-- Function to draw a filled rectangle
function drawRect(x, y, width, height, color)
    term.setBackgroundColor(color)
    term.setCursorPos(x, y)
    term.clearLine()
    for i = 1, height do
        term.setCursorPos(x, y + i - 1)
        term.write(string.rep(" ", width))
    end
end

-- Function to draw text
function drawText(x, y, text, color)
    term.setTextColor(color)
    term.setCursorPos(x, y)
    term.write(text)
end

-- Function to create a button
function drawButton(x, y, width, text, bgColor, textColor)
    drawRect(x, y, width, 3, bgColor)
    drawText(x + 1, y + 1, text, textColor)
end

-- Function to draw the main screen
function drawMainScreen()
    term.clear()
    term.setBackgroundColor(colors.black)
    term.setTextColor(colors.white)

    -- Draw header
    drawRect(1, 1, 51, 5, colors.blue)
    drawText(2, 2, "Doggy OS", colors.white)

    -- Draw navigation bar
    drawRect(1, 6, 51, 3, colors.gray)
    drawButton(2, 7, 10, "Home", colors.lightGray, colors.black)
    drawButton(13, 7, 15, "Features", colors.lightGray, colors.black)
    drawButton(30, 7, 12, "About", colors.lightGray, colors.black)
    drawButton(44, 7, 8, "Help", colors.lightGray, colors.black)

    -- Draw content area
    drawRect(1, 10, 51, 10, colors.black)
    drawText(2, 11, "Welcome to Doggy OS!", colors.white)
    drawText(2, 12, "A user-friendly and secure OS.", colors.white)
    drawText(2, 14, "Press F1, F4, F5, or F6 to navigate.", colors.white)

    -- Draw footer
    drawRect(1, 22, 51, 3, colors.blue)
    drawText(2, 23, "Doggy OS - Version 1.0", colors.white)
end

-- Function to draw the features page
function drawFeaturesPage()
    term.clear()
    term.setBackgroundColor(colors.black)
    term.setTextColor(colors.white)

    -- Draw header
    drawRect(1, 1, 51, 5, colors.blue)
    drawText(2, 2, "Doggy OS - Features", colors.white)

    -- Draw content area
    drawRect(1, 10, 51, 10, colors.black)
    drawText(2, 11, "Features of Doggy OS:", colors.white)
    drawText(2, 12, "- User-friendly Interface", colors.white)
    drawText(2, 13, "- Customizable Settings", colors.white)
    drawText(2, 14, "- Fun and Interactive", colors.white)
    drawText(2, 16, "- Advanced Security Features", colors.white)
    drawText(2, 17, "- Privacy Controls", colors.white)

    -- Draw footer
    drawRect(1, 22, 51, 3, colors.blue)
    drawText(2, 23, "Press F1 to go Home", colors.white)
end

-- Function to draw the about page
function drawAboutPage()
    term.clear()
    term.setBackgroundColor(colors.black)
    term.setTextColor(colors.white)

    -- Draw header
    drawRect(1, 1, 51, 5, colors.blue)
    drawText(2, 2, "Doggy OS - About", colors.white)

    -- Draw content area
    drawRect(1, 10, 51, 10, colors.black)
    drawText(2, 11, "Security & Privacy:", colors.white)
    drawText(2, 12, "Doggy OS prioritizes your security and privacy.", colors.white)
    drawText(2, 13, "Features include:", colors.white)
    drawText(2, 14, "- Encrypted User Data", colors.white)
    drawText(2, 15, "- Regular Security Updates", colors.white)
    drawText(2, 16, "- Privacy-focused Design", colors.white)
    drawText(2, 18, "Choose between Advanced or Simple modes.", colors.white)

    -- Draw footer
    drawRect(1, 22, 51, 3, colors.blue)
    drawText(2, 23, "Press F1 to go Home", colors.white)
end

-- Function to draw the help page
function drawHelpPage()
    term.clear()
    term.setBackgroundColor(colors.black)
    term.setTextColor(colors.white)

    -- Draw header
    drawRect(1, 1, 51, 5, colors.blue)
    drawText(2, 2, "Doggy OS - Help", colors.white)

    -- Draw content area
    drawRect(1, 10, 51, 10, colors.black)
    drawText(2, 11, "Help & Instructions:", colors.white)
    drawText(2, 12, "Use the function keys to navigate.", colors.white)
    drawText(2, 13, "Press F1 for Home", colors.white)
    drawText(2, 14, "Press F4 for Features", colors.white)
    drawText(2, 15, "Press F5 for About", colors.white)
    drawText(2, 16, "Press F6 for Help", colors.white)
    drawText(2, 18, "Follow on-screen instructions for each section.", colors.white)

    -- Draw footer
    drawRect(1, 22, 51, 3, colors.blue)
    drawText(2, 23, "Press F1 to go Home", colors.white)
end

-- Function to handle user input
function handleInput()
    while true do
        local event, key = os.pullEvent("key")
        if key == keys.f1 then
            drawMainScreen()
        elseif key == keys.f4 then
            drawFeaturesPage()
        elseif key == keys.f5 then
            drawAboutPage()
        elseif key == keys.f6 then
            drawHelpPage()
        elseif key == keys.q then
            break
        end
    end
end

-- Main Program
drawMainScreen()
handleInput()