module GraphQL::StaticValidation::FragmentSpreadsArePossible

def initialize(*)
  super
  @spreads_to_validate = []
end

def on_document(node, parent)
  super
  @spreads_to_validate.each do |frag_spread|
    frag_node = context.fragments[frag_spread.node.name]
    if frag_node
      fragment_child_name = frag_node.type.name
      fragment_child = context.warden.get_type(fragment_child_name)
      # Might be non-existent type name
      if fragment_child
        validate_fragment_in_scope(frag_spread.parent_type, fragment_child, frag_spread.node, context, frag_spread.path)
      end
    end
  end
end

def on_fragment_spread(node, parent)
  fragment_parent = context.object_types.last
  @spreads_to_validate << FragmentSpread.new(node: node, parent_type: fragment_parent, path: context.path)
  super
end

def on_inline_fragment(node, parent)
  fragment_parent = context.object_types[-2]
  fragment_child = context.object_types.last
  if fragment_child
    validate_fragment_in_scope(fragment_parent, fragment_child, node, context, context.path)
  end
  super
end

def validate_fragment_in_scope(parent_type, child_type, node, context, path)
  if !child_type.kind.fields?
    # It's not a valid fragment type, this error was handled someplace else
    return
  end
  parent_types = context.warden.possible_types(parent_type.unwrap)
  child_types = context.warden.possible_types(child_type.unwrap)
  if child_types.none? { |c| parent_types.include?(c) }
    name = node.respond_to?(:name) ? " #{node.name}" : ""
    add_error(GraphQL::StaticValidation::FragmentSpreadsArePossibleError.new(
      "Fragment#{name} on #{child_type.graphql_name} can't be spread inside #{parent_type.graphql_name}",
      nodes: node,
      path: path,
      fragment_name: name.empty? ? "unknown" : name,
      type: child_type.graphql_name,
      parent: parent_type.graphql_name
    ))
  end
end