# Test whether a given class or definition is defined
Puppet::Parser::Functions::newfunction(:defined, :type => :rvalue, :arity => -2, :doc => "Determine whether
  a given class or resource type is defined. This function can also determine whether a
  specific resource has been declared, or whether a variable has been assigned a value
  (including undef...as opposed to never having been assigned anything). Returns true
  or false. Accepts class names, type names, resource references, and variable
  reference strings of the form '$name'.  When more than one argument is
  supplied, defined() returns true if any are defined.

  The `defined` function checks both native and defined types, including types
  provided as plugins via modules. Types and classes are both checked using their names:

      defined(\"file\")
      defined(\"customtype\")
      defined(\"foo\")
      defined(\"foo::bar\")
      defined(\'$name\')

  Resource declarations are checked using resource references, e.g.
  `defined( File['/tmp/myfile'] )`. Checking whether a given resource
  has been declared is, unfortunately, dependent on the parse order of
  the configuration, and the following code will not work:

      if defined(File['/tmp/foo']) {
          notify { \"This configuration includes the /tmp/foo file.\":}
      }
      file { \"/tmp/foo\":
          ensure => present,
      }

  However, this order requirement refers to parse order only, and ordering of
  resources in the configuration graph (e.g. with `before` or `require`) does not
  affect the behavior of `defined`.

  If the future parser is in effect, you may also search using types:

      defined(Resource[\'file\',\'/some/file\'])
      defined(File[\'/some/file\'])
      defined(Class[\'foo\'])

 - Since 2.7.0
 - Since 3.6.0 variable reference and future parser types") do |vals|
    vals = [vals] unless vals.is_a?(Array)
    vals.any? do |val|
      case val
      when String
        if m = /^\$(.+)$/.match(val)
          exist?(m[1])
        else
          find_resource_type(val) or find_definition(val) or find_hostclass(val)
        end
      when Puppet::Resource
        compiler.findresource(val.type, val.title)
      else
        if Puppet.future_parser?
          case val
          when Puppet::Pops::Types::PResourceType
            raise ArgumentError, "The given resource type is a reference to all kind of types" if val.type_name.nil?
            if val.title.nil?
              find_builtin_resource_type(val.type_name) || find_definition(val.type_name)
            else
              compiler.findresource(val.type_name, val.title)
            end
          when Puppet::Pops::Types::PHostClassType
            raise  ArgumentError, "The given class type is a reference to all classes" if val.class_name.nil?
            find_hostclass(val.class_name)
          end
        else
          raise ArgumentError, "Invalid argument of type '#{val.class}' to 'defined'"
        end
      end
    end
end