schema
  @link(url: "https://specs.apollo.dev/link/v1.0")
  @link(url: "https://specs.apollo.dev/join/v0.5", for: EXECUTION) {
  query: Query
}

directive @join__enumValue(graph: join__Graph!) repeatable on ENUM_VALUE

directive @join__field(
  graph: join__Graph
  requires: join__FieldSet
  provides: join__FieldSet
  type: String
  external: Boolean
  override: String
  usedOverridden: Boolean
) repeatable on FIELD_DEFINITION | INPUT_FIELD_DEFINITION

directive @join__graph(name: String!, url: String!) on ENUM_VALUE

directive @join__implements(
  graph: join__Graph!
  interface: String!
) repeatable on OBJECT | INTERFACE

directive @join__type(
  graph: join__Graph!
  key: join__FieldSet
  extension: Boolean! = false
  resolvable: Boolean! = true
  isInterfaceObject: Boolean! = false
) repeatable on OBJECT | INTERFACE | UNION | ENUM | INPUT_OBJECT | SCALAR

directive @join__unionMember(
  graph: join__Graph!
  member: String!
) repeatable on UNION

directive @link(
  url: String
  as: String
  for: link__Purpose
  import: [link__Import]
) repeatable on SCHEMA

scalar join__FieldSet

enum join__Graph {
  LIBRARY @join__graph(name: "library", url: "http://library/graphql")
  RECOMMENDER
    @join__graph(name: "recommender", url: "http://recommender/graphql")
}

scalar link__Import

enum link__Purpose {
  EXECUTION
}

type Query @join__type(graph: LIBRARY) @join__type(graph: RECOMMENDER) {
  books: [BookListing!]! @join__field(graph: LIBRARY)
}

type BookListing
  @join__type(graph: LIBRARY, key: "edition { isbn }")
  @join__type(graph: RECOMMENDER, key: "edition { isbn }") {
  edition: BookEdition!
  isRecommended: Boolean
    @join__field(graph: RECOMMENDER, requires: "edition { book { catalogId } }")
}

type BookEdition @join__type(graph: LIBRARY) @join__type(graph: RECOMMENDER) {
  isbn: ID!
  book: Book!
    @join__field(graph: LIBRARY)
    @join__field(graph: RECOMMENDER, external: true)
}

type Book @join__type(graph: LIBRARY) @join__type(graph: RECOMMENDER) {
  catalogId: ID!
    @join__field(graph: LIBRARY)
    @join__field(graph: RECOMMENDER, external: true)
}
