117 lines
3.4 KiB
Ruby
117 lines
3.4 KiB
Ruby
module Gitlab
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module Diff
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class InlineDiff
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# Regex to find a run of deleted lines followed by the same number of added lines
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LINE_PAIRS_PATTERN = %r{
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# Runs start at the beginning of the string (the first line) or after a space (for an unchanged line)
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(?:\A|\s)
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# This matches a number of `-`s followed by the same number of `+`s through recursion
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(?<del_ins>
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-
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\g<del_ins>?
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\+
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)
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# Runs end at the end of the string (the last line) or before a space (for an unchanged line)
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(?=\s|\z)
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}x.freeze
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attr_accessor :old_line, :new_line, :offset
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def initialize(old_line, new_line, offset: 0)
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@old_line = old_line[offset..-1]
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@new_line = new_line[offset..-1]
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@offset = offset
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end
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def inline_diffs
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# Skip inline diff if empty line was replaced with content
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return if old_line == ""
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lcp = longest_common_prefix(old_line, new_line)
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lcs = longest_common_suffix(old_line[lcp..-1], new_line[lcp..-1])
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lcp += offset
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old_length = old_line.length + offset
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new_length = new_line.length + offset
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old_diff_range = lcp..(old_length - lcs - 1)
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new_diff_range = lcp..(new_length - lcs - 1)
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old_diffs = [old_diff_range] if old_diff_range.begin <= old_diff_range.end
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new_diffs = [new_diff_range] if new_diff_range.begin <= new_diff_range.end
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[old_diffs, new_diffs]
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end
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class << self
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def for_lines(lines)
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changed_line_pairs = find_changed_line_pairs(lines)
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inline_diffs = []
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changed_line_pairs.each do |old_index, new_index|
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old_line = lines[old_index]
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new_line = lines[new_index]
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old_diffs, new_diffs = new(old_line, new_line, offset: 1).inline_diffs
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inline_diffs[old_index] = old_diffs
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inline_diffs[new_index] = new_diffs
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end
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inline_diffs
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end
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private
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# Finds pairs of old/new line pairs that represent the same line that changed
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def find_changed_line_pairs(lines)
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# Prefixes of all diff lines, indicating their types
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# For example: `" - + -+ ---+++ --+ -++"`
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line_prefixes = lines.each_with_object("") { |line, s| s << line[0] }.gsub(/[^ +-]/, ' ')
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changed_line_pairs = []
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line_prefixes.scan(LINE_PAIRS_PATTERN) do
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# For `"---+++"`, `begin_index == 0`, `end_index == 6`
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begin_index, end_index = Regexp.last_match.offset(:del_ins)
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# For `"---+++"`, `changed_line_count == 3`
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changed_line_count = (end_index - begin_index) / 2
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halfway_index = begin_index + changed_line_count
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(begin_index...halfway_index).each do |i|
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# For `"---+++"`, index 1 maps to 1 + 3 = 4
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changed_line_pairs << [i, i + changed_line_count]
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end
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end
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changed_line_pairs
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end
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end
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private
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def longest_common_prefix(a, b)
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max_length = [a.length, b.length].max
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length = 0
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(0..max_length - 1).each do |pos|
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old_char = a[pos]
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new_char = b[pos]
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break if old_char != new_char
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length += 1
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end
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length
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end
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def longest_common_suffix(a, b)
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longest_common_prefix(a.reverse, b.reverse)
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end
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end
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end
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end
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