--!strict
-- ServerScriptService/Server/Services/CurrencyService.luau
local Players = game:GetService("Players")

type Balances = { [Player]: number }

local MAX_BALANCE = 1e12

local CurrencyService = {}
local balances: Balances = {}

local function publish(player: Player)
	player:SetAttribute("Coins", balances[player]) -- replicated to every client; UI listens
end

function CurrencyService.load(player: Player, saved: number?)
	balances[player] = math.clamp(saved or 0, 0, MAX_BALANCE)
	publish(player)
end

function CurrencyService.get(player: Player): number
	return balances[player] or 0
end

-- Positive amount only; returns the new balance.
function CurrencyService.add(player: Player, amount: number, _source: string): number?
	local balance = balances[player]
	if balance == nil or not math.isfinite(amount) or amount <= 0 then
		return nil
	end
	balances[player] = math.min(balance + math.floor(amount), MAX_BALANCE)
	publish(player)
	return balances[player]
end

-- Atomic check-and-spend; false if insufficient.
function CurrencyService.spend(player: Player, amount: number, _sink: string): boolean
	local balance = balances[player]
	if balance == nil or not math.isfinite(amount) or amount <= 0 or balance < amount then
		return false
	end
	balances[player] = balance - math.floor(amount)
	publish(player)
	return true
end

Players.PlayerRemoving:Connect(function(player)
	balances[player] = nil -- after the data layer has saved it
end)

return CurrencyService