WEIGHTS_CACHE_FILE = 'weights.cache'

def load_weights_cache(patterns_file)
  return nil unless File.exist?(WEIGHTS_CACHE_FILE)
  cached = Marshal.load(File.binread(WEIGHTS_CACHE_FILE))
  cached[:mtime] == File.mtime(patterns_file) ? cached[:weights] : nil
rescue
  nil
end

def save_weights_cache(weights, patterns_file)
  File.binwrite(WEIGHTS_CACHE_FILE, Marshal.dump({ mtime: File.mtime(patterns_file), weights: weights }))
end

def train_hopfield(vectors)
  n = vectors[0].length
  weights = Array.new(n) { Array.new(n, 0.0) }

  vectors.each do |v|
    n.times do |i|
      n.times do |j|
        weights[i][j] += v[i] * v[j] unless i == j
      end
    end
  end

  weights
end

def step_hopfield(weights, vector)
  n = vector.length
  Array.new(n) do |i|
    sum = 0.0
    n.times { |j| sum += weights[i][j] * vector[j] }
    sum >= 0 ? 1 : -1
  end
end

MAX_HOPFIELD_ITER = 200

def recall_hopfield(weights, input_vec)
  current = input_vec.dup
  next_vec = step_hopfield(weights, current)
  iter = 1
  while !vectors_equal?(current, next_vec) && iter < MAX_HOPFIELD_ITER
    current = next_vec
    next_vec = step_hopfield(weights, current)
    iter += 1
  end
  next_vec
end