trustieforge/lib/trustie/gitlab/inline_diff.rb

module Trustie
  module Gitlab
    class InlineDiff
      class << self

        START  = "#!idiff-start!#"
        FINISH = "#!idiff-finish!#"

        def processing(diff_arr)
          # indexes = _indexes_of_changed_lines diff_arr
          #
          # indexes.each do |index|
          #   first_line = diff_arr[index+1]
          #   second_line = diff_arr[index+2]
          #
          #   # Skip inline diff if empty line was replaced with content
          #   next if first_line == "-\n"
          #
          #   first_token = find_first_token(first_line, second_line)
          #   apply_first_token(diff_arr, index, first_token)
          #
          #   last_token = find_last_token(first_line, second_line, first_token)
          #   apply_last_token(diff_arr, index, last_token)
          # end

          diff_arr
        end

        def apply_first_token(diff_arr, index, first_token)
          start = first_token + START

          if first_token.empty?
            # In case if we remove string of spaces in commit
            diff_arr[index+1].sub!("-", "-" => "-#{START}")
            diff_arr[index+2].sub!("+", "+" => "+#{START}")
          else
            diff_arr[index+1].sub!(first_token, first_token => start)
            diff_arr[index+2].sub!(first_token, first_token => start)
          end
        end

        def apply_last_token(diff_arr, index, last_token)
          # This is tricky: escape backslashes so that `sub` doesn't interpret them
          # as backreferences. Regexp.escape does NOT do the right thing.
          replace_token = FINISH + last_token.gsub(/\\/, '\&\&')
          diff_arr[index+1].sub!(/#{Regexp.escape(last_token)}$/, replace_token)
          diff_arr[index+2].sub!(/#{Regexp.escape(last_token)}$/, replace_token)
        end

        def find_first_token(first_line, second_line)
          max_length = [first_line.size, second_line.size].max
          first_the_same_symbols = 0

          (0..max_length + 1).each do |i|
            first_the_same_symbols = i - 1

            if first_line[i] != second_line[i] && i > 0
              break
            end
          end

          first_line[0..first_the_same_symbols][1..-1]
        end

        def find_last_token(first_line, second_line, first_token)
          max_length = [first_line.size, second_line.size].max
          last_the_same_symbols = 0

          (1..max_length + 1).each do |i|
            last_the_same_symbols = -i
            shortest_line = second_line.size > first_line.size ? first_line : second_line

            if (first_line[-i] != second_line[-i]) || "#{first_token}#{START}".size == shortest_line[1..-i].size
              break
            end
          end

          last_the_same_symbols += 1
          first_line[last_the_same_symbols..-1]
        end

        def _indexes_of_changed_lines(diff_arr)
          chain_of_first_symbols = ""
          diff_arr.each_with_index do |line, i|
            chain_of_first_symbols += line[0]
          end
          chain_of_first_symbols.gsub!(/[^\-\+]/, "#")

          offset = 0
          indexes = []
          while index = chain_of_first_symbols.index("#-+#", offset)
            indexes << index
            offset = index + 1
          end
          indexes
        end

        def replace_markers(line)
          line.gsub!(START, "<span class='idiff'>")
          line.gsub!(FINISH, "</span>")
          line
        end
      end
    end
  end
end