Class: HTMLDiff::DiffBuilder

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

Instance Method Summary collapse

Constructor Details

#initialize(old_version, new_version) ⇒ DiffBuilder

Returns a new instance of DiffBuilder.



18
19
20
21
22
 
# File 'lib/prettypatch/diff.rb', line 18

def initialize(old_version, new_version)
  @old_version, @new_version = old_version, new_version
  split_inputs_to_words
  index_new_words
end

Instance Method Details

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



138
139
140
141
142
143
144
145
146
147
 
# File 'lib/prettypatch/diff.rb', line 138

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 



149
150
151
152
153
154
155
156
 
# File 'lib/prettypatch/diff.rb', line 149

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

#explode(sequence) ⇒ Object 



158
159
160
 
# File 'lib/prettypatch/diff.rb', line 158

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

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



102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
 
# File 'lib/prettypatch/diff.rb', line 102

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 



29
30
31
32
 
# File 'lib/prettypatch/diff.rb', line 29

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

#matching_blocks ⇒ Object 



81
82
83
84
85
 
# File 'lib/prettypatch/diff.rb', line 81

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

#operations ⇒ Object 



34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
 
# File 'lib/prettypatch/diff.rb', line 34

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

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



87
88
89
90
91
92
93
94
95
96
97
98
99
100
 
# File 'lib/prettypatch/diff.rb', line 87

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

#split_inputs_to_words ⇒ Object 



24
25
26
27
 
# File 'lib/prettypatch/diff.rb', line 24

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