/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

#ifndef SpanningCellSorter_h
#define SpanningCellSorter_h

/*
 * Code to sort cells by their colspan, used by BasicTableLayoutStrategy.
 */

#include "StackArena.h"
#include "nsDebug.h"
#include "nsTArray.h"
#include "nsTHashMap.h"

/**
 * The SpanningCellSorter is responsible for accumulating lists of cells
 * with colspans so that those cells can later be enumerated, sorted
 * from lowest number of columns spanned to highest.  It does not use a
 * stable sort (in fact, it currently reverses).
 */
class MOZ_STACK_CLASS SpanningCellSorter {
 public:
  SpanningCellSorter();
  ~SpanningCellSorter();

  struct Item {
    int32_t row, col;
    Item* next;
  };

  /**
   * Add a cell to the sorter.  Returns false on out of memory.
   * aColSpan is the number of columns spanned, and aRow/aCol are the
   * position of the cell in the table (for GetCellInfoAt).
   */
  bool AddCell(int32_t aColSpan, int32_t aRow, int32_t aCol);

  /**
   * Get the next *list* of cells.  Each list contains all the cells
   * for a colspan value, and the lists are given in order from lowest
   * to highest colspan.  The colspan value is filled in to *aColSpan.
   */
  Item* GetNext(int32_t* aColSpan);

 private:
  enum State { ADDING, ENUMERATING_ARRAY, ENUMERATING_HASH, DONE };
  State mState = ADDING;

  // store small colspans in an array for fast sorting and
  // enumeration, and large colspans in a hash table

  enum { ARRAY_BASE = 2 };
  enum { ARRAY_SIZE = 8 };
  Item* mArray[ARRAY_SIZE] = {};
  int32_t SpanToIndex(int32_t aSpan) { return aSpan - ARRAY_BASE; }
  int32_t IndexToSpan(int32_t aIndex) { return aIndex + ARRAY_BASE; }
  bool UseArrayForSpan(int32_t aSpan) {
    NS_ASSERTION(SpanToIndex(aSpan) >= 0, "cell without colspan");
    return SpanToIndex(aSpan) < ARRAY_SIZE;
  }

  using HashTableType = nsTHashMap<int32_t, Item*>;
  using HashTableEntry = typename HashTableType::EntryType;

  // Map from colSpan -> items
  HashTableType mHashTable;

  /* state used only during enumeration */
  uint32_t mEnumerationIndex = 0;  // into mArray or mSortedHashTable
  nsTArray<HashTableEntry*> mSortedHashTable;
};

#endif