part_2.dart

import 'dart:io';

List<List<String>> _map = [];

int TotalSpinCycleNorthBeam() {
  final data = File("Dart/Day14/input.txt").readAsLinesSync();

  var rest = 0;
  _map = List<List<String>>.from(data.map((line) => line.split('')));

  final cycle = 1000000000;
  final cache = <int, int>{};

  for (var cycleIdx = 0; cycleIdx < cycle; cycleIdx++) {
    for (var _ in Iterable.generate(4)) {
      tilt();
      turn();
    }

    final hash = _hashMap(_map);

    if (!cache.containsKey(hash)) {
      cache[hash] = cycleIdx;
    } else {
      final diff = cycleIdx - cache[hash]!;
      final head = cache[hash]!;
      rest = cycle - ((cycle - head) ~/ diff) * diff - head - 1;
      break;
    }
  }

  for (var _ in Iterable.generate(rest)) {
    for (var _ in Iterable.generate(4)) {
      tilt();
      turn();
    }
  }
  final result = countTotalLoad();
  print(result + 4);
  return result;
}

int _hashMap(List<List<String>> map) {
  return map.map((row) => row.join('')).join('').hashCode;
}

void tilt() {
  for (var i = 1; i < _map.length; i++) {
    for (var x = 0; x < _map[i].length; x++) {
      if (_map[i][x] == 'O') {
        final col = List<String>.generate(_map.length, (y) => _map[y][x]);
        var prevY = i;
        for (var y = i - 1; y >= 0; y--) {
          if (col[y] == '.') {
            _map[y][x] = 'O';
            _map[prevY][x] = '.';
            prevY = y;
          } else if (col[y] == '#') {
            break;
          }
        }
      }
    }
  }
}

List<List<String>> turn() {
  _map = List<List<String>>.generate(
    _map[0].length,
    (i) => List<String>.from(
      _map.map((row) => row[i]).toList().reversed,
    ),
  );
  return _map;
}

int countTotalLoad() {
  final height = _map.length;
  return List.generate(
    height,
    (i) => (height - i) * _map[i].where((c) => c == 'O').length,
  ).fold(0, (acc, value) => acc + value);
}