#pragma once

#include <functional>

#include <string>

#include "envoy/common/optref.h"

#include "envoy/common/pure.h"

#include "envoy/http/header_map.h"

#include "absl/strings/string_view.h"

#include "absl/types/optional.h"

namespace Envoy {

namespace Tracing {

class TraceContextHandler;

/**

 * Protocol-independent abstraction for traceable stream. It hides the differences between different

 * protocol and provides tracer driver with common methods for obtaining and setting the tracing

 * context.

 */

class TraceContext {

public:

  using IterateCallback = std::function<bool(absl::string_view key, absl::string_view val)>;

  /**

   * Get context protocol.

   *

   * @return A string view representing the protocol of the traceable stream behind the context.

   */

  virtual absl::string_view protocol() const PURE;

  /**

   * Get context host.

   *

   * @return The host of traceable stream. It typically should be domain, VIP, or service name that

   * used to represents target service instances.

   */

  virtual absl::string_view host() const PURE;

  /**

   * Get context path.

   *

   * @return The path of traceable stream. The content and meaning of path are determined by

   * specific protocol itself.

   */

  virtual absl::string_view path() const PURE;

  /**

   * Get context method.

   *

   * @return The method of traceable stream. The content and meaning of method are determined by

   * specific protocol itself.

   */

  virtual absl::string_view method() const PURE;

  /**

   * Iterate over all context entry.

   *

   * @param callback supplies the iteration callback.

   */

  virtual void forEach(IterateCallback callback) const PURE;

  /**

   * Get tracing context value by key.

   *

   * @param key The context key of string view type.

   * @return The optional context value of string_view type.

   */

  virtual absl::optional<absl::string_view> get(absl::string_view key) const PURE;

  /**

   * Set new tracing context key/value pair.

   *

   * @param key The context key of string view type.

   * @param val The context value of string view type.

   */

  virtual void set(absl::string_view key, absl::string_view val) PURE;

  /**

   * Removes the following key and its associated values from the tracing

   * context.

   *

   * @param key The key to remove if it exists.

   */

  virtual void remove(absl::string_view key) PURE;

  /**

   * Optional HTTP request headers map. This is valid for HTTP protocol or any protocol that

   * that provides HTTP request headers.

   */

};

} // namespace Tracing

} // namespace Envoy