CellIterators.h

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// -*- mode: c++; c-file-style: "linux"; c-basic-offset: 2; indent-tabs-mode: nil -*-
//
//  Copyright (C) 2020      Kuba Ober <kuba@bertec.com>
//
//  This program is free software; you can redistribute it and/or modify
//  it under the terms of the GNU General Public License as published by
//  the Free Software Foundation; either version 2 of the License, or
//  (at your option) any later version.
//
//  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 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 Street, Fifth Floor, Boston, MA 02110-1301 USA
//
//  SPDX-License-Identifier: GPL-2.0+
 
#ifndef CELLITERATORS_H
#define CELLITERATORS_H
 
#include <wx/debug.h>
#include <memory>
#include <type_traits>
#include <iterator>
#include <vector>
 
template <typename Cell> class CellListIterator final {
  static_assert(std::is_class<Cell>::value, "The type argument must be a class");
  Cell *m_ptr = {};
 
public:
  using iterator_category = std::forward_iterator_tag;
  using value_type = Cell;
  using difference_type = std::ptrdiff_t;
  using pointer = Cell *;
  using reference = Cell &;
 
  constexpr CellListIterator() = default;
  constexpr explicit CellListIterator(const std::unique_ptr<Cell> &p)
    : m_ptr(p.get()) {}
  constexpr explicit CellListIterator(Cell *p) : m_ptr(p) {}
  constexpr CellListIterator(const CellListIterator &o) = default;
  constexpr CellListIterator &operator=(const CellListIterator &o) = default;
  constexpr CellListIterator operator++(int) {
    auto ret = *this;
    return operator++(), ret;
  }
  // constexpr fails if wxASSERT contains assembler code, which is true on MinGW
  CellListIterator &operator++() {
    if (m_ptr)
    {
      const auto *const prev = m_ptr;
      m_ptr = m_ptr->GetNext();
      wxASSERT(prev != m_ptr);
    }
    return *this;
  }
  constexpr bool operator==(const CellListIterator &o) const {
    return m_ptr == o.m_ptr;
  }
  constexpr bool operator!=(const CellListIterator &o) const {
    return m_ptr != o.m_ptr;
  }
  constexpr operator bool() const { return m_ptr; }
  constexpr operator Cell *() const { return m_ptr; }
  constexpr Cell *operator->() const { return m_ptr; }
};
 
template <typename Cell> class CellListAdapter final {
  static_assert(std::is_class<Cell>::value, "The type argument must be a class");
  Cell *m_cell = {};
  using iterator = CellListIterator<Cell>;
  using const_iterator = CellListIterator<typename std::add_const<Cell>::type>;
 
public:
  explicit CellListAdapter(Cell *cell) : m_cell(cell) {}
  constexpr iterator begin() const { return iterator(m_cell); }
  static constexpr iterator end() { return {}; }
  constexpr const_iterator cbegin() const { return const_iterator(m_cell); }
  static constexpr const_iterator cend() { return {}; }
};
 
template <typename Cell>
class CellDrawListIterator final {
  static_assert(std::is_class<Cell>::value, "The type argument must be a class");
  struct Frame {
    Cell *parent;
    size_t nextIndex;
  };
  Cell *m_ptr = {};
  std::vector<Frame> m_stack;
 
public:
  using iterator_category = std::forward_iterator_tag;
  using value_type = Cell;
  using difference_type = std::ptrdiff_t;
  using pointer = Cell *;
  using reference = Cell &;
 
  CellDrawListIterator() = default;
  explicit CellDrawListIterator(const std::unique_ptr<Cell> &p) : m_ptr(p.get()) {}
  explicit CellDrawListIterator(Cell *p) : m_ptr(p) {}
  CellDrawListIterator(const CellDrawListIterator &o) = default;
  CellDrawListIterator &operator=(const CellDrawListIterator &o) = default;
  CellDrawListIterator operator++(int) {
    auto ret = *this;
    return operator++(), ret;
  }
  CellDrawListIterator &operator++()
    {
      if (!m_ptr)
        return *this;
 
      const auto *const prev = m_ptr;
      Cell *next = {};
 
      if (prev->IsBrokenIntoLines() && prev->GetBrokenCellCount() > 0) {
        // Descend into this cell's broken-form pieces. Once piece 0's own
        // chain (and anything nested inside it) is exhausted, resume here
        // at index 1.
        m_stack.push_back(Frame{const_cast<Cell *>(prev), 1});
        next = prev->GetBrokenCell(0);
      } else {
        next = prev->GetNext();
        while (!next && !m_stack.empty()) {
          Frame &frame = m_stack.back();
          if (frame.nextIndex < frame.parent->GetBrokenCellCount()) {
            next = frame.parent->GetBrokenCell(frame.nextIndex++);
            continue;
          }
          // This broken cell's pieces are all done: resume with whatever
          // originally followed it, or -- if it has no successor of its
          // own -- keep unwinding into whatever enclosing broken cell (if
          // any) we're nested inside of.
          Cell *const afterParent = frame.parent->GetNext();
          m_stack.pop_back();
          next = afterParent;
        }
      }
 
      m_ptr = next;
      wxASSERT(prev != m_ptr);
      return *this;
    }
  bool operator==(const CellDrawListIterator &o) const
    { return m_ptr == o.m_ptr; }
  bool operator!=(const CellDrawListIterator &o) const
    { return m_ptr != o.m_ptr; }
  operator bool() const { return m_ptr; }
  operator Cell*() const { return m_ptr; }
  Cell *operator->() const { return m_ptr; }
};
 
template <typename Cell> class CellDrawListAdapter final
{
  static_assert(std::is_class<Cell>::value, "The type argument must be a class");
  Cell *m_cell = {};
  using iterator = CellDrawListIterator<Cell>;
  using const_iterator = CellDrawListIterator<typename std::add_const<Cell>::type>;
 
public:
  explicit CellDrawListAdapter(Cell *cell) : m_cell(cell) {}
  constexpr iterator begin() const { return iterator(m_cell); }
  static constexpr iterator end() { return {}; }
  constexpr const_iterator cbegin() const { return const_iterator(m_cell); }
  static constexpr const_iterator cend() { return {}; }
};
 
class Cell;
 
class InnerCellIterator
{
  enum class Advance { Always, OnlyIfNull };
  const Cell *m_parentCell = {};
  Cell *m_innerCell = {};
  size_t m_index = 0;
  size_t m_endIndex = 0;
 
  static size_t GetInnerCellCount(const Cell *cell);
  static Cell *GetInnerCell(const Cell *cell, size_t index);
public:
  using iterator_category = std::forward_iterator_tag;
  using value_type = Cell;
  using difference_type = std::ptrdiff_t;
  using pointer = Cell *;
  using reference = Cell &;
 
  InnerCellIterator() = default;
  explicit InnerCellIterator(Cell *parentCell) :
    m_parentCell(parentCell),
    m_endIndex(parentCell ? GetInnerCellCount(parentCell) : 0)
    {
      FindFirstInnerCell();
    }
  InnerCellIterator(const InnerCellIterator &o) = default;
  InnerCellIterator &operator=(const InnerCellIterator &o) = default;
  InnerCellIterator operator++(int)
    {
      auto ret = *this;
      return operator++(), ret;
    }
  InnerCellIterator &operator++()
    {
      if (m_parentCell)
        AdvanceLoop(Advance::Always);
      return *this;
    }
  bool operator==(const InnerCellIterator &o) const
    { return m_innerCell == o.m_innerCell; }
  bool operator!=(const InnerCellIterator &o) const
    { return m_innerCell != o.m_innerCell; }
  operator bool() const { return m_innerCell; }
  operator Cell*() const { return m_innerCell; }
  Cell *operator->() const { return m_innerCell; }
 
private:
  void FindFirstInnerCell();
  void AdvanceLoop(Advance mode);
};
 
inline void InnerCellIterator::FindFirstInnerCell()
{
  if (m_endIndex)
  {
    m_innerCell = GetInnerCell(m_parentCell, 0);
    AdvanceLoop(Advance::OnlyIfNull);
  }
}
 
inline void InnerCellIterator::AdvanceLoop(Advance mode)
{
  const Cell *prev = m_innerCell;
  if (mode == Advance::OnlyIfNull && prev)
    return;
  for (;;)
  {
    ++m_index;
    if (m_index == m_endIndex)
    {
      m_innerCell = nullptr;
      break;
    }
    m_innerCell = GetInnerCell(m_parentCell, m_index);
    wxASSERT(!prev || prev != m_innerCell);
    if (m_innerCell)
      break;
  }
}
 
class InnerCellAdapter final {
  using iterator = InnerCellIterator;
  iterator const m_iter;
 
public:
  explicit InnerCellAdapter(const iterator &) = delete;
  explicit InnerCellAdapter(Cell *cell) : m_iter(cell) {}
  iterator begin() const { return m_iter; }
  static iterator end() { return {}; }
};
 
#endif