#pragma once

#include <string>

#include "envoy/data/accesslog/v3/accesslog.pb.h"

#include "envoy/stream_info/stream_info.h"

#include "envoy/tracing/trace_context.h"

#include "absl/container/flat_hash_map.h"

#include "absl/strings/string_view.h"

namespace Envoy {

namespace Formatter {

class Context;

}

namespace Tracing {

/**

 * The context for the custom tag to obtain the tag value.

 */

struct CustomTagContext {

  const TraceContext& trace_context;

  const StreamInfo::StreamInfo& stream_info;

  const Formatter::Context& formatter_context;

};

class Span;

/**

 * Tracing custom tag, with tag name and how it would be applied to the span.

 */

class CustomTag {

public:

  /**

   * @return the tag name view.

   */

  virtual absl::string_view tag() const PURE;

  /**

   * The way how to apply the custom tag to the span,

   * generally obtain the tag value from the context and attached it to the span.

   * @param span the active span.

   * @param ctx the custom tag context.

   */

  virtual void applySpan(Span& span, const CustomTagContext& ctx) const PURE;

  /**

   * Get string tag value from various type of custom tags. (e.g. Literal, Environment, Header,

   * Metadata)

   * @param log entry.

   * @param ctx the custom tag context.

   */

  virtual void applyLog(envoy::data::accesslog::v3::AccessLogCommon& entry,

                        const CustomTagContext& ctx) const PURE;

};

using CustomTagConstSharedPtr = std::shared_ptr<const CustomTag>;

using CustomTagMap = absl::flat_hash_map<std::string, CustomTagConstSharedPtr>;

} // namespace Tracing

} // namespace Envoy