Function SortedEvents

bridge/gitlab/event.go:173–215

SortedEvents fan-in some Event-channels into one, sorted by creation date, using CreatedAt-method. This function assume that each channel is pre-ordered.

(inputs ...<-chan Event)

// SortedEvents fan-in some Event-channels into one, sorted by creation date, using CreatedAt-method.
// This function assume that each channel is pre-ordered.
func SortedEvents(inputs ...<-chan Event) chan Event {
	out := make(chan Event)

	go func() {
		defer close(out)

		heads := make([]Event, len(inputs))

		// pre-fill the head view
		for i, input := range inputs {
			if event, ok := <-input; ok {
				heads[i] = event
			}
		}

		for {
			var earliestEvent Event
			var originChannel int

			// pick the earliest event of the heads
			for i, head := range heads {
				if head != nil && (earliestEvent == nil || head.CreatedAt().Before(earliestEvent.CreatedAt())) {
					earliestEvent = head
					originChannel = i
				}
			}

			if earliestEvent == nil {
				// no event anymore, we are done
				return
			}

			// we have an event: consume it and replace it if possible
			heads[originChannel] = nil
			if event, ok := <-inputs[originChannel]; ok {
				heads[originChannel] = event
			}
			out <- earliestEvent
		}
	}()

	return out
}