add whole new app for balance prediction, replace uwsgi, update everything

core/admin.py

@@ -0,0 +1,15 @@
+from django.contrib import admin
+
+from core.models import Subject, Transaction
+from financeplanner.admin import admin_site
+
+
+@admin.register(Subject, site=admin_site)
+class SubjectAdmin(admin.ModelAdmin):
+    pass
+
+
+@admin.register(Transaction, site=admin_site)
+class TransactionAdmin(admin.ModelAdmin):
+    list_display = ("subject", "amount", "booking_date",)
+    ordering = ("-booking_date",)

core/apps.py

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+from django.apps import AppConfig
+
+
+class CoreConfig(AppConfig):
+    name = 'core'

core/management/commands/predict_balance.py

@@ -0,0 +1,74 @@
+from datetime import datetime
+from decimal import Decimal
+
+from dateutil.relativedelta import relativedelta
+from django.core.management import BaseCommand
+
+from core.models import Subject
+from core.prediction import predict_transactions
+
+past_lookup_delta = relativedelta(weeks=2)
+future_lookup_delta = relativedelta(months=2)
+
+
+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"])
+
+        today = datetime.now().date()
+        past_lookup_bound = today - past_lookup_delta
+        future_lookup_bound = today + future_lookup_delta
+
+        transaction_dict = {}
+        for subject in Subject.objects.all():
+            transactions = []
+            for tr in subject.transactions.order_by("booking_date"):
+                if past_lookup_bound <= tr.booking_date <= future_lookup_bound:
+                    transactions.append(tr)
+            predicted_transaction, prediction_info = predict_transactions(subject)
+            if predicted_transaction:
+                first_predicted_date = predicted_transaction[0].booking_date
+                if first_predicted_date >= past_lookup_bound:
+                    # if two weeks after the first predicted transaction have passed, the subject is considered done
+                    for tr in predicted_transaction:
+                        if past_lookup_bound <= tr.booking_date <= future_lookup_bound:
+                            transactions.append(tr)
+            transaction_dict[subject] = (transactions, prediction_info)
+
+        future_transactions = []
+        for subject, prediction in transaction_dict.items():
+            transactions, info = prediction[0], prediction[1]
+            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} €"
+            )

core/migrations/0001_initial.py

@@ -0,0 +1,48 @@
+# Generated by Django 3.1.5 on 2021-01-04 13:41
+
+import core.models
+from django.db import migrations, models
+import django.db.models.deletion
+import django.utils.timezone
+
+
+class Migration(migrations.Migration):
+
+    initial = True
+
+    dependencies = [
+    ]
+
+    operations = [
+        migrations.CreateModel(
+            name='Balance',
+            fields=[
+                ('id', models.AutoField(auto_created=True, primary_key=True, serialize=False, verbose_name='ID')),
+                ('amount', core.models.PriceField(decimal_places=2, max_digits=7)),
+                ('date', models.DateField()),
+            ],
+            options={
+                'get_latest_by': 'date',
+            },
+        ),
+        migrations.CreateModel(
+            name='Subject',
+            fields=[
+                ('id', models.AutoField(auto_created=True, primary_key=True, serialize=False, verbose_name='ID')),
+                ('name', models.CharField(max_length=64)),
+                ('created_time', models.DateTimeField(default=django.utils.timezone.now)),
+            ],
+        ),
+        migrations.CreateModel(
+            name='Transaction',
+            fields=[
+                ('id', models.AutoField(auto_created=True, primary_key=True, serialize=False, verbose_name='ID')),
+                ('amount', core.models.PriceField(decimal_places=2, max_digits=7)),
+                ('booking_date', models.DateField()),
+                ('subject', models.ForeignKey(on_delete=django.db.models.deletion.CASCADE, related_name='transactions', related_query_name='transaction', to='core.subject')),
+            ],
+            options={
+                'get_latest_by': 'booking_date',
+            },
+        ),
+    ]

core/models.py

@@ -0,0 +1,49 @@
+from decimal import Decimal
+
+from django.db import models
+from django.utils import timezone
+
+
+class PriceField(models.DecimalField):
+    # allowing numbers until 99,999.99
+    max_digits = 7
+    decimal_places = 2
+
+    def to_python(self, value):
+        value = super().to_python(value)
+        if isinstance(value, Decimal):
+            return value.quantize(Decimal(10) ** -self.decimal_places)
+        return value
+
+    def __init__(self, *args, **kwargs):
+        kwargs['max_digits'] = self.max_digits
+        kwargs['decimal_places'] = self.decimal_places
+        super().__init__(*args, **kwargs)
+
+
+class Subject(models.Model):
+    name = models.CharField(max_length=64)
+    created_time = models.DateTimeField(default=timezone.now)
+
+    def __str__(self):
+        return self.name
+
+
+class Transaction(models.Model):
+    class Meta:
+        get_latest_by = "booking_date"
+
+    amount = PriceField()
+    booking_date = models.DateField()
+    subject = models.ForeignKey(
+        to=Subject, on_delete=models.CASCADE,
+        related_name="transactions", related_query_name="transaction",
+    )
+
+
+class Balance(models.Model):
+    class Meta:
+        get_latest_by = "date"
+
+    amount = PriceField()
+    date = models.DateField()

core/prediction.py

@@ -0,0 +1,87 @@
+from decimal import Decimal
+
+from dateutil.relativedelta import relativedelta
+
+from core.models import Subject, Transaction
+
+days_per_year = Decimal("365.25")
+days_per_month = days_per_year / Decimal("12")
+
+monthly_distance_threshold = 3
+certain_day_of_month_threshold = 3
+
+
+def _group_follow_up_objects(objects):
+    """
+    Creates a list of each follow-up pair of objects within a given list, like this:
+    [1, 2, 3] -> [(1, 2), (2, 3)]
+    """
+    tuples = []
+    if len(objects) >= 2:
+        for idx in range(len(objects) - 1):
+            tuples.append((objects[idx], objects[idx + 1]))
+    return tuples
+
+
+def predict_amount(subject: Subject):
+    if subject.transactions.exists():
+        return subject.transactions.latest().amount
+    return None
+
+
+def predict_booking_dates(subject: Subject):
+    dates, recurring_days, recurring_months, day_of_month = [], None, None, None
+    if subject.transactions.count() < 2:
+        return dates, recurring_days, recurring_months, day_of_month
+
+    existing_transactions = subject.transactions.order_by("booking_date")
+    last_date = existing_transactions.latest().booking_date
+    one_year_later = last_date + relativedelta(years=1)
+
+    transaction_tuples = _group_follow_up_objects(existing_transactions)
+    date_deltas = [second.booking_date - first.booking_date for first, second in transaction_tuples]
+    average_delta_in_days = Decimal(sum(delta.days for delta in date_deltas)) / Decimal(len(date_deltas))
+    average_delta_in_months = average_delta_in_days / days_per_month
+
+    days_per_month_mod = average_delta_in_days % days_per_month
+    distance_from_days_per_month = min(days_per_month_mod, days_per_month - days_per_month_mod)
+    if distance_from_days_per_month <= monthly_distance_threshold:
+        # transactions can be considered to happen every n months
+        recurring_months = round(average_delta_in_months)
+        while last_date < one_year_later and len(dates) < 10:
+            last_date += relativedelta(months=recurring_months)
+            dates.append(last_date)
+
+        days_of_month = [t.booking_date.day for t in existing_transactions]
+        if max(days_of_month) - min(days_of_month) <= certain_day_of_month_threshold:
+            # since transactions occurred in a close range around a certain day of month, we can
+            # improve our prediction
+            day_of_month = round(sum(days_of_month) / len(days_of_month))
+            for idx in range(len(dates)):
+                dates[idx] = dates[idx].replace(day=day_of_month)
+
+    else:
+        # there is no monthly pattern, just add the average delta to determine new dates
+        recurring_days = round(average_delta_in_days)
+        while last_date < one_year_later and len(dates) < 10:
+            last_date += relativedelta(days=recurring_days)
+            dates.append(last_date)
+
+    return dates, recurring_days, recurring_months, day_of_month
+
+
+def predict_transactions(subject: Subject):
+    """
+    Analyze existing transactions of a given subject and predict future transactions, up to one year in advance.
+    """
+    transactions, prediction_info = [], None
+    amount = predict_amount(subject)
+    dates, rec_days, rec_months, day_of_month = predict_booking_dates(subject)
+    if amount and dates:
+        transactions = [Transaction(amount=amount, booking_date=date, subject=subject) for date in dates]
+        prediction_info = {
+            "recurring_days": rec_days,
+            "recurring_months": rec_months,
+            "day_of_month": day_of_month,
+        }
+    return transactions, prediction_info

core/tests/test_prediction.py

@@ -0,0 +1,114 @@
+from datetime import date
+
+from django.test import TestCase
+
+from core.models import Subject, Transaction
+from core.prediction import predict_transactions
+
+
+class PredictionTestCase(TestCase):
+
+    def test_not_enough_data(self):
+        subject = Subject.objects.create(name="rent")
+        predicted_transactions, prediction_info = predict_transactions(subject)
+        self.assertEqual(predicted_transactions, [])
+        self.assertIsNone(prediction_info)
+        Transaction.objects.create(amount=-333, booking_date=date(2020, 6, 2), subject=subject)
+        predicted_transactions, prediction_info = predict_transactions(subject)
+        self.assertEqual(predicted_transactions, [])
+        self.assertIsNone(prediction_info)
+        Transaction.objects.create(amount=-333, booking_date=date(2020, 7, 2), subject=subject)
+        predicted_transactions, prediction_info = predict_transactions(subject)
+        self.assertNotEqual(predicted_transactions, [])
+        self.assertIsNotNone(prediction_info)
+
+    def test_every_month(self):
+        subject = Subject.objects.create(name="rent")
+        Transaction.objects.create(amount=-333, booking_date=date(2020, 6, 2), subject=subject)
+        Transaction.objects.create(amount=-333, booking_date=date(2020, 7, 2), subject=subject)
+        predicted_transactions, prediction_info = predict_transactions(subject)
+        first, second, last = predicted_transactions[0], predicted_transactions[1], predicted_transactions[-1]
+        self.assertEqual(first.booking_date, date(2020, 8, 2))
+        self.assertEqual(second.booking_date, date(2020, 9, 2))
+        self.assertEqual(last.booking_date, date(2021, 5, 2))
+        for tr in predicted_transactions:
+            self.assertEqual(tr.amount, -333)
+        self.assertDictEqual(
+            prediction_info,
+            {"recurring_days": None, "recurring_months": 1, "day_of_month": 2},
+        )
+
+    def test_every_3_months(self):
+        subject = Subject.objects.create(name="rent")
+        Transaction.objects.create(amount=-333, booking_date=date(2020, 6, 2), subject=subject)
+        Transaction.objects.create(amount=-333, booking_date=date(2020, 9, 2), subject=subject)
+        predicted_transactions, prediction_info = predict_transactions(subject)
+        first, second, last = predicted_transactions[0], predicted_transactions[1], predicted_transactions[-1]
+        self.assertEqual(first.booking_date, date(2020, 12, 2))
+        self.assertEqual(second.booking_date, date(2021, 3, 2))
+        self.assertEqual(last.booking_date, date(2021, 9, 2))
+        for tr in predicted_transactions:
+            self.assertEqual(tr.amount, -333)
+        self.assertDictEqual(
+            prediction_info,
+            {"recurring_days": None, "recurring_months": 3, "day_of_month": 2},
+        )
+
+    def test_every_year(self):
+        subject = Subject.objects.create(name="rent")
+        Transaction.objects.create(amount=-333, booking_date=date(2019, 6, 2), subject=subject)
+        Transaction.objects.create(amount=-333, booking_date=date(2020, 6, 2), subject=subject)
+        predicted_transactions, prediction_info = predict_transactions(subject)
+        self.assertEqual(len(predicted_transactions), 1)
+        trans = predicted_transactions[0]
+        self.assertEqual(trans.booking_date, date(2021, 6, 2))
+        self.assertEqual(trans.amount, -333)
+        self.assertDictEqual(
+            prediction_info,
+            {"recurring_days": None, "recurring_months": 12, "day_of_month": 2},
+        )
+
+    def test_monthly_varying_begin_end(self):
+        subject = Subject.objects.create(name="rent")
+        Transaction.objects.create(amount=-333, booking_date=date(2020, 1, 31), subject=subject)
+        Transaction.objects.create(amount=-333, booking_date=date(2020, 3, 1), subject=subject)
+        Transaction.objects.create(amount=-333, booking_date=date(2020, 4, 1), subject=subject)
+        Transaction.objects.create(amount=-333, booking_date=date(2020, 4, 30), subject=subject)
+        predicted_transactions, prediction_info = predict_transactions(subject)
+        first, second, last = predicted_transactions[0], predicted_transactions[1], predicted_transactions[-1]
+        self.assertEqual(first.booking_date, date(2020, 5, 30))
+        self.assertEqual(second.booking_date, date(2020, 6, 30))
+        self.assertEqual(last.booking_date, date(2021, 2, 28))
+        for tr in predicted_transactions:
+            self.assertEqual(tr.amount, -333)
+        self.assertDictEqual(
+            prediction_info,
+            {"recurring_days": None, "recurring_months": 1, "day_of_month": None},
+        )
+
+    def test_no_monthly_pattern(self):
+        subject = Subject.objects.create(name="rent")
+        Transaction.objects.create(amount=-333, booking_date=date(2020, 1, 15), subject=subject)
+        Transaction.objects.create(amount=-333, booking_date=date(2020, 2, 10), subject=subject)
+        Transaction.objects.create(amount=-333, booking_date=date(2020, 4, 25), subject=subject)
+        Transaction.objects.create(amount=-333, booking_date=date(2020, 5, 5), subject=subject)
+        predicted_transactions, prediction_info = predict_transactions(subject)
+        first, second, last = predicted_transactions[0], predicted_transactions[1], predicted_transactions[-1]
+        self.assertEqual(first.booking_date, date(2020, 6, 11))
+        self.assertEqual(second.booking_date, date(2020, 7, 18))
+        self.assertEqual(last.booking_date, date(2021, 5, 10))
+        for tr in predicted_transactions:
+            self.assertEqual(tr.amount, -333)
+        self.assertDictEqual(
+            prediction_info,
+            {"recurring_days": 37, "recurring_months": None, "day_of_month": None},
+        )
+
+    def test_amount_change(self):
+        subject = Subject.objects.create(name="rent")
+        Transaction.objects.create(amount=1337, booking_date=date(2020, 6, 2), subject=subject)
+        Transaction.objects.create(amount=1312, booking_date=date(2020, 7, 2), subject=subject)
+        Transaction.objects.create(amount=404, booking_date=date(2020, 8, 2), subject=subject)
+        predicted_transactions, prediction_info = predict_transactions(subject)
+        for tr in predicted_transactions:
+            self.assertEqual(tr.amount, 404)

core/tests/test_price_field.py

@@ -0,0 +1,47 @@
+from decimal import Decimal, InvalidOperation
+
+from django.test import TestCase
+from django.utils import timezone
+
+from core.models import Balance
+
+
+def _create_and_reload_balance(amount):
+    bal = Balance.objects.create(amount=amount, date=timezone.now().date())
+    bal.refresh_from_db()
+    return bal
+
+
+class PriceFieldTestCase(TestCase):
+
+    def test_normal_decimal(self):
+        bal = _create_and_reload_balance(Decimal("13.37"))
+        self.assertEqual(bal.amount, Decimal("13.37"))
+
+    def test_too_big_decimal(self):
+        with self.assertRaises(InvalidOperation):
+            _create_and_reload_balance(Decimal("13371337.00"))
+
+    def test_rounding_decimal(self):
+        bal = _create_and_reload_balance(Decimal("1.337"))
+        self.assertEqual(bal.amount, Decimal("1.34"))
+
+    def test_normal_int(self):
+        bal = _create_and_reload_balance(1337)
+        self.assertEqual(bal.amount, Decimal("1337.00"))
+
+    def test_too_big_int(self):
+        with self.assertRaises(InvalidOperation):
+            _create_and_reload_balance(13371337)
+
+    def test_normal_float(self):
+        bal = _create_and_reload_balance(13.37)
+        self.assertEqual(bal.amount, Decimal("13.37"))
+
+    def test_too_big_float(self):
+        with self.assertRaises(InvalidOperation):
+            _create_and_reload_balance(13371337.00)
+
+    def test_rounding_float(self):
+        bal = _create_and_reload_balance(1.337)
+        self.assertEqual(bal.amount, Decimal("1.34"))

core/views.py

@@ -0,0 +1,3 @@
+from django.shortcuts import render
+
+# Create your views here.