/*
 * Copyright 2019, gRPC Authors All rights reserved.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
import Dispatch
import Foundation
import GRPC
import NIO
import NIOHPACK
import NIOHTTP1
import NIOSSL
import OAuth2

/// Create a client and return a future to provide its value.
func makeServiceClient(
  host: String,
  port: Int,
  eventLoopGroup: MultiThreadedEventLoopGroup
) -> Google_Cloud_Language_V1_LanguageServiceNIOClient {
  let connection = ClientConnection.usingPlatformAppropriateTLS(for: eventLoopGroup)
    .connect(host: host, port: port)
  return Google_Cloud_Language_V1_LanguageServiceNIOClient(channel: connection)
}

enum AuthError: Error {
  case noTokenProvider
  case tokenProviderFailed
}

/// Get an auth token and return a future to provide its value.
func getAuthToken(
  scopes: [String],
  eventLoop: EventLoop
) -> EventLoopFuture<String> {
  let promise = eventLoop.makePromise(of: String.self)
  guard let provider = DefaultTokenProvider(scopes: scopes) else {
    promise.fail(AuthError.noTokenProvider)
    return promise.futureResult
  }
  do {
    try provider.withToken { token, error in
      if let token = token,
         let accessToken = token.AccessToken {
        promise.succeed(accessToken)
      } else if let error = error {
        promise.fail(error)
      } else {
        promise.fail(AuthError.tokenProviderFailed)
      }
    }
  } catch {
    promise.fail(error)
  }
  return promise.futureResult
}

/// Main program. Make a sample API request.
do {
  let eventLoopGroup = MultiThreadedEventLoopGroup(numberOfThreads: 1)

  // Get an auth token.
  let scopes = ["https://www.googleapis.com/auth/cloud-language"]
  let authToken = try getAuthToken(
    scopes: scopes,
    eventLoop: eventLoopGroup.next()
  ).wait()

  // Create a service client.
  let service = makeServiceClient(
    host: "language.googleapis.com",
    port: 443,
    eventLoopGroup: eventLoopGroup
  )

  // Use CallOptions to send the auth token (necessary) and set a custom timeout (optional).
  let headers: HPACKHeaders = ["authorization": "Bearer \(authToken)"]
  let callOptions = CallOptions(customMetadata: headers, timeLimit: TimeLimit.timeout(.seconds(30)))
  print("CALL OPTIONS\n\(callOptions)\n")

  // Construct the API request.
  let request = Google_Cloud_Language_V1_AnnotateTextRequest.with {
    $0.document = .with {
      $0.type = .plainText
      $0
        .content =
        "The Caterpillar and Alice looked at each other for some time in silence: at last the Caterpillar took the hookah out of its mouth, and addressed her in a languid, sleepy voice. `Who are you?' said the Caterpillar."
    }

    $0.features = .with {
      $0.extractSyntax = true
      $0.extractEntities = true
      $0.extractDocumentSentiment = true
      $0.extractEntitySentiment = true
      $0.classifyText = true
    }
  }
  print("REQUEST MESSAGE\n\(request)")

  // Create/start the API call.
  let call = service.annotateText(request, callOptions: callOptions)
  call.response.whenSuccess { response in
    print("CALL SUCCEEDED WITH RESPONSE\n\(response)")
  }
  call.response.whenFailure { error in
    print("CALL FAILED WITH ERROR\n\(error)")
  }

  // wait() on the status to stop the program from exiting.
  let status = try call.status.wait()
  print("CALL STATUS\n\(status)")
} catch {
  print("EXAMPLE FAILED WITH ERROR\n\(error)")
}