/* Copyright (c) 1997-2020
   Ewgenij Gawrilow, Michael Joswig, and the polymake team
   Technische Universität Berlin, Germany
   https://polymake.org

   This program is free software; you can redistribute it and/or modify it
   under the terms of the GNU General Public License as published by the
   Free Software Foundation; either version 2, or (at your option) any
   later version: http://www.gnu.org/licenses/gpl.txt.

   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.
--------------------------------------------------------------------------------
*/

#include "polymake/ideal/internal/singularConvertTypes.h"

namespace polymake {
namespace ideal {
namespace singular{

// Convert a Singular number to a GMP rational.
Rational convert_number_to_Rational(number n, ring ring)
{
   Rational result;
   if (rField_is_Q(ring)) {
      if (SR_HDL(n) & SR_INT) {
         result = SR_TO_INT(n);
      } else {
         switch (n->s) {
            case 0:
            case 1:
               result.copy_from(n->z, n->n);
               break;
            case 3:
               result.copy_from(n->z);
               break;
            default:
               throw std::runtime_error("unexpected number type");
         }
      }
      return result;
   }
   throw std::runtime_error("I can has number? :P");
}


// Convert a GMP rational to a Singular number.
number convert_Rational_to_number(const Rational& r)
{
   static coeffs singular_rational = nInitChar(n_Q, nullptr);
   // cast removes the const as singular just uses it to initialize its own mpz
   number num = n_InitMPZ((mpz_ptr) numerator(r).get_rep(),singular_rational);
   number denom = n_InitMPZ((mpz_ptr) denominator(r).get_rep(),singular_rational);
   number res = n_Div(num,denom,singular_rational);
   n_Delete(&num,singular_rational);
   n_Delete(&denom,singular_rational);
   return res;
}

std::pair<std::vector<Rational>, ListMatrix<Vector<Int>>> convert_poly_to_vector_and_matrix(const poly q)
{
   poly p = pCopy(q);
   poly pfull = p;
   int n = rVar(currRing);
   ListMatrix<Vector<Int>> exponents(0,n);
   std::vector<Rational> coefficients;
   while (p != nullptr) {
      number c = pGetCoeff(p);
      coefficients.push_back(convert_number_to_Rational(c, currRing));
      Vector<Int> monomial(n);
      for (int i = 1; i<=n; i++) {
         monomial[i-1] = pGetExp(p, i);
      }
      exponents /= monomial;
      pIter(p);
   }
   p_Delete(&pfull,currRing);
   return { std::move(coefficients), std::move(exponents) };
}

Polynomial<> convert_poly_to_Polynomial(const poly q)
{
   const auto decomposed = convert_poly_to_vector_and_matrix(q);
   return Polynomial<>(decomposed.first, decomposed.second);
}


poly convert_Polynomial_to_poly(const Polynomial<>& mypoly, ring ring)
{
   poly p = p_ISet(0,ring);
   for (const auto& term : mypoly.get_terms())
   {
      poly monomial = p_NSet(convert_Rational_to_number(term.second), ring);
      for (int k = 0; k < term.first.dim(); ++k)
      {
         p_SetExp(monomial, k+1, term.first[k], ring);
      }
      p_Setm(monomial,ring);
      p = p_Add_q(p, monomial,ring);
   }
   return p;
}


} // end namespace singular
} // end namespace ideal
} // end namespace polymake


