key_value_iterable.h

// Copyright The OpenTelemetry Authors
// SPDX-License-Identifier: Apache-2.0

#pragma once

#include "opentelemetry/common/attribute_value.h"
#include "opentelemetry/nostd/function_ref.h"
#include "opentelemetry/nostd/string_view.h"
#include "opentelemetry/version.h"

OPENTELEMETRY_BEGIN_NAMESPACE
namespace common
{
/**
 * Supports internal iteration over a collection of key-value pairs.
 */
class KeyValueIterable
{
public:
  KeyValueIterable()                                        = default;
  KeyValueIterable(const KeyValueIterable &)                = default;
  KeyValueIterable &operator=(const KeyValueIterable &)     = default;
  KeyValueIterable(KeyValueIterable &&) noexcept            = default;
  KeyValueIterable &operator=(KeyValueIterable &&) noexcept = default;
  virtual ~KeyValueIterable()                               = default;

  /**
   * Iterate over key-value pairs
   * @param callback a callback to invoke for each key-value. If the callback returns false,
   * the iteration is aborted.
   * @return true if every key-value pair was iterated over
   */
  virtual bool ForEachKeyValue(nostd::function_ref<bool(nostd::string_view, common::AttributeValue)>
                                   callback) const noexcept = 0;

  /**
   * @return the number of key-value pairs
   */
  virtual size_t size() const noexcept = 0;
};

/**
 * Supports internal iteration over a collection of key-value pairs.
 */
class NoopKeyValueIterable : public KeyValueIterable
{
public:
  /**
   * No-op implementation: does not invoke the callback, even if key-value pairs are present.
   * @return true without iterating or invoking the callback
   */
  bool ForEachKeyValue(
      nostd::function_ref<bool(nostd::string_view, common::AttributeValue)> /*callback*/)
      const noexcept override
  {
    return true;
  }

  /**
   * @return the number of key-value pairs
   */
  size_t size() const noexcept override { return 0; }
};

}  // namespace common
OPENTELEMETRY_END_NAMESPACE