text: // Copyright The OpenTelemetry Authors
  // SPDX-License-Identifier: Apache-2.0
  
  #include "opentelemetry/sdk/resource/resource.h"
  #include "opentelemetry/nostd/span.h"
  #include "opentelemetry/sdk/resource/experimental_semantic_conventions.h"
  #include "opentelemetry/sdk/resource/resource_detector.h"
  #include "opentelemetry/version.h"
  
  OPENTELEMETRY_BEGIN_NAMESPACE
  namespace sdk
  {
  namespace resource
  {
  
  const std::string kTelemetrySdkLanguage  = "telemetry.sdk.language";
  const std::string kTelemetrySdkName      = "telemetry.sdk.name";
  const std::string kTelemetrySdkVersion   = "telemetry.sdk.version";
  const std::string kServiceName           = "service.name";
  const std::string kProcessExecutableName = "process.executable.name";
  
  Resource::Resource(const ResourceAttributes &attributes) noexcept : attributes_(attributes) {}
  
  Resource Resource::Merge(const Resource &other) noexcept
  {
    ResourceAttributes merged_resource_attributes(other.attributes_);
    merged_resource_attributes.insert(attributes_.begin(), attributes_.end());
    return Resource(merged_resource_attributes);
  }
  
  Resource Resource::Create(const ResourceAttributes &attributes)
  {
    static auto otel_resource = OTELResourceDetector().Detect();
    auto resource = Resource::GetDefault().Merge(otel_resource).Merge(Resource(attributes));
  
    if (resource.attributes_.find(OTEL_CPP_GET_ATTR(AttrServiceName)) == resource.attributes_.end())
    {
      std::string default_service_name = "unknown_service";
      auto it_process_executable_name =
          resource.attributes_.find(OTEL_CPP_GET_ATTR(AttrProcessExecutableName));
      if (it_process_executable_name != resource.attributes_.end())
      {
        default_service_name += ":" + nostd::get<std::string>(it_process_executable_name->second);
      }
      resource.attributes_[OTEL_CPP_GET_ATTR(AttrServiceName)] = default_service_name;
    }
    return resource;
  }
  
  Resource &Resource::GetEmpty()
  {
    static Resource empty_resource;
    return empty_resource;
  }
  
  Resource &Resource::GetDefault()
  {
    static Resource default_resource(
        {{OTEL_CPP_GET_ATTR(AttrTelemetrySdkLanguage), "cpp"},
         {OTEL_CPP_GET_ATTR(AttrTelemetrySdkName), "opentelemetry"},
         {OTEL_CPP_GET_ATTR(AttrTelemetrySdkVersion), OPENTELEMETRY_SDK_VERSION}});
    return default_resource;
  }
  
  const ResourceAttributes &Resource::GetAttributes() const noexcept
  {
    return attributes_;
  }
  
  }  // namespace resource
  }  // namespace sdk
  OPENTELEMETRY_END_NAMESPACE
  