MaxRetryInterceptor.swift

import Foundation
#if !COCOAPODS
import ApolloAPI
#endif

/// An interceptor to enforce a maximum number of retries of any `HTTPRequest`
public class MaxRetryInterceptor: ApolloInterceptor {
  
  private let maxRetries: Int
  private var hitCount = 0

  public var id: String = UUID().uuidString
  
  public enum RetryError: Error, LocalizedError {
    case hitMaxRetryCount(count: Int, operationName: String)
    
    public var errorDescription: String? {
      switch self {
      case .hitMaxRetryCount(let count, let operationName):
        return "The maximum number of retries (\(count)) was hit without success for operation \"\(operationName)\"."
      }
    }
  }
  
  /// Designated initializer.
  ///
  /// - Parameter maxRetriesAllowed: How many times a query can be retried, in addition to the initial attempt before
  public init(maxRetriesAllowed: Int = 3) {
    self.maxRetries = maxRetriesAllowed
  }
  
  public func interceptAsync<Operation: GraphQLOperation>(
    chain: RequestChain,
    request: HTTPRequest<Operation>,
    response: HTTPResponse<Operation>?,
    completion: @escaping (Result<GraphQLResult<Operation.Data>, Error>) -> Void) {
    guard self.hitCount <= self.maxRetries else {
      let error = RetryError.hitMaxRetryCount(
        count: self.maxRetries,
        operationName: Operation.operationName
      )

      chain.handleErrorAsync(
        error,
        request: request,
        response: response,
        completion: completion
      )
      
      return
    }
    
    self.hitCount += 1
    chain.proceedAsync(
      request: request,
      response: response,
      interceptor: self,
      completion: completion
    )
  }
}