Big refactor to use better names and separation of concerns

services/track-changes/app/coffee/ConversionManager.coffee

@@ -1,48 +0,0 @@
-{db, ObjectId} = require "./mongojs"
-HistoryBuilder = require "./HistoryBuilder"
-logger = require "logger-sharelatex"
-
-module.exports = ConversionManager =
-	OPS_TO_LEAVE: 100
-
-	popLastCompressedOp: (doc_id, callback = (error, op) ->) ->
-		db.docHistory.findAndModify
-			query: { doc_id: ObjectId(doc_id) }
-			fields: { docOps: { $slice: -1 } }
-			update: { $pop: { docOps: 1 } }
-		, (error, history = { docOps: [] }) ->
-			return callback(error) if error?
-			callback null, history.docOps[0]
-
-	insertCompressedOps: (doc_id, docOps, callback = (error) ->) ->
-		db.docHistory.update {
-			doc_id: ObjectId(doc_id)
-		}, {
-			$push:
-				docOps:
-					$each: docOps
-		}, {
-			upsert: true
-		}, callback
-
-	convertAndSaveRawOps: (doc_id, rawOps, callback = (error) ->) ->
-		length = rawOps.length
-		if length == 0
-			return callback()
-
-
-		ConversionManager.popLastCompressedOp doc_id, (error, lastCompressedOp) ->
-			return callback(error) if error?
-
-			if !lastCompressedOp?
-				rawOps = rawOps.slice(0) # Clone so we can modify in place
-				lastCompressedOp = rawOps.shift()
-
-			uncompressedOps = [lastCompressedOp].concat rawOps
-			compressedOps = HistoryBuilder.compressOps uncompressedOps
-
-			ConversionManager.insertCompressedOps doc_id, compressedOps, (error) ->
-				return callback(error) if error?
-				logger.log doc_id: doc_id, rawOpsLength: length, compressedOpsLength: compressedOps.length, "compressed doc ops"
-				callback()
-

services/track-changes/app/coffee/HistoryBuilder.coffee

@@ -1,150 +0,0 @@
-strInject = (s1, pos, s2) -> s1[...pos] + s2 + s1[pos..]
-strRemove = (s1, pos, length) -> s1[...pos] + s1[(pos + length)..]
-
-module.exports = HistoryBuilder =
-	normalizeUpdate: (update) ->
-		if update.meta.start_ts?
-			return [update] # already normalized
-
-		updates = []
-		for op in update.op
-			updates.push
-				op: [op]
-				meta:
-					start_ts: update.meta.ts
-					end_ts: update.meta.ts
-					user_id: update.meta.user_id
-		return updates
-
-	compressUpdates: (rawUpdates) ->
-		return [] if rawUpdates.length == 0
-		normalizedUpdates = []
-		for rawUpdate in rawUpdates
-			normalizedUpdates = normalizedUpdates.concat HistoryBuilder.normalizeUpdate(rawUpdate)
-
-		return [] if normalizedUpdates.length == 0
-		firstPass = [normalizedUpdates.shift()]
-		for update in normalizedUpdates
-			lastCompressedUpdate = firstPass.pop()
-			if lastCompressedUpdate?
-				firstPass = firstPass.concat HistoryBuilder._concatTwoUpdates lastCompressedUpdate, update, false
-			else
-				firstPass.push rawUpdate
-
-		return [] if firstPass.length == 0
-		secondPass = [firstPass.shift()]
-		for update in firstPass
-			lastCompressedUpdate = secondPass.pop()
-			if lastCompressedUpdate?
-				secondPass = secondPass.concat HistoryBuilder._concatTwoUpdates lastCompressedUpdate, update, true
-			else
-				secondPass.push update
-
-		return secondPass
-
-	MAX_TIME_BETWEEN_UPDATES: oneMinute = 60 * 1000
-
-	_concatTwoUpdates: (firstUpdate, secondUpdate, mergeInsertsAndDeletes) ->
-		firstUpdate =
-			op: firstUpdate.op
-			meta:
-				user_id:  firstUpdate.meta.user_id or null
-				start_ts: firstUpdate.meta.start_ts or firstUpdate.meta.ts
-				end_ts:   firstUpdate.meta.end_ts   or firstUpdate.meta.ts
-		secondUpdate =
-			op: secondUpdate.op
-			meta:
-				user_id:  secondUpdate.meta.user_id or null
-				start_ts: secondUpdate.meta.start_ts or secondUpdate.meta.ts
-				end_ts:   secondUpdate.meta.end_ts   or secondUpdate.meta.ts
-
-		if firstUpdate.meta.user_id != secondUpdate.meta.user_id
-			return [firstUpdate, secondUpdate]
-
-		if secondUpdate.meta.start_ts - firstUpdate.meta.end_ts > HistoryBuilder.MAX_TIME_BETWEEN_UPDATES
-			return [firstUpdate, secondUpdate]
-
-		firstOp = firstUpdate.op[0]
-		secondOp = secondUpdate.op[0]
-		# Two inserts
-		if firstOp.i? and secondOp.i? and firstOp.p <= secondOp.p <= (firstOp.p + firstOp.i.length)
-			return [
-				meta:
-					start_ts: firstUpdate.meta.start_ts
-					end_ts:   secondUpdate.meta.end_ts
-					user_id:  firstUpdate.meta.user_id
-				op: [
-					p: firstOp.p
-					i: strInject(firstOp.i, secondOp.p - firstOp.p, secondOp.i)
-				]
-			]
-		# Two deletes
-		else if firstOp.d? and secondOp.d? and secondOp.p <= firstOp.p <= (secondOp.p + secondOp.d.length)
-			return [
-				meta:
-					start_ts: firstUpdate.meta.start_ts
-					end_ts:   secondUpdate.meta.end_ts
-					user_id:  firstUpdate.meta.user_id
-				op: [
-					p: secondOp.p
-					d: strInject(secondOp.d, firstOp.p - secondOp.p, firstOp.d)
-				]
-			]
-		# An insert and then a delete
-		if mergeInsertsAndDeletes and firstOp.i? and secondOp.d? and firstOp.p <= secondOp.p <= (firstOp.p + firstOp.i.length)
-			offset = secondOp.p - firstOp.p
-			insertedText = firstOp.i.slice(offset, offset + secondOp.d.length)
-			if insertedText == secondOp.d
-				insert = strRemove(firstOp.i, offset, secondOp.d.length)
-				return [] if insert == ""
-				return [
-					meta:
-						start_ts: firstUpdate.meta.start_ts
-						end_ts:   secondUpdate.meta.end_ts
-						user_id:  firstUpdate.meta.user_id
-					op: [
-						p: firstOp.p
-						i: insert
-					]
-				]
-			else
-				# This shouldn't be possible!
-				return [firstUpdate, secondUpdate]
-		else if mergeInsertsAndDeletes and firstOp.d? and secondOp.i? and firstOp.p  == secondOp.p
-			offset = firstOp.d.indexOf(secondOp.i)
-			if offset == -1
-				return [firstUpdate, secondUpdate]
-			headD = firstOp.d.slice(0, offset)
-			inserted = firstOp.d.slice(offset, secondOp.i.length)
-			tailD = firstOp.d.slice(offset + secondOp.i.length)
-			headP = firstOp.p
-			tailP = firstOp.p + secondOp.i.length
-			updates = []
-			if headD != ""
-				updates.push
-					meta:
-						start_ts: firstUpdate.meta.start_ts
-						end_ts:   secondUpdate.meta.end_ts
-						user_id:  firstUpdate.meta.user_id
-					op: [
-						p: headP
-						d: headD
-					]
-			if tailD != ""
-				updates.push
-					meta:
-						start_ts: firstUpdate.meta.start_ts
-						end_ts:   secondUpdate.meta.end_ts
-						user_id:  firstUpdate.meta.user_id
-					op: [
-						p: tailP
-						d: tailD
-					]
-			if updates.length == 2
-				updates[0].meta.start_ts = updates[0].meta.end_ts = firstUpdate.meta.start_ts
-				updates[1].meta.start_ts = updates[1].meta.end_ts = secondUpdate.meta.end_ts
-			return updates
-
-		else
-			return [firstUpdate, secondUpdate]
-

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

@@ -0,0 +1,54 @@
+{db, ObjectId} = require "./mongojs"
+UpdateCompressor = require "./UpdateCompressor"
+logger = require "logger-sharelatex"
+
+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.delete({ _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, docUpdates, callback = (error) ->) ->
+		db.docHistory.update {
+			doc_id: ObjectId(doc_id)
+		}, {
+			$push:
+				docUpdates:
+					$each: docUpdates
+		}, {
+			upsert: true
+		}, 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()
+

services/track-changes/app/coffee/UpdateCompressor.coffee

@@ -0,0 +1,118 @@
+strInject = (s1, pos, s2) -> s1[...pos] + s2 + s1[pos..]
+strRemove = (s1, pos, length) -> s1[...pos] + s1[(pos + length)..]
+
+module.exports = UpdateCompressor =
+	# Updates come from the doc updater in format
+	# {
+	# 	op:   [ { ... op1 ... }, { ... op2 ... } ]
+	# 	meta: { ts: ..., user_id: ... }
+	# }
+	# but it's easier to work with on op per update, so convert these updates to
+	# our compressed format
+	# [{
+	# 	op: op1
+	# 	meta: { start_ts: ... , end_ts: ..., user_id: ... }
+	# }, {
+	# 	op: op2
+	# 	meta: { start_ts: ... , end_ts: ..., user_id: ... }
+	# }]
+	convertRawUpdatesToCompressedFormat: (updates) ->
+		normalizedUpdates = []
+		for update in updates
+			for op in update.op
+				normalizedUpdates.push
+					op: op
+					meta:
+						start_ts: update.meta.start_ts or update.meta.ts
+						end_ts:   update.meta.end_ts   or update.meta.ts
+						user_id:  update.meta.user_id
+		return normalizedUpdates
+
+	compressRawUpdates: (lastPreviousUpdate, rawUpdates) ->
+		updates = UpdateCompressor.convertRawUpdatesToCompressedFormat(rawUpdates)
+		if lastPreviousUpdate?
+			updates.unshift(lastPreviousUpdate)
+		return UpdateCompressor.compressUpdates(updates)
+
+	compressUpdates: (updates) ->
+		return [] if updates.length == 0
+
+		compressedUpdates = [updates.shift()]
+		for update in updates
+			lastCompressedUpdate = compressedUpdates.pop()
+			if lastCompressedUpdate?
+				compressedUpdates = compressedUpdates.concat UpdateCompressor._concatTwoUpdates lastCompressedUpdate, update
+			else
+				compressedUpdates.push update
+
+		return compressedUpdates
+
+	MAX_TIME_BETWEEN_UPDATES: oneMinute = 60 * 1000
+
+	_concatTwoUpdates: (firstUpdate, secondUpdate) ->
+		firstUpdate =
+			op: firstUpdate.op
+			meta:
+				user_id:  firstUpdate.meta.user_id or null
+				start_ts: firstUpdate.meta.start_ts or firstUpdate.meta.ts
+				end_ts:   firstUpdate.meta.end_ts   or firstUpdate.meta.ts
+		secondUpdate =
+			op: secondUpdate.op
+			meta:
+				user_id:  secondUpdate.meta.user_id or null
+				start_ts: secondUpdate.meta.start_ts or secondUpdate.meta.ts
+				end_ts:   secondUpdate.meta.end_ts   or secondUpdate.meta.ts
+
+		if firstUpdate.meta.user_id != secondUpdate.meta.user_id
+			return [firstUpdate, secondUpdate]
+
+		if secondUpdate.meta.start_ts - firstUpdate.meta.end_ts > UpdateCompressor.MAX_TIME_BETWEEN_UPDATES
+			return [firstUpdate, secondUpdate]
+
+		firstOp = firstUpdate.op
+		secondOp = secondUpdate.op
+		# Two inserts
+		if firstOp.i? and secondOp.i? and firstOp.p <= secondOp.p <= (firstOp.p + firstOp.i.length)
+			return [
+				meta:
+					start_ts: firstUpdate.meta.start_ts
+					end_ts:   secondUpdate.meta.end_ts
+					user_id:  firstUpdate.meta.user_id
+				op:
+					p: firstOp.p
+					i: strInject(firstOp.i, secondOp.p - firstOp.p, secondOp.i)
+			]
+		# Two deletes
+		else if firstOp.d? and secondOp.d? and secondOp.p <= firstOp.p <= (secondOp.p + secondOp.d.length)
+			return [
+				meta:
+					start_ts: firstUpdate.meta.start_ts
+					end_ts:   secondUpdate.meta.end_ts
+					user_id:  firstUpdate.meta.user_id
+				op:
+					p: secondOp.p
+					d: strInject(secondOp.d, firstOp.p - secondOp.p, firstOp.d)
+			]
+		# An insert and then a delete
+		else if firstOp.i? and secondOp.d? and firstOp.p <= secondOp.p <= (firstOp.p + firstOp.i.length)
+			offset = secondOp.p - firstOp.p
+			insertedText = firstOp.i.slice(offset, offset + secondOp.d.length)
+			if insertedText == secondOp.d
+				insert = strRemove(firstOp.i, offset, secondOp.d.length)
+				return [] if insert == ""
+				return [
+					meta:
+						start_ts: firstUpdate.meta.start_ts
+						end_ts:   secondUpdate.meta.end_ts
+						user_id:  firstUpdate.meta.user_id
+					op:
+						p: firstOp.p
+						i: insert
+				]
+			else
+				# This shouldn't be possible!
+				return [firstUpdate, secondUpdate]
+
+		else
+			return [firstUpdate, secondUpdate]
+

services/track-changes/test/unit/coffee/ConversionManager/ConversionManagerTests.coffee

@@ -1,87 +0,0 @@
-sinon = require('sinon')
-chai = require('chai')
-should = chai.should()
-expect = chai.expect
-modulePath = "../../../../app/js/ConversionManager.js"
-SandboxedModule = require('sandboxed-module')
-
-describe "ConversionManager", ->
-	beforeEach ->
-		@ConversionManager = SandboxedModule.require modulePath, requires:
-			"./HistoryBuilder": @HistoryBuilder = {}
-			"./mongojs" : {}
-			"logger-sharelatex": { log: sinon.stub() }
-		@doc_id = "doc-id-123"
-		@callback = sinon.stub()
-
-	describe "when there are no raw ops", ->
-		beforeEach ->
-			@ConversionManager.popLastCompressedOp = sinon.stub()
-			@ConversionManager.insertCompressedOps = sinon.stub()
-			@ConversionManager.convertAndSaveRawOps @doc_id, [], @callback
-
-		it "should not need to access the database", ->
-			@ConversionManager.popLastCompressedOp.called.should.equal false
-			@ConversionManager.insertCompressedOps.called.should.equal false
-
-		it "should call the callback", ->
-			@callback.called.should.equal true
-
-	describe "when there is no compressed history to begin with", ->
-		beforeEach ->
-			@rawOps = ["mock-raw-op-1", "mock-raw-op-2"]
-			@compressedOps = ["mock-compressed-op"]
-
-			@ConversionManager.popLastCompressedOp = sinon.stub().callsArgWith(1, null, null)
-			@ConversionManager.insertCompressedOps = sinon.stub().callsArg(2)
-			@HistoryBuilder.compressOps = sinon.stub().returns(@compressedOps)
-			@ConversionManager.convertAndSaveRawOps @doc_id, @rawOps, @callback
-
-		it "should try to pop the last compressed op", ->
-			@ConversionManager.popLastCompressedOp
-				.calledWith(@doc_id)
-				.should.equal true
-		
-		it "should compress the raw ops", ->
-			@HistoryBuilder.compressOps
-				.calledWith(@rawOps)
-				.should.equal true
-		
-		it "should save the compressed ops", ->
-			@ConversionManager.insertCompressedOps
-				.calledWith(@doc_id, @compressedOps)
-				.should.equal true
-
-		it "should call the callback", ->
-			@callback.called.should.equal true
-
-	describe "when the raw ops need appending to existing history", ->
-		beforeEach ->
-			@rawOps = ["mock-raw-op-1", "mock-raw-op-2"]
-			@lastCompressedOp = "mock-last-compressed-op-0"
-			@compressedOps = ["mock-compressed-op-1"]
-
-			@ConversionManager.popLastCompressedOp = sinon.stub().callsArgWith(1, null, @lastCompressedOp)
-			@ConversionManager.insertCompressedOps = sinon.stub().callsArg(2)
-			@HistoryBuilder.compressOps = sinon.stub().returns(@compressedOps)
-			@ConversionManager.convertAndSaveRawOps @doc_id, @rawOps, @callback
-
-		it "should try to pop the last compressed op", ->
-			@ConversionManager.popLastCompressedOp
-				.calledWith(@doc_id)
-				.should.equal true
-		
-		it "should compress the last compressed op and the raw ops", ->
-			@HistoryBuilder.compressOps
-				.calledWith([@lastCompressedOp].concat(@rawOps))
-				.should.equal true
-		
-		it "should save the compressed ops", ->
-			@ConversionManager.insertCompressedOps
-				.calledWith(@doc_id, @compressedOps)
-				.should.equal true
-
-		it "should call the callback", ->
-			@callback.called.should.equal true
-		
-

services/track-changes/test/unit/coffee/HistoryBuilder/HistoryBuilderTests.coffee

@@ -1,240 +0,0 @@
-sinon = require('sinon')
-chai = require('chai')
-should = chai.should()
-expect = chai.expect
-modulePath = "../../../../app/js/HistoryBuilder.js"
-SandboxedModule = require('sandboxed-module')
-
-describe "HistoryBuilder", ->
-	beforeEach ->
-		@HistoryBuilder = SandboxedModule.require modulePath
-		@user_id = "user-id-1"
-		@other_user_id = "user-id-2"
-		@ts1 = Date.now()
-		@ts2 = Date.now() + 1000
-
-	describe "compress", ->
-		describe "insert - insert", ->
-			it "should append one insert to the other", ->
-				expect(@HistoryBuilder.compressUpdates [{
-					op: [ p: 3, i: "foo" ]
-					meta: ts: @ts1, user_id: @user_id
-				}, {
-					op: [ p: 6, i: "bar" ]
-					meta: ts: @ts2, user_id: @user_id
-				}])
-				.to.deep.equal [{
-					op: [ p: 3, i: "foobar" ]
-					meta: start_ts: @ts1, end_ts: @ts2, user_id: @user_id
-				}]
-
-			it "should insert one insert inside the other", ->
-				expect(@HistoryBuilder.compressUpdates [{
-					op: [ p: 3, i: "foo" ]
-					meta: ts: @ts1, user_id: @user_id
-				}, {
-					op: [ p: 5, i: "bar" ]
-					meta: ts: @ts2, user_id: @user_id
-				}])
-				.to.deep.equal [{
-					op: [ p: 3, i: "fobaro" ]
-					meta: start_ts: @ts1, end_ts: @ts2, user_id: @user_id
-				}]
-
-			it "should not append separated inserts", ->
-				expect(@HistoryBuilder.compressUpdates [{
-					op: [ p: 3, i: "foo" ]
-					meta: ts: @ts1, user_id: @user_id
-				}, {
-					op: [ p: 9, i: "bar" ]
-					meta: ts: @ts2, user_id: @user_id
-				}])
-				.to.deep.equal [{
-					op: [ p: 3, i: "foo" ]
-					meta: start_ts: @ts1, end_ts: @ts1, user_id: @user_id
-				}, {
-					op: [ p: 9, i: "bar" ]
-					meta: start_ts: @ts2, end_ts: @ts2, user_id: @user_id
-				}]
-
-		describe "delete - delete", ->
-			it "should append one delete to the other", ->
-				expect(@HistoryBuilder.compressUpdates [{
-					op: [ p: 3, d: "foo" ]
-					meta: ts: @ts1, user_id: @user_id
-				}, {
-					op: [ p: 3, d: "bar" ]
-					meta: ts: @ts2, user_id: @user_id
-				}])
-				.to.deep.equal [{
-					op: [ p: 3, d: "foobar" ]
-					meta: start_ts: @ts1, end_ts: @ts2, user_id: @user_id
-				}]
-				
-			it "should insert one delete inside the other", ->
-				expect(@HistoryBuilder.compressUpdates [{
-					op: [ p: 3, d: "foo" ]
-					meta: ts: @ts1, user_id: @user_id
-				}, {
-					op: [ p: 1, d: "bar" ]
-					meta: ts: @ts2, user_id: @user_id
-				}])
-				.to.deep.equal [{
-					op: [ p: 1, d: "bafoor" ]
-					meta: start_ts: @ts1, end_ts: @ts2, user_id: @user_id
-				}]
-				
-			it "should not append separated deletes", ->
-				expect(@HistoryBuilder.compressUpdates [{
-					op: [ p: 3, d: "foo" ]
-					meta: ts: @ts1, user_id: @user_id
-				}, {
-					op: [ p: 9, d: "bar" ]
-					meta: ts: @ts2, user_id: @user_id
-				}])
-				.to.deep.equal [{
-					op: [ p: 3, d: "foo" ]
-					meta: start_ts: @ts1, end_ts: @ts1, user_id: @user_id
-				}, {
-					op: [ p: 9, d: "bar" ]
-					meta: start_ts: @ts2, end_ts: @ts2, user_id: @user_id
-				}]
-
-		describe "insert - delete", ->
-			it "should undo a previous insert", ->
-				expect(@HistoryBuilder.compressUpdates [{
-					op: [ p: 3, i: "foo" ]
-					meta: ts: @ts1, user_id: @user_id
-				}, {
-					op: [ p: 5, d: "o" ]
-					meta: ts: @ts2, user_id: @user_id
-				}])
-				.to.deep.equal [{
-					op: [ p: 3, i: "fo" ]
-					meta: start_ts: @ts1, end_ts: @ts2, user_id: @user_id
-				}]
-				
-			it "should remove part of an insert from the middle", ->
-				expect(@HistoryBuilder.compressUpdates [{
-					op: [ p: 3, i: "fobaro" ]
-					meta: ts: @ts1, user_id: @user_id
-				}, {
-					op: [ p: 5, d: "bar" ]
-					meta: ts: @ts2, user_id: @user_id
-				}])
-				.to.deep.equal [{
-					op: [ p: 3, i: "foo" ]
-					meta: start_ts: @ts1, end_ts: @ts2, user_id: @user_id
-				}]
-
-			it "should cancel out two opposite updates", ->
-				expect(@HistoryBuilder.compressUpdates [{
-					op: [ p: 3, i: "foo" ]
-					meta: ts: @ts1, user_id: @user_id
-				}, {
-					op: [ p: 3, d: "foo" ]
-					meta: ts: @ts2, user_id: @user_id
-				}])
-				.to.deep.equal []
-				
-			it "should not combine separated updates", ->
-				expect(@HistoryBuilder.compressUpdates [{
-					op: [ p: 3, i: "foo" ]
-					meta: ts: @ts1, user_id: @user_id
-				}, {
-					op: [ p: 9, d: "bar" ]
-					meta: ts: @ts2, user_id: @user_id
-				}])
-				.to.deep.equal [{
-					op: [ p: 3, i: "foo" ]
-					meta: start_ts: @ts1, end_ts: @ts1, user_id: @user_id
-				}, {
-					op: [ p: 9, d: "bar" ]
-					meta: start_ts: @ts2, end_ts: @ts2, user_id: @user_id
-				}]
-
-		describe "delete - insert", ->
-			it "should redo a previous delete at the beginning", ->
-				expect(@HistoryBuilder.compressUpdates [{
-					op: [ p: 3, d: "foo" ]
-					meta: ts: @ts1, user_id: @user_id
-				}, {
-					op: [ p: 3, i: "f" ]
-					meta: ts: @ts2, user_id: @user_id
-				}])
-				.to.deep.equal [{
-					op: [ p: 4, d: "oo" ]
-					meta: start_ts: @ts1, end_ts: @ts2, user_id: @user_id
-				}]
-
-			it "should redo a previous delete from halfway through", ->
-				expect(@HistoryBuilder.compressUpdates [{
-					op: [ p: 3, d: "foobar" ]
-					meta: ts: @ts1, user_id: @user_id
-				}, {
-					op: [ p: 3, i: "oo" ]
-					meta: ts: @ts2, user_id: @user_id
-				}])
-				.to.deep.equal [{
-					op: [ p: 3, d: "f" ]
-					meta: start_ts: @ts1, end_ts: @ts1, user_id: @user_id
-				}, {
-					op: [ p: 5, d: "bar" ]
-					meta: start_ts: @ts2, end_ts: @ts2, user_id: @user_id
-				}]
-
-			it "should keep words together", ->
-				expect(@HistoryBuilder.compressUpdates [{
-					op: [ p: 3, d: "abcdefghijklmnopqrstuvwxyz hello world" ]
-					meta: ts: @ts1, user_id: @user_id
-				}, {
-					op: [ p: 3, i: "w" ]
-					meta: ts: @ts2, user_id: @user_id
-				}, {
-					op: [ p: 4, i: "o" ]
-					meta: ts: @ts2, user_id: @user_id
-				}, {
-					op: [ p: 5, i: "r" ]
-					meta: ts: @ts2, user_id: @user_id
-				}, {
-					op: [ p: 6, i: "l" ]
-					meta: ts: @ts2, user_id: @user_id
-				}, {
-					op: [ p: 7, i: "d" ]
-					meta: ts: @ts2, user_id: @user_id
-				}])
-				.to.deep.equal [{
-					op: [ p: 3, d: "abcdefghijklmnopqrstuvwxyz hello " ]
-					meta: start_ts: @ts1, end_ts: @ts2, user_id: @user_id
-				}]
-				
-
-			it "should not combine the ops if the insert text does not match the delete text", ->
-				expect(@HistoryBuilder.compressUpdates [{
-					op: [ p: 3, d: "foobar" ]
-					meta: ts: @ts1, user_id: @user_id
-				}, {
-					op: [ p: 3, i: "xy" ]
-					meta: ts: @ts2, user_id: @user_id
-				}])
-				.to.deep.equal [{
-					op: [ p: 3, d: "foobar" ]
-					meta: start_ts: @ts1, end_ts: @ts1, user_id: @user_id
-				}, {
-					op: [ p: 3, i: "xy" ]
-					meta: start_ts: @ts2, end_ts: @ts2, user_id: @user_id
-				}]
-
-			it "should cancel two equal updates", ->
-				expect(@HistoryBuilder.compressUpdates [{
-					op: [ p: 3, d: "foo" ]
-					meta: ts: @ts1, user_id: @user_id
-				}, {
-					op: [ p: 3, i: "foo" ]
-					meta: ts: @ts2, user_id: @user_id
-				}])
-				.to.deep.equal []
-				
-
-				
-				

services/track-changes/test/unit/coffee/HistoryManager/HistoryManagerTests.coffee

@@ -0,0 +1,87 @@
+sinon = require('sinon')
+chai = require('chai')
+should = chai.should()
+expect = chai.expect
+modulePath = "../../../../app/js/HistoryManager.js"
+SandboxedModule = require('sandboxed-module')
+
+describe "HistoryManager", ->
+	beforeEach ->
+		@HistoryManager = SandboxedModule.require modulePath, requires:
+			"./UpdateCompressor": @UpdateCompressor = {}
+			"./mongojs" : {}
+			"logger-sharelatex": { log: sinon.stub() }
+		@doc_id = "doc-id-123"
+		@callback = sinon.stub()
+
+	describe "when there are no raw ops", ->
+		beforeEach ->
+			@HistoryManager.popLastCompressedUpdate = sinon.stub()
+			@HistoryManager.insertCompressedUpdates = sinon.stub()
+			@HistoryManager.compressAndSaveRawUpdates @doc_id, [], @callback
+
+		it "should not need to access the database", ->
+			@HistoryManager.popLastCompressedUpdate.called.should.equal false
+			@HistoryManager.insertCompressedUpdates.called.should.equal false
+
+		it "should call the callback", ->
+			@callback.called.should.equal true
+
+	describe "when there is no compressed history to begin with", ->
+		beforeEach ->
+			@rawUpdates = ["mock-raw-op-1", "mock-raw-op-2"]
+			@compressedUpdates = ["mock-compressed-op"]
+
+			@HistoryManager.popLastCompressedUpdate = sinon.stub().callsArgWith(1, null, null)
+			@HistoryManager.insertCompressedUpdates = sinon.stub().callsArg(2)
+			@UpdateCompressor.compressRawUpdates = sinon.stub().returns(@compressedUpdates)
+			@HistoryManager.compressAndSaveRawUpdates @doc_id, @rawUpdates, @callback
+
+		it "should try to pop the last compressed op", ->
+			@HistoryManager.popLastCompressedUpdate
+				.calledWith(@doc_id)
+				.should.equal true
+		
+		it "should compress the raw ops", ->
+			@UpdateCompressor.compressRawUpdates
+				.calledWith(null, @rawUpdates)
+				.should.equal true
+		
+		it "should save the compressed ops", ->
+			@HistoryManager.insertCompressedUpdates
+				.calledWith(@doc_id, @compressedUpdates)
+				.should.equal true
+
+		it "should call the callback", ->
+			@callback.called.should.equal true
+
+	describe "when the raw ops need appending to existing history", ->
+		beforeEach ->
+			@rawUpdates = ["mock-raw-op-1", "mock-raw-op-2"]
+			@lastCompressedUpdate = "mock-last-compressed-op-0"
+			@compressedUpdates = ["mock-compressed-op-1"]
+
+			@HistoryManager.popLastCompressedUpdate = sinon.stub().callsArgWith(1, null, @lastCompressedUpdate)
+			@HistoryManager.insertCompressedUpdates = sinon.stub().callsArg(2)
+			@UpdateCompressor.compressRawUpdates = sinon.stub().returns(@compressedUpdates)
+			@HistoryManager.compressAndSaveRawUpdates @doc_id, @rawUpdates, @callback
+
+		it "should try to pop the last compressed op", ->
+			@HistoryManager.popLastCompressedUpdate
+				.calledWith(@doc_id)
+				.should.equal true
+		
+		it "should compress the last compressed op and the raw ops", ->
+			@UpdateCompressor.compressRawUpdates
+				.calledWith(@lastCompressedUpdate, @rawUpdates)
+				.should.equal true
+		
+		it "should save the compressed ops", ->
+			@HistoryManager.insertCompressedUpdates
+				.calledWith(@doc_id, @compressedUpdates)
+				.should.equal true
+
+		it "should call the callback", ->
+			@callback.called.should.equal true
+		
+

services/track-changes/test/unit/coffee/UpdateCompressor/UpdateCompressorTests.coffee

@@ -0,0 +1,176 @@
+sinon = require('sinon')
+chai = require('chai')
+should = chai.should()
+expect = chai.expect
+modulePath = "../../../../app/js/UpdateCompressor.js"
+SandboxedModule = require('sandboxed-module')
+
+describe "UpdateCompressor", ->
+	beforeEach ->
+		@UpdateCompressor = SandboxedModule.require modulePath
+		@user_id = "user-id-1"
+		@other_user_id = "user-id-2"
+		@ts1 = Date.now()
+		@ts2 = Date.now() + 1000
+
+	describe "convertRawUpdatesToCompressedFormat", ->
+		it "should split grouped updates into individual updates", ->
+			expect(@UpdateCompressor.convertRawUpdatesToCompressedFormat [{
+				op:   [ @op1 = { p: 0, i: "Foo" }, @op2 = { p: 6, i: "bar"} ]
+				meta: { ts: @ts1, user_id: @user_id }
+			}, {
+				op:   [ @op3 = { p: 10, i: "baz" } ]
+				meta: { ts: @ts2, user_id: @other_user_id }
+			}])
+			.to.deep.equal [{
+				op: @op1,
+				meta: { start_ts: @ts1, end_ts: @ts1, user_id: @user_id }
+			}, {
+				op: @op2,
+				meta: { start_ts: @ts1, end_ts: @ts1, user_id: @user_id }
+			}, {
+				op: @op3,
+				meta: { start_ts: @ts2, end_ts: @ts2, user_id: @other_user_id }
+			}]
+
+	describe "compress", ->
+		describe "insert - insert", ->
+			it "should append one insert to the other", ->
+				expect(@UpdateCompressor.compressUpdates [{
+					op: { p: 3, i: "foo" }
+					meta: ts: @ts1, user_id: @user_id
+				}, {
+					op: { p: 6, i: "bar" }
+					meta: ts: @ts2, user_id: @user_id
+				}])
+				.to.deep.equal [{
+					op: { p: 3, i: "foobar" }
+					meta: start_ts: @ts1, end_ts: @ts2, user_id: @user_id
+				}]
+
+			it "should insert one insert inside the other", ->
+				expect(@UpdateCompressor.compressUpdates [{
+					op: { p: 3, i: "foo" }
+					meta: ts: @ts1, user_id: @user_id
+				}, {
+					op: { p: 5, i: "bar" }
+					meta: ts: @ts2, user_id: @user_id
+				}])
+				.to.deep.equal [{
+					op: { p: 3, i: "fobaro" }
+					meta: start_ts: @ts1, end_ts: @ts2, user_id: @user_id
+				}]
+
+			it "should not append separated inserts", ->
+				expect(@UpdateCompressor.compressUpdates [{
+					op: { p: 3, i: "foo" }
+					meta: ts: @ts1, user_id: @user_id
+				}, {
+					op: { p: 9, i: "bar" }
+					meta: ts: @ts2, user_id: @user_id
+				}])
+				.to.deep.equal [{
+					op: { p: 3, i: "foo" }
+					meta: start_ts: @ts1, end_ts: @ts1, user_id: @user_id
+				}, {
+					op: { p: 9, i: "bar" }
+					meta: start_ts: @ts2, end_ts: @ts2, user_id: @user_id
+				}]
+
+		describe "delete - delete", ->
+			it "should append one delete to the other", ->
+				expect(@UpdateCompressor.compressUpdates [{
+					op: { p: 3, d: "foo" }
+					meta: ts: @ts1, user_id: @user_id
+				}, {
+					op: { p: 3, d: "bar" }
+					meta: ts: @ts2, user_id: @user_id
+				}])
+				.to.deep.equal [{
+					op: { p: 3, d: "foobar" }
+					meta: start_ts: @ts1, end_ts: @ts2, user_id: @user_id
+				}]
+				
+			it "should insert one delete inside the other", ->
+				expect(@UpdateCompressor.compressUpdates [{
+					op: { p: 3, d: "foo" }
+					meta: ts: @ts1, user_id: @user_id
+				}, {
+					op: { p: 1, d: "bar" }
+					meta: ts: @ts2, user_id: @user_id
+				}])
+				.to.deep.equal [{
+					op: { p: 1, d: "bafoor" }
+					meta: start_ts: @ts1, end_ts: @ts2, user_id: @user_id
+				}]
+				
+			it "should not append separated deletes", ->
+				expect(@UpdateCompressor.compressUpdates [{
+					op: { p: 3, d: "foo" }
+					meta: ts: @ts1, user_id: @user_id
+				}, {
+					op: { p: 9, d: "bar" }
+					meta: ts: @ts2, user_id: @user_id
+				}])
+				.to.deep.equal [{
+					op: { p: 3, d: "foo" }
+					meta: start_ts: @ts1, end_ts: @ts1, user_id: @user_id
+				}, {
+					op: { p: 9, d: "bar" }
+					meta: start_ts: @ts2, end_ts: @ts2, user_id: @user_id
+				}]
+
+		describe "insert - delete", ->
+			it "should undo a previous insert", ->
+				expect(@UpdateCompressor.compressUpdates [{
+					op: { p: 3, i: "foo" }
+					meta: ts: @ts1, user_id: @user_id
+				}, {
+					op: { p: 5, d: "o" }
+					meta: ts: @ts2, user_id: @user_id
+				}])
+				.to.deep.equal [{
+					op: { p: 3, i: "fo" }
+					meta: start_ts: @ts1, end_ts: @ts2, user_id: @user_id
+				}]
+				
+			it "should remove part of an insert from the middle", ->
+				expect(@UpdateCompressor.compressUpdates [{
+					op: { p: 3, i: "fobaro" }
+					meta: ts: @ts1, user_id: @user_id
+				}, {
+					op: { p: 5, d: "bar" }
+					meta: ts: @ts2, user_id: @user_id
+				}])
+				.to.deep.equal [{
+					op: { p: 3, i: "foo" }
+					meta: start_ts: @ts1, end_ts: @ts2, user_id: @user_id
+				}]
+
+			it "should cancel out two opposite updates", ->
+				expect(@UpdateCompressor.compressUpdates [{
+					op: { p: 3, i: "foo" }
+					meta: ts: @ts1, user_id: @user_id
+				}, {
+					op: { p: 3, d: "foo" }
+					meta: ts: @ts2, user_id: @user_id
+				}])
+				.to.deep.equal []
+				
+			it "should not combine separated updates", ->
+				expect(@UpdateCompressor.compressUpdates [{
+					op: { p: 3, i: "foo" }
+					meta: ts: @ts1, user_id: @user_id
+				}, {
+					op: { p: 9, d: "bar" }
+					meta: ts: @ts2, user_id: @user_id
+				}])
+				.to.deep.equal [{
+					op: { p: 3, i: "foo" }
+					meta: start_ts: @ts1, end_ts: @ts1, user_id: @user_id
+				}, {
+					op: { p: 9, d: "bar" }
+					meta: start_ts: @ts2, end_ts: @ts2, user_id: @user_id
+				}]
+
+