60 lines
1.9 KiB
Ruby
60 lines
1.9 KiB
Ruby
module RelativePositioning
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extend ActiveSupport::Concern
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MIN_POSITION = 0
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MAX_POSITION = Gitlab::Database::MAX_INT_VALUE
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def min_relative_position
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self.class.in_projects(project.id).minimum(:relative_position)
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end
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def max_relative_position
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self.class.in_projects(project.id).maximum(:relative_position)
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end
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def move_between(before, after)
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return move_to_end unless after
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return move_to_top unless before
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pos_before = before.relative_position
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pos_after = after.relative_position
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if pos_after && (pos_before == pos_after)
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self.relative_position = pos_before
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before.decrement! :relative_position
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after.increment! :relative_position
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else
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self.relative_position = position_between(pos_before, pos_after)
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end
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end
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def move_to_top
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self.relative_position = position_between(MIN_POSITION, min_relative_position)
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end
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def move_to_end
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self.relative_position = position_between(max_relative_position, MAX_POSITION)
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end
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def move_between!(*args)
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move_between(*args) && save!
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end
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private
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# This method takes two integer values (positions) and
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# calculates some random position between them. The range is huge as
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# the maximum integer value is 2147483647. Ideally, the calculated value would be
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# exactly between those terminating values, but this will introduce possibility of a race condition
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# so two or more issues can get the same value, we want to avoid that and we also want to avoid
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# using a lock here. If we have two issues with distance more than one thousand, we are OK.
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# Given the huge range of possible values that integer can fit we shoud never face a problem.
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def position_between(pos_before, pos_after)
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pos_before ||= MIN_POSITION
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pos_after ||= MAX_POSITION
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pos_before, pos_after = [pos_before, pos_after].sort
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rand(pos_before.next..pos_after.pred)
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end
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end
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