<?php

function processIncomingQueueMessage($message) {
}

\DDTrace\trace_function(
    'processIncomingQueueMessage',
    function(\DDTrace\SpanData $span, $args) {
        $message = $args[0];
        \DDTrace\set_distributed_tracing_context($message->trace_id, $message->parent_id);
    }
);

$headers = [
    "x-datadog-trace-id" => "1234567890",
    "x-datadog-parent-id" => "987654321",
];

\DDTrace\consume_distributed_tracing_headers($headers);

$headers = DDTrace\generate_distributed_tracing_headers();
// ヘッダーをどこかに保存し、アウトバウンドリクエストに挿入し、... 
// また、これらの $headers は、他のプロセスから \DDTrace\consume_distributed_tracing_headers によって読み返すことができます。

// 囲むトレースを作成します
$newTrace = \DDTrace\start_trace_span();
$newTrace->name = 'basic_get.process';
$newTrace->service = 'amqp';


// basic_get call(s) + message(s) 処理
$msg = $channel->basic_get($queue);
if ($msg) {
   $messageProcessing($msg);
}


// 完了したら、スパンを閉じます
\DDTrace\close_span();

#include <datadog/dict_reader.h>
#include <datadog/optional.h>
#include <datadog/string_view.h>

#include <unordered_map>

namespace dd = datadog::tracing;

class HTTPHeadersReader : public datadog::tracing::DictReader {
  std::unordered_map<dd::StringView, dd::StringView> headers_;

public:
  HTTPHeadersReader(std::unordered_map<dd::StringView, dd::StringView> headers)
    : headers_(std::move(headers)) {}

  ~HTTPHeadersReader() override = default;

  // Return the value at the specified `key`, or return `nullopt` if there
  // is no value at `key`.
  dd::Optional<dd::StringView> lookup(dd::StringView key) const override {
    auto found = headers_.find(key);
    if (found == headers_.cend()) return dd::nullopt;

    return found->second;
  }

  // Invoke the specified `visitor` once for each key/value pair in this object.
  void visit(
      const std::function<void(dd::StringView key, dd::StringView value)>& visitor)
      const override {
      for (const auto& [key, value] : headers_) {
        visitor(key, value);
      }
  };
};

// Usage example:
void handle_http_request(const Request& request, datadog::tracing::Tracer& tracer) {
  HTTPHeadersReader reader{request.headers};
  auto maybe_span = tracer.extract_span(reader);
  ..
}

#include <datadog/dict_writer.h>
#include <datadog/string_view.h>

#include <string>
#include <unordered_map>

using namespace dd = datadog::tracing;

class HTTPHeaderWriter : public dd::DictWriter {
  std::unordered_map<std::string, std::string>& headers_;

public:
  explicit HTTPHeaderWriter(std::unordered_map<std::string, std::string>& headers) : headers_(headers) {}

  ~HTTPHeaderWriter() override = default;

  void set(dd::StringView key, dd::StringView value) override {
    headers_.emplace(key, value);
  }
};

// Usage example:
void handle_http_request(const Request& request, dd::Tracer& tracer) {
  auto span = tracer.create_span();

  HTTPHeaderWriter writer(request.headers);
  span.inject(writer);
  // `request.headers` now populated with the headers needed to propagate the span.
  ..
}

var spanContextExtractor = new SpanContextExtractor();
var parentContext = spanContextExtractor.Extract(headers, (headers, key) => GetHeaderValues(headers, key));
var spanCreationSettings = new SpanCreationSettings() { Parent = parentContext };
using var scope = Tracer.Instance.StartActive("operation", spanCreationSettings);

// Confluent.Kafka
IEnumerable<string> GetHeaderValues(Headers headers, string name)
{
    if (headers.TryGetLastBytes(name, out var bytes))
    {
        try
        {
            return new[] { Encoding.UTF8.GetString(bytes) };
        }
        catch (Exception)
        {
            // 無視
        }
    }

    return Enumerable.Empty<string>();
}

// RabbitMQ
IEnumerable<string> GetHeaderValues(IDictionary<string, object> headers, string name)
{
    if (headers.TryGetValue(name, out object value) && value is byte[] bytes)
    {
        return new[] { Encoding.UTF8.GetString(bytes) };
    }

    return Enumerable.Empty<string>();
}

// SQS
public static IEnumerable<string> GetHeaderValues(IDictionary<string, MessageAttributeValue> headers, string name)
{
    // SQS の場合、メッセージ属性ヘッダーは最大 10 個なので、
    // Datadog のヘッダーは以下のプロパティを持つ 1 つのヘッダーに統合されます。
    // - Key: "_datadog"
    // - Value: MessageAttributeValue object
    //   - DataType: "String"
    //   - StringValue: <JSON map with key-value headers>
    if (headers.TryGetValue("_datadog", out var messageAttributeValue)
        && messageAttributeValue.StringValue is string jsonString)
    {
        var datadogDictionary = JsonConvert.DeserializeObject<Dictionary<string, string>>(jsonString);
        if (datadogDictionary.TryGetValue(name, out string value))
        {
            return new[] { value };
        }
    }
    return Enumerable.Empty<string>();
}

using (OperationContextScope ocs = new OperationContextScope(this.InnerChannel))
{
  var spanContextInjector = new SpanContextInjector();
  spanContextInjector.Inject(OperationContext.Current.OutgoingMessageHeaders, SetHeaderValues, Tracer.Instance.ActiveScope?.Span?.Context);
}


void SetHeaderValues(MessageHeaders headers, string name, string value)
{
    MessageHeader header = MessageHeader.CreateHeader(name, "datadog", value);
    headers.Add(header);
}