139 lines
3.9 KiB
Ruby
139 lines
3.9 KiB
Ruby
module RelativePositioning
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extend ActiveSupport::Concern
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MIN_POSITION = 0
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START_POSITION = Gitlab::Database::MAX_INT_VALUE / 2
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MAX_POSITION = Gitlab::Database::MAX_INT_VALUE
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IDEAL_DISTANCE = 500
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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 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
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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
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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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# If there is no place to insert an issue we need to create one by moving the before issue closer
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# to its predecessor. This process will recursively move all the predecessors until we have a place
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if (after.relative_position - before.relative_position) < 2
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before.move_before
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@positionable_neighbours = [before]
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end
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self.relative_position = position_between(before.relative_position, after.relative_position)
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end
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def move_after(before = self)
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pos_before = before.relative_position
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pos_after = before.next_relative_position
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if before.shift_after?
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issue_to_move = self.class.in_projects(project.id).find_by!(relative_position: pos_after)
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issue_to_move.move_after
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@positionable_neighbours = [issue_to_move]
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pos_after = issue_to_move.relative_position
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end
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self.relative_position = position_between(pos_before, pos_after)
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end
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def move_before(after = self)
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pos_after = after.relative_position
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pos_before = after.prev_relative_position
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if after.shift_before?
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issue_to_move = self.class.in_projects(project.id).find_by!(relative_position: pos_before)
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issue_to_move.move_before
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@positionable_neighbours = [issue_to_move]
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pos_before = issue_to_move.relative_position
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end
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self.relative_position = position_between(pos_before, pos_after)
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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 || START_POSITION, MAX_POSITION)
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end
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# Indicates if there is an issue that should be shifted to free the place
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def shift_after?
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next_pos = next_relative_position
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next_pos && (next_pos - relative_position) == 1
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end
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# Indicates if there is an issue that should be shifted to free the place
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def shift_before?
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prev_pos = prev_relative_position
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prev_pos && (relative_position - prev_pos) == 1
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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 the position between them. The range is huge as
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# the maximum integer value is 2147483647. We are incrementing position by IDEAL_DISTANCE * 2 every time
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# when we have enough space. If distance is less then IDEAL_DISTANCE we are calculating an average number
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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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halfway = (pos_after + pos_before) / 2
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distance_to_halfway = pos_after - halfway
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if distance_to_halfway < IDEAL_DISTANCE
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halfway
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else
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if pos_before == MIN_POSITION
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pos_after - IDEAL_DISTANCE
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elsif pos_after == MAX_POSITION
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pos_before + IDEAL_DISTANCE
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else
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halfway
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end
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end
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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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