"""Provide package-wide configuration.

This module is "protected" so that it is only used
via the `config` proxy at the package's top level.

That already loads the correct configuration
depending on the current environment.
"""
import datetime
import os
import random
import string
import warnings

import dotenv


dotenv.load_dotenv()


def random_schema_name() -> str:
    """Generate a random PostgreSQL schema name for testing."""
    return ''.join(
        random.choice(string.ascii_lowercase) for _ in range(10)  # noqa:S311
    )


class Config:
    """Configuration that applies in all situations."""

    # pylint:disable=too-few-public-methods

    CUTOFF_DAY = datetime.datetime(2017, 2, 1)

    # If a scheduled pre-order is made within this
    # time horizon, we treat it as an ad-hoc order.
    QUASI_AD_HOC_LIMIT = datetime.timedelta(minutes=45)

    DATABASE_URI = os.getenv('DATABASE_URI')

    # The PostgreSQL schema that holds the tables with the original data.
    ORIGINAL_SCHEMA = os.getenv('ORIGINAL_SCHEMA') or 'public'

    # The PostgreSQL schema that holds the tables with the cleaned data.
    CLEAN_SCHEMA = os.getenv('CLEAN_SCHEMA') or 'clean'

    def __repr__(self) -> str:
        """Non-literal text representation."""
        return '<configuration>'


class ProductionConfig(Config):
    """Configuration for the real dataset."""

    # pylint:disable=too-few-public-methods

    TESTING = False


class TestingConfig(Config):
    """Configuration for the test suite."""

    # pylint:disable=too-few-public-methods

    TESTING = True

    DATABASE_URI = os.getenv('DATABASE_URI_TESTING') or Config.DATABASE_URI
    CLEAN_SCHEMA = os.getenv('CLEAN_SCHEMA_TESTING') or random_schema_name()


def get_config(env: str = 'production') -> Config:
    """Get the configuration for the package.

    Args:
        env: either 'production' or 'testing'; defaults to the first

    Returns:
        config: a namespace with all configurations

    Raises:
        ValueError: if `env` is not as specified
    """  # noqa:DAR203
    config: Config
    if env.strip().lower() == 'production':
        config = ProductionConfig()
    elif env.strip().lower() == 'testing':
        config = TestingConfig()
    else:
        raise ValueError("Must be either 'production' or 'testing'")

    # Without a PostgreSQL database the package cannot work.
    if config.DATABASE_URI is None:
        warnings.warn('Bad configurartion: no DATABASE_URI set in the environment')

    return config