import 'dart:math';
import '../models/gem.dart';
import '../models/grid.dart';
import '../../utils/constants.dart';

class GravitySystem {
  static void applyGravity(GameGrid grid) {
    for (int col = 0; col < GameConstants.gridWidth; col++) {
      _dropColumn(grid, col);
    }
  }

  static List<Gem> generateGems(GameGrid grid) {
    // Fill empty spaces with new gems
    final random = Random();
    final List<Gem> newGems = [];
    for (int row = 0; row < GameConstants.gridHeight; row++) {
      for (int col = 0; col < GameConstants.gridWidth; col++) {
        if (grid.getGem(row, col) == null) {
          final gem = Gem(
            row: row,
            col: col,
            type: random.nextInt(GameConstants.gemTypes.length),
          );
          newGems.add(gem);
          grid.setGem(row, col, gem);
        }
      }
    }
    return newGems;
  }

  static void _dropColumn(GameGrid grid, int col) {
    final gems = <Gem>[];

    // Collect non-null gems from bottom to top
    for (int row = GameConstants.gridHeight - 1; row >= 0; row--) {
      final gem = grid.getGem(row, col);
      if (gem != null) {
        gems.add(gem);
      }
    }

    // Clear column
    for (int row = 0; row < GameConstants.gridHeight; row++) {
      grid.setGem(row, col, null);
    }

    // Place gems at bottom
    for (int i = 0; i < gems.length; i++) {
      final newRow = GameConstants.gridHeight - 1 - i;
      grid.setGem(newRow, col, gems[i].copyWith(row: newRow, col: col));
    }
  }
}