that this function may lead lots of memory usage if configuration data is too large,
	// you can implement this function if necessary.
	Data(ctx context.Context) (data map[string]interface{}, err error)
}

// SetAdapter sets the adapter of current Config object.
func (c *Config) SetAdapter(adapter Adapter)

// GetAdapter returns the adapter of current Config object.
func (c *Config) GetAdapter() Adapter