World.Store.swift

extension World {

    public final class Store: WorldStoreInterface {

        private let client: ApolloClientInterface

        public init(client: ApolloClientInterface) {
            self.client = client
        }

        public func fetchCountry(code: String,
                                 cachePolicy: CachePolicy = .fetchIgnoringCacheData,
                                 completion: @escaping ((Result) -> Void)) {

            let query = CountryQuery(code: code)
            let queue = DispatchQueue.global(qos: .default)

            let resultHandler: OperationResultHandler<CountryQuery> = { (result, error) in

                guard error == nil else {
                    completion(.failure(.network))
                    return
                }


                guard let country = result?.data?.country.flatMap(World.CountryDetail.init) else {
                    completion(.failure(.parsing))
                    return
                }

                completion(.success(country))

            }

            client.fetch(query: query,
                         cachePolicy: cachePolicy,
                         queue: queue,
                         resultHandler: resultHandler)
        }

        public func fetchAllCountries(cachePolicy: CachePolicy = .fetchIgnoringCacheData,
                                      completion: @escaping ((Result<[CountryLite], World.StoreError>) -> Void)) {

            let query = CountriesQuery()
            let queue = DispatchQueue.global(qos: .default)

            let resultHandler: OperationResultHandler<CountriesQuery> = { (result, error) in

                guard error == nil else {
                    completion(.failure(.network))
                    return
                }


                guard let countries = result?.data?.countries?.compactMap(CountryLite.init) else {
                    completion(.failure(.parsing))
                    return
                }

                completion(.success(countries))
            }

            client.fetch(query: query,
                         cachePolicy: cachePolicy,
                         queue: queue,
                         resultHandler: resultHandler)
        }
    }
}