/*
 * Copyright (c) 2018, 2022, Oracle and/or its affiliates.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License, version 2.0,
 * as published by the Free Software Foundation.
 *
 * This program is also distributed with certain software (including
 * but not limited to OpenSSL) that is licensed under separate terms,
 * as designated in a particular file or component or in included license
 * documentation.  The authors of MySQL hereby grant you an additional
 * permission to link the program and your derivative works with the
 * separately licensed software that they have included with MySQL.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License, version 2.0, for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301  USA
 */

#pragma once

#include <cassert>
#include <cstdint>
#include <vector>

namespace protocol {

class Page {
public:
  Page(const uint32_t size, char *data_ptr)
      : m_begin_data(reinterpret_cast<uint8_t *>(data_ptr)),
        m_end_data(m_begin_data + size),
        m_current_data(reinterpret_cast<uint8_t *>(data_ptr)) {}

  ~Page() {
    m_current_data = nullptr;
    m_next_page = nullptr;
  }

  void reset() {
    m_current_data = m_begin_data;
    m_next_page = nullptr;
  }

  bool is_at_least(const uint32_t needed_size) const {
    return m_end_data > m_current_data + needed_size;
  }
  bool is_full() const { return m_end_data <= m_current_data; }
  bool is_empty() const { return m_begin_data == m_current_data; }

  uint32_t get_used_bytes() const { return m_current_data - m_begin_data; }
  uint32_t get_free_bytes() const { return m_end_data - m_current_data; }

  uint8_t *const m_begin_data;
  uint8_t *const m_end_data;
  uint8_t *m_current_data;

  Page *m_next_page = nullptr;
};

class Encoding_pool {
public:
  explicit Encoding_pool(const uint32_t local_cache, const uint32_t page_size)
      : m_local_cache(local_cache), m_page_size(page_size) {}

  ~Encoding_pool() {
    while (m_empty_pages) {
      auto page = m_empty_pages;
      m_empty_pages = m_empty_pages->m_next_page;
      --m_pages;
      /// destruct and free
      page->~Page();
      delete[] reinterpret_cast<char *>(page);
    }
    assert(0 == m_pages);
    m_empty_pages = nullptr;
  }

  Page *alloc_page() {
    if (m_empty_pages) {
      auto result = m_empty_pages;
      m_empty_pages = m_empty_pages->m_next_page;

      result->reset();
      return result;
    }

    ++m_pages;
    auto page = new char[m_page_size];
    return new (page) Page(m_page_size - sizeof(Page), page + sizeof(Page));
  }

  void release_page(Page *page) {
    if (m_pages < m_local_cache) {
      page->m_next_page = m_empty_pages;
      m_empty_pages = page;

      return;
    }

    --m_pages;
    /// destruct and free
    page->~Page();
    delete[] reinterpret_cast<char *>(page);
  }

  uint32_t get_page_size() const { return m_page_size; }

private:
  const uint32_t m_local_cache = 0;
  const uint32_t m_page_size = 0;
  Page *m_empty_pages = nullptr;
  uint32_t m_pages = 0;
};

} // namespace protocol