added /check endpoint for documents

services/track-changes/app.coffee

@@ -22,6 +22,8 @@ app.post "/project/:project_id/doc/:doc_id/flush", HttpController.flushDoc
 
 app.get "/project/:project_id/doc/:doc_id/diff", HttpController.getDiff
 
+app.get "/project/:project_id/doc/:doc_id/check", HttpController.checkDoc
+
 app.get "/project/:project_id/updates", HttpController.getUpdates
 
 app.post "/project/:project_id/flush", HttpController.flushProject

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

@@ -11,11 +11,13 @@ module.exports = DiffGenerator =
 	ConsistencyError: ConsistencyError
 
 	rewindUpdate: (content, update) ->
-		for op in update.op by -1
+		for op, i in update.op by -1
 			try
 				content = DiffGenerator.rewindOp content, op
 			catch e
-				if e instanceof ConsistencyError
+				if e instanceof ConsistencyError and i = update.op.length - 1
+					# catch known case where the last op in an array has been
+					# merged into a later op
 					logger.error {update, op: JSON.stringify(op)}, "marking op as broken"
 					op.broken = true
 				else

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

@@ -30,6 +30,21 @@ module.exports = HttpController =
 			return next(error) if error?
 			res.send 204
 
+	checkDoc: (req, res, next = (error) ->) ->
+		doc_id = req.params.doc_id
+		project_id = req.params.project_id
+		logger.log project_id: project_id, doc_id: doc_id, "checking doc history"
+		DiffManager.getDocumentBeforeVersion project_id, doc_id, 1, (error, document, rewoundUpdates) ->
+			return next(error) if error?
+			broken = []
+			for update in rewoundUpdates
+				for op in update.op when op.broken is true
+					broken.push op
+			if broken.length > 0
+				res.send broken
+			else
+				res.send 204
+
 	getDiff: (req, res, next = (error) ->) ->
 		doc_id = req.params.doc_id
 		project_id = req.params.project_id