document editor as a service with api

I'm working on a webapp which manage documents.

I need to offer the possibility to edit a .doc and co, in the browser.

I was thinking that maybe with a provider I could do this "easily".

imaginary code ->

editor.edit(bucket.get('myFile').readAsString(), onSave: (doc) {
  bucket.save('myFile', doc);
});

Do you know a provider ? Or an other solution...

I don't want to force my users to use office365 or Google Doc to edit their documents.