class GraphQL::Analysis::AST::FieldUsage

def initialize(query)
  super
  @used_fields = Set.new
  @used_deprecated_fields = Set.new
end

def on_leave_field(node, parent, visitor)
  field_defn = visitor.field_definition
  field = "#{visitor.parent_type_definition.graphql_name}.#{field_defn.graphql_name}"
  @used_fields << field
  @used_deprecated_fields << field if field_defn.deprecation_reason
end

def result
  {
    used_fields: @used_fields.to_a,
    used_deprecated_fields: @used_deprecated_fields.to_a
  }
end