Class: HTMLDiff::DiffBuilder

Inherits:
Object
  • Object
show all
Defined in:
lib/junebug/ext/diff.rb

Constant Summary collapse

VALID_METHODS = 
[:replace, :insert, :delete, :equal]

Instance Method Summary collapse

Constructor Details

#initialize(old_version, new_version) ⇒ DiffBuilder

Returns a new instance of DiffBuilder.



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# File 'lib/junebug/ext/diff.rb', line 18

def initialize(old_version, new_version)
  @old_version, @new_version = old_version, new_version
  @content = []
end

Instance Method Details

#add_matching_words_left(match_in_old, match_in_new, match_size, start_in_old, start_in_new) ⇒ Object 



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# File 'lib/junebug/ext/diff.rb', line 144

def add_matching_words_left(match_in_old, match_in_new, match_size, start_in_old, start_in_new)
  while match_in_old > start_in_old and 
        match_in_new > start_in_new and 
        @old_words[match_in_old - 1] == @new_words[match_in_new - 1]
    match_in_old -= 1
    match_in_new -= 1
    match_size += 1
  end
  [match_in_old, match_in_new, match_size]
end

#add_matching_words_right(match_in_old, match_in_new, match_size, end_in_old, end_in_new) ⇒ Object 



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# File 'lib/junebug/ext/diff.rb', line 155

def add_matching_words_right(match_in_old, match_in_new, match_size, end_in_old, end_in_new)
  while match_in_old + match_size < end_in_old and 
        match_in_new + match_size < end_in_new and
        @old_words[match_in_old + match_size] == @new_words[match_in_new + match_size]
    match_size += 1
  end
  [match_in_old, match_in_new, match_size]
end

#build ⇒ Object 



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# File 'lib/junebug/ext/diff.rb', line 23

def build
  split_inputs_to_words
  index_new_words
  operations.each { |op| perform_operation(op) }
  return @content.join
end

#closing_tag?(item) ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/junebug/ext/diff.rb', line 193

def closing_tag?(item)
  item =~ %r!^\s*</[^>]+>\s*$!
end

#convert_html_to_list_of_words(x, use_brackets = false) ⇒ Object 



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# File 'lib/junebug/ext/diff.rb', line 258

def convert_html_to_list_of_words(x, use_brackets = false)
  mode = :char
  current_word  = ''
  words = []
  
  explode(x).each do |char|
    case mode
    when :tag
      if end_of_tag? char
        current_word << (use_brackets ? ']' : '>')
        words << current_word
        current_word = ''
        if whitespace?(char) 
          mode = :whitespace 
        else
          mode = :char
        end
      else
        current_word << char
      end
    when :char
      if start_of_tag? char
        words << current_word unless current_word.empty?
        current_word = (use_brackets ? '[' : '<')
        mode = :tag
      elsif /\s/.match char
        words << current_word unless current_word.empty?
        current_word = char
        mode = :whitespace
      else
        current_word << char
      end
    when :whitespace
      if start_of_tag? char
        words << current_word unless current_word.empty?
        current_word = (use_brackets ? '[' : '<')
        mode = :tag
      elsif /\s/.match char
        current_word << char
      else
        words << current_word unless current_word.empty?
        current_word = char
        mode = :char
      end
    else 
      raise "Unknown mode #{mode.inspect}"
    end
  end
  words << current_word unless current_word.empty?
  words
end

#delete(operation, tagclass = 'diffdel') ⇒ Object 



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# File 'lib/junebug/ext/diff.rb', line 180

def delete(operation, tagclass = 'diffdel')
   insert_tag('del', tagclass, @old_words[operation.start_in_old...operation.end_in_old])
end

#end_of_tag?(char) ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/junebug/ext/diff.rb', line 246

def end_of_tag?(char)
  char == '>'
end

#equal(operation) ⇒ Object 



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# File 'lib/junebug/ext/diff.rb', line 184

def equal(operation)
  # no tags to insert, simply copy the matching words from one of the versions
  @content += @new_words[operation.start_in_new...operation.end_in_new]
end

#explode(sequence) ⇒ Object 



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# File 'lib/junebug/ext/diff.rb', line 242

def explode(sequence)
  sequence.is_a?(String) ? sequence.split(//) : sequence
end

#extract_consecutive_words(words, &condition) ⇒ Object 



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# File 'lib/junebug/ext/diff.rb', line 201

def extract_consecutive_words(words, &condition)
  index_of_first_tag = nil
  words.each_with_index do |word, i| 
    if !condition.call(word)
      index_of_first_tag = i
      break
    end
  end
  if index_of_first_tag
    return words.slice!(0...index_of_first_tag)
  else
    return words.slice!(0..words.length)
  end
end

#find_match(start_in_old, end_in_old, start_in_new, end_in_new) ⇒ Object 



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# File 'lib/junebug/ext/diff.rb', line 108

def find_match(start_in_old, end_in_old, start_in_new, end_in_new)

  best_match_in_old = start_in_old
  best_match_in_new = start_in_new
  best_match_size = 0
  
  match_length_at = Hash.new { |h, index| h[index] = 0 }
  
  start_in_old.upto(end_in_old - 1) do |index_in_old|

    new_match_length_at = Hash.new { |h, index| h[index] = 0 }

    @word_indices[@old_words[index_in_old]].each do |index_in_new|
      next  if index_in_new < start_in_new
      break if index_in_new >= end_in_new

      new_match_length = match_length_at[index_in_new - 1] + 1
      new_match_length_at[index_in_new] = new_match_length

      if new_match_length > best_match_size
        best_match_in_old = index_in_old - new_match_length + 1
        best_match_in_new = index_in_new - new_match_length + 1
        best_match_size = new_match_length
      end
    end
    match_length_at = new_match_length_at
  end

#      best_match_in_old, best_match_in_new, best_match_size = add_matching_words_left(
#          best_match_in_old, best_match_in_new, best_match_size, start_in_old, start_in_new)
#      best_match_in_old, best_match_in_new, match_size = add_matching_words_right(
#          best_match_in_old, best_match_in_new, best_match_size, end_in_old, end_in_new)

  return (best_match_size != 0 ? Match.new(best_match_in_old, best_match_in_new, best_match_size) : nil)
end

#index_new_words ⇒ Object 



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# File 'lib/junebug/ext/diff.rb', line 35

def index_new_words
  @word_indices = Hash.new { |h, word| h[word] = [] }
  @new_words.each_with_index { |word, i| @word_indices[word] << i }
end

#insert(operation, tagclass = 'diffins') ⇒ Object 



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# File 'lib/junebug/ext/diff.rb', line 176

def insert(operation, tagclass = 'diffins')
  insert_tag('ins', tagclass, @new_words[operation.start_in_new...operation.end_in_new])
end

#insert_tag(tagname, cssclass, words) ⇒ Object

This method encloses words within a specified tag (ins or del), and adds this into @content, with a twist: if there are words contain tags, it actually creates multiple ins or del, so that they don’t include any ins or del. This handles cases like old: ‘<p>a</p>’ new: ‘<p>ab</p><p>c</b>’ diff result: ‘<p>a<ins>b</ins></p><p><ins>c</ins></p>’ this still doesn’t guarantee valid HTML (hint: think about diffing a text containing ins or del tags), but handles correctly more cases than the earlier version.

P.S.: Spare a thought for people who write HTML browsers. They live in this … every day.



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# File 'lib/junebug/ext/diff.rb', line 227

def insert_tag(tagname, cssclass, words)
  loop do
    break if words.empty?
    non_tags = extract_consecutive_words(words) { |word| not tag?(word) }
    @content << wrap_text(non_tags.join, tagname, cssclass) unless non_tags.empty?

    break if words.empty?
    @content += extract_consecutive_words(words) { |word| tag?(word) }
  end
end

#matching_blocks ⇒ Object 



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# File 'lib/junebug/ext/diff.rb', line 87

def matching_blocks
  matching_blocks = []
  recursively_find_matching_blocks(0, @old_words.size, 0, @new_words.size, matching_blocks)
  matching_blocks
end

#opening_tag?(item) ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/junebug/ext/diff.rb', line 189

def opening_tag?(item)
  item =~ %r!^\s*<[^>]+>\s*$!
end

#operations ⇒ Object 



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# File 'lib/junebug/ext/diff.rb', line 40

def operations
  position_in_old = position_in_new = 0
  operations = []
  
  matches = matching_blocks
  # an empty match at the end forces the loop below to handle the unmatched tails
  # I'm sure it can be done more gracefully, but not at 23:52
  matches << Match.new(@old_words.length, @new_words.length, 0)
  
  matches.each_with_index do |match, i|
    match_starts_at_current_position_in_old = (position_in_old == match.start_in_old)
    match_starts_at_current_position_in_new = (position_in_new == match.start_in_new)
    
    action_upto_match_positions = 
      case [match_starts_at_current_position_in_old, match_starts_at_current_position_in_new]
      when [false, false]
        :replace
      when [true, false]
        :insert
      when [false, true]
        :delete
      else
        # this happens if the first few words are same in both versions
        :none
      end

    if action_upto_match_positions != :none
      operation_upto_match_positions = 
          Operation.new(action_upto_match_positions, 
              position_in_old, match.start_in_old, 
              position_in_new, match.start_in_new)
      operations << operation_upto_match_positions
    end
    if match.size != 0
      match_operation = Operation.new(:equal, 
          match.start_in_old, match.end_in_old, 
          match.start_in_new, match.end_in_new)
      operations << match_operation
    end

    position_in_old = match.end_in_old
    position_in_new = match.end_in_new
  end
  
  operations
end

#perform_operation(operation) ⇒ Object 



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# File 'lib/junebug/ext/diff.rb', line 166

def perform_operation(operation)
  @operation = operation
  self.send operation.action, operation
end

#recursively_find_matching_blocks(start_in_old, end_in_old, start_in_new, end_in_new, matching_blocks) ⇒ Object 



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# File 'lib/junebug/ext/diff.rb', line 93

def recursively_find_matching_blocks(start_in_old, end_in_old, start_in_new, end_in_new, matching_blocks)
  match = find_match(start_in_old, end_in_old, start_in_new, end_in_new)
  if match
    if start_in_old < match.start_in_old and start_in_new < match.start_in_new
      recursively_find_matching_blocks(
          start_in_old, match.start_in_old, start_in_new, match.start_in_new, matching_blocks) 
    end
    matching_blocks << match
    if match.end_in_old < end_in_old and match.end_in_new < end_in_new
      recursively_find_matching_blocks(
          match.end_in_old, end_in_old, match.end_in_new, end_in_new, matching_blocks)
    end
  end
end

#replace(operation) ⇒ Object 



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# File 'lib/junebug/ext/diff.rb', line 171

def replace(operation)
  delete(operation, 'diffmod')
  insert(operation, 'diffmod')
end

#split_inputs_to_words ⇒ Object 



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# File 'lib/junebug/ext/diff.rb', line 30

def split_inputs_to_words
  @old_words = convert_html_to_list_of_words(explode(@old_version))
  @new_words = convert_html_to_list_of_words(explode(@new_version))
end

#start_of_tag?(char) ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/junebug/ext/diff.rb', line 250

def start_of_tag?(char)
  char == '<'
end

#tag?(item) ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/junebug/ext/diff.rb', line 197

def tag?(item)
  opening_tag?(item) or closing_tag?(item)
end

#whitespace?(char) ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/junebug/ext/diff.rb', line 254

def whitespace?(char)
  char =~ /\s/
end

#wrap_text(text, tagname, cssclass) ⇒ Object 



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# File 'lib/junebug/ext/diff.rb', line 238

def wrap_text(text, tagname, cssclass)
  %(<#{tagname} class="#{cssclass}">#{text}</#{tagname}>)
end