mysociety/alaveteli

module HighlightHelper
  include ERB::Util

  # Implementation of rails' highlight that allows regex to be passed to
  # the phrases parameter.
  # https://github.com/rails/rails/pull/11793
  def highlight_matches(text, phrases, options = {})
    if options.fetch(:sanitize, true)
      text = ActionController::Base.helpers.sanitize(text).try(:html_safe)
    end

    if text.blank? || phrases.blank?
      text
    else
      match = Array(phrases).map do |p|
        p.is_a?(Regexp) ? p.to_s : Regexp.escape(p)
      end.join('|')

      if block_given?
        text.gsub(/(#{match})(?![^<]*?>)/i) { |found| yield found }
      else
        highlighter = options.fetch(:highlighter, '<mark>\1</mark>')
        text.gsub(/(#{match})(?![^<]*?>)/i, highlighter)
      end
    end.html_safe
  end

  # Highlight words, also escapes HTML (other than spans that we add)
  def highlight_words(t, words, html = true)
    if html
      highlight_matches(h(t), words, highlighter: '<span class="highlight">\1</span>').html_safe
    else
      highlight_matches(t, words, highlighter: '*\1*')
    end
  end

  def highlight_and_excerpt(t, words, excount, html = true)
    newt = excerpt(t, words[0], radius: excount)
    newt = excerpt(t, '', radius: excount) unless newt
    highlight_words(newt, words, html)
  end

  def excerpt(text, phrase, options = {})
    return unless text && phrase

    separator = options.fetch(:separator, nil) || ""
    case phrase
    when Regexp
      regex = phrase
    else
      regex = /#{Regexp.escape(phrase)}/i
    end

    return unless (matches = text.match(regex))

    phrase = matches[0]

    unless separator.empty?
      text.split(separator).each do |value|
        if value.match(regex)
          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

  private

  def cut_excerpt_part(part_position, part, separator, options)
    return "", "" unless part

    radius   = options.fetch(:radius, 100)
    omission = options.fetch(:omission, "...")

    part = part.split(separator)
    part.delete("")
    affix = part.size > radius ? omission : ""

    part = if part_position == :first
      drop_index = [part.length - radius, 0].max
      part.drop(drop_index)
    else
      part.first(radius)
    end

    [affix, part.join(separator)]
  end
end