from pathlib import Path

from .handler import Handler
from ..exceptions import ValidationException


@Handler.register
class SubtitlesImportHandler(Handler):
    """
    This class saves uploaded subtitles to a package.
    """
    @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 the job specification contains a 'subtitles' key.
        """
        if 'subtitles' 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.

        Validity requirements are:
         - Keys in 'subtitles' and 'generate_subtitles' must be
           mututally unique.
         - If any value in the 'subtitles' object is not None, the job must
           contain an 'upload_dir' key which must point to an
           existing directory.
         - All 'subtitles' values that are not None must be existing files
           under 'upload_dir'.
        """
        super()._validate(jobspec, existing_package)
        # Check for duplicate track names
        generate_names = jobspec.get('generate_subtitles', {}).keys()
        store_names = jobspec.get('subtitles', {}).keys()
        common_names = generate_names & store_names
        if common_names:
            names_string = ', '.join(common_names)
            raise ValidationException(
                f"Duplicate subtitle track name(s): {names_string}")

        # Validate storage tasks
        for name, subsfile in jobspec.get('subtitles', {}).items():
            if not subsfile:
                continue
            if 'upload_dir' not in jobspec:
                raise ValidationException("upload_dir missing")
            subspath = Path(jobspec['upload_dir']) / subsfile
            if not subspath.is_file():
                raise ValidationException(
                    f"Error for subtitle track {name}: "
                    f"{subspath} is not a valid file")
        return True

    def _handle(self, jobspec, existing_package, tempdir):
        def apply_func(package):
            for name, subsfile in jobspec.get('subtitles', {}).items():
                subspath = None
                if subsfile:
                    subspath = Path(jobspec['upload_dir']) / subsfile
                package.set_subtitle_track(name, subspath)
        return apply_func