import “../color/hsl”;

d3.interpolateHsl = d3_interpolateHsl;

function d3_interpolateHsl(a, b) {

a = d3.hsl(a);
b = d3.hsl(b);
var ah = a.h,
    as = a.s,
    al = a.l,
    bh = b.h - ah,
    bs = b.s - as,
    bl = b.l - al;
if (isNaN(bs)) bs = 0, as = isNaN(as) ? b.s : as;
if (isNaN(bh)) bh = 0, ah = isNaN(ah) ? b.h : ah;
else if (bh > 180) bh -= 360; else if (bh < -180) bh += 360; // shortest path
return function(t) {
  a.h = ah + bh * t;
  a.s = as + bs * t;
  a.l = al + bl * t;
  return a;
};

}