/**
 * ReXGlue runtime - AC6 Recompilation project
 * Copyright (c) 2026 Tom Clay. All rights reserved.
 */

#include <algorithm>
#include <cstring>

#include <rex/logging.h>
#include <rex/system/util/object_table.h>
#include <rex/system/xobject.h>
#include <rex/system/xthread.h>

namespace rex::system::util {

ObjectTable::ObjectTable() {}

ObjectTable::~ObjectTable() {
  Reset();
}

void ObjectTable::Reset() {
  auto global_lock = global_critical_region_.Acquire();

  // Release all objects.
  for (uint32_t n = 0; n < table_capacity_; n++) {
    ObjectTableEntry& entry = table_[n];
    if (entry.object) {
      entry.object->Release();
    }
  }

  table_capacity_ = 0;
  last_free_entry_ = 0;
  free(table_);
  table_ = nullptr;
}

X_STATUS ObjectTable::FindFreeSlot(uint32_t* out_slot) {
  // Find a free slot.
  uint32_t slot = last_free_entry_;
  uint32_t scan_count = 0;
  while (scan_count < table_capacity_) {
    ObjectTableEntry& entry = table_[slot];
    if (!entry.object) {
      *out_slot = slot;
      return X_STATUS_SUCCESS;
    }
    scan_count++;
    slot = (slot + 1) % table_capacity_;
    if (slot == 0) {
      // Never allow 0 handles.
      scan_count++;
      slot++;
    }
  }

  // Table out of slots, expand.
  uint32_t new_table_capacity = std::max(16 * 1024u, table_capacity_ * 2);
  if (!Resize(new_table_capacity)) {
    return X_STATUS_NO_MEMORY;
  }

  // Never allow 0 handles.
  slot = ++last_free_entry_;
  *out_slot = slot;

  return X_STATUS_SUCCESS;
}

bool ObjectTable::Resize(uint32_t new_capacity) {
  uint32_t new_size = new_capacity * sizeof(ObjectTableEntry);
  uint32_t old_size = table_capacity_ * sizeof(ObjectTableEntry);
  auto new_table = reinterpret_cast<ObjectTableEntry*>(realloc(table_, new_size));
  if (!new_table) {
    return false;
  }

  // Zero out new entries.
  if (new_size > old_size) {
    std::memset(reinterpret_cast<uint8_t*>(new_table) + old_size, 0, new_size - old_size);
  }

  last_free_entry_ = table_capacity_;
  table_capacity_ = new_capacity;
  table_ = new_table;

  return true;
}

X_STATUS ObjectTable::AddHandle(XObject* object, X_HANDLE* out_handle) {
  X_STATUS result = X_STATUS_SUCCESS;

  uint32_t handle = 0;
  {
    auto global_lock = global_critical_region_.Acquire();

    // Find a free slot.
    uint32_t slot = 0;
    result = FindFreeSlot(&slot);

    // Stash.
    if (XSUCCEEDED(result)) {
      ObjectTableEntry& entry = table_[slot];
      entry.object = object;
      entry.handle_ref_count = 1;
      handle = XObject::kHandleBase + (slot << 2);
      object->handles().push_back(handle);

      // Retain so long as the object is in the table.
      object->Retain();

      REXSYS_DEBUG("Added handle:{:08X} for {}", handle, typeid(*object).name());
    }
  }

  if (XSUCCEEDED(result)) {
    if (out_handle) {
      *out_handle = handle;
    }
  }

  return result;
}

X_STATUS ObjectTable::DuplicateHandle(X_HANDLE handle, X_HANDLE* out_handle) {
  X_STATUS result = X_STATUS_SUCCESS;
  handle = TranslateHandle(handle);

  XObject* object = LookupObject(handle, false);
  if (object) {
    result = AddHandle(object, out_handle);
    object->Release();  // Release the ref that LookupObject took
  } else {
    result = X_STATUS_INVALID_HANDLE;
  }

  return result;
}

X_STATUS ObjectTable::RetainHandle(X_HANDLE handle) {
  auto global_lock = global_critical_region_.Acquire();

  ObjectTableEntry* entry = LookupTable(handle);
  if (!entry) {
    return X_STATUS_INVALID_HANDLE;
  }

  entry->handle_ref_count++;
  return X_STATUS_SUCCESS;
}

X_STATUS ObjectTable::ReleaseHandle(X_HANDLE handle) {
  auto global_lock = global_critical_region_.Acquire();

  ObjectTableEntry* entry = LookupTable(handle);
  if (!entry) {
    return X_STATUS_INVALID_HANDLE;
  }

  if (--entry->handle_ref_count == 0) {
    // No more references. Remove it from the table.
    return RemoveHandle(handle);
  }

  // FIXME: Return a status code telling the caller it wasn't released
  // (but not a failure code)
  return X_STATUS_SUCCESS;
}

X_STATUS ObjectTable::RemoveHandle(X_HANDLE handle) {
  X_STATUS result = X_STATUS_SUCCESS;

  handle = TranslateHandle(handle);
  if (!handle) {
    return X_STATUS_INVALID_HANDLE;
  }

  ObjectTableEntry* entry = LookupTable(handle);
  if (!entry) {
    return X_STATUS_INVALID_HANDLE;
  }

  auto global_lock = global_critical_region_.Acquire();
  if (entry->object) {
    auto object = entry->object;
    entry->object = nullptr;
    assert_zero(entry->handle_ref_count);
    entry->handle_ref_count = 0;

    // Walk the object's handles and remove this one.
    auto handle_entry = std::find(object->handles().begin(), object->handles().end(), handle);
    if (handle_entry != object->handles().end()) {
      object->handles().erase(handle_entry);
    }

    REXSYS_DEBUG("Removed handle:{:08X} for {}", handle, typeid(*object).name());

    // Remove object name from mapping to prevent naming collision.
    if (!object->name().empty()) {
      RemoveNameMapping(object->name());
    }
    // Release now that the object has been removed from the table.
    object->Release();
  }

  return X_STATUS_SUCCESS;
}

std::vector<object_ref<XObject>> ObjectTable::GetAllObjects() {
  auto lock = global_critical_region_.Acquire();
  std::vector<object_ref<XObject>> results;

  for (uint32_t slot = 0; slot < table_capacity_; slot++) {
    auto& entry = table_[slot];
    if (entry.object && std::find(results.begin(), results.end(), entry.object) == results.end()) {
      entry.object->Retain();
      results.push_back(object_ref<XObject>(entry.object));
    }
  }

  return results;
}

void ObjectTable::PurgeAllObjects() {
  auto lock = global_critical_region_.Acquire();
  for (uint32_t slot = 0; slot < table_capacity_; slot++) {
    auto& entry = table_[slot];
    if (entry.object && !entry.object->is_host_object()) {
      entry.handle_ref_count = 0;
      entry.object->Release();

      entry.object = nullptr;
    }
  }
}

ObjectTable::ObjectTableEntry* ObjectTable::LookupTable(X_HANDLE handle) {
  handle = TranslateHandle(handle);
  if (!handle) {
    return nullptr;
  }

  auto global_lock = global_critical_region_.Acquire();

  // Lower 2 bits are ignored.
  uint32_t slot = GetHandleSlot(handle);
  if (slot <= table_capacity_) {
    return &table_[slot];
  }

  return nullptr;
}

// Generic lookup
template <>
object_ref<XObject> ObjectTable::LookupObject<XObject>(X_HANDLE handle) {
  auto object = ObjectTable::LookupObject(handle, false);
  auto result = object_ref<XObject>(reinterpret_cast<XObject*>(object));
  return result;
}

XObject* ObjectTable::LookupObject(X_HANDLE handle, bool already_locked) {
  handle = TranslateHandle(handle);
  if (!handle) {
    return nullptr;
  }

  XObject* object = nullptr;
  if (!already_locked) {
    global_critical_region_.mutex().lock();
  }

  // Lower 2 bits are ignored.
  uint32_t slot = GetHandleSlot(handle);

  // Verify slot.
  if (slot < table_capacity_) {
    ObjectTableEntry& entry = table_[slot];
    if (entry.object) {
      object = entry.object;
    }
  }

  // Retain the object pointer.
  if (object) {
    object->Retain();
  }

  if (!already_locked) {
    global_critical_region_.mutex().unlock();
  }

  return object;
}

void ObjectTable::GetObjectsByType(XObject::Type type, std::vector<object_ref<XObject>>* results) {
  auto global_lock = global_critical_region_.Acquire();
  for (uint32_t slot = 0; slot < table_capacity_; ++slot) {
    auto& entry = table_[slot];
    if (entry.object) {
      if (entry.object->type() == type) {
        entry.object->Retain();
        results->push_back(object_ref<XObject>(entry.object));
      }
    }
  }
}

X_HANDLE ObjectTable::TranslateHandle(X_HANDLE handle) {
  if (handle == 0xFFFFFFFF) {
    // CurrentProcess
    // assert_always();
    return 0;
  } else if (handle == 0xFFFFFFFE) {
    // CurrentThread
    return XThread::GetCurrentThreadHandle();
  } else {
    return handle;
  }
}

X_STATUS ObjectTable::AddNameMapping(const std::string_view name, X_HANDLE handle) {
  std::lock_guard<std::mutex> name_lock(name_mutex_);
  if (name_table_.count(string::string_key_case(name))) {
    return X_STATUS_OBJECT_NAME_COLLISION;
  }
  name_table_.insert({string::string_key_case::create(name), handle});
  return X_STATUS_SUCCESS;
}

void ObjectTable::RemoveNameMapping(const std::string_view name) {
  // Names are case-insensitive.
  std::lock_guard<std::mutex> name_lock(name_mutex_);
  auto it = name_table_.find(string::string_key_case(name));
  if (it != name_table_.end()) {
    name_table_.erase(it);
  }
}

X_STATUS ObjectTable::GetObjectByName(const std::string_view name, X_HANDLE* out_handle) {
  // Names are case-insensitive.
  // Look up handle under name lock only -- do NOT hold name_mutex_ while
  // acquiring global lock (RemoveHandle takes global -> name ordering).
  X_HANDLE handle;
  {
    std::lock_guard<std::mutex> name_lock(name_mutex_);
    auto it = name_table_.find(string::string_key_case(name));
    if (it == name_table_.end()) {
      *out_handle = X_INVALID_HANDLE_VALUE;
      return X_STATUS_OBJECT_NAME_NOT_FOUND;
    }
    handle = it->second;
  }
  *out_handle = handle;

  // Retain under global lock via normal LookupObject path.
  // The handle may have been removed between releasing name_mutex_ and
  // acquiring global lock -- LookupObject returns nullptr in that case.
  auto obj = LookupObject(handle, false);
  if (obj) {
    obj->RetainHandle();
    obj->Release();
  }

  return X_STATUS_SUCCESS;
}


}  // namespace rex::system::util