"""
API Client Connector
====================

Handles client setup and auth for the YouTube API. Requires the following
environment variables to be set up and valid:
* GOOGLE_API_KEY_FILE

Source based on https://github.com/theorchard/ows-label-audit.git repo
file ows-label-audit/labelaudit/connectors/youtube_api.py
"""

import os

from googleapiclient.discovery import build
import httplib2
from oauth2client.service_account import ServiceAccountCredentials


class ServiceMapping:
    """
    Google API Service Mapping
    ==========================

    Thin wrapper around the Google client library. Lazily handles oauth setup
    and builds the service client for the partner API.
    """

    PARTNER_API_VERSION = 'v1'
    PARTNER_API_NAME = 'youtubePartner'

    def __init__(self, key_file):
        """Initialize ServiceMapping object.

        Args:
            key_file (str): file name of google api key file.

        Raises: ValueError in case of Missing Google API key file name
            or wrong access rights on it.
        """

        if not key_file:
            raise ValueError('Missing Google API key file name')

        if not os.access(key_file, os.R_OK):
            raise ValueError('Cannot read Google API key file ' + key_file)

        self.key_file = key_file
        self._client = None
        self._youtube_partner = None

    def authorize(self):
        """Create and authorize a Google API client.

        To be called when the client has not been initialized
        or its access token has expired.
        """

        credentials = ServiceAccountCredentials.from_json_keyfile_name(
            self.key_file,
            scopes=['https://www.googleapis.com/auth/youtubepartner'])

        self._client = credentials.authorize(httplib2.Http())

    @property
    def client(self):
        """Create and authorize a Google API client.

        Returns:
            httplib2.Http: httlib2 client object.
        """

        if not self._client:
            self.authorize()
        return self._client

    @property
    def youtube_partner(self):
        """Lazily initialize the YouTube API.

        Initialized object discovery resource for the partner API.

        Returns:
            googleapiclient.discovery.Resource: partner API resource.
        """

        if not self._youtube_partner:
            self._youtube_partner = build(
                self.PARTNER_API_NAME,
                self.PARTNER_API_VERSION,
                http=self.client)
        return self._youtube_partner