module Banzai
  module ReferenceParser
    class IssueParser < IssuableParser
      self.reference_type = :issue

      def nodes_visible_to_user(user, nodes)
        issues = records_for_nodes(nodes)
        issues_to_check, cross_project_issues = partition_issues(issues, user)

        readable_issues =
          Ability.issues_readable_by_user(issues_to_check, user).to_set

        nodes.select do |node|
          issue_in_node = issues[node]

          # We check the inclusion of readable issues first because it's faster.
          #
          # But we need to fall back to `read_issue_iid` if the user cannot read
          # cross project, since it might be possible the user can see the IID
          # but not the issue.
          if readable_issues.include?(issue_in_node)
            true
          elsif cross_project_issues.include?(issue_in_node)
            can_read_reference?(user, issue_in_node)
          else
            false
          end
        end
      end

      # issues - A Hash mapping HTML nodes to their corresponding Issue
      #          instances.
      # user - The current User.
      def partition_issues(issues, user)
        return [issues.values, []] if can?(user, :read_cross_project)

        issues_to_check = []
        cross_project_issues = []

        # We manually partition the data since our input is a Hash and our
        # output has to be an Array of issues; not an Array of (node, issue)
        # pairs.
        issues.each do |node, issue|
          target =
            if issue.project == project_for_node(node)
              issues_to_check
            else
              cross_project_issues
            end

          target << issue
        end

        [issues_to_check, cross_project_issues]
      end

      def records_for_nodes(nodes)
        @issues_for_nodes ||= grouped_objects_for_nodes(
          nodes,
          Issue.all.includes(
            :author,
            :assignees,
            {
              # These associations are primarily used for checking permissions.
              # Eager loading these ensures we don't end up running dozens of
              # queries in this process.
              project: [
                { namespace: :owner },
                { group: [:owners, :group_members] },
                :invited_groups,
                :project_members,
                :project_feature,
                :route
              ]
            }
          ),
          self.class.data_attribute
        )
      end
    end
  end
end