import os

from google.cloud import storage

import googleapiclient.discovery

from oauth2client.client import GoogleCredentials

credentials = GoogleCredentials.get_application_default()

def create_service():

    # Construct the service object for interacting with the Cloud Storage API -

    # the 'storage' service, at version 'v1'.

    # You can browse other available api services and versions here:

    #     http://g.co/dv/api-client-library/python/apis/

    return googleapiclient.discovery.build('storage', 'v1', credentials=credentials)

def list_bucket(bucket):

    """Returns a list of metadata of the objects within the given bucket."""

    service = create_service()

    # Create a request to objects.list to retrieve a list of objects.

    fields_to_return = \

        'nextPageToken,items(name,size,contentType,metadata(my-key))'

    req = service.objects().list(bucket=bucket, fields=fields_to_return)

    all_objects = []

    # If too many items to list in one request, list_next() will

    # automatically handle paging with the pageToken.

    while req:

        resp = req.execute()

        all_objects.extend(resp.get('items', []))

        req = service.objects().list_next(req, resp)

    return all_objects

def collect_images(bucket_name, project_name, working_dir='./'):

    all_blobs = map(lambda item: item['name'], list_bucket(bucket_name))

    client = storage.Client(project=project_name)

    bucket = client.get_bucket(bucket_name)

    for blob_item in all_blobs:

        blob = storage.Blob(blob_item, bucket)

        complete_path = os.path.join(working_dir, blob_item)

        dir_name = os.path.dirname(complete_path)

        if not os.path.exists(dir_name):

            os.makedirs(dir_name)

        if os.path.exists(complete_path):

            print("Skipping {} since it already exists.".format(blob_item))

            continue

        with open(complete_path, 'wb') as file_obj:

            try:

                blob.download_to_file(file_obj)

                print("Stored blob path: ", complete_path)

            except Exception as e:

                print("Downloading {} failed with {}.".format(complete_path, e))