class RuboCop::Cop::Layout::EmptyLineBetweenDefs

end
def b
end
def a
# good
@example
end
def b
end
def a
# bad
@example
one line methods definitions are an offense
`AllowAdjacentOneLineDefs` can be used to configure is adjacent
empty lines.
an array (e.g. [1, 2]) to specificy a minimum and a maximum of
`NumberOfEmptyLines` can be and integer (e.g. 1 by default) or
separated by one empty line.
This cop checks whether method definitions are

def self.autocorrect_incompatible_with 

def self.autocorrect_incompatible_with
  [Layout::EmptyLines]
end

def autocorrect(node) 

def autocorrect(node)
  prev_def = prev_node(node)
  # finds position of first newline
  end_pos = prev_def.loc.end.end_pos
  source_buffer = prev_def.loc.end.source_buffer
  newline_pos = source_buffer.source.index("\n", end_pos)
  count = blank_lines_count_between(prev_def, node)
  if count > maximum_empty_lines
    autocorrect_remove_lines(newline_pos, count)
  else
    autocorrect_insert_lines(newline_pos, count)
  end
end

def autocorrect_insert_lines(newline_pos, count) 

def autocorrect_insert_lines(newline_pos, count)
  difference = minimum_empty_lines - count
  where_to_insert = range_between(newline_pos, newline_pos + 1)
  lambda do |corrector|
    corrector.insert_after(where_to_insert, "\n" * difference)
  end
end

def autocorrect_remove_lines(newline_pos, count) 

def autocorrect_remove_lines(newline_pos, count)
  difference = count - maximum_empty_lines
  range_to_remove = range_between(newline_pos, newline_pos + difference)
  lambda do |corrector|
    corrector.remove(range_to_remove)
  end
end

def blank_lines_between?(first_def_node, second_def_node) 

def blank_lines_between?(first_def_node, second_def_node)
  count = blank_lines_count_between(first_def_node, second_def_node)
  (minimum_empty_lines..maximum_empty_lines).cover?(count)
end

def blank_lines_count_between(first_def_node, second_def_node) 

def blank_lines_count_between(first_def_node, second_def_node)
  lines_between_defs(first_def_node, second_def_node).count(&:blank?)
end

def check_defs(nodes) 

def check_defs(nodes)
  return if blank_lines_between?(*nodes)
  return if multiple_blank_lines_groups?(*nodes)
  return if nodes.all?(&:single_line?) &&
            cop_config['AllowAdjacentOneLineDefs']
  add_offense(nodes.last, :keyword)
end

def def_end(node) 

def def_end(node)
  node.loc.end.line
end

def def_node?(node) 

def def_node?(node)
  return unless node
  node.def_type? || node.defs_type?
end

def def_start(node) 

def def_start(node)
  node.loc.keyword.line
end

def lines_between_defs(first_def_node, second_def_node) 

def lines_between_defs(first_def_node, second_def_node)
  line_range = def_end(first_def_node)..(def_start(second_def_node) - 2)
  processed_source.lines[line_range]
end

def maximum_empty_lines 

def maximum_empty_lines
  Array(cop_config['NumberOfEmptyLines']).last
end

def minimum_empty_lines 

def minimum_empty_lines
  Array(cop_config['NumberOfEmptyLines']).first
end

def multiple_blank_lines_groups?(first_def_node, second_def_node) 

def multiple_blank_lines_groups?(first_def_node, second_def_node)
  lines = lines_between_defs(first_def_node, second_def_node)
  blank_start = lines.each_index.select { |i| lines[i].blank? }.max
  non_blank_end = lines.each_index.reject { |i| lines[i].blank? }.min
  return false if blank_start.nil? || non_blank_end.nil?
  blank_start > non_blank_end
end

def on_begin(node)

it on each def.
doing a linear scan over siblings, so we don't want to call
efficiently access a node's predecessor; #prev_node ends up
so that we can walk over pairs of consecutive nodes and
We operate on `begin` nodes, instead of using `OnMethodDef`, 
def on_begin(node)
  node.children.each_cons(2) do |prev, n|
    nodes = [prev, n]
    check_defs(nodes) if nodes.all?(&method(:def_node?))
  end
end

def prev_node(node) 

def prev_node(node)
  return nil unless node.sibling_index > 0
  node.parent.children[node.sibling_index - 1]
end