Fix overlap_find_next_in_subtree

include/interval-tree/interval_tree.hpp

@@ -707,6 +707,10 @@ namespace lib_interval_tree
         const_interval_tree_iterator& operator=(const_interval_tree_iterator const&) = default;
         const_interval_tree_iterator& operator=(const_interval_tree_iterator&&) noexcept = default;
 
+        explicit const_interval_tree_iterator(interval_tree_iterator<node_type, reverse, tree_hooks> const& other)
+            : iterator_base{other.node_, other.owner_}
+        {}
+
         template <typename T>
         friend void increment(T& iter);
         template <typename T>
@@ -1357,11 +1361,18 @@ namespace lib_interval_tree
         }
         template <typename CompareFunctionT>
         const_iterator
-        find_next_in_subtree(iterator from, interval_type const& ival, CompareFunctionT const& compare) const
+        find_next_in_subtree(const_iterator from, interval_type const& ival, CompareFunctionT const& compare) const
         {
             if (root_ == nullptr)
                 return end();
-            return iterator{find_i_ex(from.node_, ival, compare), this};
+            return const_iterator{find_i_ex(from.node_, ival, compare), this};
+        }
+        // Convenience, so that a mutable iterator does not have to be converted by hand.
+        template <typename CompareFunctionT>
+        const_iterator
+        find_next_in_subtree(iterator from, interval_type const& ival, CompareFunctionT const& compare) const
+        {
+            return find_next_in_subtree(const_iterator{from}, ival, compare);
         }
 
         /**
@@ -1377,12 +1388,17 @@ namespace lib_interval_tree
                 return lhs == rhs;
             });
         }
-        const_iterator find_next_in_subtree(iterator from, interval_type const& ival) const
+        const_iterator find_next_in_subtree(const_iterator from, interval_type const& ival) const
         {
             return find_next_in_subtree(from, ival, [](auto const& lhs, auto const& rhs) {
                 return lhs == rhs;
             });
         }
+        // Convenience, so that a mutable iterator does not have to be converted by hand.
+        const_iterator find_next_in_subtree(iterator from, interval_type const& ival) const
+        {
+            return find_next_in_subtree(const_iterator{from}, ival);
+        }
 
         /**
          *  Finds the first interval that overlaps with ival.
@@ -1447,14 +1463,26 @@ namespace lib_interval_tree
         {
             if (root_ == nullptr)
                 return end();
-            return iterator{overlap_find_i_ex(from.node_, ival, exclusive), this};
+            if (exclusive)
+                return iterator{overlap_find_i_ex<true>(from.node_, ival), this};
+            else
+                return iterator{overlap_find_i_ex<false>(from.node_, ival), this};
         }
         const_iterator
         overlap_find_next_in_subtree(const_iterator from, interval_type const& ival, bool exclusive = false) const
         {
             if (root_ == nullptr)
                 return end();
-            return const_iterator{overlap_find_i_ex(from.node_, ival, exclusive), this};
+            if (exclusive)
+                return const_iterator{overlap_find_i_ex<true>(from.node_, ival), this};
+            else
+                return const_iterator{overlap_find_i_ex<false>(from.node_, ival), this};
+        }
+        // Convenience, so that a mutable iterator does not have to be converted by hand.
+        const_iterator
+        overlap_find_next_in_subtree(iterator from, interval_type const& ival, bool exclusive = false) const
+        {
+            return overlap_find_next_in_subtree(const_iterator{from}, ival, exclusive);
         }
 
         /**
@@ -1793,9 +1821,10 @@ namespace lib_interval_tree
                 return find_i_ex(ptr, ival, compare);
         }
 
-        // excludes ptr
+        // excludes ptr, which is therefore never dereferenced for anything but its child pointers.
         template <typename ComparatorFunctionT>
-        node_type* find_i_ex(node_type* ptr, interval_type const& ival, ComparatorFunctionT const& compare) const
+        node_type*
+        find_i_ex(node_type const* ptr, interval_type const& ival, ComparatorFunctionT const& compare) const
         {
             if (ptr->left_ && ival.high() <= ptr->left_->max())
             {
@@ -1877,9 +1906,9 @@ namespace lib_interval_tree
             return true;
         }
 
-        // excludes ptr
+        // excludes ptr, which is therefore never dereferenced for anything but its child pointers.
         template <bool Exclusive>
-        node_type* overlap_find_i_ex(node_type* ptr, interval_type const& ival) const
+        node_type* overlap_find_i_ex(node_type const* ptr, interval_type const& ival) const
         {
             if (ptr->left_ && ptr->left_->max() >= ival.low())
             {

tests/find_tests.hpp

@@ -165,6 +165,71 @@ TEST_F(FindTests, CanFindAllOnConstTree)
     EXPECT_EQ(intervals[0], targetInterval);
 }
 
+TEST_F(FindTests, WillReturnEndForNextInSubtreeIfTreeIsEmpty)
+{
+    EXPECT_EQ(tree.find_next_in_subtree(tree.root(), {2, 7}), std::end(tree));
+}
+
+TEST_F(FindTests, WillFindNextExactMatchInSubtree)
+{
+    const auto targetInterval = decltype(tree)::interval_type{0, 5};
+    tree.insert(targetInterval);
+    tree.insert({10, 15});
+    tree.insert(targetInterval);
+    tree.insert({30, 35});
+
+    // The node started from is excluded, so this must find the duplicate and not the root itself.
+    const auto found = tree.find_next_in_subtree(tree.root(), targetInterval);
+    ASSERT_NE(found, std::end(tree));
+    EXPECT_EQ(*found, targetInterval);
+    EXPECT_NE(found, tree.root());
+
+    EXPECT_EQ(tree.find_next_in_subtree(tree.root(), {99, 100}), std::end(tree));
+}
+
+TEST_F(FindTests, WillFindNextExactMatchInSubtreeOnConstTree)
+{
+    const auto targetInterval = decltype(tree)::interval_type{0, 5};
+    tree.insert(targetInterval);
+    tree.insert({10, 15});
+    tree.insert(targetInterval);
+    tree.insert({30, 35});
+
+    [&targetInterval](auto const& tree) {
+        const auto found = tree.find_next_in_subtree(tree.root(), targetInterval);
+        static_assert(
+            std::is_same<decltype(found), typename std::decay_t<decltype(tree)>::const_iterator const>::value,
+            "the const overload must yield a const_iterator"
+        );
+        ASSERT_NE(found, std::end(tree));
+        EXPECT_EQ(*found, targetInterval);
+    }(tree);
+}
+
+TEST_F(FindTests, CanFindNextExactMatchInSubtreeOnConstTreeFromMutableIterator)
+{
+    const auto targetInterval = decltype(tree)::interval_type{0, 5};
+    tree.insert(targetInterval);
+    tree.insert({10, 15});
+    tree.insert(targetInterval);
+    tree.insert({30, 35});
+
+    // A mutable iterator is accepted by the const overloads without converting it by hand.
+    const auto from = tree.root();
+    const auto compare = [](auto const& lhs, auto const& rhs) {
+        return lhs == rhs;
+    };
+    [&from, &targetInterval, &compare](auto const& tree) {
+        const auto found = tree.find_next_in_subtree(from, targetInterval);
+        ASSERT_NE(found, std::end(tree));
+        EXPECT_EQ(*found, targetInterval);
+
+        const auto foundWithCompare = tree.find_next_in_subtree(from, targetInterval, compare);
+        ASSERT_NE(foundWithCompare, std::end(tree));
+        EXPECT_EQ(*foundWithCompare, targetInterval);
+    }(tree);
+}
+
 TEST_F(FindTests, FuzzyFindAllInTree)
 {
     std::mt19937 gen{0};

tests/overlap_find_tests.hpp

@@ -182,6 +182,86 @@ TEST_F(OverlapFindTests, CanOverlapFindAllOnConstTree)
     EXPECT_EQ(intervals[0], targetInterval);
 }
 
+TEST_F(OverlapFindTests, WillReturnEndForNextInSubtreeIfTreeIsEmpty)
+{
+    EXPECT_EQ(tree.overlap_find_next_in_subtree(tree.root(), {2, 7}), std::end(tree));
+}
+
+TEST_F(OverlapFindTests, WillFindNextOverlapInSubtree)
+{
+    tree.insert({0, 5});
+    tree.insert({10, 15});
+    tree.insert({20, 25});
+    tree.insert({30, 35});
+
+    const auto found = tree.overlap_find_next_in_subtree(tree.root(), {21, 22});
+    ASSERT_NE(found, std::end(tree));
+    EXPECT_EQ(*found, (decltype(tree)::interval_type{20, 25}));
+}
+
+TEST_F(OverlapFindTests, WillNotFindNextOverlapInSubtreeWithTheStartNodeItself)
+{
+    tree.insert({0, 5});
+    tree.insert({10, 15});
+    tree.insert({20, 25});
+    tree.insert({30, 35});
+
+    // The node started from is excluded and all intervals are disjoint, so nothing else can overlap it.
+    const auto rootInterval = *tree.root();
+    EXPECT_EQ(tree.overlap_find_next_in_subtree(tree.root(), rootInterval), std::end(tree));
+}
+
+TEST_F(OverlapFindTests, WillObeyExclusiveWhenFindingNextOverlapInSubtree)
+{
+    tree.insert({0, 5});
+    tree.insert({10, 15});
+    tree.insert({20, 25});
+    tree.insert({30, 35});
+
+    // {25, 27} touches {20, 25} on the border only.
+    const auto inclusive = tree.overlap_find_next_in_subtree(tree.root(), {25, 27}, false);
+    ASSERT_NE(inclusive, std::end(tree));
+    EXPECT_EQ(*inclusive, (decltype(tree)::interval_type{20, 25}));
+
+    EXPECT_EQ(tree.overlap_find_next_in_subtree(tree.root(), {25, 27}, true), std::end(tree));
+}
+
+TEST_F(OverlapFindTests, WillFindNextOverlapInSubtreeOnConstTree)
+{
+    tree.insert({0, 5});
+    tree.insert({10, 15});
+    tree.insert({20, 25});
+    tree.insert({30, 35});
+
+    const auto expected = decltype(tree)::interval_type{20, 25};
+    [&expected](auto const& tree) {
+        const auto found = tree.overlap_find_next_in_subtree(tree.root(), {21, 22});
+        ASSERT_NE(found, std::end(tree));
+        EXPECT_EQ(*found, expected);
+    }(tree);
+}
+
+TEST_F(OverlapFindTests, CanConvertIteratorToConstIteratorForNextOverlapInSubtree)
+{
+    tree.insert({0, 5});
+    tree.insert({10, 15});
+    tree.insert({20, 25});
+    tree.insert({30, 35});
+
+    // The conversion itself is explicit, but the const overloads also accept a mutable iterator directly.
+    const auto converted = decltype(tree)::const_iterator{tree.root()};
+    const auto mutableIterator = tree.root();
+    const auto expected = decltype(tree)::interval_type{20, 25};
+    [&converted, &mutableIterator, &expected](auto const& tree) {
+        const auto found = tree.overlap_find_next_in_subtree(converted, {21, 22});
+        ASSERT_NE(found, std::end(tree));
+        EXPECT_EQ(*found, expected);
+
+        const auto fromMutable = tree.overlap_find_next_in_subtree(mutableIterator, {21, 22});
+        EXPECT_EQ(fromMutable, found);
+    }(tree);
+}
+
 TEST_F(OverlapFindTests, FuzzyOverlapFindAllInTree)
 {
     std::mt19937 gen{0};