Modify json structure scala

Question

I have a json like this:

 [
  {
    "ser": 345,
    "City": "New York",
    "Gen": 1
  },
  {
    "ser": 55,
    "City": "New York",
    "Gen": 2
  },
  {
    "ser": 19,
    "City": "New York",
    "Gen": 3
  }
 ]

I want to make some query to this json ( example: SELECT SUM(ser) AS Serlab, City, Gen FROM libri GROUP BY City, Gen ORDER BY City)...i need spark rdd to make this.

After this query i should modify the structure of my input json in this new:

[ { "label": [1,2,3] //that is the Gen value, 
     "values": [ 
                 { "label":"New York" 
                   "values":["200","10","66"]  //is the ser about all Gen (for eexample 200 is ser is for label/gen 1 .. 10 is for label/gen 2 etc.
                 },
                { "label":"London" 
                  "values":["500","150","46"] 
                }, 
                { "label":"London" 
                  "values":["500","150","46"] 
                }, 
                .
                . 
                . 
                . 
                . 
               ] 
  } 
]

And then i send this new JSON to a Http request How can i make this in scala,play,spark? Please help me :)