/* Copyright (c) 1997-2024
   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/client.h"
#include "polymake/Rational.h"
#include "polymake/QuadraticExtension.h"
#include "polymake/Matrix.h"
#include "polymake/Array.h"
#include "polymake/SparseMatrix.h"

namespace polymake { namespace polytope {

namespace {

BigObject simplex_action(Int d)
{
   const Int n_gens = d == 1 ? 1 : 2;
   Array<Array<Int>> gens(n_gens);
   if (d == 1) {
      gens[0] = Array<Int>{1, 0};
   } else {
      Array<Int> gen{sequence(0,d+1)};
      gen[0]=1;
      gen[1]=0;
      gens[0]=gen;
      
      gen[0]=d;
      for (Int j = 1; j <= d; ++j) {
         gen[j]=j-1; 
      }
      gens[1]=gen;
   }

   return BigObject("group::PermutationAction", "GENERATORS", gens);
}


void add_simplex_data(BigObject& p, const Int d, const bool group_flag)
{
   p.take("CONE_DIM") << d+1;   
   p.take("N_VERTICES") << d+1;
   p.take("SIMPLICIALITY") << d;
   p.take("BOUNDED") << true;
   p.take("FEASIBLE") << true;
   p.take("POINTED") << true;
   if (group_flag) {
      BigObject g("group::Group", "fullCombinatorialGroupOnRays");
      g.set_description() << "full combinatorial group on vertices of " << d << "-dim simplex" << endl;
      p.take("GROUP") << g;
      p.take("GROUP.VERTICES_ACTION") << simplex_action(d);
   }
}

} // end anonymous namespace

template<typename Scalar>
BigObject simplex(Int d, const Scalar& s, OptionSet options)
{
   if (d < 0)
      throw std::runtime_error("dimension must be non-negative");
   if (s == 0)
      throw std::runtime_error("scale must be non-zero");

   BigObject p("Polytope", mlist<Scalar>());
   p.set_description() << "standard simplex of dimension " << d << endl;

   SparseMatrix<Scalar> V( ones_vector<Scalar>(d+1) | (zero_vector<Scalar>(d) / (s*unit_matrix<Scalar>(d))));

   p.take("VERTICES") << V;
   p.take("CONE_AMBIENT_DIM") << d+1;
   p.take("CENTERED") << (d == 0);
   add_simplex_data(p, d, options["group"]);

   return p;
}

typedef QuadraticExtension<Rational> QE;

BigObject regular_simplex(const Int d, OptionSet options)
{
   if (d < 0)
      throw std::runtime_error("dimension must be non-negative");
   if (d==0)
      return simplex< QE >(0,QE(1,0,0),options);

   BigObject p("Polytope<QuadraticExtension>");
   p.set_description() << "regular simplex of dimension " << d << endl;

   QE c(Rational(1,d), Rational(-1,d), d+1);
   SparseMatrix<QE> V( ones_vector<QE>(d+1) | (unit_matrix<QE>(d) / same_element_vector(c,d)));

   p.take("VERTICES") << V;
   p.take("CONE_AMBIENT_DIM") << d+1;
   p.take("CENTERED") << true;
   add_simplex_data(p, d, options["group"]);

   return p;
   
}

BigObject fano_simplex(Int d, OptionSet options)
{
   if (d <= 0)
      throw std::runtime_error("fano_simplex : dimension must be positive");

   BigObject p("Polytope<Rational>");
   p.set_description() << "Fano simplex of dimension " << d << endl;

   SparseMatrix<Rational> V( ones_vector<Rational>(d+1) | (unit_matrix<Rational>(d) / same_element_vector<Rational>(-1,d)) );

   p.take("VERTICES") << V;
   p.take("CONE_AMBIENT_DIM") << d+1;
   p.take("CENTERED") << true;
   p.take("REFLEXIVE") << true;
   add_simplex_data(p, d, options["group"]);

   return p;
}

BigObject lecture_hall_simplex(Int d, OptionSet options)
{
   if (d <= 0)
      throw std::runtime_error("lecture_hall_simplex : dimension must be positive");

   BigObject p("Polytope<Rational>");
   p.set_description() << "lecture hall simplex of dimension " << d << endl;

   Matrix<Rational> V(d+1,d+1);
   for (Int i = 0; i <= d; ++i) {
      V(i,0) = 1;
      for (Int k = d; k > d-i; --k) V(i,k)=k;
   }

   p.take("VERTICES") << V;
   p.take("CONE_AMBIENT_DIM") << d+1;
   p.take("CENTERED") << false;
   add_simplex_data(p, d, options["group"]);

   return p;
}


UserFunction4perl("# @category Producing regular polytopes and their generalizations"
                  "# Produce a regular //d//-simplex embedded in R^d with edge length sqrt(2)."
                  "# @param Int d the dimension"
                  "# @option Bool group"
                  "# @return Polytope"
                  "# @example To print the vertices (in homogeneous coordinates) of the regular"
                  "# 2-simplex, i.e. an equilateral triangle, type this:"
                  "# > print regular_simplex(2)->VERTICES;"
                  "# | 1 1 0"
                  "# | 1 0 1"
                  "# | 1 1/2-1/2r3 1/2-1/2r3"
                  "# The polytopes cordinate type is ''QuadraticExtension<Rational>'', thus numbers that can"
                  "# be represented as a + b*sqrt(c) with Rational numbers a, b and c. The last row vectors"
                  "# entries thus represent the number $ 1/2 * ( 1 - sqrt(3) ) $."
                  "# @example To store a regular 3-simplex in the variable $s and also calculate its"
                  "# symmetry group, type this:"
                  "# > $s = regular_simplex(3, group=>1);"
                  "# You can then print the groups generators like so:"
                  "# > print $s->GROUP->RAYS_ACTION->GENERATORS;"
                  "# | 1 0 2 3"
                  "# | 3 0 1 2",
                  &regular_simplex, "regular_simplex(Int; { group => undef } )");

UserFunctionTemplate4perl("# @category Producing a polytope from scratch"
                          "# Produce the standard //d//-simplex."
                          "# Combinatorially equivalent to a regular polytope corresponding to the Coxeter group of type A<sub>//d//-1</sub>."
                          "# Optionally, the simplex can be scaled by the parameter //scale//."
                          "# @param Int d the dimension"
                          "# @param Scalar scale default value: 1"
                          "# @option Bool group"
                          "# @return Polytope"
                          "# @example To print the vertices (in homogeneous coordinates) of the standard"
                          "# 2-simplex, i.e. a right-angled isoceles triangle, type this:"
                          "# > print simplex(2)->VERTICES;"
                          "# | (3) (0 1)"
                          "# | 1 1 0"
                          "# | 1 0 1"
                          "# The first row vector is sparse and encodes the origin."
                          "# @example To create a 3-simplex and also calculate its symmetry group, type this:"
                          "# > simplex(3, group=>1);",
                          "simplex<Scalar> [ is_ordered_field(type_upgrade<Scalar, Rational>) ] (Int; type_upgrade<Scalar>=1, { group => undef } )");

UserFunction4perl("# @category Producing a polytope from scratch"
                  "# Produce a Fano //d//-simplex."
                  "# @param Int d the dimension"
                  "# @option Bool group"
                  "# @return Polytope"
                  "# @example To create the 2-dimensional fano simplex and compute its symmetry group, type this:"
                  "# and print ints generators, do this:"
                  "# > $p = fano_simplex(2,group=>1);"
                  "# > print $p->GROUP->RAYS_ACTION->GENERATORS;"
                  "# | 1 0 2"
                  "# | 2 0 1",
                  &fano_simplex, "fano_simplex(Int; { group => undef } )");

UserFunction4perl("# @category Producing a polytope from scratch"
                  "# Produce a lecture hall //d//-simplex."
                  "# @param Int d the dimension"
                  "# @option Bool group"
                  "# @return Polytope"
                  "# @example To create the 2-dimensional lecture hall simplex and compute its symmetry group, type this:"
                  "# > $p = lecture_hall_simplex(2, group=>1);"
                  "# > print $p->GROUP->RAYS_ACTION->GENERATORS;"
                  "# | 1 0 2"
                  "# | 2 0 1",
                  &lecture_hall_simplex, "lecture_hall_simplex(Int; { group => undef } )");

} }


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