import os
import random
import string

def random_choices(population, k):
    """Emulate random.choices for Python < 3.6"""
    return [random.choice(population) for _ in range(k)]

class Config:
    SECRET_KEY = os.environ.get('SECRET_KEY') or \
            ''.join(random_choices(string.ascii_letters, k=20))
    DATA_DIR   = os.environ.get('DATA_DIR') or '/var/tmp/prolefeeder-test-data'
    OUT_DIR    = os.environ.get('OUT_DIR') or '/var/tmp/prolefeeder-test-out'
    MAX_LENGTH = os.environ.get('MAX_LENGTH') or 180
    KBITS      = os.environ.get('KBITS') or 128

    DEBUG      = False

    if not os.path.exists(DATA_DIR):
        raise RuntimeError("DATA_DIR does not exist")
    if not os.path.exists(OUT_DIR):
        raise RuntimeError("OUT_DIR does not exist")