split_by_paragraph.rb

Start_tags = {"*" => :emphasis, "{" => :footnote}
End_tags = {emphasis: "*", footnote: "}"}
Tags = Start_tags.keys.join

def split_by_paragraph(text, &block)
  mode = Start_tags[text[0]] || :normal
  if mode == :normal
    index = text[1..-1].index /[#{Tags}]/
    if index.nil?
      yield ({:type => mode, :content => text})
    else
      yield ({type: mode, content: text[0..index]})
      split_by_paragraph(text[index+1..-1], &block)
    end
  else
    index = text[1..-1].index End_tags[mode]
    raise 'Missing closing' + End_tags[mode] + ' character.' if index.nil?
    yield ({type: mode, content: text[1..index]})
    split_by_paragraph(text[index+2..-1], &block) if index < text.length
  end
end

text = "Normal text. *emphasised* {footnote} Test end."
paragraphs = []
split_by_paragraph(text) {|p| paragraphs << p}
p paragraphs

Result:

[{:type=>:normal, :content=>"Normal text. "},
{:type=>:emphasis, :content=>"emphasised"},
{:type=>:normal, :content=>" "},
{:type=>:footnote, :content=>"footnote"},
{:type=>:normal, :content=>" Test end."}]