module Auth
  class ContainerRegistryAuthenticationService < BaseService
    include Gitlab::CurrentSettings

    AUDIENCE = 'container_registry'

    def execute(capabilities: capabilities)
      @capabilities = capabilities

      return error('not found', 404) unless registry.enabled

      unless current_user || project
        return error('forbidden', 403) unless scope
      end

      { token: authorized_token(scope).encoded }
    end

    def self.full_access_token(*names)
      registry = Gitlab.config.registry
      token = JSONWebToken::RSAToken.new(registry.key)
      token.issuer = registry.issuer
      token.audience = AUDIENCE
      token.expire_time = token_expire_at

      token[:access] = names.map do |name|
        { type: 'repository', name: name, actions: %w(*) }
      end

      token.encoded
    end

    def self.token_expire_at
      Time.now + current_application_settings.container_registry_token_expire_delay.minutes
    end

    private

    def authorized_token(*accesses)
      token = JSONWebToken::RSAToken.new(registry.key)
      token.issuer = registry.issuer
      token.audience = params[:service]
      token.subject = current_user.try(:username)
      token.expire_time = self.class.token_expire_at
      token[:access] = accesses.compact
      token
    end

    def scope
      return unless params[:scope]

      @scope ||= process_scope(params[:scope])
    end

    def process_scope(scope)
      type, name, actions = scope.split(':', 3)
      actions = actions.split(',')
      return unless type == 'repository'

      process_repository_access(type, name, actions)
    end

    def process_repository_access(type, name, actions)
      requested_project = Project.find_with_namespace(name)
      return unless requested_project

      actions = actions.select do |action|
        can_access?(requested_project, action)
      end

      { type: type, name: name, actions: actions } if actions.present?
    end

    def can_access?(requested_project, requested_action)
      return false unless requested_project.container_registry_enabled?

      case requested_action
      when 'pull'
        restricted_user_can_pull?(requested_project) || privileged_user_can_pull?(requested_project)
      when 'push'
        restricted_user_can_push?(requested_project) || privileged_user_can_push?(requested_project)
      else
        false
      end
    end

    def registry
      Gitlab.config.registry
    end

    private

    def restricted_user_can_pull?(requested_project)
      # Restricted can:
      # 1. pull from it's own project (for ex. a build)
      # 2. read images from dependent projects if he is a team member
      requested_project == project ||
        has_ability?(:restricted_read_container_image, requested_project)
    end

    def privileged_user_can_pull?(requested_project)
      has_ability?(:read_container_image, requested_project)
    end

    def restricted_user_can_push?(requested_project)
      # Restricted can push only to project to from which he originates
      requested_project == project
    end

    def privileged_user_can_push?(requested_project)
      has_ability?(:create_container_image, requested_project)
    end

    def has_ability?(ability, requested_project)
      @capabilities.include?(ability) && can?(current_user, ability, requested_project)
    end
  end
end