#pragma once

#include "envoy/common/pure.h"

#include "absl/strings/string_view.h"

#include "absl/types/optional.h"

namespace Envoy {

namespace Stats {

/**

 * CustomStatNamespaces manages custom stat namespaces. Custom stat namespaces are registered

 * by extensions that create user-defined metrics, and these metrics are all prefixed

 * by the namespace. For example, Wasm extension registers "wasmcustom" as a custom stat namespace,

 * and all the metrics created by user Wasm programs are prefixed by "wasmcustom." internally.

 * This is mainly for distinguishing these "custom metrics" defined outside Envoy codebase from

 * the native metrics defined by Envoy codebase, and this way stat sinks are able to determine

 * how to expose these two kinds of metrics.

 * Note that the implementation will not be thread-safe so users of this class must be in the main

 * thread.

 */

class CustomStatNamespaces {

public:

  /**

   * @param name is the name to check.

   * @return true if the given name is registered as a custom stat namespace, false otherwise.

   */

  virtual bool registered(const absl::string_view name) const PURE;

  /**

   * Used to register a custom namespace by extensions.

   * @param name is the name to register.

   */

  virtual void registerStatNamespace(const absl::string_view name) PURE;

  /**

   * Strips the registered custom stat namespace from the given stat name's prefix if it lives in a

   * registered custom stat namespace, and the stripped string is returned. Otherwise return

   * nullopt.

   * @param stat_name is the view to modify. If it is not in any custom registered namespaces, it

   * will never be modified.

   * @return the stripped string if stat_name has a registered custom stat namespace. Otherwise,

   * return nullopt.

   */

  virtual absl::optional<absl::string_view>

  stripRegisteredPrefix(const absl::string_view stat_name) const PURE;

};

} // namespace Stats

} // namespace Envoy