Bringing various things inline with the current state of Rails develolpment

lib/diff.rb

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+# heavily based off difflib.py - see that file for documentation
+# ported from Python by Bill Atkins
+
+# This does not support all features offered by difflib; it 
+# implements only the subset of features necessary
+# to support a Ruby version of HTML Differ.  You're welcome to finish this off.
+
+# By default, String#each iterates by line.  This isn't really appropriate
+# for diff, so often a string will be split by // to get an array of one-
+# character strings.
+
+# Some methods in Diff are untested and are not guaranteed to work.  The
+# methods in HTMLDiff and any methods it calls should work quite well.
+
+# changes by DenisMertz
+# * main change:
+# ** get the tag soup away
+#    the tag soup problem was first reported with <p> tags, but it appeared also with
+#    <li>, <ul> etc... tags 
+#   this version should mostly fix these problems
+# ** added a Builder class to manage the creation of the final htmldiff
+# * minor changes:
+# ** use symbols instead of string to represent opcodes 
+# ** small fix to html2list
+#
+
+module Enumerable
+  def reduce(init)
+    result = init
+    each { |item| result = yield(result, item) }
+    result
+  end
+end
+
+module Diff
+
+  class SequenceMatcher
+    def initialize(a=[''], b=[''], isjunk=nil, byline=false)
+      a = (!byline and a.kind_of? String) ? a.split(//) : a
+      b = (!byline and b.kind_of? String) ? b.split(//) : b
+      @isjunk = isjunk || proc {}
+      set_seqs a, b
+    end
+
+    def set_seqs(a, b)
+      set_seq_a a
+      set_seq_b b
+    end
+
+    def set_seq_a(a)
+      @a = a
+      @matching_blocks = @opcodes = nil
+    end
+
+    def set_seq_b(b)
+      @b = b
+      @matching_blocks = @opcodes = nil
+      chain_b
+    end
+
+    def chain_b
+      @fullbcount = nil
+      @b2j = {}
+      pophash = {}
+      junkdict = {}
+      
+      @b.each_with_index do |elt, i|
+        if @b2j.has_key? elt
+          indices = @b2j[elt]
+          if @b.length >= 200 and indices.length * 100 > @b.length
+            pophash[elt] = 1
+            indices.clear
+          else
+            indices.push i
+          end
+        else
+          @b2j[elt] = [i]
+        end
+      end
+        
+      pophash.each_key { |elt| @b2j.delete elt }
+      
+      junkdict = {}
+        
+      unless @isjunk.nil?
+        [pophash, @b2j].each do |d|
+          d.each_key do |elt|
+            if @isjunk.call(elt)
+              junkdict[elt] = 1
+              d.delete elt
+            end
+          end
+        end
+      end
+      
+      @isbjunk = junkdict.method(:has_key?)
+      @isbpopular = junkdict.method(:has_key?)
+    end
+    
+    def find_longest_match(alo, ahi, blo, bhi)
+      besti, bestj, bestsize = alo, blo, 0
+      
+      j2len = {}
+      
+      (alo..ahi).step do |i|
+        newj2len = {}
+        (@b2j[@a[i]] || []).each do |j|
+          if j < blo
+            next
+          end
+          if j >= bhi
+            break
+          end
+          
+          k = newj2len[j] = (j2len[j - 1] || 0) + 1
+          if k > bestsize
+            besti, bestj, bestsize = i - k + 1, j - k + 1, k
+          end
+        end
+        j2len = newj2len
+      end
+      
+      while besti > alo and bestj > blo and
+          not @isbjunk.call(@b[bestj-1]) and
+          @a[besti-1] == @b[bestj-1]
+        besti, bestj, bestsize = besti-1, bestj-1, bestsize+1
+      end
+      
+      while besti+bestsize < ahi and bestj+bestsize < bhi and
+          not @isbjunk.call(@b[bestj+bestsize]) and
+          @a[besti+bestsize] == @b[bestj+bestsize]
+        bestsize += 1
+      end
+      
+      while besti > alo and bestj > blo and
+          @isbjunk.call(@b[bestj-1]) and
+          @a[besti-1] == @b[bestj-1]
+        besti, bestj, bestsize = besti-1, bestj-1, bestsize+1
+      end
+      
+      while besti+bestsize < ahi and bestj+bestsize < bhi and
+          @isbjunk.call(@b[bestj+bestsize]) and
+          @a[besti+bestsize] == @b[bestj+bestsize]
+        bestsize += 1
+      end
+      
+      [besti, bestj, bestsize]
+    end
+    
+    def get_matching_blocks
+      return @matching_blocks unless @matching_blocks.nil? or 
+        @matching_blocks.empty?
+      
+      @matching_blocks = []
+      la, lb = @a.length, @b.length
+      match_block_helper(0, la, 0, lb, @matching_blocks)
+      @matching_blocks.push [la, lb, 0]
+    end
+    
+    def match_block_helper(alo, ahi, blo, bhi, answer)
+      i, j, k = x = find_longest_match(alo, ahi, blo, bhi)
+      if not k.zero?
+        if alo < i and blo < j
+          match_block_helper(alo, i, blo, j, answer)
+        end
+        answer.push x
+        if i + k < ahi and j + k < bhi
+          match_block_helper(i + k, ahi, j + k, bhi, answer)
+        end
+      end
+    end
+    
+    def get_opcodes
+      unless @opcodes.nil? or @opcodes.empty?
+        return @opcodes
+      end
+
+      i = j = 0
+      @opcodes = answer = []
+      get_matching_blocks.each do |ai, bj, size|
+        tag = if i < ai and j < bj
+                :replace
+              elsif i < ai
+                :delete
+              elsif j < bj 
+                :insert
+              end
+
+        answer.push [tag, i, ai, j, bj] if tag
+        
+        i, j = ai + size, bj + size
+        
+        answer.push [:equal, ai, i, bj, j] unless size.zero?
+        
+      end
+      return answer
+    end
+
+    # XXX: untested
+    def get_grouped_opcodes(n=3)
+      codes = get_opcodes
+      if codes[0][0] == :equal
+        tag, i1, i2, j1, j2 = codes[0]
+        codes[0] = tag, [i1, i2 - n].max, i2, [j1, j2-n].max, j2
+      end
+      
+      if codes[-1][0] == :equal
+        tag, i1, i2, j1, j2 = codes[-1]
+        codes[-1] = tag, i1, min(i2, i1+n), j1, min(j2, j1+n)
+      end
+      nn = n + n
+      group = []
+      codes.each do |tag, i1, i2, j1, j2|
+        if tag == :equal and i2-i1 > nn
+          group.push [tag, i1, [i2, i1 + n].min, j1, [j2, j1 + n].min]
+          yield group
+          group = []
+          i1, j1 = [i1, i2-n].max, [j1, j2-n].max
+          group.push [tag, i1, i2, j1 ,j2]
+        end
+      end
+      if group and group.length != 1 and group[0][0] == :equal
+        yield group
+      end
+    end
+
+    def ratio
+      matches = get_matching_blocks.reduce(0) do |sum, triple|
+        sum + triple[-1]
+      end
+      Diff.calculate_ratio(matches, @a.length + @b.length)
+    end
+
+    def quick_ratio
+      if @fullbcount.nil? or @fullbcount.empty?
+        @fullbcount = {}
+        @b.each do |elt|
+          @fullbcount[elt] = (@fullbcount[elt] || 0) + 1
+        end
+      end
+      
+      avail = {}
+      matches = 0
+      @a.each do |elt|
+        if avail.has_key? elt
+          numb = avail[elt]
+        else
+          numb = @fullbcount[elt] || 0
+        end
+        avail[elt] = numb - 1
+        if numb > 0
+          matches += 1
+        end
+      end
+      Diff.calculate_ratio matches, @a.length + @b.length
+    end
+
+    def real_quick_ratio
+      la, lb = @a.length, @b.length
+      Diff.calculate_ratio([la, lb].min, la + lb)
+    end
+
+    protected :chain_b, :match_block_helper
+  end # end class SequenceMatcher
+
+  def self.calculate_ratio(matches, length)
+    return 1.0 if length.zero?
+    2.0 * matches / length
+  end
+
+  # XXX: untested
+  def self.get_close_matches(word, possibilities, n=3, cutoff=0.6)
+    unless n > 0
+      raise "n must be > 0: #{n}"
+    end
+    unless 0.0 <= cutoff and cutoff <= 1.0
+      raise "cutoff must be in (0.0..1.0): #{cutoff}"
+    end
+
+    result = []
+    s = SequenceMatcher.new
+    s.set_seq_b word
+    possibilities.each do |x|
+      s.set_seq_a x
+      if s.real_quick_ratio >= cutoff and
+          s.quick_ratio >= cutoff and
+          s.ratio >= cutoff
+        result.push [s.ratio, x]
+      end
+    end
+    
+    unless result.nil? or result.empty?
+      result.sort
+      result.reverse!
+      result = result[-n..-1]
+    end
+    result.collect { |score, x| x }
+  end
+
+  def self.count_leading(line, ch)
+    i, n = 0, line.length
+    while i < n and line[i].chr == ch
+      i += 1
+    end
+    i
+  end
+end
+
+
+module HTMLDiff
+  include Diff
+  class Builder
+    VALID_METHODS = [:replace, :insert, :delete, :equal]
+    def initialize(a, b)
+      @a = a
+      @b = b
+      @content = []
+    end
+
+    def do_op(opcode)
+      @opcode = opcode
+      op = @opcode[0]
+      VALID_METHODS.include?(op) or raise(NameError, "Invalid opcode #{op}")
+      self.method(op).call
+    end
+
+    def result
+      @content.join('')
+    end
+
+    #this methods have to be called via do_op(opcode) so that @opcode is set properly
+    private
+
+    def replace
+      delete("diffmod")
+      insert("diffmod")
+    end
+    
+    def insert(tagclass="diffins")
+      op_helper("ins", tagclass, @b[@opcode[3]...@opcode[4]])
+    end
+    
+    def delete(tagclass="diffdel")
+       op_helper("del", tagclass, @a[@opcode[1]...@opcode[2]])
+    end
+    
+    def equal
+      @content += @b[@opcode[3]...@opcode[4]]
+    end
+  
+    # using this as op_helper would be equivalent to the first version of diff.rb by Bill Atkins
+    def op_helper_simple(tagname, tagclass, to_add)
+      @content << "<#{tagname} class=\"#{tagclass}\">" 
+      @content += to_add
+      @content << "</#{tagname}>"
+    end
+    
+    # this tries to put <p> tags or newline chars before the opening diff tags (<ins> or <del>)
+    # or after the ending diff tags
+    # as a result the diff tags should be the "more inside" possible.
+    # this seems to work nice with html containing only paragraphs
+    # but not sure it works if there are other tags (div, span ... ? ) around
+    def op_helper(tagname, tagclass, to_add)
+      @content << to_add.shift while ( HTMLDiff.is_newline(to_add.first) or 
+                                         HTMLDiff.is_p_close_tag(to_add.first) or
+                                         HTMLDiff.is_p_open_tag(to_add.first) )
+      @content << "<#{tagname} class=\"#{tagclass}\">" 
+      @content += to_add
+      last_tags = []
+      last_tags.unshift(@content.pop) while ( HTMLDiff.is_newline(@content.last) or 
+                                         HTMLDiff.is_p_close_tag(@content.last) or
+                                         HTMLDiff.is_p_open_tag(@content.last) )
+      last_tags.unshift "</#{tagname}>"
+      @content += last_tags
+      remove_empty_diff(tagname, tagclass)
+    end
+
+    def remove_empty_diff(tagname, tagclass)
+      if @content[-2] == "<#{tagname} class=\"#{tagclass}\">" and @content[-1] == "</#{tagname}>" then
+        @content.pop
+        @content.pop
+      end
+    end
+
+  end
+  
+  def self.is_newline(x)
+    (x == "\n") or (x == "\r") or (x == "\t")
+  end
+
+  def self.is_p_open_tag(x)
+    x =~ /\A<(p|li|ul|ol|dir|dt|dl)/
+  end
+
+  def self.is_p_close_tag(x)
+    x =~ %r!\A</(p|li|ul|ol|dir|dt|dl)!
+  end
+
+  def self.diff(a, b)
+    a = html2list(a)
+    b = html2list(b)
+
+    out = Builder.new(a, b)
+    s = SequenceMatcher.new(a, b)
+
+    s.get_opcodes.each do |opcode|
+      out.do_op(opcode)
+    end
+
+    out.result 
+  end
+  
+  def self.html2list(x)
+    mode = :char
+    cur = ''
+    out = []
+    
+    x.split('').each do |c|
+      if mode == :tag
+        cur += c
+        if c == '>'
+          out.push(cur)
+          cur = ''
+          mode = :char
+        end
+      elsif mode == :char
+        if c == '<'
+          out.push cur
+          cur = c
+          mode = :tag
+        elsif c =~ /\s/
+          out.push cur + c
+          cur = ''
+        else
+          cur += c
+        end
+      end
+    end
+
+    out.push cur
+    out.find_all { |x| x != '' }
+  end
+  
+end