else_alignment.rb

# frozen_string_literal: true

module RuboCop
  module Cop
    module Layout
      # Checks the alignment of else keywords. Normally they should
      # be aligned with an if/unless/while/until/begin/def/rescue keyword, but there
      # are special cases when they should follow the same rules as the
      # alignment of end.
      #
      # @example
      #   # bad
      #   if something
      #     code
      #    else
      #     code
      #   end
      #
      #   # bad
      #   if something
      #     code
      #    elsif something
      #     code
      #   end
      #
      #   # good
      #   if something
      #     code
      #   else
      #     code
      #   end
      class ElseAlignment < Base
        include EndKeywordAlignment
        include Alignment
        include CheckAssignment
        extend AutoCorrector

        MSG = 'Align `%<else_range>s` with `%<base_range>s`.'

        def on_if(node, base = nil)
          return if ignored_node?(node)
          return unless node.else? && begins_its_line?(node.loc.else)

          check_alignment(base_range_of_if(node, base), node.loc.else)

          return unless node.elsif_conditional?

          check_nested(node.else_branch, base)
        end

        def on_rescue(node)
          return unless node.loc.respond_to?(:else) && node.loc.else

          check_alignment(base_range_of_rescue(node), node.loc.else)
        end

        def on_case(node)
          return unless node.else?

          check_alignment(node.when_branches.last.loc.keyword, node.loc.else)
        end

        def on_case_match(node)
          return unless node.else?

          check_alignment(node.in_pattern_branches.last.loc.keyword, node.loc.else)
        end

        private

        def autocorrect(corrector, node)
          AlignmentCorrector.correct(corrector, processed_source, node, column_delta)
        end

        def check_nested(node, base)
          on_if(node, base)
          ignore_node(node)
        end

        def base_range_of_if(node, base)
          if base
            base.source_range
          else
            lineage = [node, *node.each_ancestor(:if)]
            lineage.find { |parent| parent.if? || parent.unless? }.loc.keyword
          end
        end

        def base_range_of_rescue(node)
          parent = node.parent
          parent = parent.parent if parent.ensure_type?
          case parent.type
          when :def, :defs then base_for_method_definition(parent)
          when :kwbegin then parent.loc.begin
          when :block
            assignment_node = assignment_node(parent)
            if same_line?(parent, assignment_node)
              assignment_node.source_range
            else
              parent.send_node.source_range
            end
          else node.loc.keyword
          end
        end

        def base_for_method_definition(node)
          parent = node.parent
          if parent&.send_type?
            parent.loc.selector # For example "private def ..."
          else
            node.loc.keyword
          end
        end

        def check_assignment(node, rhs)
          # If there are method calls chained to the right hand side of the
          # assignment, we let rhs be the receiver of those method calls before
          # we check its indentation.
          rhs = first_part_of_call_chain(rhs)
          return unless rhs

          end_config = config.for_cop('Layout/EndAlignment')
          style = end_config['EnforcedStyleAlignWith'] || 'keyword'
          base = variable_alignment?(node.loc, rhs, style.to_sym) ? node : rhs

          return unless rhs.if_type?

          check_nested(rhs, base)
        end

        def check_alignment(base_range, else_range)
          return unless begins_its_line?(else_range)

          @column_delta = column_offset_between(base_range, else_range)
          return if @column_delta.zero?

          message = format(
            MSG,
            else_range: else_range.source,
            base_range: base_range.source[/^\S*/]
          )
          add_offense(else_range, message: message) do |corrector|
            autocorrect(corrector, else_range)
          end
        end

        def assignment_node(node)
          assignment_node = node.ancestors.first
          return unless assignment_node&.assignment?

          assignment_node
        end
      end
    end
  end
end