Method addToChannelSetHistory

db/document.go:998–1040

(channelName string, historyEntry ChannelSetEntry)

}

func (doc *Document) addToChannelSetHistory(channelName string, historyEntry ChannelSetEntry) {
	// Before adding the entry we need to verify the number of items in the document channel history to check
	// whether we need to prune them.
	// As we iterate over the existing channels we will keep track of the oldest and second oldest entries along with
	// their location in the slice. If we need to then prune we can 'merge' the oldest and second oldest and remove
	// the oldest.

	var oldestEntryStartSeq uint64 = math.MaxUint64
	var secondOldestEntryStartSeq uint64 = math.MaxUint64

	oldestEntryIdx := -1
	secondOldestEntryIdx := -1

	entryCount := 0

	for entryIdx, entry := range doc.ChannelSetHistory {
		if entry.Name == channelName {
			entryCount++

			if entry.Start < oldestEntryStartSeq {
				secondOldestEntryStartSeq = oldestEntryStartSeq
				oldestEntryStartSeq = entry.Start

				secondOldestEntryIdx = oldestEntryIdx
				oldestEntryIdx = entryIdx
				continue
			}

			if entry.Start < secondOldestEntryStartSeq {
				secondOldestEntryStartSeq = entry.Start
				secondOldestEntryIdx = entryIdx
			}
		}
	}

	if entryCount >= DocumentHistoryMaxEntriesPerChannel {
		doc.ChannelSetHistory[secondOldestEntryIdx].Start = oldestEntryStartSeq
		doc.ChannelSetHistory[secondOldestEntryIdx].Compacted = true
		doc.ChannelSetHistory = append(doc.ChannelSetHistory[:oldestEntryIdx], doc.ChannelSetHistory[oldestEntryIdx+1:]...)
	}

	doc.ChannelSetHistory = append(doc.ChannelSetHistory, historyEntry)
}

// Updates the Channels property of a document object with current & past channels.
// Returns the set of channels that have changed (document joined or left in this revision)