class RuboCop::Cop::Layout::BlockAlignment

def add_space_before(loc, delta)
  ->(corrector) { corrector.insert_before(loc, ' ' * delta) }
end

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)
  start_col = compute_start_col(ancestor_node, node)
  loc_end = node.loc.end
  delta = start_col - loc_end.column
  if delta > 0
    add_space_before(loc_end, delta)
  elsif delta < 0
    remove_space_before(loc_end.begin_pos, -delta)
  end
end

def block_end_align_target(node)
  lineage = [node, *node.ancestors]
  target = lineage.each_cons(2) do |current, parent|
    break current if end_align_target?(current, parent)
  end
  target || lineage.last
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
  register_offense(
    block_node,
    start_loc,
    end_loc,
    do_source_line_column
  )
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 disqualified_parent?(parent, node)
  parent && parent.loc && parent.first_line != node.first_line &&
    !parent.masgn_type?
end

def end_align_target?(node, parent)
  disqualified_parent?(parent, node) ||
    !block_end_align_target?(parent, node)
end

def format_message(start_loc, end_loc, do_source_line_column,
                   error_source_line_column)
  format(
    MSG,
    current: format_source_line_column(
      loc_to_source_line_column(end_loc)
    ),
    prefer: format_source_line_column(error_source_line_column),
    alt_prefer: alt_start_msg(start_loc, do_source_line_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 register_offense(block_node,
                     start_loc,
                     end_loc,
                     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
  message = format_message(start_loc, end_loc, do_source_line_column,
                           error_source_line_column)
  add_offense(block_node, location: end_loc, message: message)
end

def remove_space_before(end_pos, delta)
  range = range_between(end_pos - delta, end_pos)
  ->(corrector) { corrector.remove(range) }
end

def start_for_block_node(block_node)
  # Which node should we align the 'end' with?
  result = block_end_align_target(block_node)
  # 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

def style_parameter_name
  'EnforcedStyleAlignWith'
end