var MongoClient = require('mongodb').MongoClient;

MongoClient.connect('mongodb://localhost:27017/weather', function(err, db) {

  if(err) {
    console.log(err.message);
    return;
  }

  var query = {};
  var projection = { 'State':1,  'Temperature':1 };

  var cursor = db.collection('data').find(query, projection);

  // Sort by state and then by temperature (decreasing)
  cursor.sort({State:1,Temperature:-1});

  var state = '';	// initialize to dummy value
  var operator = {'$set':{'month_high':true}};

  cursor.each(function(err, doc) {

    if (doc === null) {
      console.log('last record');
      db.close();
      return;
    }

    if (err) { console.log(err.message); return; }
    console.log(doc);

    if (doc.State !== state) {
      // first record for each state is the high temp one
      state = doc.State;

      db.collection('data').update({'_id':doc._id}, operator, function(err, updated) {
        if (err) { console.log(err.message); return; }
      });
    }
  });
  //db.close();
});