101 lines
2.8 KiB
Ruby
101 lines
2.8 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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included do
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after_save :save_positionable_neighbours
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end
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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 prev_relative_position
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prev_pos = nil
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if self.relative_position
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prev_pos = self.class.
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in_projects(project.id).
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where('relative_position < ?', self.relative_position).
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maximum(:relative_position)
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end
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prev_pos || MIN_POSITION
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end
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def next_relative_position
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next_pos = nil
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if self.relative_position
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next_pos = self.class.
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in_projects(project.id).
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where('relative_position > ?', self.relative_position).
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minimum(:relative_position)
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end
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next_pos || MAX_POSITION
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end
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def move_between(before, after)
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return move_after(before) unless after
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return move_before(after) 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.move_before(self)
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after.move_after(self)
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@positionable_neighbours = [before, after]
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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_before(after)
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self.relative_position = position_between(after.prev_relative_position, after.relative_position)
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end
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def move_after(before)
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self.relative_position = position_between(before.relative_position, before.next_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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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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def save_positionable_neighbours
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return unless @positionable_neighbours
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status = @positionable_neighbours.all?(&:save)
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@positionable_neighbours = nil
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status
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end
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end
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