module Signore Signature = Struct.new(*%i(text author source subject tags)) do
  class << self
    undef :[]
  end

  def self.[] author: nil, source: nil, subject: nil, tags: nil, text: nil
    new text, author, source, subject, tags
  end

  def tagged_with? tag
    tags and tags.include? tag
  end

  def to_s
    wrapped  = LovelyRufus::TextWrapper.wrap text.gsub("\n", "\n\n"), width: 80
    squeezed = wrapped.gsub("\n\n", "\n").chomp
    squeezed + meta_for(squeezed)
  end

  private

  def indent_size_for text
    indent = text_width(text) - meta.size - 2
    indent < 0 ? 0 : indent
  end

  def meta
    stem = [author, subject].compact.join ' '
    stem.empty? ? "#{source}" : [stem, source].compact.join(', ')
  end

  def meta_for text
    meta.empty? ? '' : "\n#{' ' * indent_size_for(text)}[#{meta}]"
  end

  def text_width text
    text.split("\n").map(&:size).max
  end
end end