"""
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
* GOOGLE_SERVICE_EMAIL
"""

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

import os

from labelaudit import config


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, service_email, key_file):
        self.service_email = service_email
        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(
            self.service_email,
            self.key_file.contents,
            scope=['https://www.googleapis.com/auth/youtubepartner'])

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

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

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

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

    @property
    def youtube_partner(self):
        """Lazily initialize the YouTube API discovery resource for the
        partner API.

        Return:
            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


class KeyFile:
    """
    Google API key file reader
    ==================

    Lazily reads the contents of the given key file from the keys directory.
    """

    def __init__(self, file_name):
        self.file_name = file_name
        self._contents = None

    @property
    def contents(self):
        """Reads the contents of the P12 key file specified in the config.

        Return:
            bytes: contents of the key file
        """

        if self._contents:
            return self._contents

        if not self.file_name:
            raise Exception('Missing Google API key file name')

        full_key_path = os.path.join(
            os.path.realpath(os.path.dirname(__file__) + '/../..'),
            'keys',
            self.file_name)

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

        key_file = open(full_key_path, 'rb')
        self._contents = key_file.read()
        key_file.close()
        return self._contents


# Lazy is the key word here. Lazily read the key file and lazily authorize
# the API client. That gives our unit tests a chance to mock this stuff after
# importing this module.
key_file = KeyFile(config.GOOGLE_API_KEY_FILE)
mapping = ServiceMapping(
    service_email=config.GOOGLE_SERVICE_EMAIL, key_file=key_file)