pybis.py

#!/usr/bin/env python
# -*- coding: utf-8 -*-

"""
pybis.py

A class with methods for interacting with openBIS.

Created by Chandrasekhar Ramakrishnan on 2016-05-10.
Copyright (c) 2016 ETH Zuerich. All rights reserved.
"""

import os


class OpenbisCredentials:
    """Credentials for communicating with openBIS."""

    def __init__(self, token = None, uname_and_pass = None):
        """A connection can be authenticated either by a token or a username and password combination
        :param token: An authentication token for openBIS, can be None.
        :param uname_and_pass: A tuple with username and password, in that order.
        """
        self.token = token
        self.uname_and_pass = uname_and_pass

    def has_token(self):
        return self.token is not None

    def has_username_and_password(self):
        return self.uname_and_pass is not None

    @property
    def username(self):
        return self.uname_and_pass[0]

    @property
    def password(self):
        return self.uname_and_pass[1]


class OpenbisCredentialStore:
    """Cache login tokens for reuse."""

    def __init__(self, store_folder):
        """Cache credentials on the file system at store_path.
        If the store_folder does not exist, it will be created with the umask inherited from the shell.
        :param store_folder: The folder to write the credentials to. It will be created if necessary.
        """
        self.store_folder = store_folder

    @property
    def store_path(self):
        return os.path.join(self.store_folder, "bis_token.txt")

    def read(self):
        """Read the cached credentials and return a credentials object.
        :return: A credentials object with a token, or an empty credentials object if no store was found.
        """
        if not os.path.exists(self.store_path):
            return OpenbisCredentials()
        with open(self.store_path, "r") as f:
            token = f.read()
        return OpenbisCredentials(token)

    def write(self, credentials):
        """Write a credentials object to the store, overwriting any previous information.
        :param credentials: The credentials with a token to write. If it has no token, nothing is written.
        """
        if not credentials.has_token():
            return
        token = credentials.token
        if not os.path.exists(self.store_folder):
            os.makedirs(self.store_folder)
        with open(self.store_path, "w") as f:
            f.write(token)


class Openbis:
    """Interface for communicating with openBIS."""

    def __init__(self, url, credentials):
        """Initialize an interface to openBIS with information necessary to connect to the server.
        :param url:
        :param credentials:
        """
        self.url = url
        self.credentials = credentials

    def login(self):
        """Log into openBIS.
        Expects credentials with username and password and updates the token on the credentials object.
        Throw a ValueError with the error message if login failed.
        """
        if not self.credentials.has_username_and_password:
            raise ValueError('Cannot log into openBIS without a username and password')
        # TODO Implement the logic of this method.