perlinGenerator={}

perlinGenerator.permutation={};
perlinGenerator.zoom=1
perlinGenerator.oct=15
perlinGenerator.res=.5
function perlinGenerator:generateLookup(seed)
    seed=seed or os.time();
    math.randomseed(seed);
    self.permutation={}
    num=255;
    for i=0,num do
        self.permutation[i]=i
    end

    for i=0,num-1 do
        j=math.floor(math.random(0,num-i))

        zw=self.permutation[i]
        self.permutation[i]=self.permutation[i+j]
        self.permutation[i+j]=zw
    end
end

function fade(x)
    return(x*x*x*(x*(x*6-15)+10))
end

function wrapVal(x)
    while x>255 do
        x=x-255;
    end
    return x
end

function grad(hash,x,y)
    h=hash%4;
    if(h==0)then return x+y
    elseif(h==1)then return -x+y;
    elseif(h==2)then return  x-y;
    elseif(h==3)then return -x-y;
    end
end

function lerp(a,b,w)
    return(a+(b-a)*w)
end

function perlinGenerator:perlin(x,y)
    x=x
    y=y

    xf=x%1;
    yf=y%1;

    xi=math.floor(x)%255;
    yi=math.floor(y)%255;

    --u=xf
    --v=yf
    u=fade(xf)
    v=fade(yf)

    aa=self.permutation[wrapVal(self.permutation[wrapVal(xi  )]+yi  )]
    ab=self.permutation[wrapVal(self.permutation[wrapVal(xi+1)]+yi  )]
    ba=self.permutation[wrapVal(self.permutation[wrapVal(xi  )]+yi+1)]
    bb=self.permutation[wrapVal(self.permutation[wrapVal(xi+1)]+yi+1)]
    --print(aa,ab,ba,bb)

    v1=grad(aa,xf  ,yf  );
    v2=grad(ab,xf-1  ,yf);
    v3=grad(ba,xf,yf-1  );
    v4=grad(bb,xf-1,yf-1);
    return(lerp(lerp(v1,v2,u),lerp(v3,v4,u),v))

end

function perlinGenerator:perlinOctave(x,y,octaves,persistence)
    x=x/self.zoom
    y=y/self.zoom
    total=0
    frequency=1
    amplitude=1
    maxVal=0
    octaves=octaves or self.oct;
    persistence=persistence or self.res;
    for i=0,octaves do
        total=total+self:perlin(x*frequency,y*frequency)*amplitude;
        maxVal=maxVal+amplitude;
        amplitude=amplitude*persistence
        frequency=frequency*2
    end
    return(total/maxVal)
end


function perlinGenerator:new(o,dim)
    o=o or {}
    setmetatable(o,self)
    self.zoom=1
    self.__index=self
    return o
end