//
//
// Copyright 2023 gRPC authors.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
//
//

#ifndef GRPCPP_EXT_OTEL_PLUGIN_H
#define GRPCPP_EXT_OTEL_PLUGIN_H

#include <grpc/support/metrics.h>
#include <grpc/support/port_platform.h>
#include <grpcpp/server_builder.h>
#include <grpcpp/support/channel_arguments.h>
#include <stddef.h>
#include <stdint.h>

#include <memory>

#include "absl/functional/any_invocable.h"
#include "absl/status/status.h"
#include "absl/status/statusor.h"
#include "absl/strings/string_view.h"
#include "opentelemetry/metrics/meter_provider.h"

namespace grpc {
namespace internal {
class OpenTelemetryPluginBuilderImpl;
}  // namespace internal

class OpenTelemetryPluginOption {
 public:
  virtual ~OpenTelemetryPluginOption() = default;
};

namespace experimental {
/// EXPERIMENTAL API
class OpenTelemetryPlugin {
 public:
  virtual ~OpenTelemetryPlugin() = default;
  /// EXPERIMENTAL API
  /// Adds this OpenTelemetryPlugin to the channel args \a args.
  virtual void AddToChannelArguments(grpc::ChannelArguments* args) = 0;
  /// EXPERIMENTAL API
  /// Adds this OpenTelemetryPlugin to the channel arguments that will be used
  /// to create the server through \a builder.
  virtual void AddToServerBuilder(grpc::ServerBuilder* builder) = 0;
};
}  // namespace experimental

/// The most common way to use this API is -
///
/// OpenTelemetryPluginBuilder().SetMeterProvider(provider).BuildAndRegister();
///
/// The set of instruments available are -
/// grpc.client.attempt.started
/// grpc.client.attempt.duration
/// grpc.client.attempt.sent_total_compressed_message_size
/// grpc.client.attempt.rcvd_total_compressed_message_size
/// grpc.server.call.started
/// grpc.server.call.duration
/// grpc.server.call.sent_total_compressed_message_size
/// grpc.server.call.rcvd_total_compressed_message_size
class OpenTelemetryPluginBuilder {
 public:
  using ChannelScope = grpc_core::experimental::StatsPluginChannelScope;

  /// Metrics
  static constexpr absl::string_view kClientAttemptStartedInstrumentName =
      "grpc.client.attempt.started";
  static constexpr absl::string_view kClientAttemptDurationInstrumentName =
      "grpc.client.attempt.duration";
  static constexpr absl::string_view
      kClientAttemptSentTotalCompressedMessageSizeInstrumentName =
          "grpc.client.attempt.sent_total_compressed_message_size";
  static constexpr absl::string_view
      kClientAttemptRcvdTotalCompressedMessageSizeInstrumentName =
          "grpc.client.attempt.rcvd_total_compressed_message_size";
  static constexpr absl::string_view kServerCallStartedInstrumentName =
      "grpc.server.call.started";
  static constexpr absl::string_view kServerCallDurationInstrumentName =
      "grpc.server.call.duration";
  static constexpr absl::string_view
      kServerCallSentTotalCompressedMessageSizeInstrumentName =
          "grpc.server.call.sent_total_compressed_message_size";
  static constexpr absl::string_view
      kServerCallRcvdTotalCompressedMessageSizeInstrumentName =
          "grpc.server.call.rcvd_total_compressed_message_size";

  OpenTelemetryPluginBuilder();
  ~OpenTelemetryPluginBuilder();
  /// If `SetMeterProvider()` is not called, no metrics are collected.
  OpenTelemetryPluginBuilder& SetMeterProvider(
      std::shared_ptr<opentelemetry::metrics::MeterProvider> meter_provider);
  /// DEPRECATED: If set, \a target_attribute_filter is called per channel to
  /// decide whether to record the target attribute on client or to replace it
  /// with "other". This helps reduce the cardinality on metrics in cases where
  /// many channels are created with different targets in the same binary (which
  /// might happen for example, if the channel target string uses IP addresses
  /// directly).
  /// This filtration only works for the per-call metrics -
  /// grpc.client.attempt.started
  /// grpc.client.attempt.duration
  /// grpc.client.attempt.sent_total_compressed_message_size
  /// grpc.client.attempt.rcvd_total_compressed_message_size
  /// For example, the grpc.target attribute on pick first lb policy metrics
  /// defined in
  /// https://github.com/grpc/proposal/blob/master/A78-grpc-metrics-wrr-pf-xds.md
  /// will not be filtered. Please contact the grpc team if this filtration is
  /// of interest to you.
  GRPC_DEPRECATED(
      "Does not work as expected. Please raise an issue on "
      "https://github.com/grpc/grpc if this would be of use to you.")
  OpenTelemetryPluginBuilder& SetTargetAttributeFilter(
      absl::AnyInvocable<bool(absl::string_view /*target*/) const>
          target_attribute_filter);
  /// If set, \a generic_method_attribute_filter is called per call with a
  /// generic method type to decide whether to record the method name or to
  /// replace it with "other". Non-generic or pre-registered methods remain
  /// unaffected. If not set, by default, generic method names are replaced
  /// with "other" when recording metrics.
  OpenTelemetryPluginBuilder& SetGenericMethodAttributeFilter(
      absl::AnyInvocable<bool(absl::string_view /*generic_method*/) const>
          generic_method_attribute_filter);
  // Methods to manipulate which instruments are enabled in the OpenTelemetry
  // Stats Plugin.
  OpenTelemetryPluginBuilder& EnableMetrics(
      absl::Span<const absl::string_view> metric_names);
  OpenTelemetryPluginBuilder& DisableMetrics(
      absl::Span<const absl::string_view> metric_names);
  OpenTelemetryPluginBuilder& DisableAllMetrics();
  /// Add a plugin option to add to the opentelemetry plugin being built. At
  /// present, this type is an opaque type. Ownership of \a option is
  /// transferred when `AddPluginOption` is invoked. A maximum of 64 plugin
  /// options can be added.
  OpenTelemetryPluginBuilder& AddPluginOption(
      std::unique_ptr<OpenTelemetryPluginOption> option);
  /// Records \a optional_label_key on all metrics that provide it.
  OpenTelemetryPluginBuilder& AddOptionalLabel(
      absl::string_view optional_label_key);
  /// Set scope filter to choose which channels are recorded by this plugin.
  /// Server-side recording remains unaffected.
  OpenTelemetryPluginBuilder& SetChannelScopeFilter(
      absl::AnyInvocable<bool(const ChannelScope& /*scope*/) const>
          channel_scope_filter);
  /// Builds and registers a global plugin that acts on all channels and servers
  /// running on the process. Must be called no more than once and must not be
  /// called if Build() is called.
  absl::Status BuildAndRegisterGlobal();
  /// EXPERIMENTAL API
  /// Builds an open telemetry plugin, returns the plugin object when succeeded
  /// or an error status when failed. Must be called no more than once and must
  /// not be called if BuildAndRegisterGlobal() is called.
  GRPC_MUST_USE_RESULT
  absl::StatusOr<std::shared_ptr<experimental::OpenTelemetryPlugin>> Build();

 private:
  std::unique_ptr<internal::OpenTelemetryPluginBuilderImpl> impl_;
};

namespace experimental {
// TODO(yashykt): Delete this after the 1.62 release.
GRPC_DEPRECATED(
    "Use grpc::OpenTelemetryPluginBuilder instead. The experimental version "
    "will be deleted after the 1.62 release.")
typedef grpc::OpenTelemetryPluginBuilder OpenTelemetryPluginBuilder;
}  // namespace experimental

}  // namespace grpc

#endif  // GRPCPP_EXT_OTEL_PLUGIN_H
