from .handler import Handler
from ..exceptions import ValidationException


@Handler.register
class AudioHandler(Handler):
    """
    This class handles audio settings for streams.
    """
    @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.

        In order for a job to be wanted, the field 'sources' must exist
        and at least one of the source items in 'sources' must contain a
        'playAudio' field.
        """
        if 'sources' in jobspec and any('playAudio' in source
                                        for source
                                        in jobspec['sources'].values()):
            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.

        A job is valid if exactly one of the items in this job's 'sources'
        object has its 'playAudio' field set to True.
        """
        super()._validate(jobspec, existing_package)
        true_count = 0
        for name, source in jobspec['sources'].items():
            if source.get('playAudio', False) == True:
                true_count += 1
        if true_count > 1:
            raise ValidationException(
                "more than one stream set to play audio")
        return True

    def _handle(self, jobspec, existing_package, tempdir):
        def apply_func(package):
            sources = package['sources']
            for name, source in jobspec['sources'].items():
                if name not in sources:
                    sources[name] = {}
                sources[name]['playAudio'] = source.get('playAudio', False)
        return apply_func