-- Cubicle - A Minecraft ComputerCraft Window Compositor API

--- The @{Cubicle} API provides methods for compositing and window
-- management.
--
-- @module Cubicle

Cubicle = {}

--- Whether an object is an instance of a class
--
-- @tparam table o Object to compare
-- @tparam table class Class to compare
-- @treturn boolean Whether the object is an instance of class
local function instanceOf(o, class)
	while o do
		o = getmetatable(o)
		if o == class then return true end
	end
	return false
end

local function min(a, b)
	if a < b then return a
	else return b end
end

--- Wrap text to a limited length
--
-- @tparam string text The text to wrap
-- @tparam number length The length limit of each line
-- @treturn table Array of lines
-- @usage wrapText("A very long string to wrap", 10)
local function wrapText(text, length)
	_, text = assert(pcall(tostring, text))
	assert(text,
		"bad argument #1 for text (expected string got "..type(text)..")")
	assert(length and type(length) == "number",
		"bad argument #2 for length (expected number got "..type(length)..")")
    local lineCount = #text/length
    local wrappedText = {}
    for i=0,lineCount do
        table.insert(wrappedText, string.sub(text, i*length+1, (i+1)*length))
    end
    return wrappedText
end

--- Base class inherited by Button, Text, and Dialog
-- @class GraphicsElement
local GraphicsElement = {}

--- Instantiate a new GraphicsElement
--
-- While optional, creating a GraphicsElement without passing a definition is
-- not very useful.
--
-- @tparam[opt] table o Definition of the GraphicsElement
-- @treturn table Instance of class GraphicsElement
-- @usage GraphicsElement:new {
-- 	name = "graphicsElement",
-- 	title = "A GraphicsElement",
-- 	align = "center",
-- 	x = 1, y = 2,
-- 	width = 20, height = 3,
-- 	textColor = colors.black, bgColor = colors.lime,
-- 	visible = true
-- }
function GraphicsElement:new(o)
    o = o or {
        name = "graphicsElement",
        title = "graphicsElement",
        align = "center",
        x = 1, y = 1,
        width = 10, height = 1,
        textColor = colors.black, bgColor = colors.white,
		visible = true
    }

    setmetatable(o, self)
    self.__index = self
    return o 
end

--- Set the x position of the GraphicsElement
--
-- @tparam number x New x position of the GraphicsElement
function GraphicsElement:setX(x) self.x = x end

--- Set the y position of the GraphicsElement
--
-- @tparam number y New y position of the GraphicsElement
function GraphicsElement:setY(y) self.y = y end

--- Set both the x and y positions of the GraphicsElement
--
-- @tparam number x New x position of the GraphicsElement
-- @tparam number y New x position of the GraphicsElement
function GraphicsElement:move(x, y) self.x, self.y = x, y end

--- Set width of the GraphicsElement
--
-- @tparam number width New width of the GraphicsElement
function GraphicsElement:setWidth(w) self.width = w end

--- Set height of the GraphicsElement
--
-- @tparam number height New height of the GraphicsElement
function GraphicsElement:setHeight(h) self.height = h end

--- Set visibility of the GraphicsElement
--
-- @tparam boolean visibility Whether the GraphicsElement should be rendered
function GraphicsElement:setVisible(visibility) self.visible = visibility end

--- Set the text color of the GraphicsElement
--
-- @tparam number color New color of the GraphicsElement text
function GraphicsElement:setTextColor(color) self.textColor = color end

--- Set the background color of the GraphicsElement
--
-- @tparam number color New color of the GraphicsElement background
function GraphicsElement:setBackgroundColor(color) self.bgColor = color end

--- Set the title of the GraphicsElement
--
-- @tparam string title New title of the GraphicsElement
function GraphicsElement:setTitle(title) self.title = tostring(title) end

--- Render the GraphicsElement
--
-- @tparam table terminal Terminal on which to render
-- @tparam number parentX X position of the parent Window
-- @tparam number parentY Y position of the parent Window
-- @usage Render the GraphicsElement in a Window on the current terminal
-- 
-- 		local window = Window:new()
-- 		GraphicsElement:render(term.current(), window.x, window.y)
-- @usage Render the GraphicsElement on a monitor connected to the right of the
-- computer
-- 
-- 		local mon = peripheral.wrap("right")
-- 		GraphicsElement:render(mon, 1, 1)
function GraphicsElement:render(terminal, parentX, parentY)
	assert(terminal and type(terminal) == "table",
		"bad argument #1 to terminal (expected table, got "..type(terminal))
	assert(parentX and type(parentX) == "number",
		"bad argument #2 to parentX (expected number, got "..type(parentX))
	assert(parentX and type(parentX) == "number",
		"bad argument #3 to parentY (expected number, got "..type(parentY))
	
	if self.visible then
		paintutils.drawFilledBox(
			parentX + self.x - 1, parentY + self.y,
			parentX + self.x + self.width - 2,
			parentY + self.y + self.height - 1,
			self.bgColor
		)

		terminal.setTextColor(self.textColor)
		terminal.setBackgroundColor(self.bgColor)

		local wrappedText = wrapText(self.title, self.width+1)

		for k,v in ipairs(wrappedText) do
			if self.align == "left" then
				terminal.setCursorPos(
					parentX + self.x - 1,
					parentY + self.y + self.height/2 + k-1 -- - #wrappedText/2
				)
			elseif self.align == "center" then
				terminal.setCursorPos(
					parentX + self.x + self.width/2 - #v/2 - 1,
					parentY + self.y
					+ math.fmod(k-math.floor(#wrappedText/2), self.height/2)
				)
			elseif self.align == "right" then
				terminal.setCursorPos(
					parentX + self.x + self.width - #v - 1,
					parentY + self.y + self.height/2 + k-1 -- - #wrappedText/2
				)
			end

			terminal.write(v)
		end
	end
end

-- Button, Text, Input, and Window inherit base class GraphicsElement
-- @class Text
Text = GraphicsElement:new()

-- @class Button
Button = GraphicsElement:new()

--- Instantiate a new Button
--
-- Inherits @{GraphicsElement} with addition of action
--
-- While optional, creating a Button without passing a definition is not very
-- useful.
--
-- @tparam[opt] table o Definition of Button object
-- @treturn table Instance of class Button
-- @usage Button:new {
-- 	name = "buttonElement",
-- 	title = "A Button",
-- 	align = "center",
-- 	x = 1, y = 2,
-- 	width = 20, height = 3,
-- 	textColor = colors.black, bgColor = colors.lime,
-- 	visible = true,
-- 	action = function() return true end
-- }
function Button:new(o)
    o = o or {
        name = "buttonElement",
        title = "buttonElement",
        align = "center",
        x = 1, y = 1,
        width = 10, height = 1,
        textColor = colors.black, bgColor = colors.white,
		visible = true,
		action = function() return true end
    }

    setmetatable(o, self)
    self.__index = self
    return o 
end

-- @class Input
Input = GraphicsElement:new()

--- Instantiate a new Input
--
-- Inherits @{GraphicsElement} with addition of action and cursor rendering
--
-- While optional, creating an Input without passing a definition is not very
-- useful.
--
-- @tparam[opt] table o Definition of Input object
-- @treturn table Instance of class Input
-- @usage Input:new {
-- 	name = "inputElement",
-- 	value = "An Input",
-- 	x = 1, y = 2,
-- 	width = 20, height = 3,
-- 	textColor = colors.black, bgColor = colors.lime,
-- 	visible = true,
-- 	action = function() return true end
-- }
function Input:new(o)
    o = o or {
        name = "inputElement",
        value = "inputElement",
        x = 1, y = 1,
        width = 10, height = 1,
        textColor = colors.black, bgColor = colors.white,
		visible = true,
		action = function() return true end
    }

    setmetatable(o, self)
    self.__index = self
    return o 
end

--- Get the value of the Input
--
-- @treturn string Current value of the Input
function Input:getValue(value)
	return self.value
end

--- Set the value of the Input
--
-- @tparam string value New value of the Input
function Input:setValue(value)
	self.value = tostring(value)
end

--- Render the Input
--
-- Overrides inherited @{GraphicsElement:render} method while scrolling title to
-- the left and constraining to bounds of Input width.
--
-- @tparam table terminal Terminal on which to render
-- @tparam number parentX X position of the parent Window
-- @tparam number parentY Y position of the parent Window
-- @usage Render the GraphicsElement in a Window on the current terminal
-- 
-- 		local window = Window:new()
-- 		Input:render(term.current(), window.x, window.y)
-- @usage Render the GraphicsElement on a monitor connected to the right of the computer
-- 
-- 		local mon = peripheral.wrap("right")
-- 		Input:render(mon, 1, 1)
function Input:render(terminal, parentX, parentY)
	assert(terminal and type(terminal) == "table",
		"bad argument #1 to terminal (expected table, got "..type(terminal))
	assert(parentX and type(parentX) == "number",
		"bad argument #2 to parentX (expected number, got "..type(parentX))
	assert(parentX and type(parentX) == "number",
		"bad argument #3 to parentY (expected number, got "..type(parentY))

	if self.visible then
		paintutils.drawFilledBox(
			parentX + self.x - 1, parentY + self.y,
			parentX + self.x + self.width - 2,
			parentY + self.y + self.height - 1,
			self.bgColor
		)

		terminal.setTextColor(self.textColor)
		terminal.setBackgroundColor(self.bgColor)

		terminal.setCursorPos(
			parentX + self.x - 1,
			parentY + self.y + self.height/2
		)
		
		if #self.value <= self.width - 1 then
			terminal.write(self.value)
		else
			terminal.write(
				self.value:sub(#self.value - self.width + 2, #self.value)
			)
		end
	end
end

-- @class ProgressBar
ProgressBar = GraphicsElement:new()

--- Instantiate a new ProgressBar
--
-- Inherits @{GraphicsElement} with additon of progress and completeColor
--
-- While optional, creating a ProgressBar without passing a defition is not
-- very useful.
--
-- @tparam[opt] table o Definition of ProgressBar object
-- @treturn table Instance of class ProgressBar
function ProgressBar:new(o)
	o = o or {
        name = "progressBar",
        x = 1, y = 1,
        width = 20, height = 1,
        textColor = colors.black, bgColor = colors.gray,
		completeColor = colors.lime,
		-- Progress as a number between 0 and 1
		progress = 0,
		visible = true,
		-- By default, show a percentage of progress completion
		progressText = true
	}

	setmetatable(o, self)
	self.__index = self
	return o
end

function ProgressBar:setProgress(progress)
	assert(progress and type(progress) == "number",
		"bad argument #1 to progress (expected number, got "..type(progress)..")")
	assert(progress >= 0 and progress <= 1,
		"bad argument #1 to progress: progress should be between 0 and 1")

	self.progress = progress
end

function ProgressBar:render(terminal, parentX, parentY)
	assert(terminal and type(terminal) == "table",
		"bad argument #1 to terminal (expected table, got "..type(terminal)..")")
	assert(parentX and type(parentX) == "number",
		"bad argument #2 to parentX (expected number, got "..type(parentX)..")")
	assert(parentX and type(parentX) == "number",
		"bad argument #3 to parentY (expected number, got "..type(parentY)..")")

	terminal.setCursorPos(
		parentX + self.x + self.width - 3,
		parentY + self.y
	)
	terminal.setTextColor(self.textColor)
	terminal.write(tostring(self.progress*100).."%")

	if self.visible then
		if self.progressText then
			-- Background
			paintutils.drawFilledBox(
				parentX + self.x - 1, parentY + self.y,
				parentX + self.x + self.width - 5,
				parentY + self.y + self.height - 1,
				self.bgColor
			)
			if self.progress > 0 then
				-- Progress
				paintutils.drawFilledBox(
					parentX + self.x - 1, parentY + self.y,
					parentX + self.x + self.width*self.progress - 2 - 2*self.progress,
					parentY + self.y + self.height - 1,
					self.completeColor
				)
			end
		else
			-- Background
			paintutils.drawFilledBox(
				parentX + self.x - 1, parentY + self.y,
				parentX + self.x + self.width - 2,
				parentY + self.y + self.height - 1,
				self.bgColor
			)
			if self.progress > 0 then
				-- Progress
				paintutils.drawFilledBox(
					parentX + self.x - 1, parentY + self.y,
					parentX + self.x + self.width*self.progress - 2,
					parentY + self.y + self.height - 1,
					self.completeColor
				)
			end
		end

	end
end

-- @class Dataview
Dataview = GraphicsElement:new()

--- Instantiate a new Dataview
--
-- Inherits @{GraphicsElement} with addition of columns and data
--
-- While optional, creating an Dataview  without passing a definition is not
-- very useful.
--
-- @tparam[opt] table o Definition of Dataview object
-- @treturn table Instance of class Dataview
-- @usage Dataview:new {
-- 	name = "dataview",
-- 	title = "A Dataview",
-- 	x = 1, y = 1,
-- 	scrollX = 0, scrollY = 0,
-- 	width = 20, height = 10,
-- 	textColor = colors.black, headerColor = colors.white,
-- 	bgColor = colors.white,
-- 	visible = true,
-- 	columns = {
-- 		{ name = "col1", title = "Column 1", width = 10 },
-- 		{ name = "col2", title = "Column 2", width = 15 },
-- 		{ name = "col3", title = "Column 3", width = 10 }
-- 	},
-- 	data = {
-- 		{ col1 = "asdf", col2 = "1234", col3 = "hello, world!"}
-- 	}
-- }
function Dataview:new(o)
	o = o or {
        name = "dataview",
        title = "Dataview",
        x = 1, y = 1,
		scrollX = 1, scrollY = 1,
        width = 20, height = 10,
		titleHeight = 1,
        textColor = colors.white, bgColor = colors.black,
		headerColor = colors.white, selectColor = colors.lightGray,
		visible = true,
		data = {},
		columns = {},
		select = 1
	}

	setmetatable(o, self)
	self.__index = self
	return o
end

function Dataview:getColumns() return self.columns end

function Dataview:getData() return self.data end

function Dataview:setData(data)
	assert(data and type(data) == "table",
		"bad argument #1 to data (expected table, got "..type(data)..")")

	self.data = data
end

function Dataview:addRow(row)
	assert(row and type(row) == "table",
		"bad argument #1 to row (expected table, got "..type(row)..")")

	table.insert(self.data, row)
end

function Dataview:getRow(id)
	assert(id and type(id) == "number",
		"bad argument #1 to id (expected number, got "..type(id)..")")

	return self.data[id]
end

function Dataview:getSelection() return self.select end

function Dataview:setSelection(id)
	assert(id and type(id) == "number",
		"bad argument #1 to id (expected number, got "..type(id)..")")

	self.select = id
end

function Dataview:getSelectedRow() return self.data[self.select] end

function Dataview:getScrollX(n) return self.scrollX end

function Dataview:setScrollX(n)
	assert(n and type(n) == "number",
		"bad argument #1 for n (expected number, got "..type(n)..")")
	
	self.scrollX = n
end

function Dataview:getScrollY(n) return self.scrollY end

function Dataview:setScrollY(n)
	assert(n and type(n) == "number",
		"bad argument #1 for n (expected number, got "..type(n)..")")
	
	self.scrollY = n
end

function Dataview:render(terminal, parentX, parentY)
	assert(terminal and type(terminal) == "table",
		"bad argument #1 to terminal (expected table, got "..type(terminal)..")")
	assert(parentX and type(parentX) == "number",
		"bad argument #2 to parentX (expected number, got "..type(parentX)..")")
	assert(parentX and type(parentX) == "number",
		"bad argument #3 to parentY (expected number, got "..type(parentY)..")")

	if self.visible then
		-- Background
		paintutils.drawFilledBox(
			parentX + self.x - 1, parentY + self.y,
			parentX + self.x + self.width - 2,
			parentY + self.y + self.height - 1,
			self.bgColor
		)
		-- Header row
		paintutils.drawLine(
			parentX + self.x - 1, parentY + self.y,
			parentX + self.x + self.width-1 + 2*#self.columns, parentY + self.y,
			self.headerColor
		)

		terminal.setTextColor(self.textColor)
		terminal.setBackgroundColor(self.headerColor)

		local xPos = 0
		for _,v in ipairs(self.columns) do
			terminal.setCursorPos(parentX + self.x + xPos - 1, parentY + self.y)
			terminal.write("| "..v.title)
			xPos = xPos + v.width + 2
		end

		terminal.setBackgroundColor(self.bgColor)

		-- Only display as many that will fit in the bounds of the dataview body
		for i = self.scrollY, min(#self.data, self.scrollY + self.height - self.titleHeight - 1) do
			if i == self.select then
				paintutils.drawLine(
					parentX + self.x,
					parentY + self.y + self.titleHeight + i - self.scrollY,
					parentX + self.x + self.width-1 + 2*#self.columns,
					parentY + self.y + self.titleHeight + i - self.scrollY,
					self.selectColor
				)
			else
				terminal.setBackgroundColor(self.bgColor)
			end
			local xPos = 0
			for _,v in ipairs(self.columns) do
				terminal.setCursorPos(
					parentX + self.x + xPos - 1,
					parentY + self.y + self.titleHeight + i - self.scrollY
				)
				terminal.write("| "..self.data[i][v.name])
				-- Set X position of the next column
				xPos = xPos + v.width + 2
			end
			-- terminal.setCursorPos(
			-- 	parentX + self.x - 1,
			-- 	parentY + self.y + self.titleHeight + i - self.scrollY
			-- )
			-- terminal.write(i)
		end
	end
end

Window = GraphicsElement:new()

--- Instantiate a new Window
--
-- Inherits @{GraphicsElement} with addition of onLoad, onClose functions,
-- list of child elements, and title bar.
--
-- Windows can be dragged around the screen by clicking and dragging on the
-- title bar.
-- 
-- Title bar and background colors set the same and title text set to empty
-- string will effectively "hide" the title bar.
--
-- Title text will always be aligned left, and all elements can not currently
-- be aligned by the window.
--
-- @tparam[opt] table o Window
-- @treturn table Instance of class Window
-- @usage GraphicsElement:new {
-- 	name = "window",
-- 	title = "A Window",
-- 	x = 1, y = 2,
-- 	width = 20, height = 3,
-- 	textColor = colors.black, bgColor = colors.lime,
-- 	titleColor = colors.blue,
-- 	visible = true,
-- 	elements = {},
-- 	onLoad = function() return true end,
-- 	onClose = function() return true end
-- }
function Window:new(o)
	o = o or {
        name = "window",
        title = "window",
        x = 1, y = 1,
		-- TODO: Figure out if the currently displayed is less than the
		-- height, if so, allow scrolling
		scrollX = 0, scrollY = 0,
		-- Default is the resolution of a computer, since we're not passing a
		-- terminal object to the Window
        width = 51, height = 19,
		-- This will need to be handled when creating the window if the
		-- terminal does not support color
        textColor = colors.white, bgColor = colors.black,
		titleColor = colors.white,
		elements = {},
        select = 1,
		onLoad = function() return true end,
		onClose = function() return true end
	}

	setmetatable(o, self)
	self.__index = self
	return o
end

--- Add an element to the Window
--
-- @tparam table o Instance of element to add to the Window
function Window:addElement(o)
	assert(o and type(o) == "table",
		"bad argument #1 for o (expected table, got "..type(o)..")")
		
	table.insert(self.elements, o)
end

--- Remove an element from the Window
--
-- @tparam table o ID of the element to remove from the Window
function Window:removeElement(o) table.remove(self.elements, o) end

--- Get the table of elements in a Window
--
-- @treturn table Elements contained in the Window
function Window:getElements() return self.elements end

--- Get an element contained in the Window by ID
--
-- @tparam number id ID of the element to return
-- @treturn table The element with ID, if it exists in the window
function Window:getElementById(id)
	if self.elements[id] then
		return self.elements[id]
	else
		return nil
	end
end

--- Get an element contained in the Window by name
--
-- @tparam string name Name of the element to return
-- @treturn table The element with name, if it exists in the window
function Window:getElementByName(name)
    for _,v in pairs(self.elements) do
        if v.name == name then return v end
    end
end

--- Get the ID of the currently selected element
--
-- @treturn number ID of the currently selected element
function Window:getSelection() return self.select end

--- Set the selected element by ID
--
-- @tparam number id ID of the element to select
function Window:setSelection(id)
	-- Check if there is an element with this ID
	assert(self.elements[id], "No element ID "..tostring(id))
	self.select = id
end

--- Get the currently selected element
--
-- @treturn table Element which is currently selected
function Window:getSelectedElement() return self.elements[self.select] end

--- Render the Window and it's elements
--
-- @tparam table terminal Terminal on which to render the Window
function Window:render(terminal)
    -- Background
    paintutils.drawFilledBox(
        self.x, self.y,
        self.x + self.width-1, self.y + self.height,
        self.bgColor
    )
    -- Title bar
    paintutils.drawLine(
        self.x, self.y,
        self.x + self.width-1, self.y,
        self.titleColor
    )

	terminal.setTextColor(self.textColor)
	terminal.setBackgroundColor(self.titleColor)

	terminal.setCursorPos(self.x, self.y)
	terminal.write(self.title)

    -- Render each element on the window
    for k,v in pairs(self.elements) do
        v:render(terminal, self.x, self.y, self.width, self.height)

		-- Add a mark to selected button
		if self.select == k then
			if instanceOf(v, Button) then
				-- Qualify instances of buttons, because we don't want to draw
				-- this selector when it's an Input
				terminal.setCursorPos(self.x + v.x - 1, self.y + v.y + v.height/21)
				terminal.write("*")
			end
		end
    end
	
	-- If an input is selected, place the cursor in it and enable cursor
	-- Because inputs are not always the last to render (and therefore
	-- won't be able to set the cursor where they want) we have to do this
	-- here.
	local selectedElement = self:getSelectedElement()
	if instanceOf(selectedElement, Input) then
		if #selectedElement:getValue() <= selectedElement.width - 1 then
			terminal.setCursorPos(
				self.x + selectedElement.x - 1 + #selectedElement:getValue(),
				self.y + selectedElement.y
			)
		else
			terminal.setCursorPos(
				self.x + selectedElement.x - 1 + selectedElement.width - 1,
				self.y + selectedElement.y
			)
		end
		terminal.setCursorBlink(true)
	else
		terminal.setCursorBlink(false)
	end
		
end

--- Instantiate a new Compositor
--
-- @{Compositor} is the primary class in which @{Window}s reside
--
-- @tparam table terminal Terminal on which to render Windows
-- @tparam[opt] table o Compositor object
-- @treturn table Instance of class Compositor
function Compositor:new(terminal, o)
    o = o or {
		-- The last element in this table is always going to be the focused
		-- window. Focused windows will be drawn last over all other windows.
        windows = {},
        terminal = terminal,
        running = true
    }
	
	setmetatable(o, self)
	self.__index = self
	return o
end

--- Add a window
--
-- @tparam table o Window to add/open
function Compositor:addWindow(o) return table.insert(self.windows, o) end

--- Remove a window
--
-- @tparam number id ID of the Window to remove/close
function Compositor:removeWindow(id) return table.remove(self.windows, id) end

--- Get all Windows
--
-- @treturn table Table of Windows
function Compositor:getWindows() return self.windows end

--- Get a Window by its ID
--
-- @treturn table An instance of class Window
function Compositor:getWindow(id) return self.windows[id] end

--- Get a Window by its name
--
-- @treturn table An instance of class Window
function Compositor:getWindowByName(name)
	for k,v in pairs(self.windows) do
		if v.name == name then
			return v
		end
	end
end

--- Get the focused Windows
--
-- @treturn table An instance of class Window
function Compositor:getFocusedWindow() return self.windows[#self.windows] end

--- Set the focused window
--
-- @tparam number windowId ID of the window to focus
function Compositor:setFocusedWindow(windowId)
	-- Move the self.windows[windowId] to the end of the table
	self:addWindow(self:removeWindow(windowId))
	assert(pcall(self:getFocusedWindow().onLoad))
end

--- Remove / close the focused Window
function Compositor:removeFocusedWindow()
	assert(pcall(self:getFocusedWindow().onClose))
	self:removeWindow(#self.windows)
end

--- Stop the compositor
--
-- The compositor handles "terminate" events internally
function Compositor:stop() self.running = false end

--- Run the compositor, rendering @{Window}s and listening and handling events
-- to navigate and interact with @{GraphicsElement}s
--
-- Only the focused window (and all of it's contained elements) will be
-- rendered each pass to reduce screen flickering.
--
-- The compositor handles the following events internally for window and
-- element interaction and will not pass them to the eventHandler function:
-- mouse_click, mouse_up, mouse_drag, key, char, and terminate
--
-- When the last Window has been closed (is removed), the compositor will stop.
--
-- @tparam[opt] Function to be run before rendering the Windows
-- @tparam[opt] Function to be run after rendering the Windows
-- @tparam[opt] Function to handle events not handled by the compositor
function Compositor:run(preRender, postRender, eventHandler)
	preRender = preRender or function(compositor) end
	postRender = postRender or function(compositor) end
	eventHandler = eventHandler or function(compositor, event) end
    
	local window = self:getFocusedWindow()

	-- Run the first window's onLoad function
	if window.onLoad and type(window.onLoad) == "function" then
		assert(pcall(window.onLoad))
	end
	
    while self.running do

		local window = self:getFocusedWindow()

        -- Pre render
		if preRender and type(preRender) == "function" then
			assert(pcall(preRender, self))
		end

        -- Render windows
		-- We will only care about rending the focused window for now
		-- Windows behind the focused window should be ignored and overwritten
		-- by the focused window
		-- Eventually, we'll want to be able to drag smaller windows, so we
		-- will need to draw what's behind the focused window, as well, to
		-- prevent artifacting.
        -- window:render(self.terminal)

		-- Render each window
		-- Lower IDs will be rendered first. Higher IDs are 
		window:render(self.terminal)
		-- for k,v in pairs(self:getWindows()) do
		-- 	v:render(self.terminal)
		-- end
        
        -- Post render
		if postRender and type(postRender) == "function" then
			assert(pcall(postRender, self))
		end

		local selectedElement = window:getSelectedElement()

        -- Listen for events
		local event = {os.pullEventRaw()}
		if event[1] == "mouse_click" or event[1] == "monitor_touch" then
			-- Check if the mouse is down on the title bar of a Window
			-- If it is, then when a drag event comes we will reposition the window
			-- Do this *before* doing any button actions, in case the button action is to *close this Window*
			if event[2] == 1 and event[3] >= window.x and event[3] <= window.x + window.width
				and event[4] == window.y then
				window.dragging = true
			end
            -- Check to see if click falls within any element's boundaries
			for id, element in pairs(window:getElements()) do
				if event[3] >= window.x + element.x - 1
					and event[3] <= window.x + element.x + element.width - 2
					and event[4] >= window.y + element.y
					and event[4] <= window.y + element.y + element.height - 1 then
                    -- Element clicked, run the element's action function
					window:setSelection(id)
					-- Only want to run the action if it's a button
					if instanceOf(element, Button) then
						assert(pcall(element.action))
					elseif instanceOf(element, Dataview) then
						if event[4] <= #element:getData() then
							element:setSelection(event[4] - element.y + element:getScrollY() - 2)
						end
					end
				end
				
			end
		elseif event[1] == "mouse_drag" then
			if window.dragging then
				window:move(event[3], event[4])
			end
		elseif event[1] == "mouse_up" then
			window.dragging = false
		elseif event[1] == "mouse_scroll" then
			if instanceOf(selectedElement, Dataview) then
				-- event[2] scroll direction -1: up, 1: down
				if event[2] == -1 and selectedElement:getScrollY() > 1 then
					selectedElement:setScrollY(selectedElement:getScrollY() - 1)
				elseif event[2] == 1 and selectedElement:getScrollY() < #selectedElement:getData() - selectedElement.height then
					selectedElement:setScrollY(selectedElement:getScrollY() + 1)
				end
			end
		elseif event[1] == "key" then
			if event[2] == keys.enter then
                -- Enter key pressed, run the element's action function
				if selectedElement.action
					and type(selectedElement.action) == "function" then
					assert(pcall(selectedElement.action))
				end
			elseif event[2] == keys.up and window:getSelection() > 1 then
                -- Select previous option
				local selection = window:getSelection()-1
				-- Loop through the options that come before the one that is
				-- currently selected
				-- elements = { [...], selection, ... }
				for i = 1,selection do
					-- If it's a button or input, set the selection to that
					-- element's ID
					if instanceOf(window:getElementById(i), Button)
						or instanceOf(window:getElementById(i), Input) then
						window:setSelection(i)
					end
				end
			elseif event[2] == keys.down then
                -- Select next option
				local selection = window:getSelection()+1
				-- elements = { ..., selection, [...] }
				for i = selection,#window:getElements() do
					if instanceOf(window:getElementById(i), Button)
						or instanceOf(window:getElementById(i), Input) then
						window:setSelection(i)
						break
					end
				end
			elseif event[2] == keys.backspace
				and instanceOf(selectedElement, Input) then
				-- If backspace is pressed and we've selected an Input element,
				-- remove the last character from the element title
				window:getSelectedElement():setValue(
					selectedElement:getValue():sub(1, -2)
				)
			end
		elseif event[1] == "char" and instanceOf(selectedElement, Input) then
			-- Qualify with having an input selected, because otherwise we want
			-- to pass the char event to the event handler function.
			selectedElement:setValue(selectedElement:getValue()..event[2])
		elseif event[1] == "terminate" then
            -- Stop the menu
			self.running = false
		else
            -- Pass any other events to the custom event handler function
			if eventHandler and type(eventHandler) == "function" then
				assert(pcall(eventHandler, self, event))
			end
		end

		-- Stop if the last window has been closed/removed
		if #self:getWindows() < 1 then self.running = false end
	end
    
	-- Reset terminal 
	term.setBackgroundColor(colors.black)
	term.setTextColor(colors.white)
	term.clear()
	term.setCursorPos(1, 1)
end

-- vim: syntax=lua