Add Polaris FastAPI backend: models/schemas, pricing+scoring+order router, importer, Celery tasks, API routers, seed script

backend/app/engines/pricing.py

@@ -0,0 +1,87 @@
+"""Pricing engine.
+
+Applies active `price_rules` (cost -> markup bands) and computes net profit:
+
+    retail      = cost * (1 + markup_pct/100)   (floored at cost + shipping + fees)
+    net profit  = retail - cost - shipping - fees
+    margin_pct  = profit / retail * 100
+
+`min_price` (product floor) is respected — retail is never below it.
+"""
+from decimal import ROUND_HALF_UP, Decimal
+
+from app.models import PriceRule
+
+CENT = Decimal("0.01")
+
+
+def _q(value) -> Decimal:
+    try:
+        return Decimal(str(value or 0))
+    except Exception:
+        return Decimal("0")
+
+
+def get_active_rules(db):
+    return (
+        db.query(PriceRule)
+        .filter(PriceRule.active.is_(True))
+        .order_by(PriceRule.min_cost)
+        .all()
+    )
+
+
+def find_rule(db, cost):
+    cost = _q(cost)
+    for rule in get_active_rules(db):
+        if cost >= _q(rule.min_cost) and (rule.max_cost is None or cost < _q(rule.max_cost)):
+            return rule
+    return None
+
+
+def calculate_price(db, cost, shipping=0, fees=0, min_price=None):
+    """Return dict(retail, profit, margin, margin_pct, markup_pct, rule_id, ...) or None.
+
+    None means no active rule applies — callers must NOT publish such products.
+    """
+    cost = _q(cost)
+    shipping = _q(shipping)
+    fees = _q(fees)
+    rule = find_rule(db, cost)
+    if rule is None:
+        return None
+
+    markup_pct = _q(rule.markup_pct)
+    retail = (cost * (1 + markup_pct / 100)).quantize(CENT, rounding=ROUND_HALF_UP)
+
+    # floor: cost + shipping + fees, raised by min_margin_pct if configured
+    floor = (cost + shipping + fees).quantize(CENT, rounding=ROUND_HALF_UP)
+    min_margin_pct = _q(rule.min_margin_pct)
+    if min_margin_pct > 0:
+        floor = max(floor, (floor + retail * min_margin_pct / 100).quantize(CENT, rounding=ROUND_HALF_UP))
+    if retail < floor:
+        retail = floor
+
+    # never below the product's minimum price
+    if min_price is not None and retail < _q(min_price):
+        retail = _q(min_price).quantize(CENT, rounding=ROUND_HALF_UP)
+
+    profit = (retail - cost - shipping - fees).quantize(CENT, rounding=ROUND_HALF_UP)
+    margin_pct = (profit / retail * 100).quantize(Decimal("0.01")) if retail > 0 else Decimal("0")
+
+    return {
+        "cost": cost,
+        "shipping": shipping,
+        "fees": fees,
+        "retail": retail,
+        "profit": profit,
+        "margin": profit,
+        "margin_pct": float(margin_pct),
+        "markup_pct": float(markup_pct),
+        "rule_id": rule.id,
+    }
+
+
+def estimate_net_profit(retail, cost, shipping=0, fees=0):
+    """Net profit = retail - (cost + shipping + fees)."""
+    return (_q(retail) - _q(cost) - _q(shipping) - _q(fees)).quantize(CENT, rounding=ROUND_HALF_UP)