BlockSeasons/lib/game/engine/line_clear.dart

import '../models/cell.dart';
import '../models/grid.dart';

class ClearResult {
  const ClearResult({
    required this.grid,
    required this.clearedRows,
    required this.clearedCols,
    required this.gemsCleared,
  });

  final GridState grid;
  final List<int> clearedRows;
  final List<int> clearedCols;
  final int gemsCleared;

  int get linesCleared => clearedRows.length + clearedCols.length;
}

/// Detects all simultaneously full rows/columns and clears them in one pass.
ClearResult detectAndClear(GridState grid) {
  final rows = <int>[];
  final cols = <int>[];
  for (var y = 0; y < GridState.size; y++) {
    if (grid.isRowFull(y)) rows.add(y);
  }
  for (var x = 0; x < GridState.size; x++) {
    if (grid.isColFull(x)) cols.add(x);
  }
  if (rows.isEmpty && cols.isEmpty) {
    return ClearResult(
      grid: grid,
      clearedRows: const [],
      clearedCols: const [],
      gemsCleared: 0,
    );
  }

  final rowSet = rows.toSet();
  final colSet = cols.toSet();
  var gems = 0;
  var next = grid;
  for (var y = 0; y < GridState.size; y++) {
    for (var x = 0; x < GridState.size; x++) {
      if (!rowSet.contains(y) && !colSet.contains(x)) continue;
      if (grid.cellAt(x, y).type == CellType.gem) gems++;
      next = next.withCell(x, y, Cell.empty);
    }
  }
  return ClearResult(
    grid: next,
    clearedRows: rows,
    clearedCols: cols,
    gemsCleared: gems,
  );
}