Class: Refiner

Inherits:
Object
  • Object
show all
Includes:
Colors
Defined in:
lib/refiner.rb

Overview

Compute longest common substring based diff between two strings.

The diff format is first the old string:

  • in red

  • with each line prefixed with minuses

  • removed characters highlighted in inverse video

Then comes the new string:

  • in green

  • with each line prefixed with plusses

  • added characters highlighted in inverse video

Constant Summary collapse

REFINEMENT_THRESHOLD =

If either old or new would get more than this percentage of chars highlighted, consider this to be a replacement rather than a change and just don’t highlight anything.

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Constants included from Colors

Colors::BOLD, Colors::CYAN, Colors::DEFAULT_COLOR, Colors::ESC, Colors::GREEN, Colors::NOT_REVERSE, Colors::RED, Colors::RESET, Colors::REVERSE

Instance Attribute Summary collapse

Instance Method Summary collapse

Methods included from Colors

#reversed, #uncolor

Constructor Details

#initialize(old, new) ⇒ Refiner

Returns a new instance of Refiner.



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# File 'lib/refiner.rb', line 152

def initialize(old, new)
  old_highlights, new_highlights = try_highlight(old, new)
  if old_highlights.size == 0 && new_highlights.size == 0
    old_highlights, new_highlights = try_highlight_initial_lines(old, new)
  end

  if !create_one_to_many_refinements(old, new,
                                     old_highlights,
                                     new_highlights)
    create_refinements(old, new, old_highlights, new_highlights)
  end
end

Instance Attribute Details

#refined_new ⇒ Object (readonly)

Returns the value of attribute refined_new.



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# File 'lib/refiner.rb', line 20

def refined_new
  @refined_new
end

#refined_old ⇒ Object (readonly)

Returns the value of attribute refined_old.



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# File 'lib/refiner.rb', line 19

def refined_old
  @refined_old
end

Instance Method Details

#censor_highlights(old, new, old_highlights, new_highlights) ⇒ Object 



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# File 'lib/refiner.rb', line 42

def censor_highlights(old, new, old_highlights, new_highlights)
  old_highlights_percentage = 100 * old_highlights.size / old.length
  new_highlights_percentage = 100 * new_highlights.size / new.length

  if old_highlights_percentage > REFINEMENT_THRESHOLD \
     || new_highlights_percentage > REFINEMENT_THRESHOLD
    # We'll consider this a replacement rather than a change, don't
    # highlight it.
    old_highlights.clear
    new_highlights.clear
  end
end

#collect_highlights(diff, old_highlights, new_highlights) ⇒ Object 



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# File 'lib/refiner.rb', line 27

def collect_highlights(diff, old_highlights, new_highlights)
  diff.each do |section|
    section.each do |highlight|
      case highlight.action
      when '-'
        old_highlights << highlight.position
      when '+'
        new_highlights << highlight.position
      else
        fail("Unsupported diff type: <#{type}>")
      end
    end
  end
end

#create_one_to_many_refinements(old, new, old_highlights, new_highlights) ⇒ Object

After returning from this method, both @refined_old and @refined_new must have been set to reasonable values.

Returns false if the preconditions for using this method aren’t fulfilled



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# File 'lib/refiner.rb', line 119

def create_one_to_many_refinements(old, new, old_highlights, new_highlights)
  # If things have been removed from the first line, the specialized
  # highlighting won't work
  return false if old_highlights.count > 0

  # If the first line was replaced rather than updated, the specialized
  # highlighting won't work
  return false if new_highlights.count == 0

  # Specialized highlighting requires exactly one old line
  return false if old.lines.count != 1

  lines = new.lines
  # Specialized highlighting requires two or more new lines
  return false if lines.count < 2

  @refined_old = ''

  refined_line_1 =
    render_refinement(' ', '', lines[0], new_highlights,
                      highlight_color: GREEN)

  line_2_index_0 = lines[0].length
  refined_remaining_lines = render_refinement('+', GREEN,
                                              lines[1..-1].join,
                                              new_highlights,
                                              base_index: line_2_index_0)

  @refined_new = refined_line_1 + refined_remaining_lines

  return true
end

#create_refinements(old, new, old_highlights, new_highlights) ⇒ Object

After returning from this method, both @refined_old and @refined_new must have been set to reasonable values.



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# File 'lib/refiner.rb', line 110

def create_refinements(old, new, old_highlights, new_highlights)
  @refined_old = render_refinement('-', RED, old, old_highlights)
  @refined_new = render_refinement('+', GREEN, new, new_highlights)
end

#render_refinement(prefix, color, string, highlights, base_index: 0, highlight_color: '') ⇒ Object 



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# File 'lib/refiner.rb', line 98

def render_refinement(prefix, color, string, highlights,
                      base_index: 0, highlight_color: '')
  return_me = DiffString.new(prefix, color)
  string.each_char.with_index do |char, index|
    highlight = highlights.include?(index + base_index)
    return_me.add(char, highlight, highlight ? highlight_color : '')
  end
  return return_me.to_s
end

#should_highlight?(old, new) ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/refiner.rb', line 55

def should_highlight?(old, new)
  return false if old.empty? || new.empty?

  # The 15_000 constant has been determined using the "benchmark"
  # program in our bin/ directory.
  return false if old.length + new.length > 15_000

  return true
end

#try_highlight(old, new) ⇒ Object 



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# File 'lib/refiner.rb', line 65

def try_highlight(old, new)
  old_highlights = Set.new
  new_highlights = Set.new
  if should_highlight?(old, new)
    collect_highlights(Diff::LCS.diff(old, new),
                       old_highlights,
                       new_highlights)

    censor_highlights(old, new, old_highlights, new_highlights)
  end

  return old_highlights, new_highlights
end

#try_highlight_initial_lines(old, new) ⇒ Object 



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# File 'lib/refiner.rb', line 79

def try_highlight_initial_lines(old, new)
  old_line_count = old.lines.count
  new_line_count = new.lines.count
  if old_line_count == new_line_count
    return Set.new, Set.new
  end

  min_line_count = [old_line_count, new_line_count].min
  if min_line_count == 0
    return Set.new, Set.new
  end

  # Truncate old and new so they have the same number of lines
  old = old.lines[0..(min_line_count - 1)].join
  new = new.lines[0..(min_line_count - 1)].join

  return try_highlight(old, new)
end