Ensure that updates are compressed in continuous incrementing order

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

@@ -10,9 +10,25 @@ module.exports = HistoryManager =
 
 		MongoManager.popLastCompressedUpdate doc_id, (error, lastCompressedUpdate) ->
 			return callback(error) if error?
+
+			# Ensure that raw updates start where lastCompressedUpdate left off
+			if lastCompressedUpdate?
+				rawUpdates = rawUpdates.slice(0)
+				while rawUpdates[0]? and rawUpdates[0].v <= lastCompressedUpdate.v
+					rawUpdates.shift()
+
+				if rawUpdates[0]? and rawUpdates[0].v != lastCompressedUpdate.v + 1
+					return callback new Error("Tried to apply raw op at version #{rawUpdates[0].v} to last compressed update with version #{lastCompressedUpdate.v}")
+
 			compressedUpdates = UpdateCompressor.compressRawUpdates lastCompressedUpdate, rawUpdates
 			MongoManager.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()
 
+	processUncompressedUpdates: (doc_id, callback = (error) ->) ->
+		# Get lock - here or elsewhere?
+		# Get batch from Redis left hand side (oldest)
+		# pass batch to compressAndSaveRawUpdates
+		# Delete batch from redis
+		# release lock

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

@@ -29,8 +29,8 @@ describe "HistoryManager", ->
 
 	describe "when there is no compressed history to begin with", ->
 		beforeEach ->
-			@rawUpdates = ["mock-raw-op-1", "mock-raw-op-2"]
+			@rawUpdates = [{ v: 12, op: "mock-op-12" }, { v: 13, op: "mock-op-13" }]
-			@compressedUpdates = ["mock-compressed-op"]
+			@compressedUpdates = { v: 13, op: "compressed-op-12" }
 
 			@MongoManager.popLastCompressedUpdate = sinon.stub().callsArgWith(1, null, null)
 			@MongoManager.insertCompressedUpdates = sinon.stub().callsArg(2)
@@ -57,13 +57,16 @@ describe "HistoryManager", ->
 
 	describe "when the raw ops need appending to existing history", ->
 		beforeEach ->
-			@rawUpdates = ["mock-raw-op-1", "mock-raw-op-2"]
+			@lastCompressedUpdate = { v: 11, op: "compressed-op-11" }
-			@lastCompressedUpdate = "mock-last-compressed-op-0"
+			@compressedUpdates = { v: 13, op: "compressed-op-12" }
-			@compressedUpdates = ["mock-compressed-op-1"]
 
 			@MongoManager.popLastCompressedUpdate = sinon.stub().callsArgWith(1, null, @lastCompressedUpdate)
 			@MongoManager.insertCompressedUpdates = sinon.stub().callsArg(2)
 			@UpdateCompressor.compressRawUpdates = sinon.stub().returns(@compressedUpdates)
+
+		describe "when the raw ops start where the existing history ends", ->
+			beforeEach ->
+				@rawUpdates = [{ v: 12, op: "mock-op-12" }, { v: 13, op: "mock-op-13" }]
 				@HistoryManager.compressAndSaveRawUpdates @doc_id, @rawUpdates, @callback
 
 			it "should try to pop the last compressed op", ->
@@ -84,4 +87,25 @@ describe "HistoryManager", ->
 			it "should call the callback", ->
 				@callback.called.should.equal true
 
+		describe "when some raw ops are passed that have already been compressed", ->
+			beforeEach ->
+				@rawUpdates = [{ v: 10, op: "mock-op-10" }, { v: 11, op: "mock-op-11"}, { v: 12, op: "mock-op-12" }, { v: 13, op: "mock-op-13" }]
+
+				@HistoryManager.compressAndSaveRawUpdates @doc_id, @rawUpdates, @callback
+
+			it "should only compress the more recent raw ops", ->
+				@UpdateCompressor.compressRawUpdates
+					.calledWith(@lastCompressedUpdate, @rawUpdates.slice(-2))
+					.should.equal true
+
+		describe "when the raw ops do not follow from the last compressed op version", ->
+			beforeEach ->
+				@rawUpdates = [{ v: 13, op: "mock-op-13" }]
+				@HistoryManager.compressAndSaveRawUpdates @doc_id, @rawUpdates, @callback
+
+			it "should call the callback with an error", ->
+				@callback
+					.calledWith(new Error("Tried to apply raw op at version 13 to last compressed update with version 11"))
+					.should.equal true
+