Add pure-Dart engine core: RNG, grid, placement, line clear, scoring, piece generator

PCG32 seeded RNG; immutable 8x8 GridState with occupancy bitmask; placement legality + anyPlacementExists; simultaneous row/col clears with single-count gem credit; combo scoring with one-move grace; weighted-bag generator with pity bias and depth-3 solvability nudge. All TDD, 51 tests green. Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
2026-06-11 13:05:55 +09:00
parent 40528238b2
commit 0210c14858
19 changed files with 1408 additions and 0 deletions
@@ -0,0 +1,63 @@
+import 'cell.dart';
+
+/// Immutable 8x8 board state. Mutating operations return new instances.
+///
+/// Occupancy is mirrored in a 64-bit bitmask (bit y*8+x) so fullness checks
+/// and placement scans are O(1) mask operations.
+class GridState {
+  static const int size = 8;
+  static const int cellCount = size * size;
+
+  GridState.empty()
+      : _cells = List.filled(cellCount, Cell.empty),
+        _mask = 0;
+
+  const GridState._(this._cells, this._mask);
+
+  final List<Cell> _cells;
+  final int _mask;
+
+  static int _index(int x, int y) => y * size + x;
+
+  /// Raw occupancy bitmask; exposed for placement/clear mask math.
+  int get mask => _mask;
+
+  Cell cellAt(int x, int y) => _cells[_index(x, y)];
+
+  bool isOccupied(int x, int y) => (_mask >>> _index(x, y)) & 1 == 1;
+
+  int get occupiedCount {
+    var n = 0;
+    var m = _mask;
+    while (m != 0) {
+      m &= m - 1;
+      n++;
+    }
+    return n;
+  }
+
+  double get fillRatio => occupiedCount / cellCount;
+
+  GridState withCell(int x, int y, Cell cell) {
+    final cells = List.of(_cells);
+    final i = _index(x, y);
+    cells[i] = cell;
+    final mask =
+        cell.isOccupied ? (_mask | (1 << i)) : (_mask & ~(1 << i));
+    return GridState._(List.unmodifiable(cells), mask);
+  }
+
+  static int _rowMask(int y) => 0xFF << (y * size);
+
+  static int _colMask(int x) {
+    var m = 0;
+    for (var y = 0; y < size; y++) {
+      m |= 1 << _index(x, y);
+    }
+    return m;
+  }
+
+  bool isRowFull(int y) => (_mask & _rowMask(y)) == _rowMask(y);
+
+  bool isColFull(int x) => (_mask & _colMask(x)) == _colMask(x);
+}