'''
Helper module that with an abstract class containing a static method that returns a joined Pandas Dataframe made of the dog sizes and dog intelligence datasets
'''
import pandas as pd

class DogDatasets():
  '''
  Abstract helper class that helps merging the two dog breeds datasets.
  Contains two static private attibutes with the default dataset URLs
  '''
  __ds1_url = 'https://rcweb.dartmouth.edu/homes/d35398e/data/qbs101/sp21_midterm/dog_breeds.csv'
  __ds2_url = 'https://rcweb.dartmouth.edu/homes/d35398e/data/qbs101/sp21_midterm/dog_intelligence.csv'

  @staticmethod
  def join(ds1_path_or_url=None, ds2_path_or_url=None):
    '''
    Returns a single Pandas Dataframe that combines (inner join) both datasets provided in argument.
    If either dataset path is missing, or both, the default URL dataset is used.
    '''
    df1 = pd.read_csv(ds1_path_or_url if ds1_path_or_url is not None else DogDatasets.__ds1_url, index_col='breed')
    return df1.join(pd.read_csv(ds2_path_or_url if ds2_path_or_url is not None else DogDatasets.__ds2_url, index_col='breed'),how='inner')