from .handler import Handler


@Handler.register
class MetadataHandler(Handler):
    """
    This class handles package metadata.
    """
    handled_fields = ['title', 'description',
                      'created', 'duration',
                      'presenters', 'courses',
                      'tags']

    @classmethod
    def wants(cls, jobspec, existing_package):
        """
        Return True if this handler wants to process this jobspec.
        Raises an exception if the job is wanted but doesn't pass validation.

        A job is wanted if a source has been passed that contains one or
        more of the following fields:
         - title
         - description
         - created
         - presenters
         - courses
         - tags
        """
        for key in cls.handled_fields:
            if key in jobspec:
                return cls._validate(jobspec, existing_package)
        return False

    @classmethod
    def _validate(cls, jobspec, existing_package):
        """
        Return True if the job is valid for this handler.

        Does no specific validation since all handled fields are simply text.
        """
        super()._validate(jobspec, existing_package)
        return True

    def _handle(self, jobspec, existing_package, tempdir):
        def apply_func(package):
            for key in self.handled_fields:
                if key in jobspec:
                    package[key] = jobspec[key]
        return apply_func