factory.py

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""" This module implements the factory pattern for getting a database API instance. """
import os
import sys
import yaml
 
 
from databases.mongodb.mongodbadapter import MongoToCDBAPIAdapter
 
 
 
class APIFactory:
 
    def __init__(self):
        # supported_db_types is the list of different database back-ends which are supported
        self.__supported_db_types = ["mongo"]
 
    
    def construct_DB_API(self, path=None):
 
        config = self.__read_config_file(path)
 
        if config is None or len(config) <= 0:
            raise ValueError("Error in reading or accessing the configuration file")
    #evh
        #db_type = config.keys()[0]
        db_type = "mongo"
        connection_dict = config[db_type]
 
    
        if db_type not in self.__supported_db_types:
            raise NotImplementedError(db_type + " database is not supported")
 
        if db_type == "mongo":
            return MongoToCDBAPIAdapter(connection_dict)
        # FUTURE: Add more storage back-ends here
        else:
            raise NotImplementedError(db_type + " database is not supported")
 
    
    def __read_config_file(self, path):
        ret = {}
 
        if not path:
            home_dir = str(os.getenv('FAIRSHIP'))
            path = home_dir + "/conditionsDatabase/config.yml"
        else:
            path_details = path.split(".")
            file_extention = path_details[len(path_details) - 1]
            if not(file_extention == "yml" or file_extention == "yaml"):
                print("The file extension is incorrect. A YAML file is required.")
                return None
 
        try:
            with open(path, 'r') as ymlfile:
                cfg = yaml.load(ymlfile, Loader=yaml.FullLoader)
        except IOError:
            print("The configuration file does not exit or Invalid path to "
                  "the file:", str(sys.exc_info()[0]))
            return None
 
        connection_dict = {'db_name': '', 'user': None, 'password': None, 'host': "", 'port': 0}
        db_type = None
 
        try:
            db_type = cfg["db_type"]
            if db_type is None:
                print("db type should be defined")
                return None
 
            if db_type not in cfg.keys():
                print("db config is not defined")
                return None
 
            connection_dict["host"] = cfg[db_type]["host"]
            connection_dict["db_name"] = cfg[db_type]["db_name"]
            connection_dict["user"] = cfg[db_type]["user"]
            connection_dict["password"] = cfg[db_type]["password"]
            connection_dict["port"] = cfg[db_type]["port"]
            ret[db_type.lower()] = connection_dict
            #evh print
            #print (" connection_dict=",connection_dict)
            return ret
        except KeyError:
            print("Incorrect configuration file, missing some parameters. it should contain: "
                  "db_type, db_name, user, password, host, and port.")
            return None