odhash.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
  to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  copies of the Software, and to permit persons to whom the Software is
  furnished to do so, subject to the following conditions:
 
  The above copyright notice and this permission notice shall be included in all
  copies or substantial portions of the Software.
 
  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
  AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
  SOFTWARE.
*/
 
 
# include <gtest/gtest.h>
 
# include <random>
# include <set>
# include <chrono>
 
# include <tpl_odhash.H>
 
using namespace std;
using namespace testing;
using namespace Aleph;
 
TEST(ODhashTable, Simplest)
{
  ODhashTable<int> tbl(100);
 
  EXPECT_TRUE(tbl.is_empty());
  EXPECT_EQ(tbl.size(), 0);
 
  const size_t cap = tbl.capacity();
  for (size_t i = 0; i < cap; ++i)
    {
      EXPECT_EQ(tbl.size(), i);
      EXPECT_NE(tbl.insert(i), nullptr);
      EXPECT_EQ(tbl.size(), i + 1);
      EXPECT_FALSE(tbl.is_empty());
    }
 
  for (size_t i = 0; i < tbl.size(); ++i)
    {
      ASSERT_NE(tbl.search(i), nullptr);
      auto ptr = tbl.search(i);
      EXPECT_EQ(*ptr, i);
      EXPECT_FALSE(tbl.is_empty());
    }
 
  for (size_t i = 0, n = tbl.size(); i < n; ++i)
    {
      auto ptr = tbl.search(i);
      EXPECT_EQ(*ptr, i);
      tbl.remove(*ptr);
      EXPECT_EQ(tbl.size(), n - i - 1);
      EXPECT_EQ(tbl.search(i), nullptr);
      EXPECT_FALSE(tbl.contains(i));
    }
 
  EXPECT_EQ(tbl.size(), 0);
  EXPECT_TRUE(tbl.is_empty());
}
 
struct MyRecord
{
  size_t key;
  string value;
  MyRecord() {}
  MyRecord(size_t k, const string & v) : key(k), value(v) {}
  MyRecord(size_t k) : key(k) {}
  struct Eq
  {
    bool operator () (const MyRecord & r1, const MyRecord & r2) const noexcept
    {
      return r1.key == r2.key;
    }
  };
  bool operator == (const MyRecord & r) const noexcept { return Eq()(*this, r); }
};
 
inline size_t fst_hast(const MyRecord & r) noexcept
{
  return dft_hash_fct(r.key);
}
 
inline size_t snd_hash(const MyRecord & r) noexcept
{
  return snd_hash_fct(r.key);
}
 
 
TEST(ODhashTable, Map)
{
  ODhashTable<MyRecord, MyRecord::Eq> tbl(10, fst_hast, snd_hash, MyRecord::Eq());
 
  EXPECT_EQ(tbl.size(), 0);
  EXPECT_TRUE(tbl.is_empty());
 
  for (size_t i = 0; i < 100; ++i)
    {
      EXPECT_EQ(tbl.size(), i);
      tbl.emplace(i, to_string(i));
      EXPECT_EQ(tbl.size(), i + 1);
      auto ptr = tbl.search(MyRecord(i));
      EXPECT_NE(ptr, nullptr);
      EXPECT_EQ(ptr->key, i);
      EXPECT_EQ(ptr->value, to_string(i));
    }
 
  for (size_t i = 0, n = tbl.size(); i < n; ++i)
    {
      auto ptr = tbl.search(i);
      EXPECT_EQ(*ptr, i);
      tbl.remove(MyRecord(ptr->key));
      EXPECT_EQ(tbl.size(), n - i - 1);
      EXPECT_EQ(tbl.search(i), nullptr);
      EXPECT_FALSE(tbl.contains(MyRecord(i)));
    }
}
 
TEST(ODhashTable, KeyToBucketRoundTrip)
{
  ODhashTable<int> tbl;
  auto *ptr = tbl.insert(5);
  ASSERT_NE(ptr, nullptr);
 
  auto *bucket = decltype(tbl)::key_to_bucket(ptr);
  ASSERT_NE(bucket, nullptr);
  EXPECT_EQ(bucket->key, 5);
  EXPECT_EQ(bucket->status, decltype(tbl)::BUSY);
 
  EXPECT_NO_THROW(tbl.remove(5));
  EXPECT_EQ(tbl.search(5), nullptr);
}
 
// Test that removing a non-existent key does NOT corrupt the table state.
// This test exposes a bug where the old remove() would decrement N and
// corrupt probe_counters even when the key was not found.
TEST(ODhashTable, RemoveNonExistentKeyPreservesTableIntegrity)
{
  ODhashTable<int> tbl(100);
  
  // Insert some elements
  const int num_elements = 50;
  for (int i = 0; i < num_elements; ++i)
    EXPECT_NE(tbl.insert(i * 2), nullptr);  // Insert even numbers: 0, 2, 4, ..., 98
  
  EXPECT_EQ(tbl.size(), num_elements);
  
  // Try to remove keys that don't exist (odd numbers)
  // This should throw domain_error BUT NOT corrupt the table
  for (int i = 0; i < 10; ++i)
    {
      int non_existent_key = i * 2 + 1;  // Odd numbers: 1, 3, 5, ..., 19
      EXPECT_THROW(tbl.remove(non_existent_key), std::domain_error);
    }
  
  // Verify table size is unchanged
  EXPECT_EQ(tbl.size(), num_elements) 
    << "Table size should not change after failed remove attempts";
  
  // Verify all original elements are still findable
  for (int i = 0; i < num_elements; ++i)
    {
      auto ptr = tbl.search(i * 2);
      EXPECT_NE(ptr, nullptr) 
        << "Element " << i * 2 << " should still be in the table";
      if (ptr)
        EXPECT_EQ(*ptr, i * 2);
    }
  
  // Verify we can still remove elements normally
  for (int i = 0; i < num_elements; ++i)
    {
      auto ptr = tbl.search(i * 2);
      ASSERT_NE(ptr, nullptr);
      EXPECT_NO_THROW(tbl.remove(*ptr));
      EXPECT_EQ(tbl.size(), num_elements - i - 1);
    }
  
  EXPECT_TRUE(tbl.is_empty());
}
 
// Test remove with external key (key not from a bucket in the table)
TEST(ODhashTable, RemoveWithExternalKey)
{
  ODhashTable<int> tbl(100);
  
  // Insert elements
  for (int i = 0; i < 20; ++i)
    EXPECT_NE(tbl.insert(i), nullptr);
  
  EXPECT_EQ(tbl.size(), 20);
  
  // Remove using external key (not a reference from the table)
  int external_key = 10;
  EXPECT_NO_THROW(tbl.remove(external_key));
  EXPECT_EQ(tbl.size(), 19);
  EXPECT_EQ(tbl.search(10), nullptr);
  
  // Verify other elements are intact
  for (int i = 0; i < 20; ++i)
    {
      if (i == 10) continue;
      EXPECT_NE(tbl.search(i), nullptr) << "Element " << i << " should still exist";
    }
}
 
// Test remove with internal key (reference from the table bucket)
TEST(ODhashTable, RemoveWithInternalKey)
{
  ODhashTable<int> tbl(100);
  
  // Insert elements
  for (int i = 0; i < 20; ++i)
    EXPECT_NE(tbl.insert(i), nullptr);
  
  EXPECT_EQ(tbl.size(), 20);
  
  // Remove using internal key (reference from search result)
  auto ptr = tbl.search(10);
  ASSERT_NE(ptr, nullptr);
  EXPECT_NO_THROW(tbl.remove(*ptr));  // *ptr is internal reference
  EXPECT_EQ(tbl.size(), 19);
  EXPECT_EQ(tbl.search(10), nullptr);
}
 
// Test that verifies capacity doesn't change after failed remove.
// The old buggy code would call rehash() on every failed remove,
// potentially changing capacity. The new code doesn't rehash.
TEST(ODhashTable, RemoveNonExistentDoesNotRehash)
{
  ODhashTable<int> tbl(100);
  
  // Insert elements to create some collision chains
  for (int i = 0; i < 50; ++i)
    EXPECT_NE(tbl.insert(i * 2), nullptr);  // Even numbers
  
  const size_t original_capacity = tbl.capacity();
  const size_t original_size = tbl.size();
  
  // Try to remove many non-existent keys
  // Old buggy code would rehash on each failed remove
  for (int attempt = 0; attempt < 100; ++attempt)
    {
      int non_existent = attempt * 2 + 1;  // Odd numbers don't exist
      EXPECT_THROW(tbl.remove(non_existent), std::domain_error);
    }
  
  // Capacity should be unchanged (no rehash occurred)
  EXPECT_EQ(tbl.capacity(), original_capacity)
    << "Capacity changed - possible unnecessary rehash on failed remove";
  
  // Size should be unchanged
  EXPECT_EQ(tbl.size(), original_size);
  
  // All elements should still be findable
  for (int i = 0; i < 50; ++i)
    EXPECT_NE(tbl.search(i * 2), nullptr) << "Element " << i * 2 << " not found";
}
 
// ============================================================================
// STRESS TESTS / FUZZING
// ============================================================================
 
// Fuzzing test: random operations with oracle verification
TEST(ODhashTable, Fuzz_RandomOperationsWithOracle)
{
  // Use large table to avoid resize during test
  ODhashTable<int> tbl(20000);
  set<int> oracle;
  
  mt19937 rng(42);
  uniform_int_distribution<int> key_dist(0, 5000);
  uniform_int_distribution<int> op_dist(0, 2);
  
  const int num_operations = 8000;
  
  for (int i = 0; i < num_operations; ++i)
    {
      int key = key_dist(rng);
      int op = op_dist(rng);
      
      switch (op)
        {
        case 0:  // Insert
          {
            bool in_oracle = oracle.count(key) > 0;
            auto ptr = tbl.insert(key);
            if (ptr != nullptr)
              {
                EXPECT_FALSE(in_oracle) << "Insert succeeded for key " << key 
                  << " but oracle already had it";
                oracle.insert(key);
              }
            else
              {
                EXPECT_TRUE(in_oracle) << "Insert failed for key " << key 
                  << " but oracle didn't have it";
              }
            break;
          }
        case 1:  // Remove
          {
            bool in_oracle = oracle.count(key) > 0;
            if (in_oracle)
              {
                try
                  {
                    tbl.remove(key);
                    oracle.erase(key);  // Only erase if remove succeeded
                  }
                catch (const domain_error &)
                  {
                    FAIL() << "Remove threw for key " << key << " that was in oracle";
                  }
              }
            else
              {
                EXPECT_THROW(tbl.remove(key), domain_error);
              }
            break;
          }
        case 2:  // Search
          {
            auto ptr = tbl.search(key);
            bool in_oracle = oracle.count(key) > 0;
            EXPECT_EQ(ptr != nullptr, in_oracle)
              << "Search mismatch for key " << key;
            if (ptr)
              EXPECT_EQ(*ptr, key);
            break;
          }
        }
      
      ASSERT_EQ(tbl.size(), oracle.size()) 
        << "Size mismatch at operation " << i << ", key=" << key;
    }
  
  // Final verification
  for (int key : oracle)
    {
      auto ptr = tbl.search(key);
      ASSERT_NE(ptr, nullptr) << "Final check: key " << key << " missing";
    }
}
 
// Stress test: fill table to near capacity then empty it completely
TEST(ODhashTable, Stress_FillAndEmpty)
{
  ODhashTable<int> tbl(1000);
  const size_t target = tbl.capacity() - 1;  // Leave one empty as sentinel
  
  // Fill the table
  for (size_t i = 0; i < target; ++i)
    {
      auto ptr = tbl.insert(static_cast<int>(i));
      ASSERT_NE(ptr, nullptr) << "Insert failed at i=" << i;
    }
  
  EXPECT_EQ(tbl.size(), target);
  
  // Verify all elements
  for (size_t i = 0; i < target; ++i)
    {
      ASSERT_NE(tbl.search(static_cast<int>(i)), nullptr) 
        << "Element " << i << " not found after fill";
    }
  
  // Empty the table in random order
  vector<int> keys(target);
  iota(keys.begin(), keys.end(), 0);
  
  mt19937 rng(123);
  shuffle(keys.begin(), keys.end(), rng);
  
  for (size_t i = 0; i < target; ++i)
    {
      EXPECT_NO_THROW(tbl.remove(keys[i])) << "Remove failed for key " << keys[i];
      EXPECT_EQ(tbl.size(), target - i - 1);
    }
  
  EXPECT_TRUE(tbl.is_empty());
}
 
// Stress test: many collisions (all keys hash to same bucket)
TEST(ODhashTable, Stress_ManyCollisions)
{
  // Custom hash that always returns the same value - forces maximum collisions
  auto bad_hash = [](const int &) -> size_t { return 42; };
  
  ODhashTable<int> tbl(100, bad_hash, bad_hash);
  
  // Insert elements - all will collide
  const int num_elements = 50;
  for (int i = 0; i < num_elements; ++i)
    {
      auto ptr = tbl.insert(i);
      ASSERT_NE(ptr, nullptr) << "Insert failed at i=" << i << " with bad hash";
    }
  
  EXPECT_EQ(tbl.size(), num_elements);
  
  // Verify all elements are findable despite collisions
  for (int i = 0; i < num_elements; ++i)
    {
      auto ptr = tbl.search(i);
      ASSERT_NE(ptr, nullptr) << "Element " << i << " not found with collision";
      EXPECT_EQ(*ptr, i);
    }
  
  // Remove in reverse order
  for (int i = num_elements - 1; i >= 0; --i)
    {
      EXPECT_NO_THROW(tbl.remove(i));
      EXPECT_EQ(tbl.search(i), nullptr);
    }
  
  EXPECT_TRUE(tbl.is_empty());
}
 
// Stress test: repeated insert/remove cycles
TEST(ODhashTable, Stress_InsertRemoveCycles)
{
  ODhashTable<int> tbl(100);
  
  const int cycles = 100;
  const int elements_per_cycle = 50;
  
  for (int cycle = 0; cycle < cycles; ++cycle)
    {
      // Insert phase
      for (int i = 0; i < elements_per_cycle; ++i)
        {
          int key = cycle * elements_per_cycle + i;
          auto ptr = tbl.insert(key);
          ASSERT_NE(ptr, nullptr) << "Insert failed at cycle " << cycle << ", i=" << i;
        }
      
      EXPECT_EQ(tbl.size(), elements_per_cycle);
      
      // Remove phase - remove all
      for (int i = 0; i < elements_per_cycle; ++i)
        {
          int key = cycle * elements_per_cycle + i;
          EXPECT_NO_THROW(tbl.remove(key));
        }
      
      EXPECT_TRUE(tbl.is_empty());
    }
}
 
// Stress test: trigger resize operations
TEST(ODhashTable, Stress_ResizeOperations)
{
  // Start with small table that will need to resize
  ODhashTable<int> tbl(10);
  
  set<int> oracle;
  mt19937 rng(999);
  uniform_int_distribution<int> key_dist(0, 100000);
  
  // Insert many elements to trigger multiple resizes
  const int num_inserts = 5000;
  for (int i = 0; i < num_inserts; ++i)
    {
      int key = key_dist(rng);
      auto ptr = tbl.insert(key);
      if (oracle.count(key) == 0 && ptr != nullptr)
        oracle.insert(key);
    }
  
  EXPECT_EQ(tbl.size(), oracle.size());
  
  // Verify all elements survived resizes
  for (int key : oracle)
    {
      auto ptr = tbl.search(key);
      ASSERT_NE(ptr, nullptr) << "Key " << key << " lost after resize";
    }
  
  // Remove half and verify
  size_t to_remove = oracle.size() / 2;
  auto it = oracle.begin();
  for (size_t i = 0; i < to_remove; ++i, ++it)
    {
      EXPECT_NO_THROW(tbl.remove(*it));
    }
  oracle.erase(oracle.begin(), it);
  
  EXPECT_EQ(tbl.size(), oracle.size());
  
  // Verify remaining elements
  for (int key : oracle)
    {
      ASSERT_NE(tbl.search(key), nullptr) << "Key " << key << " missing after partial remove";
    }
}
 
// Fuzzing: interleaved search during insert/remove
TEST(ODhashTable, Fuzz_InterleavedOperations)
{
  // Use large table to avoid resize
  ODhashTable<int> tbl(5000);
  set<int> oracle;
  
  mt19937 rng(7777);
  uniform_int_distribution<int> key_dist(0, 1000);
  uniform_real_distribution<double> prob_dist(0.0, 1.0);
  
  const int num_ops = 5000;
  
  for (int i = 0; i < num_ops; ++i)
    {
      int key = key_dist(rng);
      double prob = prob_dist(rng);
      
      if (prob < 0.4)  // 40% insert
        {
          auto ptr = tbl.insert(key);
          if (ptr != nullptr)
            oracle.insert(key);
        }
      else if (prob < 0.6)  // 20% remove
        {
          if (oracle.count(key))
            {
              try
                {
                  tbl.remove(key);
                  oracle.erase(key);  // Only erase if remove succeeded
                }
              catch (const domain_error &)
                {
                  FAIL() << "Remove threw for key " << key << " that was in oracle";
                }
            }
        }
      else  // 40% search
        {
          auto ptr = tbl.search(key);
          bool in_oracle = oracle.count(key) > 0;
          EXPECT_EQ(ptr != nullptr, in_oracle)
            << "Search mismatch for key " << key;
        }
      
      // Periodic consistency check
      if (i % 500 == 0)
        ASSERT_EQ(tbl.size(), oracle.size()) << "Size mismatch at i=" << i;
    }
  
  // Final check
  EXPECT_EQ(tbl.size(), oracle.size());
}
 
// Stress test: with auto-resize enabled
TEST(ODhashTable, Stress_WithAutoResize)
{
  // Enable auto-resize
  ODhashTable<int> tbl(10);  // Small initial size
  set<int> oracle;
  
  mt19937 rng(333);
  uniform_int_distribution<int> key_dist(0, 50000);
  
  // Insert many elements, triggering multiple resizes
  const int num_inserts = 3000;
  for (int i = 0; i < num_inserts; ++i)
    {
      int key = key_dist(rng);
      auto ptr = tbl.insert(key);
      if (ptr != nullptr)
        oracle.insert(key);
    }
  
  // Verify size matches
  EXPECT_EQ(tbl.size(), oracle.size());
  
  // Verify all elements survived resizes
  for (int key : oracle)
    {
      auto ptr = tbl.search(key);
      ASSERT_NE(ptr, nullptr) << "Key " << key << " lost during resize";
      EXPECT_EQ(*ptr, key);
    }
  
  // Now remove some elements
  auto it = oracle.begin();
  size_t to_remove = oracle.size() / 3;
  for (size_t i = 0; i < to_remove && it != oracle.end(); ++i)
    {
      int key = *it;
      ++it;
      tbl.remove(key);
      oracle.erase(key);
    }
  
  EXPECT_EQ(tbl.size(), oracle.size());
  
  // Verify remaining elements
  for (int key : oracle)
    ASSERT_NE(tbl.search(key), nullptr);
}
 
// Stress test with string keys
TEST(ODhashTable, Stress_StringKeys)
{
  ODhashTable<string> tbl(100);
  set<string> oracle;
  
  mt19937 rng(54321);
  uniform_int_distribution<int> len_dist(1, 50);
  uniform_int_distribution<int> char_dist('a', 'z');
  
  auto random_string = [&]() {
    int len = len_dist(rng);
    string s;
    s.reserve(len);
    for (int i = 0; i < len; ++i)
      s += static_cast<char>(char_dist(rng));
    return s;
  };
  
  const int num_ops = 2000;
  
  for (int i = 0; i < num_ops; ++i)
    {
      string key = random_string();
      
      if (oracle.count(key) == 0)
        {
          auto ptr = tbl.insert(key);
          if (ptr != nullptr)
            oracle.insert(key);
        }
      else
        {
          // Remove existing key
          tbl.remove(key);
          oracle.erase(key);
        }
    }
  
  EXPECT_EQ(tbl.size(), oracle.size());
  
  // Verify all oracle keys are present
  for (const auto & key : oracle)
    {
      auto ptr = tbl.search(key);
      ASSERT_NE(ptr, nullptr) << "String key missing: " << key;
    }
}
 
// Test search_or_insert with DELETED entries (exercises hard_allocate_bucket)
TEST(ODhashTable, SearchOrInsert_WithDeletedEntries)
{
  ODhashTable<int> tbl(100);
  
  // Insert some elements
  for (int i = 0; i < 30; ++i)
    EXPECT_NE(tbl.insert(i), nullptr);
  
  // Remove some to create DELETED entries
  for (int i = 0; i < 30; i += 2)
    tbl.remove(i);  // Remove even numbers
  
  const size_t size_after_removes = tbl.size();
  
  // search_or_insert for existing keys should return existing
  for (int i = 1; i < 30; i += 2)
    {
      auto ptr = tbl.search_or_insert(i);
      ASSERT_NE(ptr, nullptr);
      EXPECT_EQ(*ptr, i);
    }
  EXPECT_EQ(tbl.size(), size_after_removes);  // Size unchanged
  
  // search_or_insert for removed keys should insert them
  for (int i = 0; i < 30; i += 2)
    {
      const size_t old_size = tbl.size();
      auto ptr = tbl.search_or_insert(i);
      ASSERT_NE(ptr, nullptr);
      EXPECT_EQ(*ptr, i);
      EXPECT_EQ(tbl.size(), old_size + 1);  // Size increased
    }
  
  // Verify all elements are searchable
  for (int i = 0; i < 30; ++i)
    {
      auto ptr = tbl.search(i);
      ASSERT_NE(ptr, nullptr) << "Key " << i << " not found";
    }
}
 
// Test contains_or_insert (uses hard_allocate_bucket)
TEST(ODhashTable, ContainsOrInsert_WithCollisions)
{
  // Bad hash to force collisions
  auto bad_hash = [](const int &) -> size_t { return 7; };
  
  ODhashTable<int> tbl(50, bad_hash, bad_hash);
  
  // Insert and remove to create DELETED entries with collisions
  for (int i = 0; i < 20; ++i)
    EXPECT_NE(tbl.insert(i), nullptr);
  
  for (int i = 0; i < 20; i += 3)
    tbl.remove(i);
  
  // contains_or_insert for new keys
  for (int i = 20; i < 30; ++i)
    {
      auto [ptr, existed] = tbl.contains_or_insert(i);
      ASSERT_NE(ptr, nullptr);
      EXPECT_FALSE(existed) << "Key " << i << " should not have existed";
      EXPECT_EQ(*ptr, i);
    }
  
  // contains_or_insert for existing keys
  for (int i = 20; i < 30; ++i)
    {
      auto [ptr, existed] = tbl.contains_or_insert(i);
      ASSERT_NE(ptr, nullptr);
      EXPECT_TRUE(existed) << "Key " << i << " should have existed";
      EXPECT_EQ(*ptr, i);
    }
}
 
// Stress test for search_or_insert with many DELETED entries
TEST(ODhashTable, Stress_SearchOrInsertWithDeleted)
{
  ODhashTable<int> tbl(200);
  std::set<int> oracle;
  std::mt19937 gen(54321);
  std::uniform_int_distribution<> key_dist(0, 500);
  std::uniform_int_distribution<> op_dist(0, 2);
  
  for (int iter = 0; iter < 5000; ++iter)
    {
      int key = key_dist(gen);
      int op = op_dist(gen);
      
      if (op == 0)  // search_or_insert
        {
          auto ptr = tbl.search_or_insert(key);
          ASSERT_NE(ptr, nullptr) << "search_or_insert returned nullptr for key " << key;
          EXPECT_EQ(*ptr, key);
          oracle.insert(key);
          // Verify immediately after insert
          auto verify_ptr = tbl.search(key);
          ASSERT_NE(verify_ptr, nullptr) 
            << "Key " << key << " not found immediately after search_or_insert at iter " << iter;
        }
      else if (op == 1 && oracle.count(key))  // remove existing
        {
          // Verify key exists before removal
          auto pre_ptr = tbl.search(key);
          ASSERT_NE(pre_ptr, nullptr) 
            << "Key " << key << " should exist before removal at iter " << iter
            << ", oracle.count=" << oracle.count(key) << ", tbl.size=" << tbl.size();
          tbl.remove(key);
          oracle.erase(key);
        }
      else  // search
        {
          auto ptr = tbl.search(key);
          if (oracle.count(key))
            ASSERT_NE(ptr, nullptr) << "Key " << key << " should exist at iter " << iter;
          else
            EXPECT_EQ(ptr, nullptr);
        }
      
      EXPECT_EQ(tbl.size(), oracle.size()) 
        << "Size mismatch at iter " << iter << ": tbl=" << tbl.size() << ", oracle=" << oracle.size();
    }
  
  // Final verification
  for (int key : oracle)
    {
      auto ptr = tbl.search(key);
      ASSERT_NE(ptr, nullptr) << "Key " << key << " missing";
    }
}
 
// Focused debug test to find the exact bug
TEST(ODhashTable, Debug_SearchOrInsertBug)
{
  ODhashTable<int> tbl(200);
  std::set<int> oracle;
  std::mt19937 gen(54321);
  std::uniform_int_distribution<> key_dist(0, 500);
  std::uniform_int_distribution<> op_dist(0, 2);
  
  // Reproduce up to iteration 701 where the bug occurs
  for (int iter = 0; iter <= 705; ++iter)
    {
      int key = key_dist(gen);
      int op = op_dist(gen);
      
      // Verify oracle consistency before operation
      for (int k : oracle)
        {
          auto p = tbl.search(k);
          ASSERT_NE(p, nullptr) 
            << "Pre-op check: Key " << k << " missing at iter " << iter 
            << " (about to do op " << op << " on key " << key << ")";
        }
      
      if (op == 0)  // search_or_insert
        {
          bool existed_before = oracle.count(key) > 0;
          size_t size_before = tbl.size();
          auto ptr = tbl.search_or_insert(key);
          ASSERT_NE(ptr, nullptr) << "search_or_insert returned nullptr at iter " << iter;
          EXPECT_EQ(*ptr, key);
          oracle.insert(key);
          
          if (!existed_before)
            EXPECT_EQ(tbl.size(), size_before + 1) 
              << "Size should increase for new key at iter " << iter;
        }
      else if (op == 1 && oracle.count(key))  // remove existing
        {
          tbl.remove(key);
          oracle.erase(key);
        }
      
      EXPECT_EQ(tbl.size(), oracle.size()) 
        << "Size mismatch at iter " << iter;
    }
}
 
// ============================================================================
// COPY/MOVE SEMANTICS TESTS
// ============================================================================
 
TEST(ODhashTable, CopyConstructor)
{
  ODhashTable<int> original(100);
  for (int i = 0; i < 50; ++i)
    original.insert(i);
  
  ODhashTable<int> copy(original);
  
  EXPECT_EQ(copy.size(), original.size());
  EXPECT_EQ(copy.capacity(), original.capacity());
  
  for (int i = 0; i < 50; ++i)
    {
      EXPECT_NE(original.search(i), nullptr);
      EXPECT_NE(copy.search(i), nullptr);
    }
  
  copy.remove(25);
  EXPECT_EQ(copy.search(25), nullptr);
  EXPECT_NE(original.search(25), nullptr);
}
 
TEST(ODhashTable, MoveConstructor)
{
  ODhashTable<int> original(100);
  for (int i = 0; i < 50; ++i)
    original.insert(i);
  
  const size_t orig_size = original.size();
  const size_t orig_cap = original.capacity();
  
  ODhashTable<int> moved(std::move(original));
  
  EXPECT_EQ(moved.size(), orig_size);
  EXPECT_EQ(moved.capacity(), orig_cap);
  
  for (int i = 0; i < 50; ++i)
    EXPECT_NE(moved.search(i), nullptr);
}
 
TEST(ODhashTable, CopyAssignment)
{
  ODhashTable<int> original(100);
  for (int i = 0; i < 50; ++i)
    original.insert(i);
  
  ODhashTable<int> copy(10);
  copy.insert(999);
  
  copy = original;
  
  EXPECT_EQ(copy.size(), original.size());
  
  for (int i = 0; i < 50; ++i)
    EXPECT_NE(copy.search(i), nullptr);
  
  EXPECT_EQ(copy.search(999), nullptr);
}
 
TEST(ODhashTable, MoveAssignment)
{
  ODhashTable<int> original(100);
  for (int i = 0; i < 50; ++i)
    original.insert(i);
  
  const size_t orig_size = original.size();
  
  ODhashTable<int> target(10);
  target.insert(999);
  
  target = std::move(original);
  
  EXPECT_EQ(target.size(), orig_size);
  
  for (int i = 0; i < 50; ++i)
    EXPECT_NE(target.search(i), nullptr);
}
 
TEST(ODhashTable, SelfAssignment)
{
  ODhashTable<int> tbl(100);
  for (int i = 0; i < 50; ++i)
    tbl.insert(i);
  
  tbl = tbl;
  
  EXPECT_EQ(tbl.size(), 50);
  for (int i = 0; i < 50; ++i)
    EXPECT_NE(tbl.search(i), nullptr);
}
 
// ============================================================================
// EDGE CASES
// ============================================================================
 
TEST(ODhashTable, EmptyTableOperations)
{
  ODhashTable<int> tbl(100);
  
  EXPECT_TRUE(tbl.is_empty());
  EXPECT_EQ(tbl.size(), 0);
  EXPECT_EQ(tbl.search(42), nullptr);
  EXPECT_FALSE(tbl.has(42));
  EXPECT_FALSE(tbl.contains(42));
  EXPECT_THROW(tbl.remove(42), std::domain_error);
}
 
TEST(ODhashTable, SingleElement)
{
  ODhashTable<int> tbl(100);
  
  tbl.insert(42);
  EXPECT_EQ(tbl.size(), 1);
  EXPECT_NE(tbl.search(42), nullptr);
  
  tbl.remove(42);
  EXPECT_EQ(tbl.size(), 0);
  EXPECT_TRUE(tbl.is_empty());
  EXPECT_EQ(tbl.search(42), nullptr);
}
 
TEST(ODhashTable, DuplicateInsertReturnsNull)
{
  ODhashTable<int> tbl(100);
  
  auto first = tbl.insert(42);
  ASSERT_NE(first, nullptr);
  
  auto second = tbl.insert(42);
  EXPECT_EQ(second, nullptr);
  
  EXPECT_EQ(tbl.size(), 1);
}
 
TEST(ODhashTable, HasAndContains)
{
  ODhashTable<int> tbl(100);
  
  EXPECT_FALSE(tbl.has(42));
  EXPECT_FALSE(tbl.contains(42));
  
  tbl.insert(42);
  
  EXPECT_TRUE(tbl.has(42));
  EXPECT_TRUE(tbl.contains(42));
  EXPECT_FALSE(tbl.has(43));
  EXPECT_FALSE(tbl.contains(43));
}
 
TEST(ODhashTable, Find)
{
  ODhashTable<int> tbl(100);
  tbl.insert(42);
  
  EXPECT_NO_THROW({
    int& ref = tbl.find(42);
    EXPECT_EQ(ref, 42);
  });
  
  EXPECT_THROW(tbl.find(999), std::domain_error);
}
 
// ============================================================================
// REHASH/RESIZE TESTS
// ============================================================================
 
TEST(ODhashTable, ManualRehash)
{
  ODhashTable<int> tbl(100);
  set<int> oracle;
  
  for (int i = 0; i < 50; ++i)
    {
      tbl.insert(i);
      oracle.insert(i);
    }
  
  for (int i = 0; i < 50; i += 2)
    {
      tbl.remove(i);
      oracle.erase(i);
    }
  
  tbl.rehash();
  
  EXPECT_EQ(tbl.size(), oracle.size());
  
  for (int key : oracle)
    EXPECT_NE(tbl.search(key), nullptr);
}
 
TEST(ODhashTable, ResizeUp)
{
  ODhashTable<int> tbl(50);
  
  for (int i = 0; i < 30; ++i)
    tbl.insert(i);
  
  const size_t old_cap = tbl.capacity();
  tbl.resize(200);
  
  EXPECT_GT(tbl.capacity(), old_cap);
  EXPECT_EQ(tbl.size(), 30);
  
  for (int i = 0; i < 30; ++i)
    EXPECT_NE(tbl.search(i), nullptr);
}
 
TEST(ODhashTable, ResizeDown)
{
  ODhashTable<int> tbl(200);
  
  for (int i = 0; i < 30; ++i)
    tbl.insert(i);
  
  tbl.resize(50);
  
  EXPECT_EQ(tbl.size(), 30);
  
  for (int i = 0; i < 30; ++i)
    EXPECT_NE(tbl.search(i), nullptr);
}
 
// ============================================================================
// ITERATOR TESTS
// ============================================================================
 
TEST(ODhashTable, IteratorBasic)
{
  ODhashTable<int> tbl(100);
  set<int> oracle;
  
  for (int i = 0; i < 50; ++i)
    {
      tbl.insert(i);
      oracle.insert(i);
    }
  
  set<int> visited;
  for (auto it = tbl.get_it(); it.has_curr(); it.next())
    visited.insert(it.get_curr());
  
  EXPECT_EQ(visited, oracle);
}
 
TEST(ODhashTable, IteratorEmpty)
{
  ODhashTable<int> tbl(100);
  
  auto it = tbl.get_it();
  EXPECT_FALSE(it.has_curr());
}
 
TEST(ODhashTable, IteratorSingleElement)
{
  ODhashTable<int> tbl(100);
  tbl.insert(42);
  
  auto it = tbl.get_it();
  ASSERT_TRUE(it.has_curr());
  EXPECT_EQ(it.get_curr(), 42);
  
  it.next();
  EXPECT_FALSE(it.has_curr());
}
 
TEST(ODhashTable, IteratorDelete)
{
  ODhashTable<int> tbl(100);
  
  for (int i = 0; i < 10; ++i)
    tbl.insert(i);
  
  auto it = tbl.get_it();
  while (it.has_curr())
    it.del();
  
  EXPECT_TRUE(tbl.is_empty());
}
 
// ============================================================================
// PROBE_COUNTER CLEANUP TESTS (ODhashTable specific)
// ============================================================================
 
// Helper to count bucket states for ODhashTable
struct ODhashBucketStats
{
  size_t empty = 0;
  size_t busy = 0;
  size_t deleted = 0;
};
 
template <typename HashTable>
ODhashBucketStats count_odhash_bucket_states(const HashTable &tbl)
{
  ODhashBucketStats stats;
  for (size_t i = 0; i < tbl.capacity(); ++i)
    {
      switch (tbl.table[i].status)
        {
        case HashTable::EMPTY: ++stats.empty; break;
        case HashTable::BUSY: ++stats.busy; break;
        case HashTable::DELETED: ++stats.deleted; break;
        }
    }
  return stats;
}
 
// ODhashTable uses probe_counter to convert DELETED->EMPTY when counter reaches 0
TEST(ODhashTable, ProbeCounterCleanup_LastInChainBecomesEmpty)
{
  auto bad_hash = [](const int &) -> size_t { return 0; };
  ODhashTable<int> tbl(100, bad_hash, bad_hash);
  
  // Insert chain
  for (int i = 0; i < 5; ++i)
    tbl.insert(i);
  
  auto before = count_odhash_bucket_states(tbl);
  EXPECT_EQ(before.busy, 5);
  EXPECT_EQ(before.deleted, 0);
  
  // Remove last element - should become EMPTY due to probe_counter
  tbl.remove(4);
  
  auto after = count_odhash_bucket_states(tbl);
  EXPECT_EQ(after.busy, 4);
  // With probe_counter, DELETED becomes EMPTY when no one depends on it
  EXPECT_EQ(after.deleted, 0) << "Last element should become EMPTY via probe_counter";
  
  for (int i = 0; i < 4; ++i)
    EXPECT_NE(tbl.search(i), nullptr);
  EXPECT_EQ(tbl.search(4), nullptr);
}
 
TEST(ODhashTable, ProbeCounterCleanup_MiddleStaysDeleted)
{
  auto bad_hash = [](const int &) -> size_t { return 0; };
  ODhashTable<int> tbl(100, bad_hash, bad_hash);
  
  for (int i = 0; i < 5; ++i)
    tbl.insert(i);
  
  // Remove middle - should stay DELETED because others depend on it
  tbl.remove(2);
  
  auto stats = count_odhash_bucket_states(tbl);
  EXPECT_EQ(stats.busy, 4);
  EXPECT_EQ(stats.deleted, 1) << "Middle should stay DELETED";
  
  for (int i = 0; i < 5; ++i)
    {
      if (i == 2)
        EXPECT_EQ(tbl.search(i), nullptr);
      else
        EXPECT_NE(tbl.search(i), nullptr);
    }
}
 
TEST(ODhashTable, ProbeCounterCleanup_ChainCleanup)
{
  auto bad_hash = [](const int &) -> size_t { return 0; };
  ODhashTable<int> tbl(100, bad_hash, bad_hash);
  
  for (int i = 0; i < 5; ++i)
    tbl.insert(i);
  
  // Remove in reverse order - each should become EMPTY
  for (int i = 4; i >= 0; --i)
    tbl.remove(i);
  
  auto stats = count_odhash_bucket_states(tbl);
  EXPECT_EQ(stats.busy, 0);
  EXPECT_EQ(stats.deleted, 0) << "All should become EMPTY when removed in reverse";
  EXPECT_TRUE(tbl.is_empty());
}
 
// ============================================================================
// FUNCTIONAL METHODS TEST  
// ============================================================================
 
TEST(ODhashTable, ForEach)
{
  ODhashTable<int> tbl(100);
  for (int i = 0; i < 10; ++i)
    tbl.insert(i);
  
  int sum = 0;
  tbl.for_each([&sum](int x) { sum += x; });
  
  EXPECT_EQ(sum, 45);
}
 
TEST(ODhashTable, All)
{
  ODhashTable<int> tbl(100);
  for (int i = 0; i < 10; ++i)
    tbl.insert(i * 2);
  
  EXPECT_TRUE(tbl.all([](int x) { return x % 2 == 0; }));
  EXPECT_FALSE(tbl.all([](int x) { return x > 5; }));
}
 
TEST(ODhashTable, Exists)
{
  ODhashTable<int> tbl(100);
  for (int i = 0; i < 10; ++i)
    tbl.insert(i);
  
  EXPECT_TRUE(tbl.exists([](int x) { return x == 5; }));
  EXPECT_FALSE(tbl.exists([](int x) { return x == 100; }));
}
 
TEST(ODhashTable, Filter)
{
  ODhashTable<int> tbl(100);
  for (int i = 0; i < 10; ++i)
    tbl.insert(i);
  
  auto evens = tbl.filter([](int x) { return x % 2 == 0; });
  
  EXPECT_EQ(evens.size(), 5);
}