Inventory System Script

-- Inventory System Script
—- Place script in ScreenGui

—-[[
ScreenGui
    InventoryFrame (Frame)
    ItemTemplate (Button)
]]

local player = game.Players.LocalPlayer
local playerGui = player:WaitForChild("PlayerGui")
local inventoryFrame = playerGui:WaitForChild("ScreenGui"):WaitForChild("InventoryFrame")
local itemTemplate = inventoryFrame:WaitForChild("ItemTemplate")

local maxInventorySize = 20
local inventory = {}

-- Function to add an item to the inventory
local function addItem(itemName, quantity)
    for _, item in ipairs(inventory) do
        if item.name == itemName then
            item.quantity = item.quantity + quantity
            item.slot.Button.Text = item.name .. " (" .. item.quantity .. ")"
            return
        end
    end

    if #inventory < maxInventorySize then
        local newItem = {
            name = itemName,
            quantity = quantity,
            slot = itemTemplate:Clone(),
        }
        newItem.slot.Parent = inventoryFrame
        newItem.slot.Button.Text = newItem.name .. " (" .. newItem.quantity .. ")"
        newItem.slot.Visible = true

        table.insert(inventory, newItem)
        updateInventoryLayout()
    else
        print("Inventory full!")
    end
end

-- Function to remove an item from the inventory
local function removeItem(itemName, quantity)
    for index, item in ipairs(inventory) do
        if item.name == itemName then
            item.quantity = item.quantity - quantity
            if item.quantity <= 0 then
                item.slot:Destroy()
                table.remove(inventory, index)
            else
                item.slot.Button.Text = item.name .. " (" .. item.quantity .. ")"
            end
            return
        end
    end
    print("Item not found in inventory!")
end

-- Function to update the inventory layout
local function updateInventoryLayout()
    local padding = 5
    local slotSize = itemTemplate.Size
    local cols = math.floor(inventoryFrame.AbsoluteSize.X / (slotSize.X.Offset + padding))

    for i, item in ipairs(inventory) do
        local row = math.floor((i - 1) / cols)
        local col = (i - 1) % cols
        item.slot.Position = UDim2.new(0, col * (slotSize.X.Offset + padding), 0, row * (slotSize.Y.Offset + padding))
    end
end

-- Function to handle item usage
local function useItem(itemName)
    for _, item in ipairs(inventory) do
        if item.name == itemName then
            print("Using item:", itemName)
            removeItem(itemName, 1)
            return
        end
    end
    print("Item not found in inventory!")
end

-- Adding drag and drop functionality
local function enableDragAndDrop()
    for _, item in ipairs(inventory) do
        local slot = item.slot
        local dragging = false
        local dragStart, startPos

        local function updateDrag(input)
            local delta = input.Position - dragStart
            slot.Position = UDim2.new(startPos.X.Scale, startPos.X.Offset + delta.X, startPos.Y.Scale, startPos.Y.Offset + delta.Y)
        end

        slot.InputBegan:Connect(function(input)
            if input.UserInputType == Enum.UserInputType.MouseButton1 then
                dragging = true
                dragStart = input.Position
                startPos = slot.Position
                input.Changed:Connect(function()
                    if input.UserInputState == Enum.UserInputState.End then
                        dragging = false
                        updateInventoryLayout() -- Re-organize layout after drop
                    end
                end)
            end
        end)

        slot.InputChanged:Connect(function(input)
            if dragging and input.UserInputType == Enum.UserInputType.MouseMovement then
                updateDrag(input)
            end
        end)
    end
end

-- Example usage
addItem("Health Potion", 5)
addItem("Mana Potion", 3)
useItem("Health Potion")
enableDragAndDrop()