class RuboCop::Cop::Lint::BlockAlignment

def alt_start_msg(start_loc, source_line_column)
  if style != :either
    ''
  elsif start_loc.line == source_line_column[:line] &&
        start_loc.column == source_line_column[:column]
    ''
  else
    ' or ' + format_source_line_column(source_line_column)
  end
end

def autocorrect(node)
  ancestor_node = start_for_block_node(node)
  source = node.source_range.source_buffer
  lambda do |corrector|
    starting_position_of_block_end = node.loc.end.begin_pos
    end_col = node.loc.end.column
    start_col = compute_start_col(ancestor_node, node)
    if end_col < start_col
      delta = start_col - end_col
      corrector.insert_before(node.loc.end, ' ' * delta)
    elsif end_col > start_col
      range_start = starting_position_of_block_end + start_col - end_col
      range = Parser::Source::Range.new(source, range_start,
                                        starting_position_of_block_end)
      corrector.remove(range)
    end
  end
end

def check_block_alignment(start_node, block_node)
  end_loc = block_node.loc.end
  return unless begins_its_line?(end_loc)
  start_loc = start_node.source_range
  return unless start_loc.column != end_loc.column ||
                style == :start_of_block
  do_source_line_column =
    compute_do_source_line_column(block_node, end_loc)
  return unless do_source_line_column
  error_source_line_column = if style == :start_of_block
                               do_source_line_column
                             else
                               loc_to_source_line_column(start_loc)
                             end
  fmt = format(
    MSG,
    format_source_line_column(loc_to_source_line_column(end_loc)),
    format_source_line_column(error_source_line_column),
    alt_start_msg(start_loc, do_source_line_column)
  )
  add_offense(block_node, end_loc, fmt)
end

def compute_do_source_line_column(node, end_loc)
  do_loc = node.loc.begin # Actually it's either do or {.
  # We've found that "end" is not aligned with the start node (which
  # can be a block, a variable assignment, etc). But we also allow
  # the "end" to be aligned with the start of the line where the "do"
  # is, which is a style some people use in multi-line chains of
  # blocks.
  match = /\S.*/.match(do_loc.source_line)
  indentation_of_do_line = match.begin(0)
  return unless end_loc.column != indentation_of_do_line ||
                style == :start_of_line
  {
    source: match[0],
    line: do_loc.line,
    column: indentation_of_do_line
  }
end

def compute_start_col(ancestor_node, node)
  if style == :start_of_block
    do_loc = node.loc.begin
    return do_loc.source_line =~ /\S/
  end
  (ancestor_node || node).source_range.column
end

def format_source_line_column(source_line_column)
  "`#{source_line_column[:source]}` at #{source_line_column[:line]}, " \
  "#{source_line_column[:column]}"
end

def loc_to_source_line_column(loc)
  {
    source: loc.source.lines.to_a.first.chomp,
    line: loc.line,
    column: loc.column
  }
end

def on_block(node)
  check_block_alignment(start_for_block_node(node), node)
end

def parameter_name
  'AlignWith'
end

def start_for_block_node(block_node)
  # Which node should we align the 'end' with?
  result = block_node
  while (parent = result.parent)
    break if !parent || !parent.loc
    break if parent.loc.line != block_node.loc.line &&
             !parent.masgn_type?
    break unless block_end_align_target?(parent, result)
    result = parent
  end
  # In offense message, we want to show the assignment LHS rather than
  # the entire assignment
  result, = *result while result.op_asgn_type? || result.masgn_type?
  result
end