os_run

local gfx = require("gfx")
local gui = require("gui")
local utils = require("utils")

Exit = false

-- The index of the current selection in the list of childen (current screen)
SelectionIndex = 0

-- Screen management
Screens = {}
CurrentScreen = 1
LastScreen = 0

function event()
    local event, key = os.pullEvent("key")
    if key == keys.e then
        Exit = true
    elseif key == keys.tab then
        local current = Screens[CurrentScreen]

        SelectionIndex = SelectionIndex + 1
        if SelectionIndex > #(current["children"]) then
            SelectionIndex = 1
        end

        if current["children"][SelectionIndex]["type"] == "button" then
            gfx.clear()
            gfx.flush()

            gui.setAllButtonsOff(Screens[CurrentScreen])
            gui.toggleButton(Screens[CurrentScreen], SelectionIndex)
            gui.show(Screens[CurrentScreen])
        end
    elseif key == keys.enter then
        local current = Screens[CurrentScreen]
        local element = current["children"][SelectionIndex]
        if element["type"] == "button" then
            local callback = element["callback"]
            if callback ~= nil then
                callback()
            end
        end
    end
end

function tick()
    if CurrentScreen ~= LastScreen then
        -- Close Last Screen
        gfx.flush()
        gfx.clear()

        -- Open New Screen
        gui.show(Screens[CurrentScreen])
    end

    gfx.display()

    LastScreen = CurrentScreen
end

function swap()
    if CurrentScreen == 1 then
        CurrentScreen = 2
    else
        CurrentScreen = 1
    end
end

function main()
    local mainScreen = gui.createParent()
    gui.addCentralXButton(mainScreen, "First Button", 6, swap)
    Screens[#Screens + 1] = mainScreen

    local secondScreen = gui.createParent()
    gui.addCentralXButton(secondScreen, "Second Button", 6, swap)
    Screens[#Screens + 1] = secondScreen

    gfx.clear()
    gfx.display()
    while true do
        if Exit then
            break
        end

        parallel.waitForAll(tick, event)
    end
end

main()