Simple Button API for Monitors in ComputerCraft

-- The `drawButton` function draws a button at the specified position with the specified label text.
-- It returns a table that contains the position and dimensions of the button.
local monitor = peripheral.find("monitor")
local buttons = {}

function drawButton(x, y, label)
  buttons[label] = {}
  buttons[label].x1 = x
  buttons[label].y1 = y
  buttons[label].width = #label + 2
  buttons[label].height = 3
  buttons[label].x2 = x + buttons[label].width - 1
  buttons[label].y2 = y + buttons[label].height - 1

  -- Draw the button frame and centered label
  monitor.setCursorPos(x, y)
  monitor.write("+" .. string.rep("-", buttons[label].width-2) .. "+")
  monitor.setCursorPos(x, y+1)
  monitor.write("|" .. centerText(label, buttons[label].width-2) .. "|")
  monitor.setCursorPos(x, y+2)
  monitor.write("+" .. string.rep("-", buttons[label].width-2) .. "+")

end

-- The `centerText` function centers the specified text within the specified width.
function centerText(text, width)
    local spacing = width - #text
    local leftSpacing = math.floor(spacing / 2)
    local rightSpacing = math.ceil(spacing / 2)
    return string.rep(" ", leftSpacing) .. text .. string.rep(" ", rightSpacing)
  end

-- The `processClick` function checks if the specified position is within any of the buttons
-- and if so, calls the attached function.
function processClick(x, y)
  for label, button in pairs(buttons) do
    if x >= button.x1 and x <= button.x2 and y >= button.y1 and y <= button.y2 then
      button.func()
      return
    end
  end
end

-- The `attachFunction` function attaches the specified function to the specified button label.
function attach(label, func)
  buttons[label].func = func
end

-- The `drawLabel` function draws a label at the specified position, centered within the specified width.
function drawLabel(x, y, width, label)
  monitor.setCursorPos(x, y)
  monitor.write(centerText(label, width))
end