xml_graph_test.cc

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/*
                          Aleph_w
 
  Data structures & Algorithms
  version 2.0.0b
  https://github.com/lrleon/Aleph-w
 
  This file is part of Aleph-w library
 
  Copyright (c) 2002-2026 Leandro Rabindranath Leon
 
  Permission is hereby granted, free of charge, to any person obtaining a copy
  of this software and associated documentation files (the "Software"), to deal
  in the Software without restriction, including without limitation the rights
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  copies of the Software, and to permit persons to whom the Software is
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*/
 
# include <gtest/gtest.h>
 
# include <cstdio>
# include <filesystem>
# include <random>
# include <stdexcept>
# include <string>
 
# include <ahSort.H>
# include <xml_graph.H>
 
using namespace Aleph;
 
namespace
{
  using G = List_Graph<Graph_Node<int>, Graph_Arc<int>>;
 
  struct NotAGraph
  {
    using Node = int;
  };
 
  template <class T>
  concept can_xml_graph = requires { typename Xml_Graph<T>; };
 
  static_assert(can_xml_graph<G>);
  static_assert(not can_xml_graph<NotAGraph> and not can_xml_graph<DynList<int>>);
 
  // Stateful writer: counts its calls so the tests can see whose copy ran.
  struct NodeWriter
  {
    int calls = 0;
 
    void operator()(G &, G::Node * p, DynArray<Attr> & attrs)
    {
      ++calls;
      attrs.append(Attr{"info", std::to_string(p->get_info())});
    }
  };
 
  struct NodeReader
  {
    void operator()(G &, G::Node * p, DynArray<Attr> & attrs)
    {
      for (size_t i = 0; i < attrs.size(); ++i)
        if (attrs(i).name == "info")
          p->get_info() = std::stoi(attrs(i).value);
    }
  };
 
  struct ArcWriter
  {
    void operator()(G &, G::Arc * a, DynArray<Attr> & attrs)
    {
      attrs.append(Attr{"w", std::to_string(a->get_info())});
    }
  };
 
  struct ArcReader
  {
    void operator()(G &, G::Arc * a, DynArray<Attr> & attrs)
    {
      for (size_t i = 0; i < attrs.size(); ++i)
        if (attrs(i).name == "w")
          a->get_info() = std::stoi(attrs(i).value);
    }
  };
 
  using XG = Xml_Graph<G, NodeReader, ArcReader, NodeWriter, ArcWriter>;
 
  // Order-independent description of a graph: node infos and
  // "src info -> tgt info : weight" for every arc.
  DynList<std::string> describe(G & g)
  {
    DynList<std::string> items;
    for (auto it = g.get_node_it(); it.has_curr(); it.next_ne())
      items.append("n" + std::to_string(it.get_curr()->get_info()));
    for (auto it = g.get_arc_it(); it.has_curr(); it.next_ne())
      {
        auto * a = it.get_curr();
        items.append(std::to_string(g.get_src_node(a)->get_info()) + "->" +
                     std::to_string(g.get_tgt_node(a)->get_info()) + ":" +
                     std::to_string(a->get_info()));
      }
    return sort(items);
  }
 
  G sample_graph()
  {
    G g;
    G::Node * n[5];
    for (int i = 0; i < 5; ++i)
      n[i] = g.insert_node(10 * (i + 1));
    g.insert_arc(n[0], n[1], 1);
    g.insert_arc(n[1], n[2], 2);
    g.insert_arc(n[2], n[3], 3);
    g.insert_arc(n[3], n[4], 4);
    g.insert_arc(n[4], n[0], 5);
    g.insert_arc(n[0], n[2], 6);
    return g;
  }
 
  // ctest runs each case in its own process, possibly in parallel: every
  // case writes to files named after itself plus a random token.
  class XmlGraphTest : public ::testing::Test
  {
    std::string prefix;
 
  protected:
    void SetUp() override
    {
      prefix = std::string("aleph_xml_graph_test_") +
               ::testing::UnitTest::GetInstance()->current_test_info()->name() +
               "_" + std::to_string(std::random_device{}()) + "_";
    }
 
    std::string file(const std::string & name) const
    {
      return (std::filesystem::temp_directory_path() / (prefix + name)).string();
    }
 
    void TearDown() override
    {
      for (const char * name : {"owned.xml", "shared.xml", "copy.xml", "names.xml"})
        std::remove(file(name).c_str());
    }
  };
} // namespace
 
// The default constructor used to keep references to temporary functors,
// which dangled as soon as it returned.
TEST_F(XmlGraphTest, RoundTripWithOwnedFunctors)
{
  G g = sample_graph();
  XG xml;
  xml(g, file("owned.xml"));
  G h = xml(file("owned.xml"));
 
  EXPECT_EQ(h.get_num_nodes(), g.get_num_nodes());
  EXPECT_EQ(h.get_num_arcs(), g.get_num_arcs());
  EXPECT_EQ(describe(h), describe(g));
}
 
// Functors passed by lvalue are shared: their state is visible to the caller,
// also through a copy of the reader/writer.
TEST_F(XmlGraphTest, SharedFunctorsStaySharedAcrossCopies)
{
  G g = sample_graph();
  NodeReader nr;
  ArcReader ar;
  NodeWriter nw;
  ArcWriter aw;
  XG shared(nr, ar, nw, aw);
  shared(g, file("shared.xml"));
  EXPECT_EQ(nw.calls, 5);
 
  XG copy = shared;
  G h = copy(file("shared.xml"));
  copy(h, file("copy.xml"));
  EXPECT_EQ(nw.calls, 10);
  EXPECT_EQ(describe(h), describe(g));
}
 
// A copy of an owning reader/writer owns its own functors.
TEST_F(XmlGraphTest, CopyOfOwnerOutlivesTheOriginal)
{
  G g = sample_graph();
  auto * original = new XG;
  XG copy = *original;
  delete original;
 
  copy(g, file("owned.xml"));
  G h = copy(file("owned.xml"));
  EXPECT_EQ(describe(h), describe(g));
}
 
namespace
{
  // Movable but not copyable, e.g. because it owns a resource.
  struct NonCopyableWriter
  {
    int calls = 0;
    NonCopyableWriter() = default;
    NonCopyableWriter(const NonCopyableWriter &) = delete;
    NonCopyableWriter(NonCopyableWriter &&) = default;
 
    void operator()(G &, G::Node * p, DynArray<Attr> & attrs)
    {
      ++calls;
      attrs.append(Attr{"info", std::to_string(p->get_info())});
    }
  };
 
  using XGNonCopyable = Xml_Graph<G, Dft_Node_Reader<G>, Dft_Arc_Reader<G>, NonCopyableWriter>;
} // namespace
 
// Copying an Xml_Graph used to require every functor type to be
// copy-constructible, even in shared mode, where no functor is ever actually
// copied: std::optional<F>'s copy constructor is deleted whenever F is not
// copy-constructible, regardless of whether the specific optional holds a
// value. Sharing (not owning) a non-copy-constructible functor must still
// allow the reader/writer itself to be copied.
TEST_F(XmlGraphTest, CopyOfSharedNonCopyableFunctorWorks)
{
  G g = sample_graph();
  Dft_Node_Reader<G> nr;
  Dft_Arc_Reader<G> ar;
  NonCopyableWriter nw;
  Dft_Arc_Writer<G> aw;
 
  XGNonCopyable shared(nr, ar, nw, aw);
  XGNonCopyable copy = shared;  // must not try to copy nw
 
  copy(g, file("owned.xml"));
  EXPECT_EQ(nw.calls, 5);
}
 
// Copying an Xml_Graph that *owns* a non-copy-constructible functor cannot
// duplicate that functor, so it must fail loudly (a runtime error, per
// CLAUDE.md), not silently share it or refuse to compile for callers who
// never attempt this copy.
TEST_F(XmlGraphTest, CopyOfOwnedNonCopyableFunctorThrows)
{
  // `XGNonCopyable owner(A(), B(), C(), D());` would parse as a function
  // declaration (most vexing parse); `=` forces expression context.
  XGNonCopyable owner =
      XGNonCopyable(Dft_Node_Reader<G>(), Dft_Arc_Reader<G>(), NonCopyableWriter(), Dft_Arc_Writer<G>());
  EXPECT_THROW((XGNonCopyable(owner)), std::runtime_error);
}
 
TEST_F(XmlGraphTest, CustomElementNamesRoundTrip)
{
  G g = sample_graph();
  XG xml;
  xml.set_graph_name("network");
  xml.set_node_name("vertex");
  xml.set_arc_name("edge");
  EXPECT_EQ(xml.get_node_name(), "vertex");
  xml(g, file("names.xml"));
 
  G h = xml(file("names.xml"));
  EXPECT_EQ(describe(h), describe(g));
 
  // With the default names nothing in the file is recognized.
  XG defaults;
  G empty = defaults(file("names.xml"));
  EXPECT_EQ(empty.get_num_nodes(), 0u);
}