module Datadog::Tracing::Contrib::SpanAttributeSchema

def self.fetch_service_name(env, default) 

def self.fetch_service_name(env, default)
  ENV.fetch(env) do
    if Datadog.configuration.tracing.contrib.global_default_service_name.enabled
      return Datadog.configuration.service
    end
    default
  end
end

def self.filter_peer_service_sources(span, sources)

This is to prevent overwriting of pre-existing peer.service tags
If peer.service exists, we do not read from any other source rather use peer.service as source
filter_peer_service_sources: returns filtered sources based on existence of peer.service tag 
def self.filter_peer_service_sources(span, sources)
  ps = span.get_tag(Tracing::Metadata::Ext::TAG_PEER_SERVICE)
  # Do not override existing peer.service tag if it exists based on schema version
  return REFLEXIVE_SOURCES if not_empty_tag?(ps)
  # Check that peer.service is only set on spankind client/producer spans
  if (span.get_tag(Tracing::Metadata::Ext::TAG_KIND) == Tracing::Metadata::Ext::SpanKind::TAG_CLIENT) ||
      (span.get_tag(Tracing::Metadata::Ext::TAG_KIND) == Tracing::Metadata::Ext::SpanKind::TAG_PRODUCER)
    return sources
  end
  NO_SOURCE
end

def self.not_empty_tag?(tag) 

def self.not_empty_tag?(tag)
  tag && (tag != '')
end

def self.set_peer_service!(span, sources) 

def self.set_peer_service!(span, sources)
  # Acquire all peer.service values as well as any potential remapping
  peer_service_val, peer_service_source = set_peer_service_from_source(span, sources)
  remap_val = Datadog.configuration.tracing.contrib.peer_service_mapping[peer_service_val]
  # Only continue to setting peer.service if actual source is found
  return false unless peer_service_source
  span.set_tag(Tracing::Contrib::Ext::Metadata::TAG_PEER_SERVICE_SOURCE, peer_service_source)
  # Set peer.service to remapped value if found otherwise normally set peer.service
  if remap_val
    span.set_tag(Tracing::Metadata::Ext::TAG_PEER_SERVICE, remap_val)
    span.set_tag(Tracing::Contrib::Ext::Metadata::TAG_PEER_SERVICE_REMAP, peer_service_val)
  else
    span.set_tag(Tracing::Metadata::Ext::TAG_PEER_SERVICE, peer_service_val)
  end
  true
end

def self.set_peer_service_from_source(span, sources = [])

Returns a peer.service value if successfully set or not
Sets the source of where the information for peer.service was extracted from
If no values are found, it checks the default list for all spans before returning false for no result

based on the list of source tags passed as a parameter.
set_peer_service_from_source: Implements the extraction logic to determine the peer.service value 
def self.set_peer_service_from_source(span, sources = [])
  # Filter out sources based on existence of peer.service tag
  sources = filter_peer_service_sources(span, sources)
  # Find a possible peer.service source from the list of source tags passed in
  sources.each do |source|
    source_val = span.get_tag(source)
    next unless not_empty_tag?(source_val)
    return source_val, source
  end
  false
end