module ClockFlip

# File lib/clock/flip.rb, line 110
def candidate_preference_index(digits, word)
  index = 0
  multiplier = 1
  digits.chars.reverse_each.with_index do |digit, position|
    options = FLIP_OPTIONS[digit] || []
    letter = word[-(position + 1)]
    option_index = options.index(letter) || options.length
    index += option_index * multiplier
    multiplier *= [options.length, 1].max + 1
  end
  index
end

# File lib/clock/flip.rb, line 47
def display_digit_string(hour, minute)
  h = display_hour(hour)
  m = minute.to_i
  raise ArgumentError, "invalid minute: #{m}" unless (0..59).cover?(m)

  digits = if h >= 10
             format("%02d%02d", h, m)
           else
             format("%03d", (h * 100) + m)
           end

  unless digits.length.between?(3, 4)
    raise ArgumentError, "clock digit string must be 3–4 digits, got #{digits.inspect}"
  end

  digits
end

# File lib/clock/flip.rb, line 31
def display_hour(hour)
  h = hour.to_i
  raise ArgumentError, "invalid hour: #{h}" unless (0..23).cover?(h)

  return 12 if h.zero? || h == 12

  h > 12 ? h - 12 : h
end

# File lib/clock/flip.rb, line 96
def flip_word?(word)
  word.to_s.match?(LETTER_PATTERN) && !word.to_s.empty?
end

# File lib/clock/flip.rb, line 40
def format_time(hour, minute)
  format("%d:%02d", display_hour(hour), minute.to_i)
end

# File lib/clock/flip.rb, line 100
def local_parts(now:, utc_offset:)
  local = now.getlocal(utc_offset)
  [local.hour, local.min, local]
end

# File lib/clock/flip.rb, line 105
def map_digits_to_word(digits, map)
  digits.chars.filter_map { |digit| map[digit] }.join
end

# File lib/clock/flip.rb, line 76
def upside_down_candidates(hour, minute)
  digits = upside_down_digits(hour, minute)
  option_lists = digits.chars.map { |digit| FLIP_OPTIONS[digit] || [] }
  return [] if option_lists.any?(&:empty?)

  words = option_lists.reduce([""]) do |acc, options|
    acc.flat_map { |prefix| options.map { |letter| "#{prefix}#{letter}" } }
  end

  ranked = words.uniq.sort_by { |word| [candidate_preference_index(digits, word), word] }
  primary = upside_down_word(hour, minute)
  ranked = [primary] + (ranked - [primary]) if primary && !primary.empty?
  ranked
end

# File lib/clock/flip.rb, line 66
def upside_down_digits(hour, minute)
  display_digit_string(hour, minute).reverse
end

# File lib/clock/flip.rb, line 72
def upside_down_word(hour, minute)
  map_digits_to_word(upside_down_digits(hour, minute), FLIP_MAP)
end

# File lib/clock/flip.rb, line 91
def valid_flip_word?(hour, minute, word)
  token = word.to_s.strip.downcase
  upside_down_candidates(hour, minute).include?(token)
end