refact: reused EstimatedDocumentCountOperation for depd count

Author: mbroadst

lib/collection.js

@@ -26,7 +26,6 @@ const CommandCursor = require('./command_cursor');
 
 // Operations
 const checkForAtomicOperators = require('./operations/collection_ops').checkForAtomicOperators;
-const count = require('./operations/collection_ops').count;
 const ensureIndex = require('./operations/collection_ops').ensureIndex;
 const findAndModify = require('./operations/collection_ops').findAndModify;
 const findAndRemove = require('./operations/collection_ops').findAndRemove;
@@ -1369,9 +1368,16 @@ Collection.prototype.count = deprecate(function(query, options, callback) {
   query = args.length ? args.shift() || {} : {};
   options = args.length ? args.shift() || {} : {};
 
-  return executeLegacyOperation(this.s.topology, count, [this, query, options, callback]);
+  if (typeof options === 'function') (callback = options), (options = {});
+  options = options || {};
+
+  return executeOperation(
+    this.s.topology,
+    new EstimatedDocumentCountOperation(this, query, options),
+    callback
+  );
 }, 'collection.count is deprecated, and will be removed in a future version.' +
-  ' Use collection.countDocuments or collection.estimatedDocumentCount instead');
+  ' Use Collection.countDocuments or Collection.estimatedDocumentCount instead');
 
 /**
  * Gets an estimate of the count of documents in a collection using collection metadata.