fix error in gitignore

2026-09-24 12:32:59 +03:30
commit 86c117ee2a
165 changed files with 5963 additions and 0 deletions
@@ -0,0 +1,117 @@
+"""Backend-authoritative pricing engine.
+
+Produces a full, explainable breakdown and is always the source of truth —
+the frontend may display estimates but must never be trusted for financial
+values.
+"""
+from decimal import Decimal, ROUND_HALF_UP
+
+CHARGE_TYPES = {"fixed", "per_kg", "per_unit", "percentage", "tiered", "fee"}
+
+
+class PricingEngine:
+    def calculate(self, weight_kg, selected_steps, currency: str = "IRR") -> dict:
+        weight = Decimal(str(weight_kg))
+        lines = []
+        subtotal = Decimal("0")
+
+        # Pass 1 — charge rules.
+        for step in selected_steps:
+            for rule in step.pricing_rules.filter(active=True, rule_type__in=CHARGE_TYPES).order_by("priority"):
+                line = self._apply_charge_rule(rule, weight)
+                if line is None:
+                    continue
+                lines.append(line)
+                subtotal += Decimal(line["amount"])
+
+        # Pass 2 — discounts (fixed or percentage of subtotal).
+        discounts = Decimal("0")
+        for step in selected_steps:
+            for rule in step.pricing_rules.filter(active=True, rule_type="discount"):
+                amt = Decimal(str(rule.amount))
+                if (rule.config or {}).get("percentage"):
+                    amt = subtotal * amt / Decimal("100")
+                discounts += amt
+                lines.append(
+                    self._line(rule, weight, "discount", Decimal("0"), amt)
+                )
+
+        # Pass 3 — taxes on (subtotal - discounts).
+        taxes = Decimal("0")
+        taxable = subtotal - discounts
+        for step in selected_steps:
+            for rule in step.pricing_rules.filter(active=True, rule_type="tax"):
+                amt = taxable * Decimal(str(rule.amount)) / Decimal("100")
+                taxes += amt
+                lines.append(self._line(rule, weight, "tax", Decimal("0"), amt))
+
+        total = subtotal - discounts + taxes
+        if total < 0:
+            total = Decimal("0")
+
+        return {
+            "currency": currency,
+            "lines": lines,
+            "subtotal": str(self._q(subtotal)),
+            "discounts": str(self._q(discounts)),
+            "taxes": str(self._q(taxes)),
+            "total": str(self._q(total)),
+        }
+
+    def _q(self, v: Decimal) -> Decimal:
+        return v.quantize(Decimal("0.01"), rounding=ROUND_HALF_UP)
+
+    def _line(self, rule, weight, kind, unit_price, amount, quantity=None) -> dict:
+        return {
+            "step_key": rule.step.key,
+            "rule": rule.name,
+            "kind": kind,
+            "quantity": str(quantity if quantity is not None else weight),
+            "unit_price": str(self._q(unit_price)),
+            "amount": str(self._q(amount)),
+        }
+
+    def _apply_charge_rule(self, rule, weight):
+        kind = rule.rule_type
+        cfg = rule.config or {}
+        amount = Decimal(str(rule.amount))
+        unit_price = Decimal("0")
+        quantity = weight
+        if kind == "fixed":
+            unit_price = amount
+        elif kind == "per_kg":
+            unit_price = amount
+            amount = amount * weight
+        elif kind == "per_unit":
+            units = Decimal(str(cfg.get("units", 1)))
+            unit_price = amount
+            amount = amount * units
+            quantity = units
+        elif kind == "percentage":
+            base = Decimal(str(cfg.get("base", 0)))
+            unit_price = amount
+            amount = base * amount / Decimal("100")
+        elif kind == "tiered":
+            unit_price = self._tier_unit_price(cfg.get("tiers", []), weight)
+            amount = unit_price * weight
+        elif kind == "fee":
+            unit_price = Decimal("0")
+        else:
+            return None
+
+        min_c = cfg.get("min_charge")
+        max_c = cfg.get("max_charge")
+        if min_c is not None and amount < Decimal(str(min_c)):
+            amount = Decimal(str(min_c))
+        if max_c is not None and amount > Decimal(str(max_c)):
+            amount = Decimal(str(max_c))
+
+        return self._line(rule, weight, kind, unit_price, amount, quantity)
+
+    def _tier_unit_price(self, tiers, weight) -> Decimal:
+        best = Decimal("0")
+        for tier in tiers or []:
+            low = Decimal(str(tier.get("from", 0)))
+            if weight >= low:
+                best = Decimal(str(tier.get("price", 0)))
+        return best