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/**************************************************************************
* *
* Regina - A Normal Surface Theory Calculator *
* Computational Engine *
* *
* Copyright (c) 1999-2025, Ben Burton *
* For further details contact Ben Burton (bab@debian.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 of the *
* License, or (at your option) any later version. *
* *
* As an exception, when this program is distributed through (i) the *
* App Store by Apple Inc.; (ii) the Mac App Store by Apple Inc.; or *
* (iii) Google Play by Google Inc., then that store may impose any *
* digital rights management, device limits and/or redistribution *
* restrictions that are required by its terms of service. *
* *
* 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. *
* *
* You should have received a copy of the GNU General Public License *
* along with this program. If not, see <https://www.gnu.org/licenses/>. *
* *
**************************************************************************/
#include "manifold/torusbundle.h"
#include "subcomplex/layeredtorusbundle.h"
#include "subcomplex/layering.h"
#include "subcomplex/txicore.h"
#include "triangulation/dim3.h"
namespace regina {
namespace {
const TxIDiagonalCore core_T_6_1(6, 1);
const TxIDiagonalCore core_T_7_1(7, 1);
const TxIDiagonalCore core_T_8_1(8, 1);
const TxIDiagonalCore core_T_8_2(8, 2);
const TxIDiagonalCore core_T_9_1(9, 1);
const TxIDiagonalCore core_T_9_2(9, 2);
const TxIDiagonalCore core_T_10_1(10, 1);
const TxIDiagonalCore core_T_10_2(10, 2);
const TxIDiagonalCore core_T_10_3(10, 3);
const TxIDiagonalCore core_T_11_1(11, 1);
const TxIDiagonalCore core_T_11_2(11, 2);
const TxIDiagonalCore core_T_11_3(11, 3);
const TxIDiagonalCore core_T_12_1(12, 1);
const TxIDiagonalCore core_T_12_2(12, 2);
const TxIDiagonalCore core_T_12_3(12, 3);
const TxIDiagonalCore core_T_12_4(12, 4);
const TxIParallelCore core_T_p;
}
std::unique_ptr<LayeredTorusBundle> LayeredTorusBundle::recognise(
const Triangulation<3>& tri) {
// Basic property checks.
if (! tri.isClosed())
return nullptr;
if (tri.countVertices() > 1)
return nullptr;
if (tri.countComponents() > 1)
return nullptr;
if (tri.size() < 6)
return nullptr;
// We have a 1-vertex 1-component closed triangulation with at least
// six tetrahedra.
// Hunt for the core thin torus bundle.
if (auto ans = hunt(tri, core_T_6_1))
return ans;
if (auto ans = hunt(tri, core_T_7_1))
return ans;
if (auto ans = hunt(tri, core_T_8_1))
return ans;
if (auto ans = hunt(tri, core_T_8_2))
return ans;
if (auto ans = hunt(tri, core_T_9_1))
return ans;
if (auto ans = hunt(tri, core_T_9_2))
return ans;
if (auto ans = hunt(tri, core_T_10_1))
return ans;
if (auto ans = hunt(tri, core_T_10_2))
return ans;
if (auto ans = hunt(tri, core_T_10_3))
return ans;
if (auto ans = hunt(tri, core_T_11_1))
return ans;
if (auto ans = hunt(tri, core_T_11_2))
return ans;
if (auto ans = hunt(tri, core_T_11_3))
return ans;
if (auto ans = hunt(tri, core_T_12_1))
return ans;
if (auto ans = hunt(tri, core_T_12_2))
return ans;
if (auto ans = hunt(tri, core_T_12_3))
return ans;
if (auto ans = hunt(tri, core_T_12_4))
return ans;
if (auto ans = hunt(tri, core_T_p))
return ans;
return nullptr;
}
std::unique_ptr<LayeredTorusBundle> LayeredTorusBundle::hunt(
const Triangulation<3>& tri, const TxICore& core) {
std::unique_ptr<LayeredTorusBundle> ans;
core.core().findAllSubcomplexesIn(tri,
[&ans, &core, &tri](const Isomorphism<3>& iso) {
// Look for the corresponding layering.
Matrix2 matchReln;
// Apply the layering to the lower boundary and see if it
// matches nicely with the upper.
Layering layering(
tri.tetrahedron(iso.tetImage(core.bdryTet(1,0))),
iso.facePerm(core.bdryTet(1,0)) * core.bdryRoles(1,0),
tri.tetrahedron(iso.tetImage(core.bdryTet(1,1))),
iso.facePerm(core.bdryTet(1,1)) * core.bdryRoles(1,1));
layering.extend();
if (layering.matchesTop(
tri.tetrahedron(iso.tetImage(core.bdryTet(0,0))),
iso.facePerm(core.bdryTet(0,0)) * core.bdryRoles(0,0),
tri.tetrahedron(iso.tetImage(core.bdryTet(0,1))),
iso.facePerm(core.bdryTet(0,1)) * core.bdryRoles(0,1),
matchReln)) {
// It's a match!
//
// Note: we cannot use make_unique here, since the class
// constructor is private.
ans.reset(new LayeredTorusBundle(core, iso,
core.bdryReln(0) * matchReln * core.bdryReln(1).inverse()));
return true;
}
// No match.
return false;
});
return ans;
}
std::unique_ptr<Manifold> LayeredTorusBundle::manifold() const {
// Note that this one-liner appears again in homology(), where
// we use the underlying TorusBundle for homology calculations.
return std::make_unique<TorusBundle>(core_->parallelReln() * reln_);
}
AbelianGroup LayeredTorusBundle::homology() const {
// It's implemented in TorusBundle, so ride on that for now.
// We'll implement it directly here in good time.
return TorusBundle(core_->parallelReln() * reln_).homology();
}
std::ostream& LayeredTorusBundle::writeCommonName(std::ostream& out,
bool tex) const {
if (tex) {
out << "B_{";
core_->writeTeXName(out);
} else {
out << "B(";
core_->writeName(out);
}
out << " | " << reln_[0][0] << ',' << reln_[0][1];
out << " | " << reln_[1][0] << ',' << reln_[1][1];
return out << (tex ? "}" : ")");
}
void LayeredTorusBundle::writeTextLong(std::ostream& out) const {
out << "Layered torus bundle: ";
writeName(out);
}
} // namespace regina
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