ApolloClient.kt

fun getApolloClient(context: Context): ApolloClient? {
        val apolloSqlHelper = ApolloSqlHelper(context, SQL_CACHE_NAME)

        //Used Normalized Disk Cache: Per node caching of responses in SQL.
        //Persists normalized responses on disk so that they can used after process death.
        val cacheFactory = LruNormalizedCacheFactory(
            EvictionPolicy.NO_EVICTION, SqlNormalizedCacheFactory(apolloSqlHelper)
        )
        
        //If Apollo Client is not null, return it else make a new Apollo Client.
        //Helps in singleton pattern.
        apClient?.let {
            return it
        } ?: kotlin.run {
            apClient = ApolloClient.builder()
                .okHttpClient(getOkhttpClient(context)!!)
                .normalizedCache(cacheFactory, cacheResolver())
                .serverUrl(BASE_URL)
                .build()
        }
      return apClient
    }