import string
import re
import random

from dbsettings.functions import getValue

import qrcode

QRCODE_CONTENT = """
BCD
002
1
SCT
%s
%s
%s
%s%s
%s
%s
%s
%s
""".strip()

def generate_rf(reference):
    reference = str(reference).upper().zfill(21) + "RF00"
    pattern = re.compile("[A-Z0-9]+")
    if not pattern.fullmatch(reference):
        raise ValueError("Not a valid reference: %s – may only contain 0-9 and A-Z!")

    code = ""

    chars = string.digits + string.ascii_uppercase

    for char in reference:
        code += str(chars.index(char))

    remainder = int(code) % 97

    checksum = 98 - remainder

    return "RF%i%s" % (checksum, reference[:-4])

def generate_reference(length=21):
    return "".join([random.SystemRandom().choice(string.digits + string.ascii_uppercase) for i in range(length)])

def generate_qrcode(amount, iban="", recipient="", bic="", reference="", currency="EUR", message="", purpose="", notice=""):
    content = QRCODE_CONTENT % (
        bic or getValue("sepa.bic", ""),
        recipient or getValue("sepa.account_holder", ""),
        iban or getValue("sepa.iban"),
        currency,
        "{:0.2f}".format(float(amount)).rstrip("0"),
        purpose,
        reference if (not reference) or str(reference).startswith("RF") or len(str(reference)) > 21 else generate_rf(reference),
        message,
        notice
    )

    return qrcode.make(content)