Solution: Masking Weave Mazes

require 'weave_grid'
require 'mask'
require 'kruskals'
class SimpleOverCell < OverCell
  def neighbors
    list = []
    list << north if north
    list << south if south
    list << east  if east
    list << west  if west
    list
  end
end
class MaskedWeaveGrid < WeaveGrid
  attr_reader :mask
  def initialize(mask)
    @mask = mask
    super(@mask.rows, @mask.columns)
  end
  def prepare_grid
    Array.new(rows) do |row|
      Array.new(columns) do |column|
        SimpleOverCell.new(row, column, self) if mask[row, column]
      end
    end
  end
  def random_cell
    row, col = mask.random_location
    self[row, col]
  end
  def size
    mask.count
  end
end
mask = Mask.from_png("10-teardrops-mask.png")
grid = MaskedWeaveGrid.new(mask)
state = Kruskals::State.new(grid)
# find the candidate locations
candidates = []
grid.each_cell do |cell|
  candidates.push cell if cell.north && cell.south && cell.east && cell.west
end
# attempt to add crossings to all the candidates, in random order
candidates.shuffle.each do |candidate|
  state.add_crossing(candidate)
end
Kruskals.on(grid, state)
grid.to_png.save("10.png")
filename="10.png"
grid.to_png.save("/usercode/output/"+filename)