module HashInitializer

# File lib/hash_initializer.rb, line 8
def [](*levels)
  unless levels_okay?(levels)
    raise InvalidLevels.new('Levels specified are invalid - note that you can only have a non :hash level at the very end')
  end

  return {} if levels.empty?

  defaults_proc = build_levels(levels)
  Hash.new(&defaults_proc)
end

# File lib/hash_initializer.rb, line 29
def build_levels levels
  return Proc.new { |h,k| h[k] = Hash.new } if levels.one? && levels.first == :hash

  level = levels.first
  case level
  when :hash
    inner_proc = build_levels(levels.drop(1))
    Proc.new { |h,k| h[k] = Hash.new(&inner_proc) }
  when :array
    Proc.new { |h,k| h[k] = Array.new }
  else
    Proc.new { |h,k| h[k] = level }
  end
end

# File lib/hash_initializer.rb, line 21
def levels_okay? levels
  return true if levels.size < 2

  levels
    .take(levels.size - 1)
    .all? { |l| l == :hash }
end