# -*- coding: utf-8 -*-
# Natural Language Toolkit: Twitter client
#
# Copyright (C) 2001-2017 NLTK Project
# Author: Ewan Klein <ewan@inf.ed.ac.uk>
#         Lorenzo Rubio <lrnzcig@gmail.com>
# URL: <http://nltk.org/>
# For license information, see LICENSE.TXT

"""
Authentication utilities to accompany :module:`twitterclient`.
"""

from __future__ import print_function

import os
import pprint
from twython import Twython

def credsfromfile(creds_file=None, subdir=None, verbose=False):
    """
    Convenience function for authentication
    """
    return Authenticate().load_creds(creds_file=creds_file, subdir=subdir, verbose=verbose)


class Authenticate(object):
    """
    Methods for authenticating with Twitter.
    """
    def __init__(self):
        self.creds_file = 'credentials.txt'
        self.creds_fullpath = None

        self.oauth = {}
        try:
            self.twitter_dir = os.environ['TWITTER']
            self.creds_subdir = self.twitter_dir
        except KeyError:
            self.twitter_dir = None
            self.creds_subdir = None


    def load_creds(self, creds_file=None, subdir=None, verbose=False):
        """
        Read OAuth credentials from a text file.

        ::
           File format for OAuth 1
           =======================
           app_key=YOUR_APP_KEY
           app_secret=YOUR_APP_SECRET
           oauth_token=OAUTH_TOKEN
           oauth_token_secret=OAUTH_TOKEN_SECRET


        ::
           File format for OAuth 2
           =======================

           app_key=YOUR_APP_KEY
           app_secret=YOUR_APP_SECRET
           access_token=ACCESS_TOKEN

        :param str file_name: File containing credentials. ``None`` (default) reads\
        data from `TWITTER/'credentials.txt'`
        """
        if creds_file is not None:
            self.creds_file = creds_file

        if subdir is None:
            if self.creds_subdir is None:
                msg = "Supply a value to the 'subdir' parameter or" +\
                      " set the TWITTER environment variable."
                raise ValueError(msg)
        else:
            self.creds_subdir = subdir

        self.creds_fullpath =\
            os.path.normpath(os.path.join(self.creds_subdir, self.creds_file))

        if not os.path.isfile(self.creds_fullpath):
            raise OSError('Cannot find file {}'.format(self.creds_fullpath))

        with open(self.creds_fullpath) as infile:
            if verbose:
                print('Reading credentials file {}'.format(self.creds_fullpath))

            for line in infile:
                if '=' in line:
                    name, value = line.split('=', 1)
                    self.oauth[name.strip()] = value.strip()

        self._validate_creds_file(verbose=verbose)

        return self.oauth

    def _validate_creds_file(self, verbose=False):
        """Check validity of a credentials file."""
        oauth1 = False
        oauth1_keys = ['app_key', 'app_secret', 'oauth_token', 'oauth_token_secret']
        oauth2 = False
        oauth2_keys = ['app_key', 'app_secret', 'access_token']
        if all(k in self.oauth for k in oauth1_keys):
            oauth1 = True
        elif all(k in self.oauth for k in oauth2_keys):
            oauth2 = True

        if not (oauth1 or oauth2):
            msg = 'Missing or incorrect entries in {}\n'.format(self.creds_file)
            msg += pprint.pformat(self.oauth)
            raise ValueError(msg)
        elif verbose:
            print('Credentials file "{}" looks good'.format(self.creds_file))


def add_access_token(creds_file=None):
    """
    For OAuth 2, retrieve an access token for an app and append it to a
    credentials file.
    """
    if creds_file is None:
        path = os.path.dirname(__file__)
        creds_file = os.path.join(path, 'credentials2.txt')
    oauth2 = credsfromfile(creds_file=creds_file)
    app_key = oauth2['app_key']
    app_secret = oauth2['app_secret']

    twitter = Twython(app_key, app_secret, oauth_version=2)
    access_token = twitter.obtain_access_token()
    tok = 'access_token={}\n'.format(access_token)
    with open(creds_file, 'a') as infile:
        print(tok, file=infile)


def guess_path(pth):
    """
    If the path is not absolute, guess that it is a subdirectory of the
    user's home directory.

    :param str pth: The pathname of the directory where files of tweets should be written
    """
    if os.path.isabs(pth):
        return pth
    else:
        return os.path.expanduser(os.path.join("~", pth))
