function SavePlayer(ply)
    local players = db:Collection("players")

    players:UpdateOneAsync(
        { steamid = ply:SteamID() },
        {
            ["$set"] = {
                username = ply:Nick(),
                credits = ply.credits,
                level = ply.level,
                last_seen = os.time()
            }
        },
        function(err) 
            if err then print("Save error:", err) end
        end
    )
end

function LoadPlayer(ply, callback)
    local players = db:Collection("players")

    players:FindOneAsync(
        { steamid = ply:SteamID() },
        function(err, data)
            if data then
                ply.credits = data.credits
                ply.level = data.level
            else
                -- New player defaults
                ply.credits = 1000
                ply.level = 1
            end
            if callback then callback() end
        end
    )
end

function GetLeaderboard(callback)
    local players = db:Collection("players")

    players:AggregateAsync({
        { ["$match"] = { banned = { ["$ne"] = true } } },
        { ["$sort"] = { score = -1 } },
        { ["$limit"] = 10 },
        { ["$project"] = { username = 1, score = 1, _id = 0 } }
    }, function(err, results)
        callback(results or {})
    end)
end