class ReeText::Excerpt

def call(text, phrase, **opts)
  options = DEFAULTS.merge(opts)
  
  return if is_blank(text) && is_blank(phrase)
  separator = options[:separator]
  case phrase
  when Regexp
    regex = phrase
  else
    regex = /#{Regexp.escape(phrase)}/i
  end
  return unless matches = text.match(regex)
  phrase = matches[0]
  unless is_blank(separator)
    text.split(separator).each do |value|
      if value.match?(regex)
        phrase = value
        break
      end
    end
  end
  first_part, second_part = text.split(phrase, 2)
  prefix, first_part   = cut_excerpt_part(:first, first_part, separator, options)
  postfix, second_part = cut_excerpt_part(:second, second_part, separator, options)
  affix = [first_part, separator, phrase, separator, second_part].join.strip
  [prefix, affix, postfix].join
end

def cut_excerpt_part(part_position, part, separator, options)
  return "", "" unless part
  radius = options[:radius]
  omission = options[:omission]
  if separator != ""
    part = part.split(separator)
    part.delete("")
  end
  affix = part.length > radius ? omission : ""
  part = if part_position == :first
    last(part, radius)
  else
    first(part, radius)
  end
  if separator != ""
    part = part.join(separator)
  end
  return affix, part
end

def first(string, limit = 1)
  string[0, limit] || raise(ArgumentError, "negative limit")
end

def last(string, limit = 1)
  string[[string.length - limit, 0].max, limit] || raise(ArgumentError, "negative limit")
end