-- Simple GUI OS v1.0 for CC:Tweaked
-- Native API only, no extra libraries required

local term = term
local colors = colors
local paintutils = paintutils

-- Button definition: position, size, text, color, action
local buttons = {
    {x=3, y=4,  w=20, h=3, text="File Manager", color=colors.blue,   action="list"},
    {x=3, y=8,  w=20, h=3, text="Run Program",  color=colors.green,  action="run"},
    {x=3, y=12, w=20, h=3, text="Native Shell", color=colors.yellow, action="shell"},
    {x=3, y=16, w=20, h=3, text="Shutdown",     color=colors.red,    action="shutdown"},
}

-- Draw single button with optional highlight effect
local function drawButton(btn, highlighted)
    local bgColor = highlighted and colors.lightGray or btn.color
    paintutils.drawFilledBox(btn.x, btn.y, btn.x + btn.w - 1, btn.y + btn.h - 1, bgColor)
    
    -- Center text on button
    local textX = btn.x + math.floor((btn.w - #btn.text) / 2)
    local textY = btn.y + math.floor(btn.h / 2)
    term.setCursorPos(textX, textY)
    term.setTextColor(colors.white)
    term.write(btn.text)
end

-- Render full UI interface
local function drawUI()
    term.clear()
    local screenW, screenH = term.getSize()
    
    -- Top title bar
    paintutils.drawFilledBox(1, 1, screenW, 1, colors.gray)
    term.setCursorPos(2, 1)
    term.setTextColor(colors.white)
    term.write("Simple GUI OS v1.0")
    
    -- Draw all buttons
    for i = 1, #buttons do
        drawButton(buttons[i], false)
    end
    
    -- Bottom status bar
    paintutils.drawFilledBox(1, screenH, screenW, screenH, colors.gray)
    term.setCursorPos(2, screenH)
    term.setTextColor(colors.white)
    term.write("Left-click a button to continue")
end

-- Check if click point is inside a button
local function pointInBox(px, py, x, y, w, h)
    return px >= x and px <= x + w - 1 and py >= y and py <= y + h - 1
end

-- ========== Feature functions ==========
local function listFiles()
    term.clear()
    term.setCursorPos(1, 1)
    print("=== File List (Root) ===")
    local files = fs.list("/")
    for i = 1, #files do
        if fs.isDir(files[i]) then
            print("[DIR]  " .. files[i])
        else
            print("[FILE] " .. files[i])
        end
    end
    print("\nPress any key to return")
    os.pullEvent("key")
end

local function runProgram()
    term.clear()
    term.setCursorPos(1, 1)
    write("Enter program name: ")
    local prog = read()
    if prog ~= "" then
        shell.run(prog)
        print("\nPress any key to return")
        os.pullEvent("key")
    end
end

-- ========== Main loop ==========
while true do
    drawUI()
    
    -- Wait for mouse click (auto yields CPU)
    local event, clickBtn, x, y = os.pullEvent("mouse_click")
    
    -- Check which button was clicked
    for i = 1, #buttons do
        local btn = buttons[i]
        if pointInBox(x, y, btn.x, btn.y, btn.w, btn.h) then
            -- Click feedback animation
            drawButton(btn, true)
            sleep(0.1)
            
            -- Execute button action
            if btn.action == "list" then
                listFiles()
            elseif btn.action == "run" then
                runProgram()
            elseif btn.action == "shell" then
                term.clear()
                term.setCursorPos(1, 1)
                print("Entered native shell. Type 'exit' to return.")
                shell.run("shell")
            elseif btn.action == "shutdown" then
                term.clear()
                term.setCursorPos(1, 1)
                print("Shutting down...")
                sleep(0.5)
                os.shutdown()
            end
            
            break
        end
    end
end