MainMenu = {}

local function getSizeOfScreen()
    local x, y = term.getSize()
    return x, y
end

local function initMenu()
    -- do a menu for computer craft
    local menuItems = {
        { name = "Get Method", action = function() shell.run("getMethodsPeripheral") end },
        { name = "Settings",   action = function() print("Opening settings...") end },
        { name = "Exit",       action = function() print("Exiting...") end }
    }
    -- put the item in MainMenu
    for _, item in ipairs(menuItems) do
        table.insert(MainMenu, item)
    end
end


local function displayMenu()
    local selected = 1
    local function drawTitle()
        local x, y = getSizeOfScreen()
        local title = " Main Menu "
        term.setTextColor(colors.yellow)
        local decorator = '='
        term.write(string.rep(decorator, math.floor((x - #title) / 2)))
        term.setCursorPos(math.floor((x - #title) / 2) + 1, 1)
        print(title)
        term.setCursorPos(math.floor((x + #title) / 2) + 1, 1)
        term.write(string.rep(decorator, math.ceil((x - #title) / 2)))
        term.setTextColor(colors.white)
        term.write(string.rep(decorator, x))
    end

    local function drawMenuItems(selected)
        for i, item in ipairs(MainMenu) do
            term.setCursorPos(1, i + 2)
            if i == selected then
                term.setTextColor(colors.yellow)
            else
                term.setTextColor(colors.white)
            end
            -- put the item in the center and add [ ] before item
            local itemText = string.format("[%s] %s", i == selected and ">" or " ", item.name)
            local x, _ = getSizeOfScreen()
            local padding = math.max(0, (x - #itemText) / 2)
            term.write(string.rep(" ", padding) .. itemText)
            term.setCursorPos(1, i + 2)
            term.write(string.rep(" ", x - padding - #itemText))
            term.setCursorPos(1, i + 2)
            term.setTextColor(colors.white)
        end
    end

    local function handleKey(selected)
        local event, key = os.pullEvent("key")
        if key == keys.up then
            selected = selected - 1
            if selected < 1 then selected = #MainMenu end
        elseif key == keys.down then
            selected = selected + 1
            if selected > #MainMenu then selected = 1 end
        elseif key == keys.enter then
            term.setTextColor(colors.white)
            term.clear()
            term.setCursorPos(1, 1)
            MainMenu[selected].action()
            return selected, true
        end
        return selected, false
    end

    while true do
        term.clear()
        term.setCursorPos(1, 1)
        drawTitle()
        term.setTextColor(colors.white)
        term.setCursorPos(1, 3)
        drawMenuItems(selected)
        selected, done = handleKey(selected)
        if done then break end
    end
    term.setTextColor(colors.white)
end

function Main()
    initMenu()
    displayMenu()
end

Main()