I think I need an IoC container…

unwieldy.js

function main () {
  return Promise.coroutine(function * () {
    const DEFAULT_MONGO_URL = 'mongodb://127.0.0.1:27017/bemuse'
    const suppliedMongoUrl = process.env.MONGO_URL || process.env.MONGODB_URI
    const db = yield connectMongo(suppliedMongoUrl || DEFAULT_MONGO_URL)
    const factory = new MongoDBRepositoryFactory({ db })
    const port = +process.env.PORT || 8008
    const app = createApiServer({
      logger: log4js.getLogger('HTTP'),
      legacyUserApiKey: requiredEnv('LEGACY_USER_API_KEY'),
      legacyUserRepository: factory.createLegacyUserRepository(),
      rankingEntryRepository: factory.createRankingEntryRepository(),
      playerRepository: factory.createPlayerRepository(),
      tokenValidator: createTokenValidator()
    })
    runApiServer(app, port)
  })()
}

function createApiServer ({
  logger,
  rankingEntryRepository,
  playerRepository,
  legacyUserApiKey,
  legacyUserRepository,
  tokenValidator
} = { }) {
  const app = express()

  // Logging
  if (logger) {
    app.use(log4js.connectLogger(logger, { level: log4js.levels.INFO }))
  }

  // Legacy user
  app.use('/legacyusers', createLegacyUserApi({
    legacyUserApiKey,
    legacyUserRepository,
    playerRepository
  }))

  // GraphQL
  if (rankingEntryRepository) {
    const rootValue = createRoot({
      rankingEntryRepository,
      legacyUserRepository,
      playerRepository,
      tokenValidator
    })
    app.use(cors())
    app.use(graphqlHTTP({ schema, rootValue, graphiql: true }))
  }

  return app
}

function createLegacyUserApi ({
  legacyUserApiKey: apiKey,
  legacyUserRepository,
  playerRepository
}) {
  const router = express.Router()
  ...
  return router
}

function createRoot ({
  rankingEntryRepository,
  legacyUserRepository,
  playerRepository,
  tokenValidator
}) {
  ...
}