add projekt cpn support

app/vat.py

@@ -0,0 +1,88 @@
+from datetime import date, datetime
+from decimal import Decimal, InvalidOperation
+
+from .extensions import db
+from .models import AppSetting
+
+KEYS = {
+    "enabled": "global_vat_override_enabled",
+    "name": "global_vat_override_name",
+    "rate": "global_vat_override_rate",
+    "start": "global_vat_override_start",
+    "end": "global_vat_override_end",
+}
+
+
+def _value(key, default=""):
+    setting = db.session.get(AppSetting, KEYS[key])
+    return setting.value if setting else default
+
+
+def global_vat_override():
+    rate_raw = _value("rate")
+    try:
+        rate = Decimal(rate_raw) if rate_raw != "" else None
+    except InvalidOperation:
+        rate = None
+    return {
+        "enabled": _value("enabled", "0") == "1",
+        "name": _value("name", "Projekt rządowy"),
+        "rate": rate,
+        "start": _parse_date(_value("start")),
+        "end": _parse_date(_value("end")),
+    }
+
+
+def _parse_date(value):
+    if not value:
+        return None
+    try:
+        return date.fromisoformat(value)
+    except ValueError:
+        return None
+
+
+def effective_vat_rate(nominal_rate, on_date=None):
+    override = global_vat_override()
+    if not override["enabled"] or override["rate"] is None:
+        return Decimal(str(nominal_rate))
+    if isinstance(on_date, datetime):
+        on_date = on_date.date()
+    on_date = on_date or date.today()
+    if override["start"] and on_date < override["start"]:
+        return Decimal(str(nominal_rate))
+    if override["end"] and on_date > override["end"]:
+        return Decimal(str(nominal_rate))
+    return override["rate"]
+
+
+def save_global_vat_override(form):
+    enabled = "enabled" in form
+    name = (form.get("name") or "Projekt rządowy").strip()
+    rate_raw = (form.get("rate") or "").strip()
+    start_raw = (form.get("start") or "").strip()
+    end_raw = (form.get("end") or "").strip()
+
+    if enabled:
+        try:
+            rate = Decimal(rate_raw)
+        except InvalidOperation as exc:
+            raise ValueError("Podaj prawidłową globalną stawkę VAT.") from exc
+        if rate < 0 or rate > 100:
+            raise ValueError("Globalna stawka VAT musi mieścić się w zakresie 0–100%.")
+        if start_raw and not _parse_date(start_raw):
+            raise ValueError("Nieprawidłowa data rozpoczęcia.")
+        if end_raw and not _parse_date(end_raw):
+            raise ValueError("Nieprawidłowa data zakończenia.")
+        if start_raw and end_raw and start_raw > end_raw:
+            raise ValueError("Data zakończenia nie może być wcześniejsza niż rozpoczęcia.")
+
+    values = {
+        KEYS["enabled"]: "1" if enabled else "0",
+        KEYS["name"]: name,
+        KEYS["rate"]: rate_raw,
+        KEYS["start"]: start_raw,
+        KEYS["end"]: end_raw,
+    }
+    for key, value in values.items():
+        db.session.merge(AppSetting(key=key, value=value))