#!/bin/env ruby
require 'pry'

lights = File.readlines('./input').map(&:chomp).map(&:chars)

@light_grids = [Marshal.load(Marshal.dump(lights)), Marshal.load(Marshal.dump(lights))]
@grid_size = lights.count
runs = 100

@part2 = false

def animate(char, x, y, grid_num)
  if @part2
    case [x, y]
    when [0, 0]
      return '#'
    when [0, @grid_size - 1]
      return '#'
    when [@grid_size - 1, 0]
      return '#'
    when [@grid_size - 1, @grid_size - 1]
      return '#'
    end
  end
  neighbors = []
  (x - 1).upto(x + 1) do |x_pos|
    next if x_pos < 0 or x_pos >= @grid_size

    (y - 1).upto(y + 1) do |y_pos|
      next if y_pos < 0 or y_pos >= @grid_size
      next if x_pos == x and y_pos == y

      # puts "#{grid_num},#{x_pos},#{y_pos}"
      neighbors.push(@light_grids[grid_num][x_pos][y_pos])
    end
  end
  on_neighbors = neighbors.count('#')
  if char == '#'
    if [2, 3].include?(on_neighbors)
      '#'
    else
      '.'
    end
  elsif on_neighbors == 3
    '#'
  else
    '.'
  end
end

def print_grid(grid)
  grid.each { |line| puts line.join }
end

@light_grids.cycle(runs / 2).with_index do |grid, i|
  current_grid = i % 2 # References the current light grid
  next_grid = current_grid == 1 ? 0 : 1
  # puts "this grid: #{current_grid}, next grid: #{next_grid}"
  grid.each_with_index do |line, x|
    line.each_with_index do |char, y|
      @light_grids[next_grid][x][y] = animate(char, x, y, current_grid)
    end
  end
end
puts @part2 == true ? "Part 2 Solution: #{@light_grids[0].flatten.count('#')}" : "Part 1 Solution: #{@light_grids[0].flatten.count('#')}"

# binding.pry