/* -*-ePiX-*- */
#include "epix.h"
using namespace ePiX;

void mirror(const P& loc, const P& refl, double thk = 0.25, double wd = 6)
{
  double my(pt_to_screen(wd)), mx(pt_to_screen(thk));

  P dir(refl - loc);
  dir *= 1.0/(norm(dir));
  P perp(J(dir)),
    p1(loc + mx*dir - my*perp),
    p2(loc + mx*dir + my*perp),
    p3(loc - mx*dir + my*perp),
    p4(loc - mx*dir - my*perp);

  quad(p1, p2, p3, p4);
}

void scope(const P& vwr, const P& pt)
{
  double mx(pt_to_screen(8)), my(pt_to_screen(2));

  P dir(pt - vwr);
  dir *= 1.0/(norm(dir));
  P perp(J(dir)),
    p1(pt - 2*mx*dir + my*perp),
    p2(pt - 2*mx*dir - my*perp),
    p3(pt - my*perp),
    p4(pt + my*perp);

  quad(p1, p2, p3, p4);
  ellipse(pt, 0.2*my*dir, my*perp);
  ellipse(pt - 2*mx*dir, 0.2*my*dir, my*perp);

  // viewer's eye
  double th(40);
  P eye(pt - 3*mx*dir);
  line(eye, eye + polar(3*my, -th));
  line(eye, eye + polar(3*my,  th));

  arc_measure(eye, cis(-th), cis(th), 4);
  arc_measure(eye, cis(-10), cis(10), 4.25);
}

int main()
{
  picture(P(-1,-1), P(1,1), "2 x 2in");

  begin();

  P O(0, 0), pA(E_1), pAp(E_2);
  degrees();

  line(O, pA);
  line(O, pAp);

  dashed();
  dash_size(6);
  line(O, -pA);
  line(O, -pAp);
  solid();

  fill(Black());
  mirror(pA, O);
  mirror(pAp, O);

  fill(White());
  mirror(P(0,0), P(-1,1), 1, 12);

  masklabel(-pAp, "*");
  label(-pAp, P(4, 0), "\\textit{Source of Light.}", r);

  scope(-pA - E_1, -pA);
  label(-pA, P(0, -12), "\\textit{Observer.}", b);

  label(pA, P(2, 0), "$A$", r);
  label(pAp, P(0, 2), "$A'$", t);

  label(0.5*pA, P(0, -4), "$l$", b);
  label(0.5*pAp, P(2, 0), "$l'$", r);

  label(P(0.5*(xmin() + xmax()), ymin()), P(0, -24), "\\textsc{Fig.~9.}", b);
  tikz_format();
  end();
}