Module: FastTree::Model::ClassMethods

Defined in:
lib/fast_tree/model.rb

Overview

Class Methods

Instance Method Summary collapse

Instance Method Details

#_create_parent_embedded_space(children) ⇒ Object 



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# File 'lib/fast_tree/model.rb', line 60

def _create_parent_embedded_space(children)
  left  = children.max {|c| c.l_ptr}.l_ptr
  right = children.min {|c| c.r_ptr}.r_ptr

  sql = <<-"EOS"
UPDATE #{self.to_s.underscore.pluralize}
  SET l_ptr = CASE
          WHEN l_ptr >= #{left}
            AND r_ptr <= #{right}
            THEN l_ptr + 1
          WHEN l_ptr > #{right}
            THEN l_ptr + 2
          ELSE l_ptr
          END,
r_ptr = CASE
          WHEN l_ptr >= #{left}
            AND r_ptr <= #{right}
            THEN r_ptr + 1
          WHEN l_ptr < #{left}
            AND r_ptr > #{right}
            THEN r_ptr + 2
          WHEN l_ptr > #{right}
            THEN r_ptr + 2
          ELSE r_ptr
        END,
depth = CASE
          WHEN l_ptr >= #{left}
            AND r_ptr <= #{right}
            THEN depth + 1
          ELSE depth
        END
  WHERE r_ptr > #{left}
  EOS

  ActiveRecord::Base.connection.execute(sql)

  # return left and right pointers between which parent is embedded
  {l_ptr: left, r_ptr: right + 2}
end

#add_parent(parent, children, &block) ⇒ Object

structure operation



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# File 'lib/fast_tree/model.rb', line 20

def add_parent(parent, children, &block)
  parent_depth = children.first.depth

  # create space for parent
  ptrs = _create_parent_embedded_space(children)

  # parent node's pointer
  parent.l_ptr = ptrs[:l_ptr]
  parent.r_ptr = ptrs[:r_ptr]
  parent.depth = parent_depth
  parent.save
end

#create_parent(attributes = {}, children, &block) ⇒ Object 



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# File 'lib/fast_tree/model.rb', line 33

def create_parent(attributes = {}, children, &block)
  parent_depth = children.first.depth

  # create space for parent
  ptrs = _create_parent_embedded_space(children)

  # parent node's pointer
  attributes[:l_ptr] = ptrs[:l_ptr]
  attributes[:r_ptr] = ptrs[:r_ptr]
  attributes[:depth] = parent_depth

  self.create(attributes, &block)
end

#create_tree(attributes = {}, &block) ⇒ Object 



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# File 'lib/fast_tree/model.rb', line 47

def create_tree(attributes={}, &block)
  root = self.find_root
  if root
    root
  else
    attributes[:l_ptr] = 0
    attributes[:r_ptr] = 1
    attributes[:depth] = 0
    self.create(attributes, &block)
  end
end

#find_root ⇒ Object

model operation



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# File 'lib/fast_tree/model.rb', line 104

def find_root
  self.find_by(l_ptr: 0)
end

#find_subtree_by_root(node) ⇒ Object 



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# File 'lib/fast_tree/model.rb', line 108

def find_subtree_by_root(node)
  l_ptr = node.l_ptr
  r_ptr = node.r_ptr

  self.where(self.arel_table[:l_ptr].gteq(l_ptr))
      .where(self.arel_table[:r_ptr].lteq(r_ptr))
end

#print_subtree(root) ⇒ Object

for debugging



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# File 'lib/fast_tree/model.rb', line 120

def print_subtree(root)
  puts("printing sub tree for #{root.name}...")
  subtree = find_subtree_by_root(root)
  subtree.order(l_ptr: :asc).each do |st_node|
    st_node.reload
    # white spaces on the left
    wsl = st_node.l_ptr.times.map{|s| "_"}.join('')
    # arrows
    ars = (st_node.r_ptr - st_node.l_ptr ).times.map{|s| "-"}.join('')
    # white spaces on the right
    wsr = (root.width + 2 - wsl.size - ars.size).times.map{|s| " "}.join('')

    puts("#{wsl}<#{ars}>#{wsr} ... #{st_node.name}")
  end
  puts("done.\n")
end