Lottery Class

-- LotteryClass
-- Used for choosing items based on weight

-- Items Format:
-- [index] = number weight

-- Functions
function shuffle(tbl)
    for i = #tbl, 2, -1 do
        local j = math.random(i)
        tbl[i], tbl[j] = tbl[j], tbl[i]
    end
    return tbl
end

-- Main
local LotteryClass = {}
LotteryClass.__index = LotteryClass

function LotteryClass.new()
    local self = setmetatable({
        _items = {},
        _totalWeight = 0
    }, LotteryClass)
    return self
end

function LotteryClass:SetItems(items)
    self._items = items
    self._totalWeight = 0
    for item, weight in pairs(items) do
        self._totalWeight += weight
        items[item] = weight
    end
end

function LotteryClass:GetChance(index)
    local ItemWeight = self._items[index] or 0
    return ItemWeight / self._totalWeight
end

function LotteryClass:Spin()
    local Selection = {}
    for index, weight in pairs(self._items) do
        for i = 1, weight do
            table.insert(Selection, index)
        end
    end

    Selection = shuffle(Selection)

    -- Pick and return the result
    local Index = math.random(#Selection)
    local Result = Selection[Index]
    return Result, Selection, Index
end

return LotteryClass