class RuboCop::Cop::Style::SpaceAroundBlockParameters

def autocorrect(range)
  lambda do |corrector|
    case range.source
    when /^\s+$/ then corrector.remove(range)
    else              corrector.insert_after(range, ' ')
    end
  end
end

def check_each_arg(args)
  args.children.butfirst.each do |arg|
    expr = arg.source_range
    check_no_space(range_with_surrounding_space(expr, :left).begin_pos,
                   expr.begin_pos - 1, 'Extra space before')
  end
end

def check_inside_pipes(args, opening_pipe, closing_pipe)
  if style == :no_space
    check_no_space_style_inside_pipes(args, opening_pipe, closing_pipe)
  elsif style == :space
    check_space_style_inside_pipes(args, opening_pipe, closing_pipe)
  end
end

def check_no_space(space_begin_pos, space_end_pos, msg)
  return if space_begin_pos >= space_end_pos
  range = Parser::Source::Range.new(processed_source.buffer,
                                    space_begin_pos, space_end_pos)
  add_offense(range, range, "#{msg} block parameter detected.")
end

def check_no_space_style_inside_pipes(args, opening_pipe, closing_pipe)
  first = args.first.source_range
  last = args.last.source_range
  check_no_space(opening_pipe.end_pos, first.begin_pos,
                 'Space before first')
  check_no_space(last_end_pos_inside_pipes(last.end_pos),
                 closing_pipe.begin_pos, 'Space after last')
end

def check_space(space_begin_pos, space_end_pos, range, msg)
  return if space_begin_pos != space_end_pos
  add_offense(range, range, "Space #{msg} missing.")
end

def check_space_style_inside_pipes(args, opening_pipe, closing_pipe)
  first = args.first.source_range
  last = args.last.source_range
  last_end_pos = last_end_pos_inside_pipes(last.end_pos)
  check_space(opening_pipe.end_pos, first.begin_pos, first,
              'before first block parameter')
  check_space(last_end_pos, closing_pipe.begin_pos, last,
              'after last block parameter')
  check_no_space(opening_pipe.end_pos, first.begin_pos - 1,
                 'Extra space before first')
  check_no_space(last_end_pos + 1, closing_pipe.begin_pos,
                 'Extra space after last')
end

def last_end_pos_inside_pipes(pos)
  processed_source.buffer.source[pos] == ',' ? pos + 1 : pos
end

def on_block(node)
  _method, args, body = *node
  opening_pipe = args.loc.begin
  closing_pipe = args.loc.end
  return unless !args.children.empty? && opening_pipe
  check_inside_pipes(args.children, opening_pipe, closing_pipe)
  if body
    check_space(closing_pipe.end_pos, body.source_range.begin_pos,
                closing_pipe, 'after closing `|`')
  end
  check_each_arg(args)
end

def parameter_name
  'EnforcedStyleInsidePipes'
end