Love Game Engine

require("class")

engine = {} -- Engine package

-- Love wrappers

function love.load()
    engine.game:load()
end

function love.quit()
    engine.game:quit()
end

function love.focus(f)
    engine.game:focus(f)
end

function love.update(dt)
    engine.game:update(dt)
end

function love.draw()
    engine.game:draw()
end

-- Engine class

engine.Engine = newClass()

function engine.Engine:init()
    self:setSize()
    self:setTitle()
    self.focused = true
    self.fading = false
    self.fade = 1
    self.fadeSpeed = 0.5
    self.fadeColor = {255, 255, 255}
    self:setScene(engine.Entity)
end

-- Sets the engine subclass to load

function engine.Engine:setGame()
    engine.game = self:new()
end

-- Engine methods

function engine.Engine:setTitle(title)
    self.title = title or "Game Engine"
    love.graphics.setCaption(self.title)
end

function engine.Engine:setSize(width, height)
    self.width = width or 640
    self.height = height or 480
    love.graphics.setMode(self.width, self.height)
end

function engine.Engine:fadeToScene(scene, ...)
    self.fadeTo = scene
    self.fadeArgs = ...
    self.fading = true
end

function engine.Engine:setScene(scene, ...)
    if self.scene then self.scene:destroy() end
    self.scene = scene:new(self)
    self.scene:setup(...)
end

function engine.Engine:toggleFullscreen()
    love.graphics.toggleFullscreen()
end

-- Wrapped Love functions

function engine.Engine:load()
    self:setup()
end

function engine.Engine:quit()
end

function engine.Engine:focus(f)
    self.focused = f
end

function engine.Engine:update(dt)
    if self.fading then
        if self.fade >= 1 then
            self.fade = 1
            self.fading = false
            self:setScene(self.fadeTo, self.fadeArgs)
        else
            self.fade = self.fade + self.fadeSpeed * dt
            if self.fade > 1 then self.fade = 1 end
        end
    else
        if self.fade <= 0 then
            self.fade = 0
        else
            self.fade = self.fade - self.fadeSpeed * dt
            if self.fade < 0 then self.fade = 0 end
        end
    end
    self.scene:masterUpdate(dt)
end

function engine.Engine:draw()
    self.scene:render()
    love.graphics.setCanvas()
    self.scene:postRender()
    self:drawFade()
end

-- Private methods

function engine.Engine:drawFade()
    love.graphics.setBlendMode("alpha")
    love.graphics.setColor(self.fadeColor[1], self.fadeColor[2], self.fadeColor[3], (math.cos((1 - self.fade) * math.pi) + 1) * 127)
    love.graphics.polygon("fill", 0, 0, self.width, 0, self.width, self.height, 0, self.height)
end

-- Virtual methods

function engine.Engine:setup()
end

-- Entity class

engine.Entity = newClass()

function engine.Entity:init(engine)
    self.engine = engine
    self:setSize()
    self:setPosition()
    self:setOrientation()
    self:setScale()
    self:setColor()
    self.children = {}
end

function engine.Entity:addChild(child, ...)
    table.insert(self.children, child)
    child:setup(...)
end

function engine.Entity:removeChild(child)
    table.remove(self.children, child)
    child:destroy()
end

function engine.Entity:setColor(color)
    self.color = color or {255, 255, 255}
end

function engine.Entity:setPosition(x, y)
    self.x = x or 0
    self.y = y or 0
end

function engine.Entity:setOrientation(r)
    self.orientation = r or 0
end

function engine.Entity:setScale(x, y)
    self.scaleX = x or 1
    self.scaleY = y or 1
end

function engine.Entity:setSize(width, height)
    self.width = width or self.engine.width
    self.height = height or self.engine.height
    self.canvas = love.graphics.newCanvas(self.width, self.height)
end

function engine.Entity:render()
    love.graphics.setCanvas(self.canvas)
    love.graphics.setColor(love.graphics.getBackgroundColor())
    love.graphics.setBlendMode("alpha")
    love.graphics.polygon("fill", 0, 0, self.width, 0, self.width, self.height, 0, self.height)

    self:preDraw()

    for k, v in pairs(self.children) do
        v:render()
        love.graphics.setCanvas(self.canvas)
        v:postRender()
    end

    self:draw()
end

function engine.Entity:postRender()
    love.graphics.setBlendMode("alpha")
    love.graphics.setColor(self.color[1], self.color[2], self.color[3])
    love.graphics.drawq(self.canvas, love.graphics.newQuad(0, 0, self.width, self.height, self.width, self.height), self.x + self.width / 2, self.y + self.height / 2, self.orientation, self.scaleX, self.scaleY, self.width / 2, self.height / 2)
end

function engine.Entity:masterUpdate(dt)
    for k, v in pairs(self.children) do
        v:masterUpdate(dt)
    end
    self:update(dt)
end

-- Virtual methods

function engine.Entity:setup(...)
end

function engine.Entity:destroy()
end

function engine.Entity:update(dt)
end

function engine.Entity:preDraw()
end

function engine.Entity:draw()
end