Corona Lua RPG Experience Bar via Pathfinder rules

ExperienceBar.lua

ExperienceBar = {}
 
function ExperienceBar:new(x, y, targetWidth, targetHeight)
	local group = display.newGroup()
	group.x = x
	group.y = y
 
	local grayBar = display.newRect(0, 0, targetWidth, targetHeight)
	group:insert(grayBar)
	grayBar:setFillColor(102, 102, 102, 200)
	grayBar:setStrokeColor(51, 51, 51)
	grayBar.strokeWidth = 2
 
	local greenBar = display.newRect(0, 0, targetWidth - 2, targetHeight - 2)
	greenBar:setReferencePoint(display.TopLeftReferencePoint)
	group:insert(greenBar)
	greenBar:setFillColor(0, 153, 0)
	greenBar.x = 1
	greenBar.y = 1
 
	function group:setValue(current, max)
		local percent = current / max
		if percent > 1 then
			error("You cannot have a percent over 100%")
		end
		local desiredWidth = (targetWidth - 2) * percent
		if percent ~= 0 then
			greenBar.xScale = percent
			greenBar.isVisible = true
		else
			greenBar.isVisible = false
		end
		greenBar.x = grayBar.x + greenBar.xReference
	end
 	
	return group
end
 
return ExperienceBar

LevelModel.lua

LevelModel = {}

function LevelModel:new(startingXP)
	if startingXP == nil then
		startingXP = 0
	end
	
	local model = display.newGroup()
	model.xp = startingXP
	model.level = 1
	model.LEVEL_TABLE = {
		2000,
		5000,
		9000,
		15000,
		23000,
		35000,
		51000,
		75000,
		105000,
		155000,
		220000,
		315000,
		445000,
		635000,
		890000,
		1300000,
		1800000,
		2550000,
		3600000
	}
	
	function model:setLevel(value)
		if self.level ~= value then
			self.level = value
			self:dispatchEvent({name="levelChanged", target=self})
		end
	end
	
	function model:setXP(value)
		if self.xp ~= value then
			self.xp = value
			self:updateLevel()
			self:dispatchEvent({name="xpChanged", target=self})
		end
	end
	
	function model:getCurrentLevelXP()
		return self.LEVEL_TABLE[self.level]
	end
	
	function model:updateLevel()
		assert(self.xp ~= nil, "You cannot have nil xp.")
		local i = 1
		while self.LEVEL_TABLE[i] do
			local value = self.LEVEL_TABLE[i]
			if self.xp < value then
				self:setLevel(i)
				return true
			end
			i = i + 1
		end
	end
	
	function model:addXP(value)
		local newValue = self.xp + value
		self:setXP(newValue)
	end
	
	model:updateLevel()
	
	return model
end

return LevelModel

main.lua

require "ExperienceBar"
require "LevelModel"

bar = ExperienceBar:new(40, 100, 200, 20)
myText = display.newRetinaText("", 0, 0, native.systemFont, 16)
myText:setReferencePoint(display.TopLeftReferencePoint)
myText:setTextColor(255)
myText.x = 100
myText.y = 50

function onXPChanged(event)
	local max = levelModel:getCurrentLevelXP()
	local xp = levelModel.xp
	bar:setValue(xp, max)
	myText.text = "Level: " .. levelModel.level .. ", XP: " .. xp .. " / " .. max
	myText.x = bar.x + myText.width / 2
end

levelModel = LevelModel:new(0)
levelModel:addEventListener("xpChanged", onXPChanged)

increment = 100
function onIncreaseXP()
	levelModel:addXP(increment)
	increment = math.floor(increment * 1.01)
end

timer.performWithDelay(100, onIncreaseXP, 0)