src/Tulsi/EventLogger.swift

// Copyright 2016 The Tulsi 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 Foundation
import TulsiGenerator


/// Writes events to the console.
final class EventLogger {
  private let verboseLevel: TulsiMessageLevel
  private var observer: NSObjectProtocol? = nil

  init(verboseLevel: TulsiMessageLevel) {
    self.verboseLevel = verboseLevel
  }

  deinit {
    if let observer = self.observer {
      NotificationCenter.default.removeObserver(observer)
    }
  }

  func startLogging() {
    observer = NotificationCenter.default.addObserver(forName: NSNotification.Name(rawValue: TulsiMessageNotification),
                                                      object: nil,
                                                      queue: nil) {
      [weak self] (notification: Notification) in
        guard let item = LogMessage(notification: notification),
            let verboseLevel = self?.verboseLevel,
            verboseLevel.logRank.rawValue >= item.level.logRank.rawValue else {
          return
        }
        self?.logItem(item)
    }
  }

  // MARK: - Private methods

  private func logItem(_ item: LogMessage) {
    let level: String = item.level.rawValue
    let details: String
    if let itemDetails = item.details {
      details = " \(itemDetails)"
    } else {
      details = ""
    }
    print("[\(level)] \(item.message)\(details)")
  }
}