Roblox developer product handler script

-- Developer product handler: ProcessReceipt.
-- Developer products can be bought many times (unlike game passes).
-- Roblox keeps calling ProcessReceipt until you return PurchaseGranted.
-- Needs player.leaderstats.Coins (use the Save data script, or coins are lost when the player leaves).

local Players = game:GetService("Players")
local MarketplaceService = game:GetService("MarketplaceService")
local DataStoreService = game:GetService("DataStoreService")

local receiptStore = DataStoreService:GetDataStore("Receipts_v1")

local function addCoins(player, amount)
	local leaderstats = player:FindFirstChild("leaderstats")
	local coins = leaderstats and leaderstats:FindFirstChild("Coins")
	if not coins then
		return false
	end
	coins.Value += amount
	return true
end

-- [product ID] = function that gives the reward. It must return true if it worked.
local productHandlers = {
	[0] = function(player) -- replace 0 with your developer product ID (100 coins)
		return addCoins(player, 100)
	end,
	-- [0] = function(player) -- another product (1000 coins)
	--	return addCoins(player, 1000)
	-- end,
}

MarketplaceService.ProcessReceipt = function(receiptInfo)
	local player = Players:GetPlayerByUserId(receiptInfo.PlayerId)
	if not player then
		-- The player left. Roblox will ask again when they rejoin.
		return Enum.ProductPurchaseDecision.NotProcessedYet
	end

	-- Has this exact purchase already been given?
	local key = receiptInfo.PlayerId .. "_" .. tostring(receiptInfo.PurchaseId)
	local readOk, alreadyGiven = pcall(function()
		return receiptStore:GetAsync(key)
	end)
	if not readOk then
		return Enum.ProductPurchaseDecision.NotProcessedYet
	end
	if alreadyGiven then
		return Enum.ProductPurchaseDecision.PurchaseGranted
	end

	local handler = productHandlers[receiptInfo.ProductId]
	if not handler then
		warn("No handler for product ID " .. tostring(receiptInfo.ProductId))
		return Enum.ProductPurchaseDecision.NotProcessedYet
	end

	local grantOk, granted = pcall(handler, player)
	if not grantOk or not granted then
		return Enum.ProductPurchaseDecision.NotProcessedYet
	end

	-- Remember the purchase so it is never given twice.
	local writeOk, writeError = pcall(function()
		receiptStore:SetAsync(key, true)
	end)
	if not writeOk then
		warn("Could not record receipt " .. key .. ": " .. tostring(writeError))
	end

	return Enum.ProductPurchaseDecision.PurchaseGranted
end