ability.rb

class Ability
  class << self
    def allowed(object, subject)
      case subject.class.name
      when "Project" then project_abilities(object, subject)
      when "Issue" then issue_abilities(object, subject)
      when "Note" then note_abilities(object, subject)
      when "Snippet" then snippet_abilities(object, subject)
      when "MergeRequest" then merge_request_abilities(object, subject)
      else []
      end
    end

    def project_abilities(user, project)
      rules = []

      rules << [
        :read_project,
        :read_wiki,
        :read_issue,
        :read_milestone,
        :read_snippet,
        :read_team_member,
        :read_merge_request,
        :read_note,
        :write_project,
        :write_issue,
        :write_note
      ] if project.guest_access_for?(user)

      rules << [
        :download_code,
        :write_merge_request,
        :write_snippet
      ] if project.report_access_for?(user)

      rules << [
        :write_wiki,
        :push_code
      ] if project.dev_access_for?(user)

      rules << [
        :push_code_to_protected_branches
      ] if project.master_access_for?(user)

      rules << [
        :modify_issue,
        :modify_snippet,
        :modify_merge_request,
        :admin_project,
        :admin_issue,
        :admin_milestone,
        :admin_snippet,
        :admin_team_member,
        :admin_merge_request,
        :admin_note,
        :accept_mr,
        :admin_wiki
      ] if project.master_access_for?(user) || project.owner == user

      rules.flatten
    end

    [:issue, :note, :snippet, :merge_request].each do |name|
      define_method "#{name}_abilities" do |user, subject|
        if subject.author == user
          [
            :"read_#{name}",
            :"write_#{name}",
            :"modify_#{name}",
            :"admin_#{name}"
          ]
        elsif subject.respond_to?(:assignee) && subject.assignee == user
          [
            :"read_#{name}",
            :"write_#{name}",
            :"modify_#{name}",
          ]
        else
          subject.respond_to?(:project) ? project_abilities(user, subject.project) : []
        end
      end
    end
  end
end