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

const P LdY(0, 4);
const P LdX(4, 0);

std::string sfmt(const std::string& msg)
{
#ifdef SANSSERIF
  return "$\\mathsf{"+msg+"}$";
#else
  return "$"+msg+"$";
#endif
}

const double th(M_PI_2*(0.2));
const double dM(Sin(th)); // distance to moon
 
const P ptE(1,0); // Earth
const P ptS(0,0); // Sun
const P ptM(ptE + polar(dM, M_PI_2+th)); // moon

void ray(const P& tail, const P& head, double s)
{
  line(tail, tail + (1+0.01*s)*(head-tail));
}

P ptF(0,1), ptG(0.5,1), ptH(1-Tan(th), 1);

int main()
{
  picture(P(0,0), P(1,1), "3.5 x 3.5in");

  begin();

  rect(P(0,0), P(1,1));

  arc(ptE,  1, M_PI_2, M_PI);
  arc(ptE, dM, M_PI_2, M_PI);

  line(ptE, ptF);
  line(ptE, ptG);
  line(ptE, ptH);

  ray(ptS, ptM, 20);

  label(ptS, -LdY, sfmt("S"), b);
  label(ptE, -LdY, sfmt("E"), b);

  label(ptF,  LdY, sfmt("F"), t);
  label(ptG,  LdY, sfmt("G"), t);
  label(ptH,  LdY, sfmt("H"), t);
  label(P(1,1),  LdY, sfmt("A"), t);

  label(ptM, 2*LdY, sfmt("M"), tr);

  tikz_format();
  end();
}