Class: Irwi::Comparators::DiffLcs

Inherits:
Base
  • Object
show all
Defined in:
lib/irwi/comparators/diff_lcs.rb

Instance Method Summary collapse

Methods inherited from Base

#render_changes

Constructor Details

#initialize ⇒ DiffLcs

Returns a new instance of DiffLcs.



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# File 'lib/irwi/comparators/diff_lcs.rb', line 5

def initialize
  super

  require 'diff/lcs'
end

Instance Method Details

#build_changes(old_text, new_text) ⇒ Object 



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# File 'lib/irwi/comparators/diff_lcs.rb', line 11

def build_changes( old_text, new_text )
  diffs = Diff::LCS.sdiff( (old_text || '').mb_chars, (new_text || '').mb_chars ) # Building symmetric diff sequence
  changes = [] # Array for our result changes

  diffs.each do |change|
    case change.action
      when '=' then
        if !changes.empty? && changes.last.action == '=' # Append to last not changed span, if exists
          changes.last.value << change.old_element
        else
          changes << new_not_changed( change.old_element )
        end

      when '+' then
        if !changes.empty? && changes.last.action == '+' # Append to last addition, if exists
          changes.last.new_value << change.new_element
        elsif !changes.empty? && changes.last.action == '!' # Append to last replace, if exists (it's necessary when replacing short string with a new long)
          changes.last.new_value << change.new_element
        else
          changes << new_changed( '+', nil, change.new_element )
        end

      when '-' then
        if !changes.empty? && changes.last.action == '-' # Append to last deletion, if exists
          changes.last.old_value << change.old_element
        else
          changes << new_changed( '-', change.old_element, nil )
        end

      when '!' then
        if !changes.empty? && changes.last.action == '!' # Append to last replace, if exists
          changes.last.old_value << change.old_element
          changes.last.new_value << change.new_element
        else
          changes << new_changed( '!', change.old_element, change.new_element )
        end

    end
  end

  changes
end