discourse/lib/gaps.rb

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# frozen_string_literal: true
#
# This is used for finding the gaps between a subset of elements in an array
# and the original layout. We use this in Discourse to find gaps between posts.
#
# Note that we will only return a gap as 'before' or 'after', not both. We only
# want to display the gap once.
#
class Gaps
attr_reader :before, :after
def initialize(subset, original)
@before = {}
@after = {}
@subset = subset
@original = original
find_gaps
end
def empty?
@before.size == 0 && @after.size == 0
end
def find_gaps
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return if @subset.nil? || @original.nil?
i = j = 0
gaps = {}
current_gap = []
while
e1 = @subset[i]
e2 = @original[j]
if (e1 == e2)
if current_gap.size > 0
@before[e1] = current_gap.dup
current_gap = []
end
i = i + 1
else
current_gap << e2
end
j = j + 1
break if (i == @subset.size) || (j == @original.size)
end
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@after[@subset[i - 1]] = @original[j..-1] if j < @original.size
end
end