/**
Extension that helps to find the week's previous/next weekday.  
e.g. if it's sunday, what was last monday's date?

usage: Date().get(direction: .previous, dayName: .monday, considerToday: true)
*/
extension Date {
  // weekday is in form 1...7
  enum WeekDay: Int {
    case sunday = 1, monday, tuesday, wednesday, thursday, friday, saturday
  }
  
  enum SearchDirection {
    case next
    case previous
    
    var calendarOptions: NSCalendar.Options {
      switch self {
      case .next:
        return .matchNextTime
      case .previous:
        return [.searchBackwards, .matchNextTime]
      }
    }
  }
  
  func get(direction: SearchDirection, dayName: WeekDay, considerToday consider: Bool = false) -> Date {
    
    let nextWeekDayIndex = dayName.rawValue
    let today = self
    let calendar = NSCalendar(calendarIdentifier: NSCalendar.Identifier.gregorian)!
    
    if consider && calendar.component(.weekday, from: today as Date) == nextWeekDayIndex {
      return today
    }
    
    var nextDateComponent = DateComponents()
    nextDateComponent.weekday = nextWeekDayIndex
    
    let date = calendar.nextDate(after: today, matching: nextDateComponent, options: direction.calendarOptions)!
    return date
  }
  
}