Leaderboard with ip-based vote restriction.

leaderboard.js

Players = new Meteor.Collection("players");
IPs = new Meteor.Collection('ips');

if (Meteor.isClient) {
  Template.leaderboard.players = function () {
    return Players.find({}, {sort: {score: -1, name: 1}});
  };

  Template.leaderboard.selected_name = function () {
    var player = Players.findOne(Session.get("selected_player"));
    return player && player.name;
  };

  Template.player.selected = function () {
    return Session.equals("selected_player", this._id) ? "selected" : '';
  };

  Template.leaderboard.events({
    'click input.inc': function() {
      var playerId = Session.get('selected_player');
      Meteor.call('givePoints', playerId, function(err) {
        if (err)
          alert(err.reason);
      });
    }
  });

  Template.player.events({
    'click': function () {
      Session.set("selected_player", this._id);
    }
  });
}

// On server startup, create some players if the database is empty.
if (Meteor.isServer) {
  Meteor.methods({
    givePoints: function(playerId) {
      check(playerId, String);

      // we want to use a date with a 1-day granularity
      var startOfDay = new Date;
      startOfDay.setHours(0, 0, 0, 0);

      // the IP address of the caller
      ip = this.connection.clientAddress;

      // check by ip and date (these should be indexed)
      if (IPs.findOne({ip: ip, date: startOfDay})) {
        throw new Meteor.Error(403, 'You already voted!');
      } else {
        // the player has not voted yet
        Players.update(playerId, {$inc: {score: 5}});

        // make sure she cannot vote again today
        IPs.insert({ip: ip, date: startOfDay});
      }
    }
  });

  Meteor.startup(function () {
    if (Players.find().count() === 0) {
      var names = ["Ada Lovelace",
                   "Grace Hopper",
                   "Marie Curie",
                   "Carl Friedrich Gauss",
                   "Nikola Tesla",
                   "Claude Shannon"];
      for (var i = 0; i < names.length; i++)
        Players.insert({name: names[i], score: Math.floor(Random.fraction()*10)*5});
    }
  });
}