HKWorkout+ActivePeriods

import HealthKit

public extension HKWorkout {

	public func predicateForSamplesDuringActivePeriods() -> NSPredicate {

		let subpredicates = activePeriods.map { start, end -> NSPredicate in

			HKQuery.predicateForSamplesWithStartDate(start, endDate: end, options: .StrictStartDate | .StrictEndDate)
		}

		return NSCompoundPredicate(type: .OrPredicateType, subpredicates: subpredicates)
	}



	public var activePeriods: [(start: NSDate, end: NSDate)] {
		get {

			var activePeriods: [(start: NSDate, end: NSDate)] = []
			var start: NSDate? = self.startDate

			func addActivePeriod(start: NSDate?, end: NSDate) {
				if let start = start {
					activePeriods.append((start: start, end: end))
				}
			}

			if let events = self.workoutEvents as? [HKWorkoutEvent] {

				for event in events {

					switch event.type {

					case .Pause:
						addActivePeriod(start, event.date)
						start = nil

					case .Resume:
						start = event.date
					}
				}
			}
			
			addActivePeriod(start, self.endDate)
			return activePeriods
		}
	}
}