module Biscotti

# File lib/biscotti.rb, line 26
def find_words(input, min_word_length: 2, dictionary: [])
  # puts "#{dictionary.count} words in dictionary"

  letters = input.split('').sort

  letters_frequency_idx = Biscotti.letters_frequency_idx(letters)

  words = letters.count.downto(min_word_length).each_with_object([]) do |letter_count, w|
    w.concat(letters.permutation(letter_count).to_a.map(&:join))
  end

  letters_count = letters.count
  word_length_range = (min_word_length..letters_count).freeze

  words & dictionary
          .map(&:chomp)
          .select { |word| word_length_range.include?(word.length) }
          .map { |word| word.strip.downcase.split('') }
          .select { |word| (word - letters).empty? }
          .select { |word| word.all? { |l0| word.count { |l1| l1 == l0 } <= letters_frequency_idx[l0] } }
          .map(&:join)
end

# File lib/biscotti.rb, line 8
def letters_frequency_idx(letters)
  Hash[
    letters
    .group_by { |x| letters.count { |y| x == y } }
    .flat_map do |k, v|
      v.uniq.map { |l| [l, k] }
    end
  ]
end

# File lib/biscotti.rb, line 18
def load_dictionary(dictionary_file)
  File.open(dictionary_file, 'r').readlines
end

# File lib/biscotti.rb, line 22
def word_length_idx(words)
  words.group_by(&:length)
end