# frozen_string_literal: true

module RuboCop
  module Cop
    # Common functionality for dealing with frozen string literals.
    module FrozenStringLiteral
      module_function

      FROZEN_STRING_LITERAL = '# frozen_string_literal:'
      FROZEN_STRING_LITERAL_ENABLED = '# frozen_string_literal: true'
      FROZEN_STRING_LITERAL_TYPES_RUBY27 = %i[str dstr].freeze

      private_constant :FROZEN_STRING_LITERAL_TYPES_RUBY27

      def frozen_string_literal_comment_exists?
        leading_comment_lines.any? { |line| MagicComment.parse(line).valid_literal_value? }
      end

      private

      def frozen_string_literal?(node)
        frozen_string = if target_ruby_version >= 3.0
                          uninterpolated_string?(node) || frozen_heredoc?(node)
                        else
                          FROZEN_STRING_LITERAL_TYPES_RUBY27.include?(node.type)
                        end

        frozen_string && frozen_string_literals_enabled?
      end

      def uninterpolated_string?(node)
        node.str_type? || (node.dstr_type? && node.each_descendant(:begin).none?)
      end

      def frozen_heredoc?(node)
        return false unless node.dstr_type? && node.heredoc?

        node.children.all?(&:str_type?)
      end

      def frozen_string_literals_enabled?
        ruby_version = processed_source.ruby_version
        return false unless ruby_version

        # TODO: Ruby officially abandon making frozen string literals default
        # for Ruby 3.0.
        # https://bugs.ruby-lang.org/issues/11473#note-53
        # Whether frozen string literals will be the default after Ruby 3.0
        # or not is still unclear as of January 2019.
        # It may be necessary to add this code in the future.
        #
        #   return true if ruby_version >= 3.1
        #
        # And the above `ruby_version >= 3.1` is undecided whether it will be
        # Ruby 3.1, 3.2, 4.0 or others.
        # See https://bugs.ruby-lang.org/issues/8976#note-41 for details.
        leading_comment_lines.any? { |line| MagicComment.parse(line).frozen_string_literal? }
      end

      def frozen_string_literals_disabled?
        leading_comment_lines.any? do |line|
          MagicComment.parse(line).frozen_string_literal == false
        end
      end

      def frozen_string_literal_specified?
        leading_comment_lines.any? do |line|
          MagicComment.parse(line).frozen_string_literal_specified?
        end
      end

      def leading_comment_lines
        first_non_comment_token = processed_source.tokens.find { |token| !token.comment? }

        if first_non_comment_token
          # `line` is 1-indexed so we need to subtract 1 to get the array index
          processed_source.lines[0...first_non_comment_token.line - 1]
        else
          processed_source.lines
        end
      end
    end
  end
end