Add count() method

Author: thekid

ChangeLog.md

@@ -3,6 +3,8 @@ MongoDB for XP Framework ChangeLog
 
 ## ?.?.? / ????-??-??
 
+* Added new method `Collection::count()` to count documents in a collection
+  (@thekid)
 * Added new method `Collection::aggregate()` to perform aggregations, see
   https://docs.mongodb.com/manual/reference/command/aggregate/ and
   https://docs.mongodb.com/manual/reference/operator/aggregation/lookup/

src/main/php/com/mongodb/Collection.class.php

@@ -85,6 +85,21 @@ public function find($filter= []): Cursor {
     return new Cursor($this->proto, $result['body']['cursor']);
   }
 
+  /**
+   * Count documents in this collection
+   *
+   * @param  [:var] $filter
+   * @return com.mongodb.result.Cursor
+   */
+  public function count($filter= []): int {
+    $result= $this->proto->msg(0, 0, [
+      'count'  => $this->name,
+      'query'  => $filter ?: (object)[],
+      '$db'    => $this->database,
+    ]);
+    return $result['body']['n'];
+  }
+
   /**
    * Perfom aggregation over documents this collection
    *