-- Weighted randomness.

local function add(self, value, weight)
    self.size = self.size + weight
    table.insert(self, { value = value,
                 weight = weight,
    })
end


local function get(self, count)

    if count == nil then count = 1 end

    local max = self.size

    if max == 0 then return {} end

    local nums = {}
    local random = math.random

    for i = 1, count do
        table.insert(nums, random(max))
    end

    table.sort(nums)

    local result = {}

    local numI = 1
    local elemI = 1

    local curNum = nums[numI]
    local curElem = self[elemI]

    local pos = curElem.weight

    while curNum ~= nil and curElem ~= nil do

        if curNum <= pos then
            table.insert(result, curElem.value)
            numI = numI + 1
            curNum = nums[numI]
        else
            elemI = elemI + 1
            curElem = self[elemI]

            pos = pos + curElem.weight
        end
    end

    return result
end


local methods = { add = add,
          get = get,
}


local function newWRandom()
    local wr = { size = 0 }
    setmetatable(wr, { __index = methods })
    return wr
end


return newWRandom