//=== llvm/unittest/ADT/DepthFirstIteratorTest.cpp - DFS iterator tests ---===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//

#include "llvm/ADT/DepthFirstIterator.h"
#include "TestGraph.h"
#include "gtest/gtest.h"

#include <array>
#include <iterator>
#include <type_traits>

#include <cstddef>

using namespace llvm;

namespace llvm {

template <typename T> struct CountedSet {
  typedef typename SmallPtrSet<T, 4>::iterator iterator;

  SmallPtrSet<T, 4> S;
  int InsertVisited = 0;

  std::pair<iterator, bool> insert(const T &Item) {
    InsertVisited++;
    return S.insert(Item);
  }

  size_t count(const T &Item) const { return S.count(Item); }
  
  void completed(T) { }
};

template <typename T> class df_iterator_storage<CountedSet<T>, true> {
public:
  df_iterator_storage(CountedSet<T> &VSet) : Visited(VSet) {}

  CountedSet<T> &Visited;
};

TEST(DepthFirstIteratorTest, ActuallyUpdateIterator) {
  typedef CountedSet<Graph<3>::NodeType *> StorageT;
  typedef df_iterator<Graph<3>, StorageT, true> DFIter;

  Graph<3> G;
  G.AddEdge(0, 1);
  G.AddEdge(0, 2);
  StorageT S;
  for (auto N : make_range(DFIter::begin(G, S), DFIter::end(G, S)))
    (void)N;

  EXPECT_EQ(3, S.InsertVisited);
}

static_assert(
    std::is_convertible_v<decltype(*std::declval<df_iterator<Graph<3>>>()),
                          typename df_iterator<Graph<3>>::reference>);

// df_iterator should be (at-least) a forward-iterator
static_assert(std::is_base_of_v<std::forward_iterator_tag,
                                df_iterator<Graph<4>>::iterator_category>);

// df_ext_iterator cannot provide multi-pass guarantee, therefore its only
// an input-iterator
static_assert(std::is_same_v<df_ext_iterator<Graph<4>>::iterator_category,
                             std::input_iterator_tag>);

TEST(DepthFirstIteratorTest, MultiPassSafeWithInternalSet) {
  Graph<4> G;
  G.AddEdge(0, 1);
  G.AddEdge(1, 2);
  G.AddEdge(1, 3);

  std::array<decltype(G)::NodeType *, 4> NodesFirstPass, NodesSecondPass;

  auto B = df_begin(G), E = df_end(G);

  std::size_t I = 0;
  for (auto It = B; It != E; ++It)
    NodesFirstPass[I++] = *It;

  I = 0;
  for (auto It = B; It != E; ++It)
    NodesSecondPass[I++] = *It;

  EXPECT_EQ(NodesFirstPass, NodesSecondPass);
}
}