from decimal import Decimal

from django.core.management import BaseCommand
from django.utils import timezone

from core.models import Subject
from core.prediction import predict_all


class Command(BaseCommand):

    def add_arguments(self, parser):
        parser.add_argument(
            "--start", default="0", help="the current balance to use as a starting point for prediction",
        )

    def handle(self, *args, **options):
        start_balance = Decimal(options["start"])

        prediction_list = predict_all(Subject.objects.order_by("name"))
        today = timezone.now().date()

        future_transactions = []
        for subject, transactions, info in prediction_list:
            print(f">>> {subject}")
            if info:
                rec_days, rec_months, day_of_month = \
                    info["recurring_days"], info["recurring_months"], info["day_of_month"]
                if rec_months and day_of_month:
                    print(f"~~~ predicted transaction on day-of-month {day_of_month} every {rec_months} month(s)")
                elif rec_months:
                    print(f"~~~ predicted transaction every {rec_months} month(s)")
                elif rec_days:
                    print(f"~~~ predicted transaction every {rec_days} day(s)")
            else:
                print("~~~ no prediction possible")
            for tr in transactions:
                print(f"  {tr.booking_date:%d.%m.%Y} | {tr.amount} € | {'stored' if tr.pk else 'predicted'}")
                if tr.booking_date > today:
                    future_transactions.append(tr)
            print()

        current_balance = start_balance
        print(f"starting calculation with amount {current_balance} €")
        for tr in sorted(future_transactions, key=lambda t: t.booking_date):
            current_balance += tr.amount
            print(
                f"{tr.booking_date:%d.%m.%Y} | "
                f"{tr.subject.name:<18} | "
                f"{tr.amount:>8} €  ==> "
                f"{current_balance:>8} €"
            )