Path management accessible from analysis

[thclark]

For 0.1.3 I removed the cumbersome path-based system for running analyses, upgrading to the Runner() class.

However, this has the side effect of no longer having self-made paths. It'll be more flexible, because a dataset can sit there on a system with a fixed path regardless of which analysis it belongs to... but means there's no baked-in path on the dataset.

We need to resolve this, either by attaching a path index to the Analysis instance which manages that all... or by doing something like a mixin that gets instantiated with the appropriate path and local_path_prefix.

Inspired by the Datafile class this might look something like the following, but I haven't figured out a way to instantiate it yet which will then be easily used.

import os
import uuid

from octue.exceptions import InvalidInputException
from octue.utils import gen_uuid


class Pathable:
    """ Mixin to allow a class to have a path attribute (which may be a directory or file path and name)

    Prevents setting path after an object is instantiated.

    ```
    class MyResource(Pathable):
        pass

    MyResource().id  # Some generated uuid
    MyResource(id='not_a_uuid')  # Raises exception
    MyResource(id='a10603a0-194c-40d0-a7b7-fcf9952c3690').id  # That same uuid
    ```
    """

    _path_field = None

    def __init__(self, *args, path=None, local_path_prefix=".", **kwargs):
        """ Constructor for Pathable class

        # TODO Update datafile to use this mixin
        """
        super().__init__(*args, **kwargs)
        path = path or self._get_default_path()
        self._path = self._clean_path(path)

        self.local_path_prefix = str(os.path.abspath(local_path_prefix))

    def _get_default_path(self):
        if self._path_field is not None:
            return str(getattr(self, self._path_field))

    @staticmethod
    def _clean_path(path):
        if path is not None:
            return str(os.path.normpath(path)).lstrip(r"\/")

    @property
    def name(self):
        return str(os.path.split(self.path)[-1])

    @property
    def full_path(self):
        return os.path.join(self.local_path_prefix, self.path)

    @property
    def path(self):
        return self._path