Computercraft UI api WIP

local ui = {}
ui.elements = {
  button = {
    clickedColor = colors.white, label = "", _onPressed = function(self) end, _onReleased = function(self) end,
    update = function(self)
    end,
    draw = function(self, x, y)
      local color = self.color
      if self.isPressed then color = self.clickedColor end
      paintutils.drawFilledBox(x, y, x+self.w-1, y+self.h-1, color)
    end,
    onClick = function(self)
      self.isPressed = true
    end,
    onMouse_up = function(self)
      self.isPressed = false
    end
  },
  label = {
    x = 1, y = 1, w = 1, h = 1, color = colors.gray, textColor = colors.white, text = "",
    draw = function(self, x, y)
      term.write(self.text)
    end
  },
  checkbox = {
    ticked = false,
    draw = function(self, x, y)
      if ticked then
        term.write("x")
      else
        term.write(" ")
      end
    end
  },
  panel = {}
}
ui.new = setmetatable({}, {__index = function(self, elementType)
  return function(args)
    return setmetatable(setmetatable(args, {__index = ui.elements[elementType]}), {x = 1, y = 1, w = 1, h = 1, color = colors.gray, textColor = colors.white})
  end
end})
ui.draw = function(elements)
  term.setBackgroundColor(colors.gray)
  term.clear()
  parent = parent or {x = 1, y = 1}
  if not parent.w then
    parent.w, parent.h = term.getSize()
  end
  for elementName, element in pairs(elements) do
    term.setCursorPos(element.x, element.y)
    term.setBackgroundColor(element.color)
    term.setTextColor(element.textColor)
    element:draw(parent.x+element.x-1, parent.y+element.y-1)
    if element.children then
      ui.draw(element.children, element)
    end
  end
end
ui.update = function(elements, parent)
  local event, var1, var2, var3 = os.pullEvent()
  parent = parent or {x = 1, y = 1}
  if not parent.w then
    parent.w, parent.h = term.getSize()
  end
  for elementName, element in pairs(elements) do
    term.setCursorPos(element.x, element.y)
    local eventMethod = element["on"..string.upper(string.sub(event, 1, 1))..string.sub(event, 2)]
    if eventMethod then
      eventMethod(element, var1, var2, var3)
    end
    if element.onClick and event == "mouse_click" and var2 >= element.x and var3 >= element.y and var2 < element.x+element.w and var3 < element.y+element.h then
      element:onClick(var1, element.x-var2, element.y-var3)
    end
    element:update(parent.x+element.x-1, parent.y+element.y-1, event, var1, var2, var3)
    if element.children then
      ui.update(element.children, element)
    end
  end
end

return ui