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# Redmine - project management software

# Copyright (C) 2006-2014  Jean-Philippe Lang

#

# This program is free software; you can redistribute it and/or

# modify it under the terms of the GNU General Public License

# as published by the Free Software Foundation; either version 2

# of the License, or (at your option) any later version.

#

# This program is distributed in the hope that it will be useful,

# but WITHOUT ANY WARRANTY; without even the implied warranty of

# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

# GNU General Public License for more details.

#

# You should have received a copy of the GNU General Public License

# along with this program; if not, write to the Free Software

# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.

require 'diff'

module Redmine

  module Helpers

    class Diff

      include ERB::Util

      include ActionView::Helpers::TagHelper

      include ActionView::Helpers::TextHelper

      attr_reader :diff, :words

      def initialize(content_to, content_from)

        @words = content_to.to_s.split(/(\s+)/)

        @words = @words.select {|word| word != ' '}

        words_from = content_from.to_s.split(/(\s+)/)

        words_from = words_from.select {|word| word != ' '}

        @diff = words_from.diff @words

      end

      def to_html

        words = self.words.collect{|word| h(word)}

        words_add = 0

        words_del = 0

        dels = 0

        del_off = 0

        diff.diffs.each do |diff|

          add_at = nil

          add_to = nil

          del_at = nil

          deleted = ""

          diff.each do |change|

            pos = change[1]

            if change[0] == "+"

              add_at = pos + dels unless add_at

              add_to = pos + dels

              words_add += 1

            else

              del_at = pos unless del_at

              deleted << ' ' unless deleted.empty?

              deleted << h(change[2])

              words_del  += 1

            end

          end

          if add_at

            words[add_at] = '<span class="diff_in">'.html_safe + words[add_at]

            words[add_to] = words[add_to] + '</span>'.html_safe

          end

          if del_at

            words.insert del_at - del_off + dels + words_add, '<span class="diff_out">'.html_safe + deleted + '</span>'.html_safe

            dels += 1

            del_off += words_del

            words_del = 0

          end

        end

        words.join(' ').html_safe

      end

    end

  end

end