59 lines
1.8 KiB
Ruby
59 lines
1.8 KiB
Ruby
# frozen_string_literal: true
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module Gitlab
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module Diff
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class PairSelector
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include Enumerable
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# Regex to find a run of deleted lines followed by the same number of added lines
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# rubocop: disable Lint/MixedRegexpCaptureTypes
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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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# rubocop: enable Lint/MixedRegexpCaptureTypes
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def initialize(lines)
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@lines = lines
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end
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# Finds pairs of old/new line pairs that represent the same line that changed
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# rubocop: disable CodeReuse/ActiveRecord
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def each
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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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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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yield [i, i + changed_line_count]
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end
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end
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end
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# rubocop: enable CodeReuse/ActiveRecord
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private
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attr_reader :lines
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end
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end
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end
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