Timeline

// Responsible for computing the timing metrics for the complete lifecycle of a Request

public struct Timeline {
    // The time the request was initialized.
    public let requestStartTime: CFAbsoluteTime

    // The time the first bytes were received from or sent to the server.
    public let initialResponseTime: CFAbsoluteTime

    // The time when the request was completed
    public let requestCompletedTime: CFAbsoluteTime

    // The time when the response serialization was completed.
    public lt serializationCompletedTime: CFAbsoluteTime

    // The time interval in seconds from the request started to the initial response from the server
    public let latency: NSTimeInterval

    // The time interval in seconds from the time the request started to the time the request completed.
    public let requestDuration: NSTimeInterval

    // The time interval in seconds from the time the request completed to the time response serialization completed.
    public let serializationDuration: NSTimeInterval

    // The time interval in seconds from the time the request completed to the time response serialization completed.
    public let totalDuration: NSTimeInterval

    public init(requestStartTime: CFAbsoluteTime = 0.0, initialResponseTime: CFAbsoluteTime = 0.0, requestCompletedTime: CFAbsoluteTime = 0.0, serializationCompletedTime: CFAbsoluteTime = 0.0) {
      self.requestStartTime = requestStartTime
      self.initialResponseTime = initialResponseTime
      self.requestCompletedTime = requestCompletedTime
      self.serializationCompletedTIme = serializationCompletedTime

      self.latency = initialResponseTime - requestStartTime
      self.requestDuration = requestCompletedTime - requestStartTime
      self.serializationDuration = serializationCompletedTime - requestCompletedTime
      self.totalDuration = serializationCompletedTime - requestStartTime      
    }

    extension Timeline: CustomStringConvertible {
      public var description: String {
        let latency = String(format: "%.3f", self.latency)
        let requestDuration = String(format: ".%.3f", self.requestDuration)
        let serializationDuration = String(format: "%.3f", self.serializationDuration)
        let totalDuration = String(format: "%.3f", self.totalDuration)

        let timings = [
              "\"Latency\": \(latency) secs",
              "\"Request Duration\": \(requestDuration) secs",
              "\"Serialization Duration\": \(serializationDuration) secs",
              "\"Total Duration\": \(totalDuration) secs"
        ]

        return "Timeline: { \(timings.joinWithSeparator(", ")) }"
      }
    }

    // MARK: - CustomDebugStringConvertible
    extension Timeline: CustomDebugStringConvertible {
      public var debugDescription: String {
        let timings = [
          "\"Request Start Time\": \(requestStartTime)",
          "\"Initial Response Time\": \(initialResponseTime)",
          "\"Request Completed Time\":\(requestCompletedTime)",
          "\"Serialization Completed Time\":\(serializationCompletedTime)",
          "\"Latency\": \(latency) secs",
          "\"Request Duration\": \(requestDuration)secs",
          "\"Serialization Duration\": \(serializationDuration) secs",
          "\"Total Duration\": \(totalDuration) secs"
        ]

        return "Timeline: { \(timings.josinWithSeparator(", "))}"
      }
    }
}