overleaf/services/track-changes/app/coffee/HistoryManager.coffee

{db, ObjectId} = require "./mongojs"
UpdateCompressor = require "./UpdateCompressor"
logger = require "logger-sharelatex"
async = require "async"

module.exports = HistoryManager =
	getLastCompressedUpdate: (doc_id, callback = (error, update) ->) ->
		db.docHistory
			.find(doc_id: ObjectId(doc_id.toString()))
			.sort(timestamp: -1)
			.limit(1)
			.toArray (error, compressedUpdates) ->
				return callback(error) if error?
				return callback null, compressedUpdates[0] or null

	deleteCompressedUpdate: (id, callback = (error) ->) ->
		db.docHistory.remove({ _id: ObjectId(id.toString()) }, callback)

	popLastCompressedUpdate: (doc_id, callback = (error, update) ->) ->
		HistoryManager.getLastCompressedUpdate doc_id, (error, update) ->
			return callback(error) if error?
			if update?
				HistoryManager.deleteCompressedUpdate update._id, (error) ->
					return callback(error) if error?
					callback null, update
			else
				callback null, null

	insertCompressedUpdates: (doc_id, updates, callback = (error) ->) ->
		jobs = []
		for update in updates
			do (update) ->
				jobs.push (callback) -> HistoryManager.insertCompressedUpdate doc_id, update, callback
		async.series jobs, callback

	insertCompressedUpdate: (doc_id, update, callback = (error) ->) ->
		logger.log doc_id: doc_id, update: update, "inserting compressed update"
		db.docHistory.insert {
			doc_id: ObjectId(doc_id.toString())
			op:     update.op
			meta:   update.meta
		}, callback

	compressAndSaveRawUpdates: (doc_id, rawUpdates, callback = (error) ->) ->
		length = rawUpdates.length
		if length == 0
			return callback()

		HistoryManager.popLastCompressedUpdate doc_id, (error, lastCompressedUpdate) ->
			return callback(error) if error?
			compressedUpdates = UpdateCompressor.compressRawUpdates lastCompressedUpdate, rawUpdates
			HistoryManager.insertCompressedUpdates doc_id, compressedUpdates, (error) ->
				return callback(error) if error?
				logger.log doc_id: doc_id, rawUpdatesLength: length, compressedUpdatesLength: compressedUpdates.length, "compressed doc updates"
				callback()