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|
# frozen_string_literal: true
module RelativePositioning
extend ActiveSupport::Concern
MIN_POSITION = 0
START_POSITION = Gitlab::Database::MAX_INT_VALUE / 2
MAX_POSITION = Gitlab::Database::MAX_INT_VALUE
IDEAL_DISTANCE = 500
included do
after_save :save_positionable_neighbours
end
class_methods do
def move_to_end(objects)
objects = objects.reject(&:relative_position)
return if objects.empty?
max_relative_position = objects.first.max_relative_position
self.transaction do
objects.each do |object|
relative_position = position_between(max_relative_position, MAX_POSITION)
object.relative_position = relative_position
max_relative_position = relative_position
object.save(touch: false)
end
end
end
# This method takes two integer values (positions) and
# calculates the position between them. The range is huge as
# the maximum integer value is 2147483647. We are incrementing position by IDEAL_DISTANCE * 2 every time
# when we have enough space. If distance is less then IDEAL_DISTANCE we are calculating an average number
def position_between(pos_before, pos_after)
pos_before ||= MIN_POSITION
pos_after ||= MAX_POSITION
pos_before, pos_after = [pos_before, pos_after].sort
halfway = (pos_after + pos_before) / 2
distance_to_halfway = pos_after - halfway
if distance_to_halfway < IDEAL_DISTANCE
halfway
else
if pos_before == MIN_POSITION
pos_after - IDEAL_DISTANCE
elsif pos_after == MAX_POSITION
pos_before + IDEAL_DISTANCE
else
halfway
end
end
end
end
def min_relative_position(&block)
calculate_relative_position('MIN', &block)
end
def max_relative_position(&block)
calculate_relative_position('MAX', &block)
end
def prev_relative_position
prev_pos = nil
if self.relative_position
prev_pos = max_relative_position do |relation|
relation.where('relative_position < ?', self.relative_position)
end
end
prev_pos
end
def next_relative_position
next_pos = nil
if self.relative_position
next_pos = min_relative_position do |relation|
relation.where('relative_position > ?', self.relative_position)
end
end
next_pos
end
def move_between(before, after)
return move_after(before) unless after
return move_before(after) unless before
# If there is no place to insert an issue we need to create one by moving the before issue closer
# to its predecessor. This process will recursively move all the predecessors until we have a place
if (after.relative_position - before.relative_position) < 2
before.move_before
@positionable_neighbours = [before] # rubocop:disable Gitlab/ModuleWithInstanceVariables
end
self.relative_position = self.class.position_between(before.relative_position, after.relative_position)
end
def move_after(before = self)
pos_before = before.relative_position
pos_after = before.next_relative_position
if before.shift_after?
issue_to_move = self.class.in_parents(parent_ids).find_by!(relative_position: pos_after)
issue_to_move.move_after
@positionable_neighbours = [issue_to_move] # rubocop:disable Gitlab/ModuleWithInstanceVariables
pos_after = issue_to_move.relative_position
end
self.relative_position = self.class.position_between(pos_before, pos_after)
end
def move_before(after = self)
pos_after = after.relative_position
pos_before = after.prev_relative_position
if after.shift_before?
issue_to_move = self.class.in_parents(parent_ids).find_by!(relative_position: pos_before)
issue_to_move.move_before
@positionable_neighbours = [issue_to_move] # rubocop:disable Gitlab/ModuleWithInstanceVariables
pos_before = issue_to_move.relative_position
end
self.relative_position = self.class.position_between(pos_before, pos_after)
end
def move_to_end
self.relative_position = self.class.position_between(max_relative_position || START_POSITION, MAX_POSITION)
end
def move_to_start
self.relative_position = self.class.position_between(min_relative_position || START_POSITION, MIN_POSITION)
end
# Indicates if there is an issue that should be shifted to free the place
def shift_after?
next_pos = next_relative_position
next_pos && (next_pos - relative_position) == 1
end
# Indicates if there is an issue that should be shifted to free the place
def shift_before?
prev_pos = prev_relative_position
prev_pos && (relative_position - prev_pos) == 1
end
private
# rubocop:disable Gitlab/ModuleWithInstanceVariables
def save_positionable_neighbours
return unless @positionable_neighbours
status = @positionable_neighbours.all? { |issue| issue.save(touch: false) }
@positionable_neighbours = nil
status
end
# rubocop:enable Gitlab/ModuleWithInstanceVariables
def calculate_relative_position(calculation)
# When calculating across projects, this is much more efficient than
# MAX(relative_position) without the GROUP BY, due to index usage:
# https://gitlab.com/gitlab-org/gitlab-ce/issues/54276#note_119340977
relation = self.class
.in_parents(parent_ids)
.order(Gitlab::Database.nulls_last_order('position', 'DESC'))
.limit(1)
.group(self.class.parent_column)
relation = yield relation if block_given?
relation
.pluck(self.class.parent_column, "#{calculation}(relative_position) AS position")
.first&.
last
end
end
|
